Abbreviations
AFP
alpha‐fetoprotein
HCC
hepatocellular carcinoma
HCV
hepatitis C virus
LT
liver transplantation
MELD
Model for End‐Stage Liver Disease
OPTN
Organ Procurement and Transplantation Network
TT
transplantable tumor
UCSF
University of California San Francisco
UNOS
United Network for Organ Sharing
Training for details produces tunnel vision, and men of broader perspective are required
for useful application of scientific progress.
Michael Shimkin
Nearly every day, the issue of liver transplantation (LT) for hepatocellular carcinoma
(HCC) is debated worldwide during rounds, publications, meetings, and—more importantly—in
front of patients with liver cancer who are seeking their doctors' advice, often after
the digital information media have left them and their families empty‐handed.
Physicians have realized how their certainties can weaken and can strongly differ,
regardless of whether the prediction of post‐LT outcome is applied to large populations
or to single individuals with liver cancer. In addition, liver‐dedicated physicians
with nontransplantation expertise may find themselves puzzled when dealing with the
existing restrictions on the distribution of the scarce resource of donated organs.1,
2, 3 Allocation rules are in fact continuously released based on adjustments adopted
within the transplantation community to maximize patient benefit—defined as an improvement
in quantum of life in each patient independent of tumor stage—while avoiding harm
to other patients who are waiting for a liver graft. Putting this into practice, the
mission of doing justice in transplantation is attempted either through application
of the utility principle (i.e., when organs are allocated to patients who have the
best post‐LT predicted survival) or in adherence to the mandate to care for the “sickest
patient first.”4
In transplantation candidates with HCC, the main obstacle to a smooth organ allocation
is the lack of instruments able to determine, with sufficient detail, exactly how
sick a patient is, how specific a given tumor presentation is, and how likely the
tumor response to various treatments will be. Scores modulated on HCC characteristics
have been proposed,4, 5, 6, 7, 8 but the estimation of the risk of pretransplantation
dropout or posttransplantation benefit remains suboptimal. What is missing to fully
accomplish the “nearly impossible mission” to frame the complex scenario of LT for
HCC is the ability to capture, in a weighty manner, the evolution of a given cancer
in relation to treatment, as this could be the main driver to predict posttransplantation
outcome in patients who have cirrhosis with HCC, similarly to what the Model for End‐Stage
Liver Disease (MELD) system does in noncancer candidates. Notably, the lack of precise
prognostication tools for transplantation candidates with HCC has been repeatedly
reported as causing detrimental effects for non‐HCC patients, who may be disfavored
by unbalances in points systems that oversupply cancer patients.4, 9
Looking at the magnitude of the information presented on LT for HCC and at its diffuse
interpretation, any further attempt to create new prognostication scores seems inadequate
unless a precise description of the objective granularity of tumor presentation and
of its spectrum of responses to different treatment options is taken into account.
Also, as modern discussions on LT in HCC move into the broaden concept of a medicine
made of economic, social and ethical components, a more accountable description of
the tumor conditions could be instrumental to move the scale of priorities into a
more realistic and treatment‐oriented approach to HCC.
Priority in organ allocation and patient selection are crucial factors that are difficult
to merge because they have endpoints that are inherently far from one another. Optimization
of a given resource in the case of organ allocation and maximization of outcomes when
patient selection is targeted are in fact the driving forces that tend to split LT
for HCC apart. Yet the attempt to reconcile these postulates is often referred to
as an effort to “square the circle.”
In this article, the impossible task to square the closed circle of patient selection
and graft allocation in LT for HCC is approached as it would be during a math class,
solving this same problem by multiplying the square of the radius (r2) by π: an irrational
number (i.e., a number that never ends) used to approximate a solution that otherwise
would be to the infinitum. To do this, a comprehensive assessment of HCCs examined
for transplantation is proposed.
In the proposed model, tumor presentation and response to therapy are used as a “π”:
a sort of rectifying factor to be used within the challenging contexts of listing
and prioritization, with the aim of improving their mutual efficiency in optimizing
patient outcome and resource allocation in the field of LT for HCC.
Background: The Fruits of Long Endeavors
The likelihood of patient survival after transplantation remains an essential criterion
when deciding on LT for HCC and represents the most important factor for indicating
such a demanding therapeutic option.1, 3, 4, 10 About two decades ago, the Milan criteria
defined the benchmark for achieving the best post‐LT survival in HCC.11 Since then,
these restricted criteria (single nodule ≤5 cm or multiple [≤3] nodules ≤3 cm in size)
have become the best predictor of excellent post‐LT outcome and cost‐effective transplantation.
This result strongly influenced staging systems for HCC, guidelines, recommedations,
and allocation policies for deceased donor liver grafts.12, 13, 14
Starting with the University of California San Francisco (UCSF) criteria (single nodule
≤6.5 cm; 2 to 3 lesions each ≤5 cm or 4 to 5 lesions each ≤3 cm, with the maximum
sum of diameters ≤8 cm in all cases)15 multiple other metrics have been established
over time in an attempt to predict the results of LT for HCC.16 Most of these metrics
have shown the same good survival results achieved when restricted indications were
met, even though subsequent observations revealed a progressively increased rate of
cancer recurrence in tumors transplanted beyond conventional limits.
Clearly, the expanded criteria mechanism built on pure morphologic tumor indexes (i.e.,
largest diameter and number of tumor nodules) did not help in defining which patients
with cirrhosis and HCC beyond the Milan criteria should be offered LT first, but did
unravel the negative prognostic influence of biological and pathological features
rarely observed in patients meeting conventional criteria (such as high alpha‐fetoprotein
[AFP] serum level, presence of microvascular invasion, and poorly differentiated [G3]
tumors).4, 16
Conventional selection criteria have persisted, however, in guidelines and organ procurement
organization policies, while the “transplantable HCC” category (i.e., curable with
transplantation only) has been enriched over time, with cases at worse prognosis (i.e.,
T3 stage according to the United Network for Organ Sharing [UNOS] system) defined
as transplantable on the basis of local dynamics of the waiting list that did not
prejudice other noncancer recipients with a better prognosis.17 It is conceivable
that 25%‐40% of the current HCC patients listed for LT belong to such a T3 subgroup
receiving exception points and presumably some form of tumor downstaging.4, 18
The introduction of direct antiviral agents in daily practice19 will further increase
organ availability for patients with HCC in the near future, as a significant number
of patients with decompensated cancer‐free hepatitis C virus (HCV) cirrhosis will
likely be inactivated and delisted within 1 year just by the introduction of second‐generation
direct antiviral agents. In a recent multicenter European study, it was estimated
that 33% and 25% of HCV cancer‐free listed cirrhosis will be inactivated or delisted,
respectively.20 In parallel, the practice of downstaging tumors in patients who were
originally thought to be ineligible for transplantation21 will increase the number
of borderline HCC cases presented to liver transplantation boards for decision.
Emboldened by its own success, transplantation for HCC—a neglected indication just
20 years ago—is likely to become the leading indication for liver replacement in the
near future.
The Inverse Perspective of Case Selection: From Tumor Presentation to Response to
Therapy
Tumor subclasses correlating with diverse molecular assays and clinicopathologic behavior
have been discovered progressively,22, 23 with gene signatures also playing a role
in the prognostication of LT patients beyond the Milan criteria.24 However, the extreme
molecular heterogeneity of HCC still represents a significant limitation to the full
introduction of precision medicine in patients within the transplantation landscape.23
Despite the absence of reliable biomarkers or genetic alterations influencing clinical
decisions, a different kind of individualized medicine has progressively gained credit
from multidisciplinary tumor board discussions in which all tumor and individual characteristics
of each patient are weighed by different specialties and routed to variegated therapeutic
alternatives. Perhaps the less known but most relevant result of this approach is
the inverse perspective that has emerged in centers with a large referral of HCC patients
regardless of their indication for transplantation.
In practice, rather than considering up front patients with HCC as being eligible
for LT according to disease presentation, most patients with HCC remain within the
spectrum of eligibility for LT—the exclusions determined only by macrovascular invasion,
extrahepatic spread, comorbidities, and age beyond limits—and are assigned to different
forms of combined therapy that, if sufficiently effective within a certain time, may
allow liver transplantation listing.
A flexible approach aimed at merging tumor stage and results of treatment is going
to be adopted in a large European region25 and is based on the observations that post‐LT
survival outcomes in HCC beyond Milan criteria with objective and sustained response
to pre‐LT therapy are not significantly different compared with those patients who
meet conventional criteria at presentation.17 In order to avoid the risks of uncontrolled
expansion of HCC criteria, such an “inverse selection approach” based on response
to therapy requires a few restrictions:
All suitable patients with cirrhosis who have treatable HCC by nontransplantation
means should be treated, regardless of whether LT is in their therapeutic future.
The best available option (i.e., monotherapy or combination therapy) should be determined
after thorough multidisciplinary discussion.
A minimal observation period after the conclusion of a given (combination) treatment
is mandatory, because time is a surrogate of tumor aggressiveness and therefore an
additional factor in the selection process.17, 21, 23 Time as a covariate is also
required to assess tumor response and evolutionary posttreatment outcome.23
All possible information on tumor biology should be collected and discussed before
the board. With this particular aim, absolute values and variations of AFP serum levels
over time, as well as tissue biopsies (obtained during percutaneous ablation, laparoscopic
staging, or resection), should be collected.26
The minimal expected survival for patients undergoing LT under this conditions should
be increased from the conventional limit of 50% at 5 years to 60% or higher. In doing
so, the benefit achievable in HCC beyond conventional criteria could be adjusted to
acceptable levels of posttransplantation utility4, 7, 25 while avoiding any harm to
patients who remain on waiting lists.17, 27, 28
Transplantable Tumors
Based on these and other observations, a possible reappraisal of patients with HCC
who are eligible for and curable with transplantation could be attempted within a
comprehensive frame able to capture the large majority of tumor presentations and
describe in a simplified manner the granularity of possible responses to therapy.
Figure 1 presents a scale of HCC disease severity that is designed to prioritize classes
capable of routing organ allocation by means of points systems determined according
to national and regional scenarios. Accordingly, transplantable tumors (TTs) will
be defined following the Milan, UCSF, or expanded criteria together with the donor
rate in each allocation area, the proportion of enlisted HCC/non‐HCC patients and
the dynamic of the waiting list.
Figure 1
Staging and allocation for HCC within the spectrum of LT eligibility. Classes of progression
and allocation priority within the TT stages identified for HCC in well‐compensated
cirrhosis. LT eligibility and priority are not determined completely up front, but
they both come into focus after the best available therapy has been applied. Details
on application rules are given in Table 1.
Classes of progression within TTs range from patients with “zeroed” HCC (i.e., disease
completely removed by surgery, ablation, or embolo‐therapies) to patients carrying
conventional criteria tumors either at diagnosis or as late recurrence (after >2 years
from a previous curative treatment) considered as de novo cancers on cirrhotic oncogenic
livers rather than intrahepatic metastases.23, 29 Finally, patients in whom transplantable
criteria are still met—whether at inception or after complete or near‐complete response
to downstaging treatment—should be ranked as the highest priority. These are patients
who have achieved a suboptimal response (i.e., a partial response) despite adequate
locoregional treatment or patients presenting with early cancer recurrence (≤2 years
from a previous curative treatment) and whose cumulative tumor staging still correspond
to a potentially transplantable tumor. The main principles governing what can be called
an adaptive approach are summarized in Table 1, which should be consulted in conjunction
with Figure 1.
Table 1
Application Rules for Staging and Allocation
1
The system applies only to early and intermediate stage HCC presenting in compensated
cirrhosis/chronic liver diseases (stages BCLC‐A and BCLC‐B). Exclusion criteria are
vascular invasion, extrahepatic spread and comorbidities. HCC arising in decompensated
(Child‐Pugh class C) cirrhosis is determined by laboratory MELD score and receives
priority accordingly.
2
In principle, any HCC arising in compensated cirrhosis is considered as TT once inclusion/exclusion
criteria are satisfied. Morphology criteria (i.e., tumor size and number) used for
transplantation eligibility should be defined a priori at a regional level depending
on the dynamics of the waiting list, proportion of enlisted HCC versus non‐HCC patients,
harm to patients who remain on the waiting list, donor availability, etc., and should
not be modified at any time during patient follow‐up (i.e., up to LT, dropout, or
death). Morphology criteria reported objectively should be integrated with pathologic/biologic
information (e.g., tumor biopsy, AFP levels) when available, and all information should
be discussed before the tumor transplantation board (see points 3 and 4 below). AFP
cutoff levels able to exclude transplantation eligibility even in presence of permissive
tumor morphology conditions should be defined a priori as well, as that limit currently
ranges from 200 to 1000 ng/mL21, 32, 39, 41, 42, 43 or according to steady increase
over time.32
3
All TT should be treated with the single/combined best available treatment according
to internal protocols and/or accepted guidelines and should be reconsidered for class
assignment at the end of each treatment course. Accordingly, any decision regarding
treatment of a TT should take into account the transplantation implications before
and after therapy courses.
4
Reproducible criteria for imaging, diagnosis, classification, and reporting in HCC
before and after treatment should follow common accepted standards determined a priori
30, 31 and should also consider the contribution of tumor growth rate49 and patterns
of residual disease determination.50 Digital imaging should be accessible for internal
or external audits.
5
If TT are not treatable due to technical or medical reasons not captured by MELD score
(i.e., ascites), the patient should be classified as having untreatable HCC (TTUT)
and prioritized accordingly.
6
Point assignment and priority class should be managed dynamically, because disease
status may change over time depending on biology and therapy. Stepwise assessments
should be undertaken at a minimum of four possible time points:
a) at tumor presentation (baseline assessment), if TT meets points n.1 and 2 above;
b) in stabilized tumor conditions (i.e., stable disease for a sufficient period of
time [at least 3 months])7, 17, 21;
c) in case of tumor progression during treatment;a
d) at the end of each treatment course.
7
Patients included in downstaging protocols should be considered as TT0NT (intermediate
priority) in case of complete response at the end of treatment—due to the initial
tumor stage exceeding conventional criteria—or as TTDR (high priority) in case of
suboptimal downsizing and/or residual tumor remaining reasonably stable over time
in patients still meeting transplantation criteria. For patients included in “extended
limits for downstaging” protocols, LT listing could be considered only after complete
response and if part of prospective investigations.
8
Because changes that occur in serum AFP levels while patients are on the waiting list
correspond closely to changes in posttransplantation mortality,51 AFP trends should
parallel radiologic tumor response (or progression) of a transplantable tumor during
treatment and/or follow‐up. In principle, patients who have a major drop in AFP level
after treatment should be considered at a more significant level than those who do
not. In patients included in downstaging protocols (see point 7 above), differential
drop and absolute APF level could help in discriminating various levels of response—and
priority‐among different patients with similar radiology‐assessed posttreatment response.
9
Recurrent HCC should be approached similarly to naïve HCC, with identical treatment
aims and general requirements as listed above in points 1‐5. Recurrent HCC may be
classified as TTFR or TTDR according to the time of recurrence, whether this is ≤2
years (i.e., early recurrence) or >2 years (i.e., late recurrence) from the original
curative treatment. This yields different priorities because of the higher risk of
dropout in early recurring tumors.
• Early recurrences should be listed only if the tumor meets transplantable criteria
both at the time of original treatment and after cumulative staging, which is calculated
at the time of transplantation consideration. The cumulative stage of an early recurring
HCC considers one tumor entity as the sum of the first presenting HCC + recurrent
tumor.
• Late recurrences should be listed if meeting transplantation criteria at the time
of transplantation consideration, as they could be rated as TTFR regardless of the
stage of the first‐presenting HCC curatively removed >2 years ago.
10
Exceptions to the general frame of stage progression and priorities are allowed with
approval from a regional reviewer board. In the current scenario, exceptions may be
related to: experimental de principe transplantation strategies applied to resected
tumors (TT0c); observational strategies pausing treatment for <2 cm lesions (TT1);
downgrade in priority for recurrent although nontreatable HCCs; complete posttreatment
responses of segmental portal vein thrombosis; and salvage surgery to achieve complete
response in TTPR tumors (and consequent reduction in TTNT stage, etc.).
Rules apply to the system shown in Fig. 1.
a
HCC progression should be rated in order of severity as (A) progression of the treated
tumor; (B) appearance of an additional nodule; (C) evidence of vascular invasion;
or (D) extrahepatic tumor spread. In this model, tumor progression types A and B may
indicate further treatment, upgrade in priority, or dropout depending on whether the
detected progression still meets transplantation criteria; progression types C and
D exclude the patient from transplantation consideration (i.e., dropout from the waiting
list).
Following the line of reasoning proposed in this approach, the heterogeneities of
HCC's presentations and treatments are routed into different subclasses that include
current standards, variations in local capabilities and resource allocation, and evolutionary
conditions related to treatment response, as well as HCC tumor recurrence, AFP fluctuations,
and objective tumor assessment with up‐to‐date radiology criteria.30, 31, 32 Although
with different relative weight, all these conditions play a role in the current decision‐making
on LT for HCC and are incorporated in a system in which transplantation eligibility
and priority are not completely determined up front but they both come into focus
after all relevant components have been considered and therapy has been applied.
Such a definition of a “transplantable tumor” is inherently open to more specific
contribution of staging and allocation updates and is in line with recent UNOS policies
of HCC exceptions, in which inclusive tumor subclasses of “growing,” “treated,” and
“exceeding T2” have been identified to increase convergence among tumor staging parameters
and points in priority (i.e., classes 5A‐g, 5T, and 5X in the Organ Procurement and
Transplantation Network [OPTN] Policy 2015) for liver allocation in HCC1 in which
standardized radiology criteria for imaging, diagnosis and classification are incorporated.31
Priority as a Function of Allocation Principles
Questions may arise regarding the scale of priority in the proposed approach. Indeed,
priority itself is a concept with several practical applications, depending on which
allocation principle prevails. In addition, the priority endpoints may be weighted
differently, ranging from the minimization of pre‐LT risk to drop out (or death) when
the urgency principle is adopted to the maximization of post‐LT outcome in case the
utility is targeted, particularly for the transplantation benefit— namely, the net
survival obtained by subtracting the survival achieved with LT by the survival obtainable
with nontransplantation options.23, 33, 34
In addition, patients, physicians, and society at large significantly influence the
perception of priority as well as decision‐making with subjective convictions. Complex
statistical models have been advocated to balance all of these components; however,
controversies persist, because within this context even a very light shift in the
design of surveys or variation in predetermined assumptions lead to quite different
conclusions.33, 34, 35
In the proposed concept of TTs, a series of relatively straightforward observations
support the existence of a continuity in HCC subgroups whose severity—and consequently
priority—evolves, not only as a consequence of tumor biology, but also as a product
of medical and surgical interventions. The list of premises upon which each priority
class is identified is summarized in Table 2.
Table 2
Staging and Priority Classification of HCC in the LT Setting: Patient Stratification
According to Allocation Principles
TT Categories
Priority According to HCC Dropout Models
Priority According to Transplantation Benefit
Priority Perception of Patient and Societal Expectations
TT0C
Very Low
Low
Low
No residual tumor after curative treatment of HCC
Very low risk of dropout in cured HCC
Transplantation benefit depends on MELD score only
The patient should not undergo transplantation
TT0L
Low‐Intermediate
Low
Intermediate
No residual tumor after locoregional embolo‐therapies for transplantable HCC
Low risk of dropout in cured HCC
Transplantation benefit depends on HCC‐MELD
The patient was eligible for transplantation but can be placed on hold because the
tumor seems to be cured
TT1
Low
Low
Low
Single HCC ≤2 cm
Low risk of dropout in very early HCC
Low benefit in presence of alternative nontransplantation treatments
The patient should not undergo transplantation if there are other treatment options
TT0NT
Not Applicable
Low
Low
No residual tumor after treatment of a nontransplantable HCC (successful downstaging)
NT HCC should not be listed up front, similarly to non‐HCC in patients with low MELD
scores
Transplantation benefit depends on MELD score only
The patient was not eligible for transplantation and has been cured by other means
TTFR
Intermediate
Intermediate
High
Transplantable HCC > T1 at first presentation or recurrent HCC >2 years after curative
treatment
Demonstrated increase of dropout risk over time for both size and number parameters
Benefit depends on true applicability of alternative treatments
This patient has the best posttransplantation survival (utility)
TTUT
Intermediate
High
High
Transplantable HCC judged untreatable for reasons not captured by MELD (i.e., ascites)
Increased dropout risk; short time to liver decompensation
There is no therapeutic alternative for HCC
The patient is expected to have good utility posttransplantation
TTPR
Intermediate/High
High
High
Partial response after complete bridge therapy in a transplantable tumor
Risk of selection of biologically aggressive clones with increased proliferative activity
Failure of a bridge therapy with no residual therapeutic alternative
The patient is expected to have good utility posttransplantation
TTDR
Intermediate/High
High
High
Transplant eligibility after downstaging (sustained partial response) or recurrent
HCC <2 years after curative treatment of any HCC
High dropout risk over time for both size and number parameters
Benefit depends on absence of true alternative treatments
Transplantation should be offered in relatively stable patients before it is too late
After all, the apparent distance between the assumptions defining each priority class
can be normalized through composite evaluations of the need of transplantation that
correspond to a stepwise increment of a numeric point scale. Obviously, the entity
of progression into the priority scale has to be determined at a regional and/or national
level.
Selection and Allocation Principles Reconciled: Has the Circle Been Squared?
Over the years, the growing number of analyses advocating adjustments not just in
selection but also in allocations rules for LT in HCC, has elicited the current effort
to place transplantation decisions for patients with HCC within a modern perspective.
The assumption is that transplantation eligibility and allocation in HCC could be
moderately loosened without undue prejudice to other recipients; this is very likely
to occur, as we will soon witness a net decrease in transplantation indication for
HCV‐related cirrhosis and an increase in the practice of downstaging HCC. The proposed
system might be capable of transforming downstaged tumor responses from exceptions
to drivers for both the selection and allocation processes (Table 1, points 7 and
8).
The attempt to square the circles and reconcile tumor stage, effects of treatment,
and priority in allocation is by definition imperfect, and there is an actual risk
that several factors may render this proposal into wishful thinking. In order to consolidate
the model, the following important areas will need to be implemented.
System Solidity and Flexibility Should Be Reinforced
Although inclusive by all means, the application of the proposed model of priority
leans slightly toward transplantation benefit (i.e., utility‐based) endpoints.4, 23,
33, 34 This may be criticized by those who consider crude long‐term survival as a
more important target to be achieved compared with life‐years gained.17, 36 However,
the redefinition of transplantable HCC by way of pretransplantation treatment, rather
than precluding ideal transplantation candidates from such a curative option simply
delays their priority in favor of patients who are still within transplantation criteria
but are at a higher risk of dropout due to tumor progression or incomplete response
at the end of successful treatment courses (see also Table 1). In fact, a benefit‐oriented
approach combines both pre‐ and posttransplantation outcomes, integrates the results
of alternative treatment strategies, makes obvious the unacceptable survival targets
for transplantation, and allows a comparison between patients with and without HCC.7,
23, 29 Following the same line of reasoning, a variable age threshold beyond which
the net benefit for HCC patients does not justify LT over resection or ablation seems
questionable, at least until a transplantation‐ versus nontransplantation‐related
benefit comparison is adjusted on reference cohorts derived from the general population
matched by sex, age, and years of diagnosis. It is worth noting that within the context
of patient benefit, both the absolute number of years of life gained and years of
life lost with respect to life span (i.e., relative survival) should be considered
when assessing the efficacy of surgical therapies offered to older patients.37
Conversely, a more realistic wait time and priority score based on assumptions shown
in Table 2 could silence both the utilitarian and urgency aims while including patients
and societal perspectives—a process that seems essential to improve the flexibility
of the transplantation system in HCC with respect to noncancer indications.
Common Criteria for Staging, Treatment, and Response Assessment Should Be Adopted
In the proposed system, each patient with HCC who has reasonably stable cirrhosis
stays within the heterogeneous group of TTs while staging and priority is determined
according to the results of the applied therapies. This means that the only condition
required to obtain an optimal result is the management of patients with similar pretransplantation
locoregional treatments, response, monitoring, and delisting criteria.17, 25, 30,
31, 38 Such practices should be enforced within each liver allocation system and among
HCC referral centers, as they are essential to help the implementation of the models
detailed above.
Transplantation Criteria and Minimum Accepted Survival Should Be Defined
A precise definition of transplantation criteria should be determined a priori within
large geographic regions according to the principles detailed above (Table 1, point
2). This definition should incorporate a minimum expected survival (which should target
at least 50% at 10 years, rather than 5 years) and also the likelihood of complete/partial
response achievable with nontransplantation treatment strategies.
The use of treatment response as a selection tool to complement other prognostic pathologic/biologic
covariates in patients exceeding Milan and/or UNOS criteria appears crucial to promote
the use of expanded HCC criteria on a routine basis. Considering the unfeasibility
of randomized trials in this field, the search for a credible hierarchy within the
expanded criteria (i.e., up to seven, total tumor volume, morphology adjusted on AFP7,
23, 39, 40) could be aided by comparing of prospective cohorts generated by variegated
applications of these criteria to the presented model.
Limits for Downstaging Strategies Should Be Agreed Upon
Because downstaging is a strategy aimed at selecting more favorable tumor biology,
the downstaged HCC population must be a fraction of the total amount of patients with
HCC who have a potential indication to transplantation. By definition, downstaged
patients are at higher risk of dropout, and opposite success rates are observed depending
on whether more restrictive or more relaxed tumor burdens are targeted as endpoints.
Restrictive criteria for downstaging eligibility should be agreed upon within the
framework of the adopted transplantation criteria. Evidence supporting this statement
has come from the most recent update of the UCSF downstaging protocol, in which the
upper limit to indicate downstaging was determined up front (see “Background: The
Fruits of Long Endeavors” section). In this experience, 65% of patients with HCC were
converted to Milan criteria, whereas only 7.5% of patients had posttransplantation
tumor recurrence.21
Whatever strategy of downstaging will be determined, AFP trends over time should parallel
radiologic tumor response (or progression) during treatment and at the time of the
final prelisting assessment. AFP cutoff levels able to exclude transplantation eligibility
even in the presence of permissive tumor morphology conditions should be defined a
priori as well, as that limit currently ranges from 200 to 1000 ng/mL21, 32, 39, 41,
42, 43 or according to steady increase over time.32
Waiting Time Duration and Posttransplantation Tumor Recurrences Should Be Monitored
It is well known that HCC variables predicting dropout from the waiting list are also
associated with poorer posttransplantation survival and a higher tumor recurrence
rate,44, 45 with dropout largely depending on waiting time length. Therefore, the
dynamic shifts of transplantation candidates with HCC within the proposed frame implies
an even closer monitoring of waiting times and posttransplantation outcomes. Optimization
of waiting list time and post‐LT results will minimize tumor recurrence, even though
a minimal observation time for disease stabilization after treatment is highly suggested,
to decrease the risk of selecting patients with rapidly progressing lesions. The length
of the “no transplantation” observation period should be determined on a regional
basis and should consider the current standard of 3 months.3, 46
Envisioned Future and Conclusion
To some extent, the history of disease comprises a metamorphosis in treatments and
paradigm shifts anticipating by far the conclusions of large and structured clinical
investigations. For transplantation in the particular setting of HCC, this model proposed
herein is consistent with previous reports47, 48 and will surely undergo validation
studies in a large European region according to a strategy that is in line with modern
perspectives of HCC management. Figure 2 summarizes such a change in perspective as
it relates to the two most paradigmatic conditions in which patients are within or
beyond predetermined transplantation criteria. Even at first glance, the envisioned
future of these two conditions appears to be enriched by expansions of therapeutic
options, transplantation selection, listing, and priority (Tables 1 and 2 provide
additional details in this respect). Future studies are warranted to ascertain whether
this perspective may develop into an implementable system capable of incorporating
the current complexities of HCC management into LT mechanisms.
Figure 2
Paradigm shift in the management of LT in patients with HCC. The multistep process
covers the diagnosis of HCC to LT in patients who are within (A) and beyond (B) the
criteria. With respect to the current rules, the proposed system uses tumor response
to bridging or downstaging as the main drivers for patient selection and priority
allocation.
Over the last two decades, tangible advancement in survival and in knowledge of HCC
have been fueled not only by major scientific achievements but also by changes in
the way physicians have dealt with the role of LT in liver cancer therapy. The shift
in perspective explained in Figs. 1 and 2 is geared toward maximizing all tumor and
therapy heterogeneities in a model that utilizes variations in HCC presentation and
response to treatment as adjusting factors to reconcile selection and allocation logistics,
with the ultimate aim of increasing the benefit, effectiveness, and justice of transplantation
for cancer. As new factors emerge and show significant impacts on HCC, treatment strategies
with an even more pronounced passion for details should be employed. It is difficult
to think of an investment in transplantation that would have a greater impact than
one that creates robust frames within which to improve the quality of medical indications
and resource allocation for patients with liver cancer.