The Janus kinase 1/2 inhibitor ruxolitinib has been shown in a pivotal placebo-controlled
phase III study (Controlled Myelofibrosis Study with Oral JAK Inhibitor Treatment
I (COMFORT-I)) to significantly reduce splenomegaly and symptoms in patients with
intermediate-2 or high-risk myelofibrosis (MF). Although splenomegaly is the most
common manifestation of MF-associated extramedullary hematopoiesis, up to 65% of patients
may also have hepatomegaly,
1, 2
which is often highly symptomatic and can lead to serious complications.
3
Here, we present the results from a COMFORT-I post hoc analysis that assessed changes
in liver volume and their relationship with concomitant changes in splenomegaly and
measures of metabolic status.
As previously reported,
4
COMFORT-I was a randomized, double-blind, placebo-controlled phase III study in patients
with intermediate-2 or high-risk MF and a baseline spleen length ⩾5 cm below the left
costal margin. Patients randomized to placebo were allowed to cross over to ruxolitinib
if they met prespecified criteria for disease progression. The primary end point was
the proportion of patients who achieved a ⩾35% reduction in spleen volume at week
24.
4
Liver and spleen volumes were determined by magnetic resonance imaging or computed
tomography per protocol; palpable liver length was not assessed. Percentage changes
of spleen and liver volumes from baseline to week 144 were calculated for observed
cases. For patients who crossed over from placebo to ruxolitinib, liver volume values
obtained after crossover were excluded from the analysis for placebo and analyzed
separately. In these individuals, baseline was defined as the last observation before
crossover. Percentage changes in liver volume at week 24 were compared between treatment
arms by analysis of covariance, with baseline liver volume as the covariate. Correlations
of clinical parameters were assessed by Pearson's correlation coefficient with associated
test for zero correlation and the R
2 statistic calculated by simple linear regression. A 5% significance level was applied
to all statistical tests, without adjustment for multiple testing.
A total of 139 of 155 patients randomized to ruxolitinib and 105 of 154 patients randomized
to placebo had evaluable liver volume data at baseline and week 24. Median (range)
liver volume at baseline was 2452 cm3 (1268–4833 cm3) in the ruxolitinib arm, and
2485 cm3 (1298–5230 cm3) in the placebo arm (see Supplementary Table S1 for additional
baseline characteristics). At week 24, patients treated with ruxolitinib had a mean
percentage change (decrease) in liver volume of −7.9% (median change, −8.7% range,
−26.0% to +17.5%) compared with a mean increase of 3.5% (median change, 4.1% range,
36.0% to +41.7%) in the placebo arm (P<0.0001; Figures 1a and b). The extent of liver
volume reductions tended to be greater among patients who achieved average doses of
20 or 25 mg twice daily during weeks 21–24 (mean changes at week 24: −9.7% and −9.8%,
respectively) than among patients with lower average doses during weeks 21–24 (mean
changes: −5.1% with <10 mg twice daily, −6.0% with 10 mg twice daily and −6.5% with
15 mg twice daily).
In the ruxolitinib arm, liver volumes decreased rapidly during the first 12 weeks
and continued to decrease until approximately week 48, with a mean percentage change
of −10.6% at week 48 (range, −35.9 to +23.0). Improvement was maintained through week
144 (Figure 1c). In contrast, in the placebo group, liver volume increased over time,
resulting in a mean percentage change of 6.0% at week 48 (range, −21.6% to +43.0%)
when most patients in the placebo group had discontinued or crossed over to ruxolitinib.
Patients who crossed over from placebo to ruxolitinib experienced decreases in liver
volume from the point of crossover, with an overall time course similar to that observed
in patients randomized to ruxolitinib (Figure 1c).
We sought to determine whether the percentage changes in liver volume in the ruxolitinib
arm were affected by baseline liver volume. Patients in the first (n=37), second (n=35),
third (n=36) and fourth (n=31) quartile had median (range) baseline liver volumes
of 1929 cm3 (1268–2115 cm3), 2323 cm3 (2131–2483 cm3), 2661 cm3 (2488–3014 cm3) and
3417 cm3 (3028–4833 cm3), respectively. Patients experienced similar reductions in
hepatomegaly at week 24 regardless of baseline liver volume, with mean±s.d. percentage
changes in liver volume of −8.3%±7.9%, −6.4%±7.5%, −7.8%±8.6% and −9.1%±8.8% in the
first, second, third and fourth quartile, respectively. Changes in liver volume over
time observed for the entire study population were reflected in each quartile (Figure
1d). Although the mean values for each quartile showed some differences after week
60, the interpatient variability in each quartile (represented by the standard error)
was greater than the interquartile variability of the means.
Percentage changes in liver volume at week 24 significantly correlated with changes
in splenomegaly, both for the entire evaluable population (n=138; R
2=0.3062; Pearson correlation coefficient (PCC)=0.5534; P<0.0001; Figure 2) and for
patients with both baseline liver and spleen volumes in the third or fourth quartile
(n=44; R
2=0.2284; PCC=0.4779; P=0.0010). Nearly all patients who experienced a liver volume
reduction also had a spleen volume reduction (Figure 2). Significant negative correlations
were observed between changes in liver volume at week 24 and corresponding changes
in body weight (R
2=0.0446; PCC=−0.2111; P=0.0129), leptin (R
2=0.1036; PCC=−0.3219; P=0.0001) and albumin (R
2=0.0472; PCC=−0.2172; P=0.0102). Increases in these parameters were observed in most
patients who had a decrease in liver volume (Supplementary Figure S1).
The results of this exploratory analysis from COMFORT-I, a placebo-controlled study
with a large study population, provide evidence suggesting that ruxolitinib is effective
in providing rapid and sustained reduction in MF-related hepatomegaly. This has not
been objectively demonstrated to date with other medical therapies. Overall, patients
achieved most of their treatment benefit regarding the magnitude of liver volume reductions
after ~48 weeks of treatment. By comparison, the time frame for maximal mean spleen
volume responses in the COMFORT studies was ~24 weeks.
4, 5
Percentage reductions in liver volume were largely independent of the liver volume
at baseline. Improvement in hepatomegaly was associated with previously reported improvements
in splenomegaly, weight gain and increases in albumin and leptin,
4, 6
raising the possibility of shared underlying mechanisms. The correlation between liver
volume reductions and increases in albumin levels is notable, as albumin is a measure
of the biosynthetic function of the liver.
Reduction of hepatomegaly would be a benefit of particular clinical significance for
patients undergoing splenectomy, as most of these patients eventually develop symptomatic
hepatomegaly.
7
As COMFORT-I was not designed to evaluate liver volume reductions in patients who
had undergone splenectomy, we cannot speculate about the efficacy of ruxolitinib in
alleviating hepatomegaly in these patients. However, maximum liver size reductions
of 50–68% (based on palpation) have been observed in three patients with symptomatic
hepatomegaly (palpable length, 14–16 cm) and previous splenectomy who were treated
with ruxolitinib in the phase II study.
8
Our study used volumetric liver size assessment based on magnetic resonance imaging
and computed tomography scans to evaluate the treatment effect of ruxolitinib on liver
size compared with placebo. A considerable advantage of this approach over palpation
is that it allows for the greatest precision and accuracy in the quantitative measurement
of liver size. However, because of substantial interindividual variability in healthy
individuals, liver volume alone is not always a sufficient indicator of the degree
of hepatomegaly. A recent study estimated the mean volume±s.d. of enlarged livers
at 2.32±0.75 l compared with 1.51±0.25 l for normal livers.
9
This suggests that a majority of patients in COMFORT-I, including most, if not all,
in the second, third and fourth baseline liver volume quartiles of the ruxolitinib
arm had mild to massive hepatomegaly at baseline. Although liver volume reductions
were observed across quartiles, the clinical significance of a 6–9% reduction in liver
volume is limited by the lack of a corresponding patient-reported outcome measure
to assess reduction in hepatomegaly-related symptoms. However, the correlations between
reductions in spleen size and liver volume observed in this analysis along with previously
published results showing a relationship between reductions in spleen volume and MF-related
symptoms,
10
and the correlations between liver volume and albumin and weight suggest that the
reductions in hepatomegaly are clinically meaningful.
In conclusion, ruxolitinib provided significant reductions in liver volume compared
with placebo in COMFORT-I. Liver volumes decreased rapidly during the first 12 weeks
and continued to decrease through week 60, with benefit maintained with longer-term
treatment. Percentage reductions in liver volume were associated with improvements
in splenomegaly and metabolic status. Overall, these findings suggest that ruxolitinib
may improve MF-related hepatomegaly.