To the Editor:
We have read with an interest the letter to the Editor titled “New technologies for
non-melanoma skin cancer”. In this letter, the authors comment on our article [1]
about the clinical implementation of a new system for skin brachytherapy (Esteya®
electronic brachytherapy by Elekta, Stockholm, Sweden) and they asked for a reply
to their letter. We would like to thank the authors for their interest in our publication
and would like to respond to their letter.
First of all we need to clarify that in our study we chose to exclude irregularly
shaped lesions, lesions with a diameter > 2 cm, and lesions with a depth larger than
4 mm because of the design of the radiation therapy system that was used. Lesions
included in our work using the specific features of the Esteya® device, in fact represent
the vast majority of non-melanoma skin cancer primary presentations.
The Esteya® electronic brachytherapy system (E-eBT) is delivered with a set of applicators
up to 3 cm in diameter. When treating non-melanoma skin cancer, typically a margin
of 0.5 cm is added to the GTV. Consequently, the maximum diameter of lesions to be
treated is 2 cm. The system has a dose-gradient of about 8% per mm, therefore with
lesions deeper than 0.4 cm, the overdose at the first skin layers will exceed 130%
and this might impact cosmetic outcome. This is the reason we limited inclusion to
lesions with a depth of 4 mm or less. Finally, E-eBT applicators are designed with
a flat surface to allow full contact with the skin. Avoiding air gaps between applicator
and skin is a prerequisite because of the significant impact of air gaps on the dose
to the lesion. Nowadays, we have the possibility to use a new set of more precise
applicators for treatment of lesions in difficult areas.
When we say that irregular areas are not suitable for EBT, we only mean those locations
that, despite applying some pressure, are not entirely in contact with the applicator.
These cases should be treated with other types of brachytherapy/radiotherapy. In our
experience there are only a few locations where one cannot get a flat surface by applying
mild pressure. Only larger lesions in areas with angled surfaces result in bone or
cartilage, for example impeding/preventing a flat surface being obtained; this can
be on the inner canthus of the eye, or for example on the pinna, and on the peri-alar
nose groove. We have, however, successfully treated several “difficult cases” of BCC
located on for example the nasal tip, retroauricular region, and scalp with E-eBT.
It is our experience that the vast majority of NMSC lesions can be treated with the
Esteya® electronic brachytherapy system.
We disagree with the authors of the letter stating that “NMSC often have irregular
shapes and a diameter longer than 2 cm”, and “most cases of NMSC are recurrent and
located in the periorbital area (i.e. inner canthus)”. In fact, most NMSC are small,
usually less than 20 mm, and the majority of lesions are located on the face, especially
on the nose. Both surgery and radiation therapy are very effective and recurrence
is usually found in less than 10% of cases. There is, however, a bias of patients
submitted to radiotherapy since only difficult cases and lesions that have failed
other treatments are referred. Better communication and cooperation between dermatology
and RT services will improve referral and benefit both patients and care givers. For
the less frequent appearing lesions with dimensions and shapes that are outside of
the range included in our study, other radiotherapy treatment solutions besides Esteya®
electronic brachytherapy are available such as brachytherapy moulds, isotope based
brachytherapy with interstitial-or flap applicators, and treatment with electrons.
We have read with great interest the article of Pontoriero et al. [2] that the authors
of the letter to the Editor referred to. In this article, Pontoriero et al. reported
their experience treating a deeply invasive lesion on the inner canthus of the eye
with the Cyberknife system. Although in their case report the patient seems to have
a good clinical outcome, we do have some concerns with promoting this technology in
general for skin cancer treatment around the eye based on this single case. We consider
the risk of intrafraction-movement as high because of very long treatment time associated
with the large number of beams. In addition, there are challenges associated with
the dose build up in the first layers of the skin beam, the inverse planning calculation
algorithm on the first fractions of millimeter of the skin, and the use of a bolus.
Also, protecting the eye from radiation damage is not easy. In our opinion, more robust
research is needed to prove this technique as safe and beneficial when other therapies,
such as interstitial brachytherapy with more substantial evidences are available.
That new sophisticated techniques such as “Cyber Knife®” – as Dr. Pontoriero described
in his letter – or particulate radiation, as a proton beam therapy, etc., could be
used in selected cases, complying properly the goals for treatment of theses tumors.
But on the other hand, even when it is desirable, a good knowledge on the part of
radiation oncologist specialist of the full potential of these new techniques is required.
The cost and complexity of these techniques, together with the necessary investment
in human resources to fit the goal of these treatments, as well as short follow up
of every single case referred, become, at least in our opinion, the accurate approach
as a non-elective treatment for non-melanoma skin cancer.
In our practice, this type of lesions on the inner canthus use to be treated with
an HDR interstitial implant, with catheters just subcutaneous, and the eyes protected
with a lead sheet. Although it is small invasive procedure, in our hospitals we prefer
it to IMRT because of the robustness, simplicity, eye protection, dose gradient through
normal tissue, and guarantee of full coverage of the lesion. In our group, we have
accumulated over years a great experience treating successfully this kind of difficult
tumors with this approach.
We want to express our gratitude to both the letter authors and the Journal Editor,
to have the opportunity to include this discussion.