Silvia Rodriguez

Non-melanoma skin cancer treated with HDR Valencia applicator: clinical outcomes.

Purpose Radiotherapy (RT) has played a significant role in treating non melanoma skin cancer (NMSC). High-dose-rate brachytherapy (HDR-BT) approaches have a paramount relevance due to their adaptability, patient protection, and variable dose fractionation schedules. Several innovative applicators have been introduced to the brachytherapy community. The Valencia applicator is a new superficial device that improves the dose distribution compared with the Leipzig applicator. The purpose of this work is to assess the tumor control, cosmesis, and toxicity in patients with NMSC treated with the Valencia applicator and a new regimen of hypofractionation. Material and methods From January 2008 to March 2010, 32 patients with 45 NMSC lesions were treated with the Valencia applicator in the Hospital La Fe. The gross tumor volume was visually assessed, but the tumor depth was evaluated using ultrasound imaging. All lesions for the selected cases were limited to 4 mm depth. The prescription dose was 42 Gy in 6 or 7 fractions (biologically effective dose [BED] ≈ 70 Gy), delivered twice a week. Results Ninety-eight percent of the lesions were locally controlled at 47 months from treatment. Ninety-three percent of patients were out at least 36 months from treatment. The treatment was well tolerated in all cases. The highest skin toxicity was grade 1 RTOG/EORTC, having resolved with topical treatment at 4 weeks in all but one case which required 2 months. There were no grade 2 or higher late adverse events. Conclusions In patients with superficial basal cell carcinoma lesions less than 25 mm in maximum diameter, HDRBT treatment with the Valencia applicator using a hypofractionated regimen provides excellent results, for both cosmetic and local control at a minimum of 3 years follow-up. Moreover, the shorter hypofractionated regimen facilitates compliance, which is very relevant for the elderly patients in our series. Valencia applicators offer a simple, safe, quick, and attractive nonsurgical treatment option.

Exclusive MRI-based tandem and colpostats reconstruction in gynaecological brachytherapy treatment planning

PURPOSE According to the GYN GEC-ESTRO Recommendations, MRI is needed with the modality of T2 weighted. CT-MR compatible tandem plus colpostats (T/C) (Nucletron) is widely used in cervical brachytherapy. The major challenge of MRI is the lack of dummy catheters. Therefore, an additional imaging modality is usually required. One disadvantage of sliced-based reconstruction is that resolution in longitudinal directions can be affected by the slice thickness. The aim of this study is to present a modified T/C applicator in which the catheter visibility is significantly improved. METHODS AND MATERIALS A modification to the existing T/C applicator has been made available, increasing the catheter entrance diameter. It allows a greater dummy catheter diameter, and consequently it can be filled with more material per unit length. Visibility was studied with different materials. RESULTS The catheter filled with saline water plus iodine compound was clearly seen in both axial and longitudinal acquisitions. To avoid uncertainties introduced by the slice thickness, a simple procedure is presented using longitudinal acquisitions. CONCLUSIONS The modified applicator plus catheter allows a powerful signal in T2 weighted MRI, using a very simple and accessible material. Also, a method is proposed to solve the problem of the uncertainty derived from slice thickness using few longitudinal acquisitions.

Aspects of dosimetry and clinical practice of skin brachytherapy: The American Brachytherapy Society working group report

PURPOSE Nonmelanoma skin cancers (NMSCs) are the most common type of human malignancy. Although surgical techniques are the standard treatment, radiation therapy using photons, electrons, and brachytherapy (BT) (radionuclide-based and electronic) has been an important mode of treatment in specific clinical situations. The purpose of this work is to provide a clinical and dosimetric summary of the use of BT for the treatment of NMSC and to describe the different BT approaches used in treating cutaneous malignancies. METHODS AND MATERIALS A group of experts from the fields of radiation oncology, medical physics, and dermatology, who specialize in managing cutaneous malignancies reviewed the literature and compiled their clinical experience regarding the clinical and dosimetric aspects of skin BT. RESULTS A dosimetric and clinical review of both high dose rate ((192)Ir) and electronic BT treatment including surface, interstitial, and custom mold applicators is given. Patient evaluation tools such as staging, imaging, and patient selection criteria are discussed. Guidelines for clinical and dosimetric planning, appropriate margin delineation, and applicator selection are suggested. Dose prescription and dose fractionation schedules, as well as prescription depth are discussed. Commissioning and quality assurance requirements are also outlined. CONCLUSIONS Given the limited published data for skin BT, this article is a summary of the limited literature and best practices currently in use for the treatment of NMSC.

Clinical implementation of a new electronic brachytherapy system for skin brachytherapy

Although surgery is usually the first-line treatment for nonmelanoma skin cancers, radiotherapy (RT) may be indicated in selected cases. Radiation therapy as primary therapy can result in excellent control rates, cosmetics, and quality of life. Brachytherapy is a radiation treatment modality that offers the most conformal option to patients. A new modality for skin brachytherapy is electronic brachytherapy. This involves the placement of a high dose rate X-ray source directly in a skin applicator close to the skin surface, and therefore combines the benefits of brachytherapy with those of low energy X-ray radiotherapy. The Esteya electronic brachytherapy system is specifically designed for skin surface brachytherapy procedures. The purpose of this manuscript is to describe the clinical implementation of the new Esteya electronic brachytherapy system, which may provide guidance for users of this system. The information covered includes patient selection, treatment planning (depth evaluation and margin determination), patient marking, and setup. The justification for the hypofractionated regimen is described and compared with others protocols in the literature. Quality assurance (QA) aspects including daily testing are also included. We emphasize that these are guidelines, and clinical judgment and experience must always prevail in the care of patients, as with any medical treatment. We conclude that clinical implementation of the Esteya brachytherapy system is simple for patients and providers, and should allow for precise and safe treatment of nonmelanoma skin cancers.

The use of nomograms in LDR-HDR prostate brachytherapy

Purpose The common use of nomograms in Low Dose Rate (LDR) permanent prostate brachytherapy (BT) allows to estimate the number of seeds required for an implant. Independent dosimetry verification is recommended for each clinical dosimetry in BT. Also, nomograms can be useful for dose calculation quality assurance and they could be adapted to High Dose Rate (HDR). This work sets nomograms for LDR and HDR prostate-BT implants, which are applied to three different institutions that use different implant techniques. Material and methods Patients treated throughout 2010 till April 2011 were considered for this study. This example was chosen to be the representative of the latest implant techniques and to ensure consistency in the planning. A sufficient number of cases for both BT modalities, prescription dose and different work methodology (depending on the institution) were taken into account. The specific nomograms were built using the correlation between the prostate volume and some characteristic parameters of each BT modality, such as the source Air Kerma Strength, number of implanted seeds in LDR or total radiation time in HDR. Results For each institution and BT modality, nomograms normalized to the prescribed dose were obtained and fitted to a linear function. The parameters of the adjustment show a good agreement between data and the fitting. It should be noted that for each institution these linear function parameters are different, indicating that each centre should construct its own nomograms. Conclusions Nomograms for LDR and HDR prostate brachytherapy are simple quality assurance tools, specific for each institution. Nevertheless, their use should be complementary to the necessary independent verification.

I-125 seed calibration using the SeedSelectron® afterloader: a practical solution to fulfill AAPM-ESTRO recommendations

Purpose SeedSelectron® v1.26b (Nucletron BV, The Netherlands) is an afterloader system used in prostate interstitial permanent brachytherapy with I-125 selectSeed seeds. It contains a diode array to assay all implanted seeds. Only one or two seeds can be extracted during the surgical procedure and assayed using a well chamber to check the manufacturer air-kerma strength (SK) and to calibrate the diode array. Therefore, it is not feasible to assay 5–10% seeds as required by the AAPM-ESTRO. In this study, we present a practical solution of the SeedSelectron® users to fulfill the AAPM- ESTRO recommendations. Material and methods The method is based on: a) the SourceCheck® well ionization chamber (PTW, Germany) provided with a PTW insert; b) n = 10 selectSeed from the same batch and class as the seeds for the implant; c) the Nucletron insert to accommodate the n = 10 seeds on the SourceCheck® and to measure their averaged SK. Results for 56 implants have been studied comparing the SK value from the manufacturer with the one obtained with the n = 10 seeds using the Nucletron insert prior to the implant and with the SK of just one seed measured with the PTW insert during the implant. Results We are faced with SK deviation for individual seeds up to 7.8%. However, in the majority of cases SK is in agreement with the manufacturer value. With the method proposed using the Nucletron insert, the large deviations of SK are reduced and for 56 implants studied no deviation outside the range of the class were found. Conclusions The new Nucletron insert and the proposed procedure allow to evaluate the SK of the n = 10 seeds prior to the implant, fulfilling the AAPM-ESTRO recommendations. It has been adopted by Nucletron to be extended to seedSelectron® users under request.

A practical MRI-based reconstruction method for a new endocavitary and interstitial gynaecological template

Purpose There are perineal templates for interstitial implants such as MUPIT and Syed applicators. Their limitations are the intracavitary component deficit and the necessity to use computed tomography (CT) for treatment planning since both applicators are non-magnetic resonance imaging (MRI) compatibles. To overcome these problems, a new template named Template Benidorm (TB) has been recently developed. Titanium needles are usually reconstructed based on their own artifacts, mainly in T1-weighted sequence, using the void on the tip as the needle tip position. Nevertheless, patient tissues surrounding the needles present heterogeneities that complicate the accurate identification of these artifact patterns. The purpose of this work is to improve the titanium needle reconstruction uncertainty for the TB case using a simple method based on the free needle lengths and typical MRI pellets markers. Material and methods The proposed procedure consists on the inclusion of three small A-vitamin pellets (hyperintense on MRI images) compressed by both applicator plates defining the central plane of the plates arrangement. The needles used are typically 20 cm in length. For each needle, two points are selected defining the straight line. From such line and the plane equations, the intersection can be obtained, and using the free length (knowing the offset distance), the coordinates of the needle tip can be obtained. The method is applied in both T1W and T2W acquisition sequences. To evaluate the inter-observer variation of the method, three implants of T1W and another three of T2W have been reconstructed by two different medical physicists with experience on these reconstructions. Results and conclusions The differences observed in the positioning were significantly smaller than 1 mm in all cases. The presented algorithm also allows the use of only T2W sequence either for contouring or reconstruction purposes. The proposed method is robust and independent of the visibility of the artifact at the tip of the needle.

A method to incorporate interstitial components into the TPS gynecologic rigid applicator library

Purpose T2 magnetic resonance imaging (MRI) is recommended as the imaging modality for image-guided brachytherapy. In locally advanced cervical carcinoma, combined endocavitary and interstitial applicators are appropriate (Vienna or Utrecht). To cover extensive disease, Template Benidorm (TB) was developed. Treatment planning system applicator libraries are currently unavailable for the Utrecht applicator or the TB. The purpose of this work is to develop an applicator library for both applicators. Material and methods The library developed in this work has been used in the Oncentra Brachytherapy TPS, version 4.3.0, which has a brachytherapy module that includes a library of rigid applicators. To add the needles of the Utrecht applicator and to model the TB, we used FreeCAD and MeshLab. The reconstruction process was based on the points that the rigid section and the interstitial part have in common. This, together with the free length, allowed us to ascertain the position of the tip. Results In case of the Utrecht applicator, one of the sources of uncertainty in the reconstruction was determining the distance of the tip of needle from the ovoid. In case of the TB, the large number of needles involved made their identification time consuming. The developed library resolved both issues. Conclusions The developed library for the Utrecht and TB is feasible and efficient improving accuracy. It allows all the required treatment planning to proceed using just a T2 MRI sequence. The additional use of specific free available software applications makes it possible to add this information to the already existing library of the Oncentra Brachytherapy TPS. Specific details not included on this manuscript will be available under request. This library is also currently being implemented also into the Sagiplan v 2.0 TPS.

Pre-plan technique feasibility in multi-interstitial/endocavitary perineal gynecological brachytherapy

Purpose To present the implementation of a magnetic resonance imaging (MRI) pre-planning technique in multi-interstitial perineal and endocavitary gynecological brachytherapy. Material and methods We used a new fully MRI-compatible applicator that is capable to engage titanium needles, and an intrauterine tandem, developed in our department for the treatment of gynecological cervical cancer patients. This applicator is an attempt to combine the technical advantages of the Martinez universal perineal interstitial template (MUPIT) with the improvement in dose distribution by adding an intrauterine probe with the imaging advantages of MRI-based brachytherapy, thus preserving the stability, geometry, and robustness of the implant, avoiding possible errors of free-hand needle placement. A pre-brachytherapy MRI T2 acquisition is carried out with the template in place 3-5 days before the implant. On this image set, clinical target volume (CTV) is drawn. The required needles and their depths are selected accordingly to encompass the CTV (as conformal as possible). To facilitate this task, a Java based application linked to the treatment planning system has been developed. From this procedure, each needle identification and its depth are obtained previously to the implantation. With this information, the radiation oncologist proceeds with implant and then, a post-implant MRI is carried out, in which the contouring, needles, tandem reconstruction, and optimization are established. Results This pre-planning procedure has been successfully applied in 10 patients. An excellent reproduction of the virtual pre-planning has been achieved. Conclusions We describe a virtual pre-planning technique using a multi-interstitial and endocavitary perineal template. It is based on a virtual work with MRI images. This procedure has shown to be feasible and efficient in clinical practice by facilitating the work of specialists, and reducing uncertainties of the application.

In reply to the Letter to the Editor titled: "Comments on: Clinical implementation of a new electronic brachytherapy system for skin brachytherapy".

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.