A pilot study of ultrasound-guided electronic brachytherapy for skin cancer

Ultrasound of Skin Cancer: What We Need to Know

Ultrasound is an imaging technique that can provide critical anatomical information about malignant skin tumors that cannot be deducted by clinical examination, dermoscopy, or even biopsy. This data can support detecting and assessing the extent of the primary tumor and its differential diagnosis, surgical planning, and locoregional staging. Moreover, this non-invasive technique can help to follow-up and detect recurrences. This review aims to address the most common indications for ultrasound in skin oncology and provide a comprehensive guide to the grayscale and color-Doppler findings in cutaneous melanoma, squamous cell carcinoma, basal cell carcinoma, and other cutaneous malignant tumors.

Advances in Skin Brachytherapy: Cosmesis and Function Preservation

Skin brachytherapy represents an excellent alternative treatment for patients with non-melanoma skin cancers. It offers superior conformity of dose distribution with rapid dose fall off, reducing the risk of radiotherapy-related treatment toxicity. A smaller treatment volume in brachytherapy, when compared with external beam radiotherapy, is conducive for hypofractionation, which is an attractive option for decreasing outpatient visits to the cancer centre, especially for elderly and frail patients. Skin brachytherapy is an excellent option to preserve function and cosmesis, especially in skin cancers located in the head and neck region. Electronic brachytherapy, image-guided superficial brachytherapy and 3D printed moulds are all emerging advances in skin brachytherapy.

Electronic brachytherapy for treatment of non-melanoma skin cancers: clinical results and toxicities

Purpose

Although surgical approaches are standard for most non-melanomatous skin cancers, some patients are not candidates due to medical co-morbidities or functional or cosmetic or lesion location. High-dose-rate electronic brachytherapy (HDR-EBT) may be an alternative treatment modality.

Material and methods

A retrospective chart review was conducted from April 2011 to April 2013. All lesions were pathologically confirmed as malignant basal cell or squamous cell carcinoma. A HDR-EBT system delivered a median biological equivalent dose of 50 Gy total to a depth of 0.1-0.5 cm using various sizes of applicators. Treatment feasibility, acute and late toxicity, cosmetic outcomes, and local recurrence were assessed.

Results

Thirty-three patients with a mean age of 76 years with 50 cutaneous lesions were treated. Locations included 17 extremity lesions and 33 head and neck lesions. After treatments, acute grade 3 moist desquamation developed in 9 of the lesions (18%). Acute grade 4 ulceration developed in 3 lesions in the lower extremity (6%) and 1 upper lip lesion (2%). These toxicities were improved after a median of 20 days. Amongst the 4 lesions with grade 4 toxicities, a greater proportion were in lower extremity lesions compared to head and neck lesions (75% vs. 25%). There was no difference in the rate of grade 3 and 4 toxicities between patients aged ≤ 75 years and aged > 75 years (p = 0.082). With a mean long-term follow-up of 45.6 months, there was 1 local recurrence treated with surgery and no reported late toxicities.

Conclusions

Our experience with HDR-EBT for non-melanomatous skin cancers is encouraging in terms of efficacy and convenience for patients. Our long-term follow-up shows a good response in all treated sites. Caution should be used for extremity sites, and more fractionated regimens should be considered to avoid severe acute toxicities.

Acute and late complications and toxicities of skin brachytherapy

Skin cancer is the most prevalent malignancy, and its incidence is rising. Surgery is the primary treatment, however, morbidity of surgical resection in certain parts of the body warrant alternate treatment options such as radiation therapy. Complex topology of the skin can pose a challenge for treatment with photon and electron external beam radiotherapy techniques. Brachytherapy can be an attractive radiotherapy technique for these regions. Furthermore, brachytherapy results in lower dose to the underlying deep organs. The goal of this manuscript is to provide a brief overview of the role of brachytherapy for skin malignancies and to outline potential acute and long-term toxicities.

The American Brachytherapy society consensus statement for skin brachytherapy

PURPOSE

Keratinocyte carcinoma (KC, previously nonmelanoma skin cancer) represents the most common cancer worldwide. While surgical treatment is commonly utilized, various radiation therapy techniques are available including external beam and brachytherapy. As such, the American Brachytherapy Society has created an updated consensus statement regarding the use of brachytherapy in the treatment of KCs.

METHODS

Physicians and physicists with expertise in skin cancer and brachytherapy created a consensus statement for appropriate patient selection, data, dosimetry, and utilization of skin brachytherapy and techniques based on a literature search and clinical experience.

RESULTS

Guidelines for patient selection, evaluation, and dose/fractionation schedules to optimize outcomes for patients with KC undergoing brachytherapy are presented. Studies of electronic brachytherapy are emerging, although limited long-term data or comparative data are available. Radionuclide-based brachytherapy represents an appropriate option for patients with small KCs with multiple techniques available.

CONCLUSIONS

Skin brachytherapy represents a standard of care option for appropriately selected patients with KC. Radionuclide-based brachytherapy represents a well-established technique; however, the current recommendation is that electronic brachytherapy be used for KC on prospective clinical trial or registry because of a paucity of mature data.

On the use of the absorbed depth-dose measurements in the beam calibration of a surface electronic high-dose-rate brachytherapy unit, a Monte Carlo-based study

PURPOSE

To evaluate the use of the absorbed depth-dose as a surrogate of the half-value layer in the calibration of a high-dose-rate electronic brachytherapy (eBT) equipment. The effect of the manufacturing tolerances and the absorbed depth-dose measurement uncertainties in the calibration process are also addressed.

METHODS

The eBT system Esteya^® (Elekta Brachytherapy, Veenendaal, The Netherlands) has been chosen as a proof-of-concept to illustrate the feasibility of the proposed method, using its 10 mm diameter applicator. Two calibration protocols recommended by the AAPM (TG-61) and the IAEA (TRS-398) for low-energy photon beams were evaluated. The required Monte Carlo (MC) simulations were carried out using PENELOPE2014. Several MC simulations were performed modifying the flattening filter thickness and the x-ray tube potential, generating one absorbed depth-dose curve and a complete set of parameters required in the beam calibration (i.e., HVL, backscatter factor (B_w ), and mass energy-absorption coefficient ratios (µ_en /ρ)_water,air ), for each configuration. Fits between each parameter and some absorbed dose-ratios calculated from the absorbed depth-dose curves were established. The effect of the manufacturing tolerances and the absorbed dose-ratio uncertainties over the calibration process were evaluated by propagating their values over the fitting function, comparing the overall calibration uncertainties against reference values. We proposed four scenarios of uncertainty (from 0% to 10%) in the dose-ratio determination to evaluate its effect in the calibration process.

RESULTS

The manufacturing tolerance of the flattening filter (±0.035 mm) produces a change of 1.4% in the calculated HVL and a negligible effect over the B_w , (µ_en /ρ)_water,air , and the overall calibration uncertainty. A potential variation of 14% of the electron energies due to manufacturing tolerances in the x-ray tube (69.5 ± ~10 keV) generates a variation of 10% in the HVL. However, this change has a negligible effect over the B_w and (µ_en /ρ)_water,air , adding 0.1% to the overall calibration uncertainty. The fitting functions reproduce the data with an uncertainty (k = 2) below 1%, 0.5%, and 0.4% for the HVL, B_w , and (µ_en /ρ)_water,air , respectively. The four studied absorbed dose-ratio uncertainty scenarios add, in the worst-case scenario, 0.2% to the overall uncertainty of the calibration process.

CONCLUSIONS

This work shows the feasibility of using the absorbed depth-dose curve in the calibration of an eBT system with minimal loss of precision.

Skin cancer: findings and role of high-resolution ultrasound

Currently available high-resolution transducers allow a detailed ultrasound (US) assessment of skin tumors. US complements clinical examination, dermoscopy, and biopsy in the initial differential diagnosis, surgical planning, locoregional staging, and follow-up of patients with skin malignancies. It is important for dermatologists, skin surgeons, and US operators to be aware of the US imaging findings and to recognize the clinical scenarios where imaging is indicated in the management of skin cancer. The purpose of this review article is to address the most common indications for US in skin oncology and to provide a comprehensive guide to the gray-scale and color-Doppler findings in cutaneous malignant tumors.

Skin CanceR Brachytherapy vs External beam radiation therapy (SCRiBE) meta-analysis

BACKGROUND AND PURPOSE

To compare cosmesis and local recurrence (LR) of definitive external beam radiation therapy (EBRT) vs brachytherapy (BT) for indolent basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) of the skin.

MATERIALS AND METHODS

Studies including patients with T1-2 N0 SCCs/BCCs treated with definitive EBRT/BT and ≥10 months follow-up were analyzed. The primary endpoint was post-treatment cosmesis, categorized as "good," "fair," or "poor." The secondary endpoint was LR. Mixed effects regression models were used to estimate weighted linear relationships between biologically equivalent doses with α/β = 3 (BED3) and cosmetic outcomes.

RESULTS

A total of 9965 patients received EBRT and 553 received BT across 24 studies. Mean age was 73 years, median follow-up was 36 months, and median dose was 45 Gy/10 fractions at 4.4 Gy/fraction. At BED3 of 100 Gy, "good" cosmesis was more frequently observed in patients receiving BT, 95% (95% CI: 88-100%) vs 79% (95% CI: 60-82%), p < 0.05. Similar results were found for "good" cosmesis at BED3 >100 Gy. No difference in "poor" cosmesis was noted at any BED3. LR was <7% for both at one year.

CONCLUSION

BT has favorable cosmesis over EBRT for skin SCCs/BCCs at common fractionation regimens. Prospective studies comparing EBRT vs BT are warranted.

GEC-ESTRO ACROP recommendations in skin brachytherapy

PURPOSE

The aim of this publication is to compile available literature data and expert experience regarding skin brachytherapy (BT) in order to produce general recommendations on behalf of the GEC-ESTRO Group.

METHODS

We have done an exhaustive review of published articles to look for general recommendations.

RESULTS

Randomized controlled trials, systemic reviews and meta-analysis are lacking in literature and there is wide variety of prescription techniques successfully used across the radiotherapy centers. BT can be delivered as superficial application (also called contact BT or plesiotherapy) or as interstitial for tumours thicker than 5 mm within any surface, including very irregular. In selected cases, particularly in tumours located within curved surfaces, BT can be advantageous modality from dosimetric and planning point of view when compared to external beam radiotherapy. The general rule in skin BT is that the smaller the target volume, the highest dose per fraction and the shortest overall length of treatment can be used.

CONCLUSION

Skin cancer incidence is rising worldwide. BT offers an effective non-invasive or minimally invasive and relative short treatment that particularly appeals to elder and frail population.

The feasibility of using ultrasound during follow-up for superficial non-melanoma skin cancers after electronic brachytherapy

Purpose

Non-melanoma skin cancers (NMSCs) can be treated with a number of modalities including surgery, topical chemotherapy, or radiotherapy. Amongst the radiotherapeutic options, electronic brachytherapy (eBT) is an appealing treatment as it is usually given in a few fractions, it leads to good outcomes, and is increasingly being used. However, currently no follow-up imaging is routinely used or recommended to evaluate treatment response of NMSC. We aimed to use ultrasound (US) in follow-up after eBT for superficial NMSC to assess its feasibility in detecting possible tumor response.

Material and methods

Fourteen patients were treated between 2013-2015 for a NMSC using eBT. US guidance was used for treatment planning prior to eBT initiation. After completion of eBT, patients were seen in follow-up for both clinical exam and a repeat US at 1 month to evaluate if tumor response was detectable.

Results

Of the 14 patients, 6 were male and 8 were female. The mean age was 71 years. With a median follow-up of 20.5 months, all patients had a complete response based on physical exam. Eleven patients appeared to have a complete response based on US obtained > 1 month after completing eBT. To date, there have been no local recurrences or progression, and all patients are alive.

Conclusions

US is an objective imaging modality that may be able to assess NMSC response after eBT. Based on follow-up imaging, further treatment or observation may be recommended. Although this study is hypothesis generating, larger studies with pathologic confirmation of recurrences would be needed to validate US use for follow-up, avoiding possible painful and scarring biopsies in case of low suspicion of recurrence.

Updates on the Management of Non-Melanoma Skin Cancer (NMSC)

Non-melanoma skin cancers (NMSCs) are the most common malignancy worldwide, of which 99% are basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) of skin. NMSCs are generally considered a curable diseases, yet they currently pose an increasing global healthcare problem due to rising incidence. This has led to a shift in emphasis on prevention of NMSCs with development of various skin cancer prevention programs worldwide. This article aims to summarize the most recent changes and advances made in NMSC management with a focus on prevention, screening, diagnosis, and staging.

Hypofractionated radiation therapy for basal and squamous cell skin cancer: A meta-analysis

PURPOSE

To characterize the cosmetic outcomes and local recurrence (LR) rates of various hypofractionated radiation therapy (RT) regimens for skin basal and squamous cell cancers (BCCs/SCCs).

METHODS

A PICOS/PRISMA/MOOSE selection protocol was performed to identify 344 articles published between 1985-2016 evaluating patients with T1-2 N0 SCCs/BCCs treated with definitive RT. Biologically equivalent doses with α/β=3 (BED3s) were calculated. The primary endpoint was post-treatment cosmesis. Mixed effects regression models were used to estimate weighted linear relationships between BED3 and cosmetic outcomes.

RESULTS

A total of 21 studies were identified detailing the treatment of 9729 skin BCC/SCC patients, across seven countries, with external beam RT (n=9255) or brachytherapy (n=474). Median follow-up was 36months (range: 12-77). Median dose was 45Gy/11 fractions (interquartile range: 37.5Gy/6-55Gy/18) at 4Gy/fraction (interquartile range: 2.5-6Gy); most hypofractionated 18.75Gy/1. There was a trend to decreased "good" cosmesis with higher total dose: -3.4% "good" cosmesis/10Gy BED3, p=0.01. Similarly, there was a trend to increased "fair" cosmesis with higher dose: +3.8% "fair" cosmesis/10Gy BED3,p=0.006. At a BED3 of 100Gy, the expected rate of "good" cosmesis is 79% (95% confidence interval: 70%, 88%). Hypofractionated schedules produced similar cosmesis to conventionally fractionated schedules, at the same BED3. Fewer than 8% of patients experienced "poor" cosmesis, independent of dose or fractionation regimen.

CONCLUSION

Hypofractionated RT has favorable cosmesis for patients with skin BCCs/SCCs. We recommend clinicians consider these commonly-used regimens, which all have BED3 of ∼100Gy: 50Gy/15 fractions, 36.75Gy/7 fractions, or 35Gy/5 fractions, as they result in "good" cosmesis in 80% of patients.

Does ultrasound measurement improve the accuracy of electronic brachytherapy in the treatment of superficial non-melanomatous skin cancer?

Purpose

Electronic brachytherapy (eBT) is a form of contact radiation therapy used for thin superficial non-melanomatous skin cancers (NMSCs). An accurate measurement of diameter and depth is important for eBT treatment planning. Therefore, we compared clinical measurements by an experienced physician to measurements obtained using ultrasound (US), an objective imaging modality, in order to determine if clinical measurements were accurate enough for adequate NMSC treatment.

Material and methods

Eighteen patients with 20 biopsy-proven NMSCs first had a clinical examination and then an US evaluation prior to starting eBT. One physician provided a clinical measurement for diameter and depth based on physical examination during radiation oncology consultation. The patients then had an US evaluation with a 14 or 18 MHz US unit, to determine both the diameter and depth measurements; eBT dose prescription was done using the US derived measurements. The clinical measurements and US measurements were compared using a t-test.

Results

Seventeen lesions were basal cell carcinoma and 3 lesions were squamous cell carcinoma. The most common location was the nose (10 lesions). The difference between the clinical and the US derived measurements for the second largest diameter was found to be statistically significant (p = 0.03), while the difference for the largest diameter of the lesions was not (p = 0.24). More importantly, the depth measurements obtained with US were also found to be significantly different from the clinical estimates (p = 0.02). All patients have had a complete response to therapy with a median follow-up of 24 months.

Conclusions

Statistically different measurements were obtained in 2 of 3 parameters used in choosing applicator size and prescription depth using an US assessment. The data presented suggests that US is a more objective modality than clinical judgment for determining superficial NMSC diameter and prescription depth for personalized eBT planning.

Failure mode and effects analysis of skin electronic brachytherapy using Esteya® unit

Purpose

Esteya^® (Nucletron, an Elekta company, Elekta AB, Stockholm, Sweden) is an electronic brachytherapy device used for skin cancer lesion treatment. In order to establish an adequate level of quality of treatment, a risk analysis of the Esteya treatment process has been done, following the methodology proposed by the TG-100 guidelines of the American Association of Physicists in Medicine (AAPM).

Material and methods

A multidisciplinary team familiar with the treatment process was formed. This team developed a process map (PM) outlining the stages, through which a patient passed when subjected to the Esteya treatment. They identified potential failure modes (FM) and each individual FM was assessed for the severity (S), frequency of occurrence (O), and lack of detection (D). A list of existing quality management tools was developed and the FMs were consensually reevaluated. Finally, the FMs were ranked according to their risk priority number (RPN) and their S.

Results

146 FMs were identified, 106 of which had RPN ≥ 50 and 30 had S ≥ 7. After introducing the quality management tools, only 21 FMs had RPN ≥ 50. The importance of ensuring contact between the applicator and the surface of the patient’s skin was emphasized, so the setup was reviewed by a second individual before each treatment session with periodic quality control to ensure stability of the applicator pressure. Some of the essential quality management tools are already being implemented in the installation are the simple templates for reproducible positioning of skin applicators, that help marking the treatment area and positioning of X-ray tube.

Conclusions

New quality management tools have been established as a result of the application of the failure modes and effects analysis (FMEA) treatment. However, periodic update of the FMEA process is necessary, since clinical experience has suggested occurring of further new possible potential failure modes.

Skin surface brachytherapy: A survey of contemporary practice patterns

PURPOSE

The aim of this study was to define current patterns of care among radiation oncologists who use skin surface brachytherapy for the treatment of cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC) in academic and community settings.

METHODS AND MATERIALS

A 30-question electronic survey was administered to clinician members of the American Brachytherapy Society. The respondents were asked to provide details regarding their clinical practice and their approach to skin surface brachytherapy.

RESULTS

A total of 16 surveys were returned. Among the respondents, aggregate experience varied from 8 to 1800 cases. Most preferred brachytherapy over external beam radiation because of shorter treatment course, conformality of treatment for irregular or curved targets, and shallow dose deposition. Of the total, 60% of respondents routinely estimated lesion depth via ultrasound before initiating treatment. Treatment margin on gross disease varied widely (range, 3-15 mm; median, 5 mm). Hypofractionation was the preferred dose schedule. Prescribed doses ranged from 30 Gy in five fractions to 64 Gy in 32 fractions (EQD2, 40 Gy-65 Gy). There was a tendency to increase the number of fractions for larger targets, although some used the same fractionation regardless of anatomic location or lesion size. There was no consensus on dosimetric constraints, and some respondents reported cases of severe toxicity, particularly when treating the pretibial skin.

CONCLUSIONS

This pattern of care study suggests that skin brachytherapy can be a convenient and safe tool for treatment of BCC and cSCC. Prospective trials and the development of expert consensus guidelines would be beneficial for optimizing skin surface brachytherapy and reducing practice variation.

Clinical comparison of brachytherapy versus hypofractionated external beam radiation versus standard fractionation external beam radiation for non-melanomatous skin cancers

Purpose

Non-melanomatous skin cancer (NMSC) is the single most common cancer in the US. Radiation therapy is an excellent treatment alternative to surgery. High-dose-rate (HDR) brachytherapy and external beam radiotherapy (EBRT) are commonly used radiation treatment modalities but little data is published comparing these modalities. We present our institution's experience and outcomes with these therapeutic options.

Material and methods

From June 2005 to March 2013, 61 patients were treated with HDR brachytherapy (n = 9), hypofractionated EBRT (n = 30), or standard fractionation EBRT (n = 22) for NMSC. The primary outcome measure was local control at most remote follow-up and secondary outcome measures were overall survival, cosmetic outcome, and toxicity. Univariate analysis was performed to compare outcomes between treatment modalities. Kaplan-Meier analysis and log-rank test were used to compare overall survival.

Results

Median follow-up was 30 months. The most common histologies were BCC (47%) and SCC (44%); mean patient age was 83.3 years. Local control was 81% and 2-year actuarial overall survival was 89%. There was no statistical difference in local control or overall survival between treatment modalities. There was no statistical difference in cosmetic outcome or toxicity between treatment modalities, although five of six “poor” cosmetic outcomes and the only grade 3 toxic events were found in the standard fractionation EBRT group.

Conclusions

All modalities investigated represent effective treatments for NMSC and have good cosmetic outcomes and acceptable toxicity profiles. The finding of higher grade toxicity and a greater portion of patients experiencing toxicity among standard fractionation therapy is counter to expectations. There was no statistical significance to the finding and it is not likely to be meaningful.