PO116: Use of Iridium-192 High Dose Brachytherapy for the Definitive Treatment of Non-Melanoma Skin Cancers in Elderly Patients

Purpose Non-melanoma skin cancer is the most common cancer worldwide and its treatment in the elderly can pose significant challenges. We established a skin brachytherapy program primarily to treat older patients using the hypofractionated courses and superficial treatment depth afforded by this technique. Here we describe the first patients treated at our institution, including our initial oncologic results and toxicities. Materials and Methods This is a single-institution retrospective review of non-melanoma skin cancer patients treated at our institution from March 2020 to October 2022 with high dose rate brachytherapy with iridium-192. Either the 2 or 3 cm Valencia applicator was used to treat 25 of 27 lesions with a prescription depth of 3 mm. The Valencia was fixed in place using a clamp and patients were immobilized using a custom head sponge. The other two lesions were treated using a custom array of catheters in Aquaplast and a Freiburg flap. Baseline characteristics and treatment-related variables were summarized using descriptive statistics. Acute and late radiation toxicities were graded using RTOG Common Toxicity Criteria. Local control was evaluated using the Kaplan Meier method. Results Twenty-one patients were identified (n=11 F; n=10 M), with twenty-seven lesions. Median age 81 years (range, 55 to 104), with 85.2% basal- and 14.8% squamous-cell carcinoma. Median follow up was 10.1 months (1.0 to 31.8). Treated lesions were located on the face (n=14), head (n=6), lower extremity (n=5), and neck (n=2), with median lesion size of 8 millimeters (2.5 to 30). Patients were treated with median 40 Gy (40 to 48.5) in 8 fractions (5 to 16) prescribed to depth of 3 mm (3 to 5). RTOG grade 1 skin toxicity (mild erythema) was present in 17 lesions and grade 2 toxicity (brisk erythema) was present in 10 lesions. The most common late toxicity was hypopigmentation in 3 patients. One patient developed a late grade 3 ulcer in a poorly perfused lower limb. Local control was 95.7% on a per lesion basis at one year with a marginal failure in 1/27 lesions. Conclusions Our initial experience with non-melanoma skin brachytherapy has shown good local control with an acceptable safety profile in a predominantly elderly population. Treatment of non-melanoma skin cancers on the lower extremity in elderly patients remains an ongoing challenge due to the risk of late toxicity. Further studies are needed to compare the acute and late toxicity of surface brachytherapy to widely available external beam techniques such as electron beam radiation therapy. Currently, the excellent local control and short treatment courses provide a great treatment option for superficial, early stage non-melanoma skin cancers. Non-melanoma skin cancer is the most common cancer worldwide and its treatment in the elderly can pose significant challenges. We established a skin brachytherapy program primarily to treat older patients using the hypofractionated courses and superficial treatment depth afforded by this technique. Here we describe the first patients treated at our institution, including our initial oncologic results and toxicities. This is a single-institution retrospective review of non-melanoma skin cancer patients treated at our institution from March 2020 to October 2022 with high dose rate brachytherapy with iridium-192. Either the 2 or 3 cm Valencia applicator was used to treat 25 of 27 lesions with a prescription depth of 3 mm. The Valencia was fixed in place using a clamp and patients were immobilized using a custom head sponge. The other two lesions were treated using a custom array of catheters in Aquaplast and a Freiburg flap. Baseline characteristics and treatment-related variables were summarized using descriptive statistics. Acute and late radiation toxicities were graded using RTOG Common Toxicity Criteria. Local control was evaluated using the Kaplan Meier method. Twenty-one patients were identified (n=11 F; n=10 M), with twenty-seven lesions. Median age 81 years (range, 55 to 104), with 85.2% basal- and 14.8% squamous-cell carcinoma. Median follow up was 10.1 months (1.0 to 31.8). Treated lesions were located on the face (n=14), head (n=6), lower extremity (n=5), and neck (n=2), with median lesion size of 8 millimeters (2.5 to 30). Patients were treated with median 40 Gy (40 to 48.5) in 8 fractions (5 to 16) prescribed to depth of 3 mm (3 to 5). RTOG grade 1 skin toxicity (mild erythema) was present in 17 lesions and grade 2 toxicity (brisk erythema) was present in 10 lesions. The most common late toxicity was hypopigmentation in 3 patients. One patient developed a late grade 3 ulcer in a poorly perfused lower limb. Local control was 95.7% on a per lesion basis at one year with a marginal failure in 1/27 lesions. Our initial experience with non-melanoma skin brachytherapy has shown good local control with an acceptable safety profile in a predominantly elderly population. Treatment of non-melanoma skin cancers on the lower extremity in elderly patients remains an ongoing challenge due to the risk of late toxicity. Further studies are needed to compare the acute and late toxicity of surface brachytherapy to widely available external beam techniques such as electron beam radiation therapy. Currently, the excellent local control and short treatment courses provide a great treatment option for superficial, early stage non-melanoma skin cancers.