Successful management of Australian patients with extensive skin field cancerization (ESFC) with widefield volumetric arc radiation therapy (VMAT): Report with 12-month follow-up.

9582 Background: Non-melanomatous skin cancer (NMSC) diagnoses are associated with a high risk of developing new skin cancers in adjacent areas. Patients with extensive skin field cancerization (ESFC) have large areas (generally ≥50cm2) of compromised skin characterized by pre-cancerous actinic keratoses often requiring repeated interventions. Lesion-directed therapies have excellent cure rates, but therapies targeting a wider region have limited durability, including topical agents such as 5-flurouracil. The development of volumetric modulated arc radiation therapy (VMAT) to precisely target large, curved skin surfaces has generated interest in its application to ESFC. This is a report on the efficacy, safety, and cosmetic outcomes of VMAT in the management of patients with ESFC at facilities across five Australian states. Methods: Sixty-three ESFC zones on 60 patients were prescribed widefield VMAT and prospectively enrolled in the National (Australian) Dermatology Radiation Oncology Registry (NDROR). Over 80% of patients had received up to 4 prior non-radiotherapy interventions. Fields included lower and upper limb, face, scalp, or trunk regions. Total widefield VMAT RT doses ranged from 45-50 Gy delivered in 25-30 daily fractions across 5-7 weeks. 3-, 6-, and 12-month follow-up assessments rated the percentage of disease clearance, cosmesis using the Lovett’s scale, and toxicity based on CTCAE. Results: At 12-month follow-up, 97% of treated zones had achieved and maintained clinical success, defined as > 90% field clearance. Five percent of patients exhibited recurrence of original disease, whereas 10% of patients developed a new actinic keratosis or NMSC. Cosmesis was rated as excellent or good in 98% of patients. Most patients exhibited grade 1-2 radiation-induced dermatitis during therapy, which resolved by 3-month follow-up. Grade 3 dermatitis at end of treatment was exhibited in 7% of the patients, which also resolved. Eight percent of patients discontinued treatment due to acute toxicities. The most common persistent toxicity at 12-month follow-up was localized grade 1 xerosis (dryness) at 43% and/or alopecia at 33%. Conclusions: Widefield VMAT achieved very promising clinical success in patients with ESFC for whom other therapies had failed. VMAT yielded favorable cosmetic outcomes, and treatment-related toxicity was manageable and transient in most patients. While additional follow up is necessary, these results demonstrate that widefield VMAT may be an excellent option for some patients with increasingly unmanageable presentations of ESFC.