Successful management of Australian patients with locally advanced keratinocyte cancer (KC) and/or extensive skin field cancerization (ESFC), using widefield volumetric arc radiation therapy (VMAT): Report with 24-month follow-up.
Authors: Potter Andrew , Baker Christopher , Curran Walter J , Boike Thomas Pence , Spelman Lynda , Shumack Stephen , Foley Peter 
Published: June 2023

9586 Background: Keratinocyte cancer (KC) diagnoses are associated with an elevated risk of developing new skin lesions. Patients with extensive skin field cancerization (ESFC) have large areas (generally ≥50cm2) of actinic keratoses and often, frequent keratinocyte cancers, necessitating repeated interventions. Volumetric modulated arc radiation therapy (VMAT) can precisely target large, complex surfaces with modulated doses, as required, leading to its increasing application to ESFC +/- KC. This is a follow-up 24-month report on the efficacy, safety, cosmetic, and quality of life outcomes of VMAT in the management of patients with ESFC +/- KC at Australian facilities. Methods: Two hundred and twenty-four fields for 194 patients with ESFC +/- KC have been prescribed widefield VMAT and prospectively enrolled in the National (Australian) Dermatology Radiation Oncology Registry (NDROR). One hundred and six fields are now beyond 24-months post-treatment. Over 80% of patients had received up to 4 prior non-radiotherapy interventions. Fields included lower and upper limb, face, scalp, or trunk regions. 3-, 6-, 12-, 18-, and 24-month follow-up assessments rated the percentage of field clearance, lesion response, new lesion events, cosmesis using the Lovett’s scale, toxicity based on CTCAE, and quality of life as assessed using a EQ-5D-5L visual analogue scale (VAS). Results: Median dose delivered to ESFC-only and ESFC + KC fields were 45 Gy (16.2-60 Gy) and 47 Gy (22-60 Gy), respectively, in 25 daily fractions (7-30) across 7 weeks (2-13). At 24-month follow-up of 106 fields, 96% and 94% of ESFC-only and ESFC + KC fields, respectively had clinical success, defined as > 90% field clearance. Cosmesis was graded excellent or good in 98% of fields. The incidence of new KC within the field out to 24-months was 11%. Grade 1-2 radiation dermatitis was induced in all fields during treatment, but resolved by 3-month follow-up. Six percent of fields exhibited grade 3 dermatitis. Twelve percent of patients discontinued treatment due to acute toxicities (Median 88% dose delivered). The most common persistent toxicity at 24-month follow-up was localized grade 1-2 xerosis (51%), alopecia (43%), and/or pruritis (8%). Quality of life was sustainably improved in patients at 24-month follow-up (3.67; p= 0.026). Conclusions: Widefield VMAT has a promising profile of clinical efficacy, safety, and cosmesis in patients with ESFC +/- KC for whom other therapies had failed. Treatment was also associated with significant and durable improvements in quality of life. While long-term follow-up of patients continues, these results provide further support for widefield VMAT as a suitable option for patients with increasingly unmanageable presentations of ESFC and locally-advanced KC. Clinical trial information: ACTRN12618000627257 .