Radiotherapy, Utilizing Volumetric Modulated Arc Therapy, for Extensive Skin Field Cancerization: A Retrospective Case Series Assessing Efficacy, Safety, and Cosmetic Outcomes at 12 Months After Treatment

Extensive Skin Field Cancerization (ESFC) describes multiple actinic keratoses, with and without keratinocyte skin cancers. These areas are characterised by dysplastic keratoses, are prone to new malignancies, involve significant morbidity, have a poor cosmetic appearance, and impact negatively on quality of life. Available topical field therapies have limited durability of efficacy. Volumetric modulated arc therapy (VMAT) is an advanced form of intensity-modulated radiotherapy which achieves highly modulated and conformal dosimetry, delivering a homogeneous dose, particularly over curved surfaces, for example, scalps and limbs. This series describes the 12-month follow-up analysis of 41 VMAT treated fields from 32 (21 M, 11 F) patients. Consent was obtained after VMAT treatment to allow access to outcomes data. Conditions treated include ESFC, Bowen’s disease/SCC in situ, cutaneous squamous cell carcinoma, and basal cell carcinoma (BCC). Efficacy was measured by the percentage reduction of visible pathology within the treatment field. The primary endpoint for this review was the assessment of treatment success, defined as >90% clearance of the treatment field. As part of this definition, the appearance of isolated keratoses at 12 months was considered not significant if the field overall was clear. The development of new or recurrent cancers within the 12-month follow-up period was recorded. Thirty-six fields (87%) achieved a clinical clearance >90%. Of those, 33 (80%) fields achieved complete clearance >99% of visible actinic keratosis or keratinocyte cancers. Three fields (7%) demonstrated 91–99% clinical clearance, and no treatment failures were recorded. Two newly occurring lesions (1 BCC and 1 SCC in situ) were identified within a treated field at 12 months. The reported toxicities at 12-month post-treatment were grade 1 or 2 only, with no cases of persistent radiation dermatitis. Toxicities reported in more than 5% of cases included: alopecia (n = 4); dryness (n= 3); erythema (n = 2); and telangiectasia ulceration (n = 4). The high rate of complete clearance at 12 months seen in this case series compares very favourably with other treatments, including topical 5-fluorouracil, imiquimod, and photodynamic therapy. Toxicities reported in our patient population demonstrated that VMAT was well tolerated at 12-month post-treatment. VMAT treatment may play a growing role in future therapy for ESFC with and without keratinocyte cancers.