Innovative Widefield Volumetric Arc Radiation Therapy (VMAT) Approach to Simultaneously Treat Extensive Skin Field Cancerization (ESFC) + In-Field Keratinocyte Carcinoma (KC) in Australian Patients: Report with 12 Month Follow-Up

Abstract

<h3>Purpose/Objective(s)</h3> Patients with extensive skin field cancerization (ESFC) have large areas of diffuse hyperkeratotic actinic keratoses (AK), often with concomitant keratinocyte carcinoma (KC) or other cancer. Treatment can involve numerous interventions including cryotherapy, topical agents, and/or surgery, which can be ineffective or prohibitively invasive. The design of innovative widefield volumetric modulated arc radiation therapy (VMAT) protocols, has extended the high lesion cure rates of radiation to the treatment of patients with ESFC and in-field cancer. This is a report on treatment planning, and the efficacy, safety, and cosmetic outcomes of VMAT for the management of patients with ESFC + in-field cancer at facilities across five Australian states. <h3>Materials/Methods</h3> Twenty-six patients with ESFC plus a KC or lentigo melanoma (n=1), 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. In-field cancer, defined as KC (cutaneous squamous cell carcinoma or basal cell carcinoma), or lentigo melanoma, were generally prescribed a simultaneous integrated boost (SIB) of 55Gy. 3-, 6-, and 12-month follow-up assessed the percentage of field disease clearance, lesion complete response, cosmesis using the Lovett's scale, and toxicity based on CTCAE. <h3>Results</h3> At 12-month follow-up, 88% of treated fields had achieved and maintained clinical success, defined as >90% clearance. A complete lesion response for boosted in-field cancer was observed in 96% of patients. Four percent of patients exhibited recurrence of original disease, whereas 15% of patients developed a new lesion. Cosmesis was rated as excellent or good in 96% of patients. Most patients exhibited grade 1-2 radiation-induced dermatitis during therapy, which resolved by 3-month follow-up. Nineteen percent (5/26) of patients discontinued treatment due to acute toxicities, though achieved complete responses without recurrence or new lesions, indicating a reduced dose and associated toxicity may be possible without compromising efficacy. <h3>Conclusion</h3> Widefield VMAT yielded promising clinical success in patients with ESFC plus in-field cancer, in addition to favorable cosmetic outcomes, and a manageable toxicity profile in most patients. Scheduled 24-month follow-up will be undertaken shortly to provide further insight into dosage and durability. These results demonstrate that widefield VMAT may be an excellent option for some patients with ESFC and in-field cancer, for whom other therapies have failed.