Definitive Radiation Therapy is a Viable Treatment for Locally Advanced Basal Cell Carcinoma Otherwise Requiring Radical or Disfiguring Resection

Purpose: Standard treatment for basal cell carcinoma (BCC) is surgical resection. However, a subset of locally advanced BCCs may be unresectable, or surgery would result in unacceptable functional or cosmetic defects. Outcomes after definitive radiation therapy for locally advanced BCC in the contemporary era are not well established. We sought to determine locoregional control and disease-specific survival after definitive radiation therapy for locally advanced BCC.

Methods and materials: Patients with locally advanced BCC treated with definitive radiation therapy between 2005 and 2020 from 4 academic tertiary care institutions were included. Locally advanced BCCs were defined as patients with unresectable disease, or locations where margin negative resection would lead to unacceptable cosmetic or functional deficit. Additionally, a set of 5 risk factors (size ≥4 cm, the presence of bone invasion, PNI, immunocompromised patient, and recurrent disease) was separately defined and outcomes were investigated.

Results: Six hundred eight locally advanced BCC cases were identified, of which 140 were treated with definitive radiation therapy. Median follow-up was 22.9 months (1.5-207.2 months). One hundred one (72.1%) tumors were treated with upfront definitive radiation therapy, whereas 39 (27.9%) were treated for a recurrence. Five-year Kaplan-Meier estimated locoregional control was 78%. The majority of locoregional failures were local recurrences (95.5%). Larger tumor diameter was a risk factor for locoregional failure (P = .045), whereas recurrent disease was not (P = .29). Cumulative incidence of BCC-related mortality at 5 years was 9.5%. Patients with 0 risk factors had a 5-year FF-LRF of 92.4%, whereas those with 1+ risk factors had a 5-year freedom from locoregional failure of 68.5% (P = .004).

Conclusions: Definitive radiation therapy for locally advanced BCC has excellent locoregional control, with tumor size representing the only risk factor for recurrence in this study.