A Multi-Institutional Study of Definitive Radiotherapy for Locally Advanced Basal Cell Carcinoma

Abstract

<h3>Purpose/Objective(s)</h3> The gold standard for management of basal cell carcinoma (BCC) is surgical resection with negative margins, which is associated with excellent control rates. However, a subset of locally advanced BCCs may not be amenable to resection alone. This includes disease that is locally invasive or located in a cosmetically or functionally challenging anatomic location. Definitive radiotherapy can be used in these cases; however, outcomes data is sparse and typically limited to small single-institutional series or case reports. We conducted a modern multi-institutional cohort study of locally advanced BCC treated with definitive radiation to further evaluate treatment outcomes. <h3>Materials/Methods</h3> Patients with locally advanced BCC treated with upfront definitive radiation between 2006-2020 from 3 academic institutions were included. Locally advanced BCCs were defined as patients with unresectable disease, or locations where surgery to achieve negative margins would lead to unacceptable cosmetic or functional deficit. Patient and tumor clinical characteristics, radiation treatment details, and outcomes were collected from medical records. <h3>Results</h3> A total of 474 locally advanced BCC cases were identified, of which 76 were treated with upfront definitive radiotherapy with a median follow up of 2.44 years. Patient characteristics are shown in Table 1. Median radiation dose used was 5000 cGy (range 2800-7000 cGy), with median 250 cGy per fraction (range 200-1000 cGy). Most patients (73.7%) were treated with electrons. Disease free survival was 81.6% (62/76 patients). There were 9 (11.8%) local recurrences, 2 (2.6%) with nodal metastases and 3 (3.9%) with distant metastases. On linear regression analysis, tumor size was predictive of recurrence (p=0.00035). Overall survival at time of most recent follow up was 61.8% with 6 (7.9%) of the deaths attributed to BCC. <h3>Conclusion</h3> In this modern study, definitive radiotherapy for locally advanced unresectable BCC has excellent local control rates, with tumor size remaining a risk factor for recurrence. Nodal and distant metastases are rare despite locally advanced disease and most long-term mortality in this cohort tends to be from non-BCC related causes.