Sequential combination of sonic hedgehog inhibitors followed by consolidation radiotherapy in locally advanced basal cell carcinoma

BACKGROUND: Sonic hedgehog inhibitors (SHHis) are an effective treatment in locally advanced basal cell carcinoma (laBCC). However, the use of these drugs is limited by adverse events, and relapse at discontinuation in around one-half of patients. A few cases of patients treated concomitantly by radiotherapy (RT) and SHHis have been reported in the literature, suggesting that the combination results in an improved overall response. Maintaining complete response after stopping treatment is a concern, especially as resuming treatment in the case of relapse does not guarantee a new therapeutic response. The optimal combination and sequence of treatment to improve local control of laBCCs are not yet defined. OBJECTIVES: We hypothesized that consolidation RT after complete response to SHHis could reduce the risk of relapse at discontinuation. METHODS: We present a case series of patients with laBCCs who achieved complete response after SHHi treatment and were treated with consolidation RT. Patients were evaluated by a skin cancer board. The closure RT technique and dosage were refined by a radiotherapist. RESULTS: Eleven patients were included. SHHis were prescribed for a median 5 months (range 4-11). Consolidation RT was performed after complete response to SHHis and discontinuation. RT was delivered at a median dose of 45 Gy (range 40.5-66) in 10 fractions (range 9-33). With a median follow-up of 23 months, all patients maintained complete clinical response. This strategy was well tolerated with no grade 3 adverse events. CONCLUSIONS: SHHi treatment followed by consolidation RT after drug discontinuation seems effective and safe. Further studies are needed to develop a precise strategy for the management of laBCCs.