Locally advanced basal cell carcinoma (BCC) are large BCCs or BCCs located in areas subject to functional and aesthetic risk following surgery or radiotherapy. In these particular situations, surgery and radiotherapy are sometimes not appropriate, and Sonic Hedgehog inhibitors (SHHi) (Vismodegib and Sonidegib) can be proposed. SHHi are effective treatments in laBCC but most CR patients discontinue treatment because of tolerability. Approximately 65% of the population experience a relapse after discontinuation. A few cases of patients treated concomitantly by radiotherapy and vismodegib have been reported in the literature, suggesting that combining vismodegib and concomitant radiotherapy results in an improved overall response compared to a single modality treatment. There is no study evaluating a "consolidation radiotherapy" after complete response to SHHi. We carry out a prospective multicenter study in order to evaluate consolidation radiotherapy in patients with laBCC after achieving complete response with SHHi, with the hypothesis of reducing recurrence after discontinuation of SHHi.

Inclusion Criteria:

• Patient over 18 years
• Locally advanced non-recurrent BCC in complete response after first course of SHHi
• Complete response has to be confirmed histologically
• Available photography or CT scan before SHHi treatment allowing delineation of the initial tumor

Exclusion Criteria:

• Patients with distant metastasis
• Patients with Gorlin's syndrome
• Prior radiotherapy to the region of the studied cancer that would result in overlap of radiation therapy fields
• Pregnant women
• Life expectancy less than 1 year
• Inability to receive informed consent
• Inability to participate in the entire study
• Lack of social security coverage
• Refusal to sign consent