Background
Patients with large cutaneous squamous cell carcinoma of the scalp are a treatment challenge. We report a case of dramatic radiotherapy response of a patient with a giant cutaneous squamous cell carcinoma of the scalp with extensive skull destruction and suspected infiltration of the dura mater and superior sagittal sinus. This case is the first report of this kind in the literature that shows that large bone defects can heal with the resolution of tumor and inflammation by secondary intention without surgical reconstruction. We want to put an end to concerns about radiocurability of tumors with extensive bone involvement, and show sustained complete response after definitive radiotherapy and programmed cell death protein-1 inhibiting antibody therapy.

Case presentation
A 74-year-old White man presented with a 7.2 × 6.8 × 5.5 cm painless tumor on the right parietal region of the scalp. Medical imaging revealed widespread destruction of the skull and suspected infiltration of the dura mater and superior sagittal sinus. Biopsies showed cutaneous squamous cell carcinoma (cT4a cN0 cM0, stage IVA). The patient was treated with a total dose of 60 Gy, at 2 Gy per daily fraction with volumetric modulated arc therapy using 6 megavoltage photons. The biologically effective dose (alpha/beta 10 Gy) was 72 Gy. The tumor response correlated with dose received. The patient had a massive tumor necrosis secondary to tumor shrinkage after 18 fractions (36 Gy, biologically effective dose 43.2 Gy). Leakage of cerebrospinal fluid did not occur. Radiotherapy did not hamper the patient’s quality of life. The patient had a clear regression of the initial tumor on the final day of radiotherapy. The bone defect healed by secondary intention without surgical interventions. The patient achieved a complete response with a good cosmetic result after 82 days follow-up. He started a programmed cell death protein-1 inhibiting antibody therapy with cemiplimab 2 months after radiotherapy, and is now at 10 months follow-up without evidence of recurrence.

Conclusion
Definitive radiotherapy is a safe and highly effective therapy for giant tumors of the scalp with extensive bone destruction. We report a sustained complete response with a good cosmetic result after secondary wound healing.