Radiotherapy for skin cancer

Radiotherapy has two quite different roles in skin cancer, and confusing them is easy.

The first is as a substitute for surgery. One randomised trial has ever tested that, at the Institut Gustave Roussy from 1982: 347 patients with a facial basal cell carcinoma under 4 cm were randomised to surgery or radiotherapy, given as interstitial brachytherapy in 55 per cent, contact therapy in 33 per cent and conventional external beam in 12 per cent. The four-year failure rate was 0.7 per cent after surgery and 7.5 per cent after radiotherapy (p=0.003), and four of five independent judges rated the cosmetic result significantly better after surgery, 87 against 69 per cent good by the patient's own rating and 79 against 40 per cent by the dermatologist's. The reason the gap widened over time is that a surgical scar improves for years while irradiated skin stays the same or deteriorates. Those techniques are not today's techniques, which is the strongest argument against treating 7.5 per cent as a current number, but no one has repeated the comparison.

So radiotherapy as primary treatment is chosen for particular people rather than particular tumours: someone in whom an operation would cost an eyelid, a nostril or a lip; someone whose age or illness makes surgery unwise; someone who refuses it. It is also the usual answer after an incomplete excision where re-operation is not possible.

The second role is adjuvant, after surgery for high-risk squamous cell carcinoma, and there it is not a substitute for anything. TROG 05.01 randomised 321 patients with high-risk head and neck cutaneous squamous cell carcinoma, most with involved nodes, to postoperative radiotherapy of 60 to 66 Gy with or without weekly carboplatin, and found no benefit from the chemotherapy: freedom from locoregional relapse at five years of 87 against 83 per cent, hazard ratio 0.84 (0.46 to 1.55, p=0.58). The control arm of that trial is the useful number, because it says that surgery followed by radiotherapy already controls more than four in five of the most dangerous skin squamous cancers.

What has changed since is what is added instead of chemotherapy. C-POST showed that adjuvant cemiplimab after surgery and radiotherapy raises two-year disease-free survival from 64.1 to 87.1 per cent in high-risk disease, so the adjuvant conversation in 2026 is about immunotherapy on top of radiotherapy rather than about the radiotherapy dose.