Background
ASTRO Clinical Practice Guideline for definitive and postoperative RT in basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) of the skin. Evidence-based guideline addressing RT indications, dose/fractionation, technique, and special populations (elderly, unresectable, perineural invasion). Developed by a multidisciplinary task force with systematic evidence review.
Interventions and follow up
Treatment: ASTRO clinical practice guideline (not a clinical trial)
Primary endpoint: Guideline recommendations
mFollow up: N/A
Primary endpoint: Guideline recommendations
mFollow up: N/A
Results
RT indications: Primary — inoperable or patient preference; Postoperative — positive/close margins, perineural invasion, lymph node involvement, deeply invasive/high-risk features
Dose for perineural invasion: 60-66 Gy to involved nerve; field to cover nerve course to skull base if named nerve involved
Target volumes: GTV + 1-2 cm CTV; PTV per institutional practice
Technique: Electrons preferred for superficial lesions; IMRT/3DCRT for complex anatomy
Dose for perineural invasion: 60-66 Gy to involved nerve; field to cover nerve course to skull base if named nerve involved
Target volumes: GTV + 1-2 cm CTV; PTV per institutional practice
Technique: Electrons preferred for superficial lesions; IMRT/3DCRT for complex anatomy
Adverse events
Acute: Dermatitis, mucositis (perioral lesions), dry eye (periorbital)
Late: Telangiectasia, hypopigmentation, subcutaneous fibrosis, in-field alopecia, cataracts (periorbital), osteonecrosis (overlying bone — rare with modern technique)
Late: Telangiectasia, hypopigmentation, subcutaneous fibrosis, in-field alopecia, cataracts (periorbital), osteonecrosis (overlying bone — rare with modern technique)
Conclusions
RT is effective definitive or adjuvant treatment for BCC and SCC with local control 90-95% for well-selected lesions, providing equivalent local control to surgery with superior cosmetic outcomes in facial locations. Postoperative RT is indicated for high-risk features including perineural invasion, lymph node spread, and close/positive margins.
Key Limitations
Evidence base largely retrospective with heterogeneous patient selection, RT techniques, and historical comparison; optimal dose/fractionation for modern RT remains unclear; limited data on elderly-specific fractionation and cosmetic outcomes; evolving role of immunotherapy (cemiplimab, pembrolizumab) for advanced cSCC not addressed.
Clinical Context
ASTRO 2020 is the current standard reference for RT in non-melanoma skin cancer, particularly in defining RT's role in high-risk SCC (perineural invasion to named nerves, parotid/neck node involvement). Should be read alongside TROG 05.01 for postoperative decisions in high-risk cSCC of the head and neck. RT is appropriate for BCC/SCC patients who are not surgical candidates or prefer organ preservation (nose, ear, lip, eyelid), and for postoperative RT in high-risk features; definitive dose 50-66 Gy in 2 Gy/fraction (conventional), with hypofractionation 35-45 Gy in 2.5-3 Gy/fraction acceptable for older patients.