What is the recommended radiation therapy fractionation for basal cell carcinoma, including conventional and hypofractionation (high dose per fraction) regimens?

Radiation Therapy Fractionation for Basal Cell Carcinoma

For basal cell carcinoma requiring radiation therapy, hypofractionated regimens (44-55 Gy in 10-20 fractions) are the preferred approach, offering equivalent tumor control to conventional fractionation with superior patient convenience, while protracted conventional fractionation (64-66 Gy in 32-33 fractions) should be reserved for cosmetically sensitive facial areas where optimal aesthetic outcomes are paramount. 1, 2

Recommended Hypofractionation Regimens

For tumors <2 cm:

• 44 Gy in 10 fractions over 2 weeks - This is the most evidence-supported hypofractionated schedule, demonstrating 96.9% 3-year local control for BCC with excellent patient convenience 3
• 50 Gy in 15 fractions over 3 weeks - Moderate hypofractionation option 2
• 55 Gy in 20 fractions over 4 weeks - Standard hypofractionation with robust efficacy 1, 2
• 35 Gy in 5 fractions over 5 days - Ultra-hypofractionated option for select cases 1, 2

For tumors ≥2 cm:

• 55 Gy in 20 fractions over 4 weeks 2
• 66 Gy in 33 fractions over 6-6.6 weeks for larger lesions requiring higher total dose 1, 2

Conventional Fractionation Regimens

When cosmetic outcome is the priority (particularly facial lesions):

• 64 Gy in 32 fractions over 6-6.4 weeks for tumors <2 cm 1, 2
• 57 Gy in 19 fractions (5 × 3 Gy/week) - Slightly hypofractionated schedule achieving 100% local control with excellent cosmesis in 94% of cases 4

The evidence strongly supports that protracted fractionation schedules produce superior cosmetic results compared to hypofractionated regimens, making them preferable for cosmetically sensitive areas despite the inconvenience of more treatment sessions 1, 2, 4.

Postoperative Adjuvant Radiation

For positive margins after surgery:

• 50 Gy in 20 fractions over 4 weeks 1
• 60 Gy in 30 fractions over 6 weeks 1

Treatment Margins

Field margins must account for beam characteristics:

• 1-1.5 cm margins for tumors <2 cm 1
• 1.5-2 cm margins for tumors ≥2 cm 1
• Electron beam requires wider margins than orthovoltage x-rays due to beam penumbra, though tighter margins can be used adjacent to critical structures with lead skin collimation 1

Evidence Supporting Hypofractionation

The strongest research evidence comes from a 2010 study of 434 epithelial skin cancers (332 BCCs) comparing 54 Gy in 18 fractions versus 44 Gy in 10 fractions, which found equivalent 3-year local recurrence-free rates (97.6% vs 96.9%, not statistically significant) with median follow-up of 42.8 months 3. This demonstrates that hypofractionation achieves similar tumor control with significantly fewer treatment visits.

A German study using 57 Gy in 19 fractions achieved 100% local control with excellent or good cosmesis in 94% of cases, supporting that slightly hypofractionated schedules can optimize both efficacy and aesthetics 4.

Clinical Decision Algorithm

Choose hypofractionation (44-55 Gy in 10-20 fractions) when:

• Patient convenience is a priority 3
• Tumor location is non-facial or cosmetically less sensitive 2
• Patient has limited ability to attend daily treatments 2
• Cure is the primary endpoint over cosmesis 3

Choose conventional fractionation (64-66 Gy in 32-33 fractions) when:

• Tumor is on cosmetically sensitive facial areas (nose, eyelids, lips) 1, 4
• Patient prioritizes optimal aesthetic outcome 2, 4
• Patient can reliably attend 6+ weeks of daily treatment 2

Critical Contraindications

Radiation therapy is absolutely contraindicated in:

• Basal cell nevus syndrome (Gorlin syndrome) 1
• Xeroderma pigmentosum 1
• Scleroderma and other connective tissue diseases 1

Common Pitfalls to Avoid

• Do not use hypofractionation indiscriminately on facial lesions - The convenience of fewer fractions comes at the cost of inferior cosmetic outcomes, which is particularly problematic in visible areas 2, 4
• Do not underestimate margin requirements with electron beam - Wider margins are mandatory compared to orthovoltage due to beam penumbra characteristics 1
• Do not use radiation in patients under 60 years unless absolutely necessary - Long-term sequelae including secondary malignancies and chronic tissue changes are concerns in younger patients 2
• Ensure adequate bolus with electron beam - Failure to achieve adequate surface dose will compromise tumor control 1