A tumor control probability model for anal squamous cell carcinoma

Area of Science:

• Radiation oncology
• Medical physics
• Cancer research

Background:

• RTOG 9811 data show varied relapse rates for anal cancer post-chemoradiotherapy (CRT).
• The dose-response relationship for anal cancer remains unknown, hindering optimal treatment.
• Intensity-modulated radiotherapy (IMRT) is increasingly used, with available published data.

Purpose of the Study:

• To fit a tumor control probability (TCP) model to published IMRT data for anal cancer.
• To establish a dose-response relationship for anal cancer treated with IMRT.
• To explore the potential for dose-individualization in anal cancer radiotherapy.

Main Methods:

• Systematic review of PubMed and Embase databases.
• Inclusion of thirteen papers comprising 625 patients.
• Fitting a standard linear quadratic TCP model with repopulation using least squares minimization.

Main Results:

• A dose-response relationship was identified with α=0.196 Gy(-1).
• For early-stage tumors, reducing dose from 50 Gy to 45 Gy slightly decreases 2-year local control (98% to 95%).
• For late-stage tumors, escalating dose from 50 Gy to 55 Gy significantly improves 2-year local control (approx. 50% to 80%).

Conclusions:

• Published IMRT data align with a linear quadratic dose-response model.
• Dose-individualization warrants further investigation in clinical trials for anal cancer.
• Optimizing radiation dose may enhance treatment outcomes for anal squamous cell carcinoma.