Published in:
01-03-2021 | Radiotherapy | Original Research
Optimal Radiotherapy Dose in Anal Cancer: Trends in Prescription Dose and Association with Survival
Published in: Journal of Gastrointestinal Cancer | Issue 1/2021
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Purpose
Definitive chemoradiotherapy represents a standard of care treatment for localized anal cancer. National Comprehensive Cancer Network guidelines recommend radiotherapy (RT) doses of ≥ 45 Gy and escalation to 50.4–59 Gy for advanced disease. Per RTOG 0529, 50.4 Gy was prescribed for early-stage disease (cT1-2N0), and 54 Gy for locally advanced cancers (cT3-T4 and/or node positive). We assessed patterns of care and overall survival (OS) with respect to the RT dose.
Methods
The National Cancer Database identified patients with non-metastatic anal squamous cell carcinoma from 2004 to 2015 treated with chemoradiotherapy. Patients were stratified by RT dose: 40–< 45, 45–< 50, 50–54, and > 54–60 Gy. Crude and adjusted hazard ratios (HR) were computed using Cox regression modeling.
Results
A total of 10,524 patients were identified with a median follow-up of 40.7 months. The most commonly prescribed RT dose was 54 Gy. On multivariate analysis, RT doses of 40–< 45 Gy were associated with worse OS vs. 50–54 Gy (HR 1.68 [1.40–2.03], P < 0.0001). There was no significant difference in OS for patients who received 45–< 50 or > 54–60 Gy compared with 50–54 Gy. For early-stage disease, there was no significant association between RT dose and OS. For locally advanced disease, 45–< 54 Gy was associated with worse survival vs. 54 Gy (HR 1.18 [1.04–1.34], P = 0.009), but no significant difference was detected comparing > 54–60 Gy vs. 54 Gy (HR 1.08 [0.97–1.22], P = 0.166).
Conclusions
For patients with localized anal cancer, RT doses of ≥ 45 Gy were associated with improved OS. For locally advanced disease, 54 Gy but not > 54 Gy was associated with improved OS.