Pooled Analysis of external-beam RADiotherapy parameters in phase II and phase III trials in radiochemotherapy in Anal Cancer (PARADAC).

Concomitant external-beam radiochemotherapy (5-fluorouracil-mitomycin C) has become the standard of care in anal cancer since the '90s. A pooled analysis of individual patient data from 7 major trials was performed quantifying the effect of radiation therapy (RT)–related parameters on the outcome of patients with anal cancer. Pooling databases from combined modality trials, the impact of RT parameters (total dose, gap duration, OTT: overall treatment time) on outcome including locoregional failure (LRF), 5-year progression free survival (PFS) and toxicities were investigated. Individual patient data were received for 10/13 identified published studies conducted from 1987 to 2008 (n = 3031). A Cox regression model was used (landmark = 3 months after RT for first follow-up). After data inspection indicating severe heterogeneity between trials, only 1343 patients from 7/10 studies received were analysed (the most recent ones, since 1994; median follow-up = 4.1 years). A higher overall 5-year LRF rate [22.8% (95% confidence interval [CI] 22.3–27.3%)] significantly correlated with longer OTT (p = 0.03), larger tumour size (p < 0.001) and male gender (p = 0.045). Although significant differences were not observed, subset analyses for LRF (dose range: 50.4–59 Gy) seemed to favour lower doses (p = 0.412), and when comparing a 2-week gap versus 3 (dose: 59.4 Gy), results suggested 3 weeks might be detrimental (p = 0.245). For a 2-week gap versus none (dose range: 55–59.4 Gy), no difference was observed (p = 0.89). Five-year PFS was 65.7% (95% CI: 62.8–68.5%). Higher PFS rates were observed in women (p < 0.001), smaller tumour sizes (p < 0.001) and shorter OTT (p = 0.025). Five-year overall survival [76.7% (95% CI: 73.9%–79.3%)] correlated positively with female gender (p < 0.001), small tumour size (p = 0.027) and short OTT (p = 0.026). Descriptive toxicity data are presented. For patients receiving concurrent external-beam doublet chemoradiation, a longer OTT seems detrimental to outcome. Further trials involving modern techniques may better define optimal OTT and total dose. • Radiochemotherapy remains the standard treatment for anal cancer since the '90s. • Our results suggest that a longer overall treatment time may be detrimental to outcome. • In the dose range of 50.4–59 Gy, lower doses seem to be preferred. • A longer than 2-week gap might be detrimental. • Findings may guide trials to define optimal overall treatment time and dose level. [ABSTRACT FROM AUTHOR]