Abstract
Background and purposeA recent update of the RTOG 9811, reported differing relapse rates for early and late anal squamous cell carcinoma following chemoradiotherapy (CRT). There may be a role for dose-individualization, however the dose–response relationship for anal cancer is not currently known.Intensity-modulated radiotherapy (IMRT) has been widely adopted with multiple series published. The aim is to fit a tumor control probability (TCP) model to the published IMRT data. Materials and methodsWe performed a systematic review of PubMed and Embase databases to identify thirteen appropriate papers, including 625 patients. Predefined data fields were collected. A standard linear quadratic TCP model, which included repopulation, was fit by least squares minimization. ResultsThe fitted TCP curve demonstrated a dose–response relationship with α=0.196Gy–1. The curve suggests: in early stage tumours, a dose reduction from 50Gy to 45Gy reduces 2year local control from 98% to 95%; in late stage tumours, a dose escalation from 50Gy to 55Gy improves the 2year local control rate from approximately 50% to 80%. ConclusionsThe published data are broadly consistent with a linear quadratic dose–response model. Dose-individualization in anal cancer should be further investigated in the context of clinical trials.
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