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BACKGROUND AND PURPOSE: A 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 METHODS: We 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. RESULTS: The fitted TCP curve demonstrated a dose-response relationship with α=0.196 Gy(-1). The curve suggests: in early stage tumours, a dose reduction from 50 Gy to 45 Gy reduces 2 year local control from 98% to 95%; in late stage tumours, a dose escalation from 50 Gy to 55 Gy improves the 2 year local control rate from approximately 50% to 80%. CONCLUSIONS: The 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.

Original publication

DOI

10.1016/j.radonc.2015.07.014

Type

Journal article

Journal

Radiother Oncol

Publication Date

08/2015

Volume

116

Pages

192 - 196

Keywords

Anal cancer, Dose de-escalation, Dose escalation, Modelling, TCP, Anus Neoplasms, Carcinoma, Squamous Cell, Dose-Response Relationship, Radiation, Humans, Least-Squares Analysis, Linear Models, Neoplasm Recurrence, Local, Probability, Radiotherapy Dosage, Radiotherapy, Intensity-Modulated