A tumor control probability model for anal squamous cell carcinoma

Journal article

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.

Authors: Muirhead, R; Partridge, M; Hawkins, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Radiotherapy and Oncology
• Volume: 116
• Issue: 2
• Pages: 192-196
• Publication date: 2015-08-01
• Acceptance date: 2015-07-16
• DOI: 10.1016/j.radonc.2015.07.014
• ISSN: 0167-8140
• Pmid: 26243680
• Keywords: dose escalation; TCP; modelling; anal cancer; dose de-escalation