Aim: This study aimed to determine the prognostic significance of length of tumour (mrT stage) and depth of extramural spread (mrEMS) in anal squamous cell cancer (SCC) treated by chemoradiation with curative intent. Locally advanced anal SCC (T3-4 N+) have poorer prognosis, but it is unknown whether the lateral spread of the tumour (extramural spread beyond the bowel wall) also confers poor prognosis in anal SCC, as it does for rectal cancer. T stage and mrEMS can be readily assessed by pelvic magnetic resonance imaging (MRI) routinely undertaken to stage anal SCC.
Materials and methods: 125 patients were included. Baseline mrT, mrN and mrEMS were assessed with response to chemoradiation and outcomes. Receiver operating curve (ROC) curve was used to determine a binary cut-off for mrEMS according to 3-year progression- free survival (PFS).
Results: 43% were mrT3-4 and 38% were mrEMSpoor at baseline. 87% achieved mrCR. 3-year PFS and overall survival (OS) were 70.6% and 82%. On univariate analysis worse 3-year PFS was seen for mrT3-4 (HR 3.105), mrEMSpoor (HR 4.924) and failure to achieve mrCR (HR 20.591). By univariate analysis, worse 3-year OS was seen for mrT3-4 (HR 4.134), mrEMSpoor (HR 10.251) and failure to achieve mrCR (HR 19.289). On multivariate analysis, only mrEMSpoor and failure to achieve mrCR remained prognostic. mrN was not prognostic.
Conclusion: MrEMSpoor is a simple prognostic imaging biomarker for poorer survival which can be readily assessed by radiologists on routine imaging. mrEMS should be considered as a future stratification variable to identify high-risk SCC and consider escalation of treatment and surveillance strategies.
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