Session Item

Chemoradiotherapy is the standard of care for non metastatic anal cancer. Despite a good prognosis, some patients will present relapses during follow-up. The aim of this study was to identify predictive factors of relapse on pre-therapeutic 18F-PET/CT.

122 patients with PET/CT who underwent radio-chemotherapy for ASCC between February 2008 and April 2018 were retrospectively analyzed. Two regions of interest (Gross Tumoral Volume for tumor and metastatic lymph nodes) were segmented. Morphological and PET-related features (intensity; volumes; radiomics) were extracted with the Quantimage^TM Platform. Kaplan Meier curves and Cox proportional hazards regression model were used to find associations between these parameters and local control (LC), locoregional control (LRC), progression-free survival (PFS), distant metastatis-free survival (DMFS) and overall survival (OS).

Median follow-up was 48 months (range : 1,93 – 143). LC, LRC, OS, PFS, DMFS rates were respectively 79%, 73%, 69%, 50% and 69% at 5 years. In multivariate analysis, an altered performance status (PS2 versus PS0) was significantly associated with worse OS [HR 4,73 (95% IC : 1,45 – 15,49), p = 0,0008], PFS [HR 2,92 (95% IC: 1,07 – 7,96), p = 0,014] and DMFS [HR 4,30 (95% IC : 1,33 – 13,92), p = 0,002]. A high pre-treatment Tumoral Lesion Glycolysis (TLG) of the primary tumor (> 65,2) with an absolute SUV threshold ≥ 2,5 was predictive for worse OS [HR 2,49 (95% IC : 1,29 – 4,82), p = 0,0068] and DMFS [HR 2,54 (95% IC : 1,32 – 4,87), p = 0,005]. A Metabolic Tumoral Volume (MTV) in the lymph nodes >2,2 mL was associated with worse PFS [HR 1,06 (95% IC :  1,03 – 1,10), p<0,001], using an MTV definition of voxels ≥ 45% of SUV Max. Finally, a higher cumulative distance between the barycenter of each metastasis and the barycenter of all metastases (d > 7,9 cm) was predictive for worse OS [HR 6,76 (95% IC : 2,39 – 19,16), p = 0,0003] and DMFS [HR 5,5 (95% IC : 2,16 – 14,01), p = 0,0004].

Pre-therapeutic parameters extracted from PET/CT seem to be associated with prognosis in patients treated for non metastatic anal cancer treated with chemoradiotherapy. These results must be validated in an independent cohort. In association with other parameters, predictive models could allow us to better individualize the management of these patients.