Abstract
PurposeIncidence of anal squamous cell carcinoma (ASCC) is increasing, with curative chemoradiotherapy (CRT) as the primary treatment of non-metastatic disease. A significant proportion of patients have locoregional treatment failure (LRF), but distant relapse is uncommon. Accurate prognostication of progression-free survival (PFS) would help personalisation of CRT regimens. The study aim was to evaluate novel imaging pre-treatment features, to prognosticate for PFS in ASCC.MethodsConsecutive patients with ASCC treated with curative intent at a large tertiary referral centre who underwent pre-treatment FDG-PET/CT were included. Radiomic feature extraction was performed using LIFEx software on baseline FDG-PET/CT. Outcome data (PFS) was collated from electronic patient records. Elastic net regularisation and feature selection were used for logistic regression model generation on a randomly selected training cohort and applied to a validation cohort using TRIPOD guidelines. ROC-AUC analysis was used to compare performance of a regression model encompassing standard clinical prognostic factors (age, sex, tumour and nodal stage—model A), a radiomic feature model (model B) and a combined radiomic/clinical model (model C).ResultsA total of 189 patients were included in the study, with 145 in the training cohort and 44 in the validation cohort. Median follow-up was 35.1 and 37. 9 months, respectively for each cohort, with 70.3% and 68.2% reaching this time-point with PFS. GLCM entropy (a measure of randomness of distribution of co-occurring pixel grey-levels), NGLDM busyness (a measure of spatial frequency of changes in intensity between nearby voxels of different grey-level), minimum CT value (lowest HU within the lesion) and SMTV (a standardized version of MTV) were selected for inclusion in the prognostic model, alongside tumour and nodal stage. AUCs for performance of model A (clinical), B (radiomic) and C (radiomic/clinical) were 0.6355, 0.7403, 0.7412 in the training cohort and 0.6024, 0.6595, 0.7381 in the validation cohort.ConclusionRadiomic features extracted from pre-treatment FDG-PET/CT in patients with ASCC may provide better PFS prognosis than conventional staging parameters. With external validation, this might be useful to help personalise CRT regimens in the future.
Highlights
The incidence of anal cancer is rising in populations across the world [1,2,3]
The aim of this study was to evaluate if radiomic features extracted from baseline FDG-PET/CT are predictive for progression-free survival (PFS) in patients with anal squamous cell carcinoma (ASCC) treated with curative-intent CRT compared with conventional staging
A total of 118 patients were excluded, reasons included; FDG-PET/CT imaging performed after excision of primary lesion—31 patients; FDG-PET/CT not performed—23 patients; non-ASCC histology—17 patients; treatment not administered with curative intent—13 patients; primary lesion too small for analysis (< 4 cm3, 64 voxels)—16 patients; primary tumour not visible on FDG-PET/CT—7 patients; incomplete imaging or clinical data—11 patients
Summary
The incidence of anal cancer is rising in populations across the world [1,2,3] This is mostly due to an increase in incidence of squamous cell carcinoma, the predominant histological type of anal cancer (ASCC). CRT has been demonstrated to be the best curative treatment option for achieving local control, recurrence-free and/or progression-free survival (PFS) in ASCC compared with surgery or radiotherapy alone [4,5,6,7] At present, this involves chemotherapy (mitomycin C and 5fluorouracil) and concurrent radiotherapy, most commonly using 45–54 Gy in 1.8 Gy fractions depending on tumour stage [7]
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