Anal cancer maximum F-18 fluorodeoxyglucose uptake on positron emission tomography is correlated with prognosis

Purpose: To evaluate anal cancer uptake of F-18 fluorodeoxyglucose (FDG) measured as the maximum standardized uptake value (SUV_max) by positron emission tomography (PET) and its correlation with prognostic factors. Patients and methods: The study population consisted of 77 patients with stages 0-IIIB anal cancer who underwent pre-treatment FDG-PET. Tumor histology included 65 squamous cell, 11 basaloid, and 1 small cell cancers. SUV_max and sites of lymph node metastasis were recorded. We analyzed the association between SUV_max and prognostic factors. Results: The mean SUV_max was 10.0 (range 1.0-43.1). The stage distribution included: 2 stage 0, 7 stage I, 49 stage II, 10 stage IIIA, 9 stage IIIB. SUV_max and clinical tumor size were not associated (R² = 0.338). Histology did not significantly influence SUV_max (mean SUV_max 10.0 for squamous versus 9.90 for basaloid). Higher SUV_max was associated with an increased risk of nodal metastasis at diagnosis (p < 0.0001). Higher SUV_max was associated with worse disease-free survival (p = 0.05). Patients with high anal tumor SUV_max at diagnosis were at an increased risk of persistent or recurrent disease on post-therapy FDG-PET performed less than 4 months after completing therapy (p = 0.0402). Conclusions: SUV_max is a valuable biomarker of anal cancer prognosis, predicting increased risk of lymph node metastasis and worse disease-free survival.