Metabolic tumour volume of anal carcinoma on (18)FDG PET/CT before combined radiochemotherapy is the only independant determinant of recurrence free survival

Abstract

Aim: to determine whether [(18)F]2-fluoro-2-deoxyglucose (FDG) positron emission tomography and X-ray computed tomography (PET/CT) findings and metabolic parameters before combined chemo- and radiotherapy (CRT) have a prognostic value in patients with anal carcinoma.

Materials and methods: 45 patients with anal cancer who underwent pre-treatment FDG-PET/CT were included. Metabolic parameters, recurrence and anal carcinoma specific survival were analyzed.

Results: SUV max and metabolic volume of the primary tumour were significantly higher in patients with lymph node or distant metastases than in those with locally confined disease (p=0.020 and p=0.015, respectively). The extent of disease (local tumour only, lymph node or distant metastases) was highly predictive of both for recurrence free and disease specific survival (p=0.010 and p<0.001, respectively). Recurrence free (p=0.010) and anal carcinoma specific survival (p=0.006) differed significantly between patients with a metabolic volume ≤45ml and >45ml. Multivariate analysis revealed that a metabolic volume >45ml was the only significant independent determinant (p=0.19) for recurrence free survival whereas for anal carcinoma specific survival the extent of disease was identified as the only significant independent determinant (p=0.002).

Conclusions: the extent of disease on FDG PET/CT before combined radio-chemotherapy is strongly predictive of prognosis in anal cancer. Furthermore, patients with a large metabolic volume of the primary tumour (>45ml) are at significantly higher risk of recurrence.

Keywords: Anal carcinoma; FDG PET/CT; Prognosis; Radiation therapy planning; Radiochemotherapy.