Contrast-enhanced [(18)F]fluorodeoxyglucose-positron emission tomography/computed tomography for staging and radiotherapy planning in patients with anal cancer

The practice of surgical staging and treatment of anal cancer has been replaced by noninvasive staging and combined modality therapy. For appropriate patient management, accurate lymph node staging is crucial. The present study evaluated the feasibility and diagnostic accuracy of contrast-enhanced [(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG)-positron emission tomography/computed tomography (PET/CT) for staging and radiotherapy planning of anal cancer.

A total of 22 consecutive patients (median age, 61 years old) with anal cancer underwent complete staging evaluation including physical examination, biopsy of the primary tumor, and contrast-enhanced (ce)-PET/CT. Patients were positioned as they would be for their subsequent radiotherapy. PET and CT images were evaluated independently for detectability and localization of the primary tumor, pelvic and inguinal lymph nodes, and distant metastasis. The stage, determined by CT or PET alone, and the proposed therapy planning were compared with the stage and management determined by ce-PET/CT. Data from ce-PET/CT were used for radiotherapy planning.

ce-PET/CT revealed locoregional lymph node metastasis in 11 of 22 patients (50%). After simultaneous reading of PET and CT data sets by experienced observers, 3 patients (14%) were found to have sites of disease not seen on CT that were identified on PET. Two patients had sites of disease not seen on PET that were identified on CT. In summary, 2 patients were upstaged, and 4 patients were downstaged due to ce-PET/CT. However, radiotherapy fields were changed due to the results from ce-PET/CT in 23% of cases compared to CT or PET results alone.

ce-PET/CT is superior to PET or CT alone for staging of anal cancer, with significant impact on therapy planning.