The utility of PET scanning in the management of squamous cell carcinoma of the anus

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Background: PET scanning is an established modality that is useful in the clinical management of squamous cell carcinoma (SCC) of the head and neck and esophagus. This study evaluates the usefulness of PET scans in the management of anal SCC. Methods: Prospective case series of all patients treated for SCC of the anus between 2002 and 2006 in a multi-disciplinary oncology practice group. All patients had staging studies at diagnosis of anal SCC that included CT scan of the chest/abdomen/pelvis and PET scan. All patients with palpable inguinal adenopathy or PET scans positive for inguinal adenopathy underwent fine needle aspiration (FNA) of inguinal nodes. All patients were evaluated by physical exam (PE) and biopsy (Bx), when appropriate, within 3 months of completing treatment. All patients who completed combined chemoradiation for anal SCC and had a post-treatment PET scan were included in this study. Results: 14 of 20 treated patients met criteria for this study. Sensitivity of pre-treatment PET scan was 100% for primary tumor. Extra-pelvic sites with PET SUV<4.0 were uniformly negative for tumor. 66% of inguinal nodes identified by PET scan were FNA positive for metastatic disease. Post-treatment, combined PE and Bx accurately predicted presence or absence of disease in 93%. Post-treatment scans were obtained a mean of 7.6 months after chemoradiation (range 1 to 42 months). In these patients, PET scan sensitivity = 50%, specificity = 72%, predictive value positive (PVP) = 50%, predictive value negative = 80%. 64% of scans were performed within 6 months of treatment; in these, PVP = 33% and PVN = 66%. Conclusions: PET scanning for anal SCC provides accurate staging of disease at presentation and may alter treatment planning by identifying inguinal node involvement not apparent on clinical examination. In this series, PET scan results did not change post-chemoradiation management in any case. Importantly, resolution of primary tumor defined by PET scan was accurate only 80% of the time. PE and Bx within 3 months of treatment were more accurate than PET scan in assessing disease. Post-treatment evaluation of anal SCC should continue to include careful PE, CT scan and Bx when appropriate.

No significant financial relationships to disclose.