[Value of FDG PET-CT associated with pathology in diagnosing residual tumor in patients with nasopharyngeal carcinoma after radiotherapy].

OBJECTIVE:To find a rational way in early detecting the residual tumor in patients with nasopharyngeal carcinoma (NPC) after radiotherapy. METHODS:A total of 47 NPC patients who were diagnosed residual tumor after radiotherapy and treated in our hospital from Dec 2009 to Aug 2012 were included in this study and their clinicopathological and follow-up data were reviewed and analyzed. The patients were checked by nasopharynx MRI, FDG PET-CT and were examined by biopsy of the residual tumors within two weeks after radiotherapy. The diagnosis of relapses was determined by pathological re-examination. RESULTS:All the 47 patients were followed up for 10-42 months. Three of them had nasopharynx relapse. The others had not tumor relapse and their residual tumors disappeared completely. The specificity of MRI, FDG PET-CT and pathological tumor response in diagnosing residual tumors were 9.1%, 77.3%, and 95.5% (P<0.001). Their accuracy rates were 14.9%, 78.9%, and 95.7%, respectively (P<0.001). The M of SUVmax in the team who had moderate and severe pathologic tumor response (team A) was 3.05 and that in the team who had mild pathologic tumor response (team B) was 4.68 (P=0.012). None of patients in the team A had nasopharynx relapse. Three patients in the team B who had SUVmax ≥4 had nasopharynx relapses, and in other 2 patients who had SUVmax <4, the residual tumors disappeared during the following-up. The specificity and accuracy in diagnosing residual tumors were increased when mild pathologic tumor response combined with SUVmax4 were used. CONCLUSION:PET-CT combined with pathologic tumor response is beneficial for early diagnosis of residual nasopharyngeal tumors after radiotherapy.