OBJECTIVETo investigate the prognostic value of interim and post-therapy PET-CT in patients with diffuse large B-cell lymphoma.

METHODSA retrospective analysis was conducted on data from 116 patients with newly diagnosed diffuse large B-cell lymphoma. 43 patients underwent interim PET-CT after 4 cycles of chemotherapy, 48 patients underwent post-therapy PET-CT after 6-8 cycles of chemotherapy, and 25 patients underwent both interim PET-CT and post-therapy PET-CT. The patients were divided into three groups: complete response group, partial response group and no response group. The therapeutic response was assessed by comparing with baseline PET-CT. PET-CT status was assessed for its ability to predict progression-free survival (PFS) and overall survival (OS). The 2-year PFS rate and 3-year OS rate were evaluated using chi-square test. PFS and OS were estimated according to the Kaplan-Meier method and survival curves were compared by log-rank test.

RESULTSInterim PET-CT: The interim PET-CT findings of 42 patients were judged as complete response, 15 were judged as partial response, and the rest 11 were judged as no response. The 2-year PFS rates of the complete response group, partial response group and no response group were 61.9%, 60.0%, and 18.2%, respectively, and the 3-year OS rates were 52.4%, 46.7% and 9.1%, respectively. There were no significant differences between the complete response group and partial response group in 2-year PFS rate and 3-year OS rate (P > 0.05 for both). But there was a significant difference between the partial response group and no response group (P < 0.05). The post-therapy PET-CT findings of 50 patients was judged as complete response, 11 as partial response, and the rest 12 were judged as no response. The 2-year PFS rate of the complete response group, partial response group and no response group were 82.0%, 45.5%, and 8.3%, respectively, and the 3-year OS rates were 88.0%, 54.5%, and 8.3%, respectively. There were significant differences between the complete response group and partial response group in 2-year PFS rate and 3-year OS rate (P < 0.05), and there was a significant difference between the partial response group and no response group (P < 0.05).

CONCLUSIONSCompared with the interim PET-CT, post-therapy PET-CT can accurately evaluate the prognosis of patients with DLBCL. Interim PET-CT cannot define the prognosis of the complete response and partial response patients.