Limited prognostic value of interim PET/CT during B-cell lymphoma treatment

1. In a prospective cohort study of 138 patients undergoing the combination of rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) for diffuse large B-cell lymphoma (DLBCL), patients with interim negative PET/CT scans did not demonstrate a greater event free survival compared to patients with interim positive PET/CT scans.

Evidence Rating Level: 2 (Good)   

Study Rundown: The current chemotherapy regimen for patients with DLBCL is R-CHOP. Current cure rates with R-CHOP are variable, ranging from 30-70%. Previous studies have demonstrated that PET/CT scans have a high sensitivity for detecting sites of DLBCL and end-of-treatment PET/CT scans have a high predictive value for overall survival. However, the prognostic value of PET/CT during the R-CHOP cycle is unclear. The purpose of this prospective cohort study of patients undergoing R-CHOP was to assess the prognostic value of interim PET/CT in this population. This was a prospective trial of 138 patients with DLBCL who underwent PET/CT scan after two cycles of R-CHOP. At the conclusion of the trial, having a negative interim PET/CT scan was significantly associated with an increase in 2-year event free survival compared to patients with positive PET/CT scans. However, there was no difference in the overall survival between the positive and negative interim PET/CT scan groups. The results of the study support the conclusion that interim PET/CT scans have limited prognostic value for patients with DLBCL treated with R-CHOP and are not sufficiently accurate to be used to guide treatment decisions. The strength of the study is the large, multi-centered study design. However, the study is limited by a short period of follow-up (2 years), which may not be sufficient to detect changes in overall survival.

Click to read the study in JCO

Relevant Reading: Prognostic value of interim 18F-FDG PET in patients with diffuse large B-cell lymphoma: SUV-based assessment at 4 cycles of chemotherapy

In-Depth [prospective cohort]: This study was a multicenter, prospective, single-arm study that enrolled a total of 138 patients with DLBCL who were scheduled to undergo standard R-CHOP therapy (6 cycles of R-CHOP followed by two cycles of rituximab). PET/CT scans were performed in all patients at the time of diagnosis, after the first two chemotherapy cycles, and at the end of treatment. Those with progressive disease at interim PET/CT had no further scans, while those with positive scans at 2 cycles had a repeat scan after 4 cycles. No treatment decisions were made by the results of these scans unless progressive disease was seen. The primary end point was event-free survival at 2 years (2-year EFS), with events defined as disease progression, death, or initiation of non-protocol cancer treatment or radiotherapy. Secondary endpoint included two-year overall survival. Of the initial 138 patients, 129 completed the initial, 2-cycle, and end of treatment scans. At the conclusion of the trial, patients with PET-positive interim scans had significant decreased 2-year EFS compared to patients with PET-negative scans (48.2%; 95% CI: 33.1-58.4 vs. 74.2%; 95% CI: 60.3-83.8; p = 0.002). There was no difference in overall survival at 2 years for those with positive or negative results after 2 cycles (87.7% vs. 90.6%, p = 0.6).

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