# Prognostic Value of Very Early Interim FDG PET/CT After Single Cycle of Chemotherapy for 10-Year Survival in Diffuse Large B-Cell Lymphoma

## TL;DR

This study found that FDG PET/CT scans after one cycle of chemotherapy do not predict long-term survival in diffuse large B-cell lymphoma, but end-of-therapy scans are more useful for predicting outcomes.

## Contribution

The study demonstrates that early FDG PET/CT scans are not reliable for predicting long-term survival, while end-of-therapy scans provide more accurate prognostic information.

## Key findings

- FDG PET/CT after one cycle of chemotherapy did not correlate with 10-year survival outcomes.
- End-of-therapy FDG PET/CT results were independently predictive of overall and progression-free survival.
- Tumor regression early in treatment was less clinically relevant than the presence of viable tumor at the end of therapy.

## Abstract

Through FDG PET/CT obtained at four different time points, lymphoma lesions were followed during first-line therapy and FDG PET/CT had prognostic value for long-term survival at 10 years. The rate of tumor regression very early into first-line chemotherapy was not as relevant as the presence of viable tumor on FDG PET/CT at the end of therapy for predicting long-term outcomes.

Background/Objectives This study aimed to evaluate whether very early interim 18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) after a single cycle of first-line chemotherapy predicts long-term survival outcome in patients with diffuse large B-cell lymphoma (DLBCL). Methods A total of 51 patients (31 males and 20 females; mean age 55 years) had four FDG PET/CT studies, at baseline and after one, three, and six cycles of chemotherapy (PET0, PET1, PET3, and PET6). Visually and quantitatively assessed PET parameters were analyzed for associations with long-term survival. Results The estimated 10-year progression-free survival (PFS) and overall survival (OS) was 48% and 61%, respectively. During a median follow-up of 63 months (range 9–134), 17 patients (33%) exhibited disease progression and 15 (29%) died. On PET1, all but one showed decreased FDG uptake, and all showed decreased metabolic tumor volume. None of the PET1 or PET3 parameters were associated with survival. The PET6 parameters retained independent predictive value for OS after adjustment for the International Prognostic Index. Negative PET6 was associated with longer PFS (mean 99 vs. 50 mo, p = 0.04) and OS (mean 107 vs. 57 mo, p = 0.02). Con-clusions The FDG PET/CT parameters obtained after a single cycle of chemotherapy were not associated with long-term survival in DLBCL, while negative end-of-therapy FDG PET/CT was associated with longer PFS and OS. Tumor regression very early into first-line chemotherapy was not as clinically relevant as the presence of viable tumor on FDG PET/CT at the end of therapy for predicting long-term outcomes.