In diffuse large B-cell lymphoma (DLBCL), the response to first-line immunochemotherapy remains somewhat unpredictable. Interim [ 18F] fluorodeoxyglucose-positron emission tomography (FDG-PET) (PET-int) analysis could be an important tool in the prompt shift to intensified regimens. We prospectively evaluated the effectiveness of PET-int carried out at mid-treatment with standard immunochemotherapy in predicting relapse in a series of 85 consecutive patients with DLBCL. PET-int results were dichotomized as positive or negative using the recently validated five-point scale scoring system. This examination was also compared with interim computed tomography (CT-int) and final PET (PET-fin). End-points were: complete remission (CR), positive predictive value (PPV) of refractoriness and relapse, negative predictive value (NPV), overall survival (OS) and progression-free survival (PFS). Observation time was fixed to 24 months unless preceded by a DLBCL-related event. The PPV of PET-int was 58% and the NPV was 77%. CR was correlated with both PET-int and CT-int (p <0.0001), but in multivariate analysis only CT-int was correlated with CR (p = 0.002). CT-int and PET-fin were predictive of both OS and PFS, whereas PET-int was predictive only of OS (p = 0.013). In Cox regression only PET-fin was predictive for both OS (p = 0.004) and PFS (p = 0.005). PET-int was unable to discriminate those chemosensitive patients who would later relapse. We therefore believe that the use of this expensive radioactive tool is not justified as an interim analysis.
ASJC Scopus subject areas
- Cancer Research