Significance of increased 18F-FDG uptake in determining pathological status in post-chemotherapy lymphoma cases involving head-neck region on PET-CT

Abstract

BackgroundCurrently, all follow-up cases of lymphoma showing fluorodeoxyglucose (FDG) avid uptake on positron emission tomography/computed tomography (PET-CT) in head-neck region undergo biopsy for tissue confirmation of diagnosis. There are no consensus or practice guidelines in literature pertaining, whether to biopsy all such FDG avid lesions post-chemotherapy. Hence, this study was conducted to determine the significance of PET-CT (SUVmax 5.0 or above) in determining remission or pathological status in these patients. MethodsA retrospective cohort analysis conducted between July 2019 and May 2023 at our institute of 40 follow-up cases of lymphoma post-chemotherapy (Group A) showing FDG Uptake with SUVmax 5.0 or above on PET-CT in Waldeyer's Ring (WR) or neck, and 40 non- lymphoma cases (Group B) showing FDG Uptake with similar SUVmax in WR or neck. All cases in group A underwent tonsillectomy and results of histopathology were correlated with PET-CT findings. All cases in group B underwent thorough clinical correlation with respect to PET-CT findings. A Receiver Operating Characteristic (ROC) curve for SUVmax was plotted to statistically analyse this data. ResultsStatistical analysis of our observations by plotting a ROC curve for SUVmax revealed a sensitivity of 90% with 10% specificity and an insignificant p-value of 0.733. ConclusionWe propose that unnecessary biopsy in all cases with FDG avid uptake must not be encouraged unless accompanied by a suspicious holistic clinical picture of asymmetry, significant lymph node involvement with FDG avid uptake and counterpart finding on CT. A tissue confirmation in all such cases may result in unnecessary risk and increase the cost of therapy.