Prognostic value of PET/CT characteristics and combined IPI in follicular lymphoma and diffuse large B-cell lymphoma

Objective The international prognostic index (IPI) has limited ability to distinguish risk levels in patients with follicular lymphoma and diffuse large B-cell lymphoma (FL/DLBCL). This study aims to investigate the diffe-rences in imaging features between FL/DLBCL and DLBCL, and to integrate baseline PET/CT characteristics with clinical parameters to improve the ability of IPI to predict prognosis in FL/DLBCL patients. Methods A total of 65 patients with pathologically confirmed FL/DLBCL treated at our hospital between January 2015 and January 2022 were collected (follow-up duration: 2.4-113.0 months), and a 1∶1 matched group of patients diagnosed with DLBCL during the same period was selected (follow-up duration: 2.9-91.6 months). PET/CT features and survival differences between the two groups were compared. Cox regression analysis was used to identify independent prognostic factors for progression-free survival (PFS) in FL/DLBCL patients, which were incorporated into a nomogram. The predictive value of the model was evalua-ted using the concordance index (C-index) and receiver operating characteristic (ROC) curves. Results Compared with DLBCL, FL/DLBCL patients had a greater maxium distance between two lesions (Dmax) on PET/CT images (55.07 vs. 33.82, P=0.031) and a greater number of total lesions throughout the body (7 vs. 4, P=0.002). The IPI could only distinguish between low-risk and non-low-risk FL/DLBCL groups (P=0.010), but failed to identify patients at high risk of progression (P=0.743). Integrated analysis of PET/CT imaging features and clinical parameters showed that Dmax (HR=3.151, 95%CI: 1.253-7.922, P=0.015) and IPI (HR=3.285, 95%CI: 1.208-8.932, P=0.020) were independent prognostic factors for PFS in FL/DLBCL patients. On this basis, a nomogram was constructed, with a C-index of 0.701. All three global tests (likelihood ratio test, Wald test, and score test) showed high statistical significance (P<0.001). Conclusion FL/DLBCL exhibits more disseminated characteristics on PET/CT images compared to DLBCL. Additionally, Dmax is a highly promising para-meter for prognostic evaluation in FL/DLBCL, and the nomogram constructed based on Dmax and IPI demonstrates excellent discriminatory ability and predictive accuracy in predicting FL/DLBCL survival outcomes.