Evaluation of invasiveness, staging, and correlation with interim therapeutic response based on baseline ¹⁸F-FDG PET/CT SUVmax in patients with follicular lymphoma

Objective: To study the value of baseline ¹⁸F-FDG PET/CT maximum standardized uptake value (SUVmax) in evaluating the invasiveness, staging, and correlation between baseline SUVmax and the interim therapeutic response in patients with follicular lymphoma (FL). Methods: Forty-eight FL patients who underwent baseline ¹⁸F-FDG PET/CT scan before chemotherapy, with the combination regimen of rituximab, cyclophosphamide, hydroxydaunomycin, oncovin and prednisolone (R-CHOP), were studied. Eighteen patients underwent ¹⁸F-FDG PET/CT scan again after 3 cycles of R-CHOP treatment to evaluate the interim therapeutic response. Two-sample t-test and Mann-Whitney U test were used to evaluate the differences in the baseline SUVmax between the following: low-grade group (pathological grades 1-2 and 3a) and high-grade group (pathological grade not lower than grade 3b); non-disseminated stage group and disseminated stage group; and complete response (CR) group and non-CR group. Spearman's rank correlation coefficient was used to estimate the relation between the baseline SUVmax and the Ann Arbor staging. Results: The baseline SUVmax was significantly different between the low-and high-grade groups (6.23 ± 4.68 vs. 13.20 ± 6.68, t = 3.919, P < 0.001), and the area under the receiver operating characteristic curve (AUC) was 0.835. No significant relation was found between the baseline SUVmax and the Ann Arbor staging (r = 0.242, P = 0.098). The baseline SUVmax of the non-disseminated stage group was significantly lower than that of the disseminated stage group among low-grade FL patients (median: 1.20 vs. 7.85, U = 24.000, P < 0.001), and the AUC was 0.905. Tbe baseline SUVmax of the CR group was significantly lower than that of the non-CR group after the interim R-CHOP therapy (5.16 ± 3.05 vs. 10.99 ± 7.45, t = 2.172, P = 0.045). Conclusions: The baseline ¹⁸F-FDG PET/CT SUVmax is effective in evaluating invasiveness and staging and is related to the interim therapeutic response among FL patients. Moreover, the baseline SUVmax is related to the disease dissemination among low-grade FL patients. (authors)