17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Abstract

Introduction and Aim: Recently, in an ancillary study of FOLL12 trial (NCT02063685), total Metabolic Tumor Volume (tMTV) assessed before treatment has been demonstrated to be an independent predictor of PFS in patients receiving frontline immune chemotherapy (1). During the segmentation procedure, it has been observed that frequently spleen MTV (sMTV) heavily influenced the tMTV value, particularly in case of diffuse spleen uptake included in tMTV calculation. High tMTV could be a negative prognostic factor as it represents the tumor burden. On this basis, the aim of the current study was to evaluate the effect of the sMTV defined on baseline PET on tMTV calculation and its impact on outcome, particularly 5y-PFS (Progression Free Survival), in follicular lymphoma patients. Methods and Results: Overall, 690 patients with baseline PET were included in the analysis, 48% were older than 60 years, 89% had stage III-IV disease and 40% had a high-risk FLIPI-2 score. Overall, the 5y-PFS was 79% (95% CI, 76%–82%). Among 690 patients 469 (67.9%) did not have spleen involvement while 128 (18.5%) and 93 (13.4%) showed focal and diffuse spleen involvement, respectively. The 5y-PFS (95% CI) according the spleen status was 67% (62–72), 58% (48–67) and 61% (49–61) in patients without, with focal and with diffuse spleen involvement, respectively (p not significant). MTV calculation was performed with a threshold of 41% for segmentation. In the whole population of 690 patients, the tMTV threshold to categorized low and high tumor burden was 224 and 194 ml with and without sMTV, respectively. Assuming 200 ml as a tMTV threshold, only 16/693 pts (2.3%) changed from low to high tumor burden when the sMTV was included in the tMTV. Including sMTV in tMTV, with a threshold of 200 ml, the 5y-PFS in patients with low and high tMTV was 73% (95% CI: 67–78) and 58% (95% CI: 53–64), respectively, with a HR of 1.83 (p < 0.001). Excluding sMTV from tMTV, the 5y-PFS in patients with low and high tMTV was 72% (95% CI: 67–77) and 58% (95% CI: 52–64) with a HR of 1.80 (p < 0.001). In the two groups, HRs values for tMTV >200 ml showed negligible difference, independently from sMTV inclusion. Conclusion: These preliminary data of the FOLL12 trial showed that tMTV correlated with outcome in terms of PFS; on the contrary the metabolic spleen status defined in the baseline PET do not seem to show any prognostic added value, neither in case of focal nor in case of diffuse uptake. Finally, the inclusion/exclusion of the sMTV into the tMTV did not significantly change either the risk classification of the patients or the outcome in terms of PFS. Larger patients population are needed to confirm these data.