Absolute number of new lesions on 18F-FDG PET/CT is more predictive of clinical response than SUV changes in metastatic melanoma patients receiving ipilimumab

Abstract

Our results show that a cut-off of four newly emerged F-FDG-avid lesions on posttherapy PET/CT gives a reliable indication of treatment failure in patients under ipilimumab treatment. Moreover, the functional size of the new lesions plays an important role in predicting the clinical response. Validation of these results in larger cohorts of patients is warranted.

FDG PET/CT for assessing tumour response to immunotherapy

“…CB also appears to be the main goal for the criteria recently proposed by the group from Heidelberg for FDG PET evaluation of response to immunotherapy in patients with melanoma [24, 25]. The PERCIMT (PET Response Evaluation Criteria for Immunotherapy) classification takes into consideration the observed relevance of the absolute number of new lesions on FDG PET scan and its more robust predictive role compared to pure SUV changes during the course of treatment with ipilimumab.…”

“…Another recent study prospectively enrolled 41 patients with metastatic melanoma treated with ipilimumab [24] and evaluated at baseline and 3 months later. Changes in SUVmax and SUVmean during the course of immunotherapy were not correlated with clinical response ( t test; p  = 0.06 and 0.05, respectively), whereas the number of new lesions was able to define disease progression (Tables 1 and 2), improving the identification of patients who will show CB (Wilcoxon test, p  < 0.0001).…”

“…In patients with apparent disease progression, the number and location of new lesions should be reported, excluding pathological foci in organs deemed to be due to the immune infiltrate. Indeed, a recent study suggested that the appearance of four or more new lesions of less than 1 cm in functional diameter or three or more new lesions of more than 1 cm in functional diameter is likely to be due to a real progression rather than pseudoprogression [24] (Table 2). Figures 1 and 2 show imaging in example patients with hyperprogression and pseudoprogression identified on FDG PET.…”

Evaluating response to immunotherapy with 18F-FDG PET/CT: where do we stand?

“…When it comes to 18 F-FDG PET/CT for therapy monitoring, the nuclear medicine community has been very active in the last decade, coming up with various response criteria [6,7] including the PERCIMT (PET Response Evaluation Criteria for Immunotherapy) [9], PECRIT (PET/CT Criteria for Early Prediction of Response to Immune Checkpoint Inhibitor Therapy) [10], iPERCIST [11], or other PERCIST (PET Response Criteria in Solid Tumors)-adapted criteria [12]. A good example is represented by imPERCIST5 [13], developed by the Memorial Sloan-Kettering Cancer Center group in patients receiving ipilimumab.…”

Metastatic melanoma: can FDG-PET predict success of anti-PD-1 therapy and help determine when it can be discontinued?

“…In one study, neither of RECIST 1.1, immune-related response, PERCIST, or EORTC criteria demonstrated sufficient accuracy [17]. 18F-FDG PET/CT offered better accuracy at 4 months from the start of treatment, and with the use of some modified response criteria [18][19][20].…”