Comparison of FDG-PET/CT and CT for evaluation of tumor response to nivolumab plus ipilimumab combination therapy and prognosis prediction in patients with unresectable malignant pleural mesothelioma

// Kazuhiro Kitajima 1 , Kozo Kuribayashi 2 , Toshiyuki Minami 2 , Hiroyuki Yokoyama 1 , Akifumi Nakamura 3 , Masaki Hashimoto 3 , Takashi Kijima 2 , Seiki Hasegawa 3 , Hayato Kaida 4 and Koichiro Yamakado 1 1 Department of Radiology, Hyogo Medical University, Nishinomiya, Hyogo, Japan 2 Division of Respiratory Medicine, Department of Internal Medicine, Hyogo Medical University, Nishinomiya, Hyogo, Japan 3 Department of Thoracic Surgery, Hyogo Medical University, Nishinomiya, Hyogo, Japan 4 Department of Radiology, Kindai University Faculty of Medicine, Osaka, Japan Correspondence to: Kazuhiro Kitajima, email: kazu10041976@yahoo.co.jp , ORCID: orcid.org/0000-0002-9553-996X Keywords: mesothelioma; immunotherapy; FDG (fluorodeoxyglucose); PET-CT (positron emission tomography-computed tomography); immunotherapy-modified PERCIST (positron emission tomography response criteria in solid tumors) Received: March 09, 2024 Accepted: June 05, 2024 Published: June 20, 2024 Copyright: © 2024 Kitajima et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ABSTRACT Objectives: Results for malignant pleural mesothelioma (MPM) patients following first-line treatment with nivolumab plus ipilimumab obtained with immunotherapy-modified PERCIST (imPERCIST), shown by [ 18 F]fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), and modified RECIST (mRECIST), shown by CT, were compared for response evaluation and prognosis prediction. Results: imPERCIST indicated nine progressive metabolic disease (PMD), eight stable metabolic disease (SMD), four partial metabolic response (PMR), and five complete metabolic response (CMR) cases. mRECIST showed nine with progressive disease (PD), nine stable disease (SD), seven partial response (PR), and one complete response (CR). Although high concordance was noted (κ = 0.827), imPERCIST correctly judged a greater percentage with CMR (15.4%). Following a median 10.0 months, 15 patients showed progression and eight died from MPM. With both, progression-free survival (PFS) and overall survival (OS) were significantly longer in patients without progression (CMR/PMR/SMD, CR/PR/SD, respectively) as compared to PMD/PD patients (imPERCIST p < 0.0001 and p = 0.015, respectively; mRECIST p < 0.0001 and p = 0.015, respectively). Methods: Twenty-six patients (23 males, 3 females; median 73.5 years) with histologically proven MPM and no curative surgery received nivolumab plus ipilimumab combination therapy. FDG-PET/CT and diagnostic CT scanning at the baseline, and after 2–4 cycles (2 in three, 3 in 17, 4 in six patients) were performed. Therapeutic response findings evaluated using imPERCIST and mRECIST were compared. PFS and OS analyses were done using log-rank and Cox methods. Conclusion: For unresectable MPM patient examinations, FDG-PET and CT provide accurate findings for evaluating tumor response and also prognosis prediction following first-line nivolumab plus ipilimumab immunotherapy (approximately three cycles).