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FDG-PET/CT response and outcome of neoadjuvant immunotherapy for clinical stage III melanoma.

2021; Lippincott Williams & Wilkins; Volume: 39; Issue: 15_suppl Linguagem: Inglês

10.1200/jco.2021.39.15_suppl.e21569

1527-7755

Milton Barros, Caio Dabbous de Liz, Marcos Rezende Teixeira, José Augusto Rinck, Monique Celeste Tavares, Daniel de la Iglesia, João Paulo da Silveira Nogueira Lima, Matheus Lobo, Clóvis A. Lopes Pinto, Marcelo Cavicchioli, Eduardo Nóbrega Pereira Lima, Eduardo Bertolli, André Sapata Molina, Kenneth J. Gollob, Amanda Braga Figueiredo, João Pedreira Duprat Neto,

Cancer Genomics and Diagnostics

e21569 Background: Neoadjuvant immunotherapy with nivolumab 3mg/kg and ipilimumab 1mg/kg for two cycles(N3+I1) or anti-PD1 for 3-8 weeks for clinical stage III melanoma have shown rates of pCR/near-pCR about 60% or 30%, respectively. The prognosis of this group seems to be excellent so far. On the other hand, patients classified as pathological non-response have a worse outcome and early identification of this group may allow us to tailor treatment before surgery. Methods: We conducted a retrospective analysis of patients with clinical stage III melanoma treated with neoadjuvant immune checkpoint blockade who did baseline and pre-operative FDG-PET/CT. The total number of FGD avid lesions and the percentual difference between the maximum SUV per lesion was calculated. The pathological results were correlated to FGD-PET/CT findings. Results: Between January 2019 and January 2021, nine patients with clinical stage III melanoma were identified. Six patients received Nivolumab 3m/kg and Ipilimumab 1mg/kg for two cycles and 3 received anti-PD1 for 60 days. Baseline FDG-PET/CT showed just one avid lesion in 7 patients, 2 avid lesions in one patient and 3 avid lesions in one patient. All known lesions identified by CT scan were also captured by FGD-PET/CT. After the neoadjuvant treatment, 4 patients achieved pCR/near-pCR. All of them were treated with N3+I1. Two of them had metabolic complete response (including the one with 3 PET- avid lesions) and 2 had reduction on FDG concentration (-31% and – 76%). Three patients had absence of response: 100% of viable tumor cells (VTC), all of them with increase in FDG concentration (+12% to + 307%) and appearance of a new lesion in one case. Two out of them were treated with anti-PD1. One patient had partial response (40% of VTC). Interestingly, this patient developed sarcoidosis-like reaction with increase of SUV in the index lesion (+68%) and appearance of mediastinal lymph-nodes. One patient, who had two lesions, presented a mixed response: complete response in one and 90% of VTC in the other. FDG-PET/CT was able to detect both responses (metabolic complete response and increase of FGD concentration of 17%, respectively). Conclusions: Reduction in FGD-PET/CT concentration with no appearance of new lesion(s) is associated with significant pathological response. An increase of SUV or appearance of new lesion(s) should be carefully interpreted.