Prostate Cancer Patient With Lymph-node Metastasis Treated Only With Methionine Restriction Has Stable Disease for Two Years Demonstrated With PET/CT and PSMA-PET Scanning and PSA Testing.

Metastatic prostate cancer is a recalcitrant disease. Our laboratory has previously treated prostate-cancer patients with methionine restriction effected by a low methionine diet and oral recombinant methioninase (o-rMETase), both alone and in combination with other agents. The present case is a 66-year-old patient who had a radical prostatectomy in 2019 with a Gleason score 3+3 and 3+4. The patient subsequently was treated with immunotherapy in 2021 and salvage proton-beam therapy in 2022, and subsequently treated only with o-rMETase and a low-methionine diet. The aim of the present study was to determine the long-term efficacy of methionine restriction on the patient's prostate cancer.

Starting in September 2022, the patient started methionine restriction with a low methionine-diet and o-rMETase, twice a day, after meals, at 250 units/dose. Since the start of methionine restriction, the patients' prostate-specific antigen (PSA) has remained stable, under 2 ng/ml. Positron emission tomography/computed tomography (PET/CT) and prostate specific membrane antigen (PSMA)-PET imaging indicated in September 2023 a right pelvic-side-wall metastatic lymph node that was stable when the PSMA-PET scan was repeated in March 2024, with the standardized uptake value (SUV) decreasing from 19.39 to 14.98. A very small possible metastatic external-iliac lymph node was detected in March 2024. Thus, the lymph-node metastases were stable and did not increase.

During the time the patient was on methionine restriction alone, effected by a low-methionine diet and o-rMETase, the metastatic prostate cancer did not progress. Further clinical studies of methionine restriction and metastatic prostate cancer are needed, including randomized clinical trials.

Cancer diagnosis & prognosis. 2025 Jan 03*** epublish ***

Sei Morinaga, Qinghong Han, Kohei Mizuta, Byung Mo Kang, Norio Yamamoto, Katsuhiro Hayashi, Hiroaki Kimura, Shinji Miwa, Kentaro Igarashi, Takashi Higuchi, Hiroyuki Tsuchiya, Satoru Demura, Robert M Hoffman

AntiCancer Inc., San Diego, CA, U.S.A., Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan.