Oral 5-aminolevulinic Acid for Patients With Localized Prostate Cancer Undergoing Low-dose-rate Brachytherapy: AMBER Trial.

Background/aim: Radiotherapy is one of the most frequently used options for prostate cancer (PCa). However, adverse effects related to irradiation of surrounding normal organs are significant clinical concerns. Specifically, genitourinary toxicity can dramatically reduce the quality of life. This clinical trial investigated the efficacy of oral 5-aminolevulinic acid phosphate combined with sodium ferrous citrate (ALA-SFC) in patients treated with low-dose-rate brachytherapy (LDR-BT) using an iodine-125 seed source.

Patients and methods: The AMBER study was a prospective single-center trial involving patients with localized PCa who underwent LDR-BT without external-beam radiotherapy (jRCTs051190077). Fifty patients were included and instructed to take capsules of ALA-SFC twice a day (200 mg phosphate salt and 229.42 mg per day) for six months from the day of seed implantation (prescribed radiation dose of 160 Gy). Patient data were collected before implantation, during ALA-SFC treatment, and at 1, 3, 6, 9, and 12 months post-LDR-BT. The primary endpoint of this trial was urinary frequency at three months. Other patient-reported outcomes, investigator-reported adverse events, and oncological outcomes were secondary endpoints.

Results: Of 50 enrolled cases (45 in the per-protocol analysis, 49 in the safety analysis), urinary frequency and its increase from baseline did not differ from 141 historical controls at any time point, including at three months post-LDR-BT. Propensity score matched analysis confirmed no time-course differences in frequency, volume, or urinary symptom scores between groups. Biochemical failure-free and metastasis-free survival also remained similar.

Conclusion: Oral supplementation of ALA-SFC to LDR-BT did not alleviate radiation-induced toxicity or improve oncological outcomes.