The prognosis of patients with prostate cancer receiving permanent seed implantation stratified by prostate volume: Should we be reluctant to treat with brachytherapy because of a very small prostate (<15 cc)?

•We study a relationship between prostate volume (PV) and prognosis in 6721 prostate cancer patients treated by permanent seed implantation (PI) who were recruited by the national Japanese prospective large cohort study (J-POPS).•We evaluated treatment outcomes (biochemical freedom from failure (bFFF), prostate cancer-specific mortality (PCSM), all-cause mortality (ACM)) and genitourinary (GU)/ gastrointestinal (GI) toxicity in the three PV categories:<15 cc, 15–20 cc and > 20 cc.•Our results showed no difference in treatment outcome and grade 2 toxicity in each PV group.•PI in small prostates (even < 15 cc) remains an effective treatment option.