Analysis of urinary function and prostate volume changes in localized prostate cancer patients treated with carbon-ion radiotherapy; a prospective study

Abstract Background The potential of carbon ion radiation therapy (CIRT) as a curative treatment for localized prostate cancer (PCa) has garnered attention due to its characteristic dose distribution. We prospectively collected and analyzed over five years to investigate the outcomes of localized PCa treated with CIRT at our institution. Patients and methods The study included patients with histologically confirmed prostate adenocarcinoma. CIRT treatment was administered at a total dose of 57.6 Gy (RBE) in 16 fractions over four weeks. Uroflowmetry (UFM) and residual urine measurements were performed at various time points: before CIRT treatment, one month after starting CIRT, three months after treatment, and annually for five years starting from 1 year after the completion of CIRT. Prostate volume was measured using transrectal ultrasonography (TRUS). Results A total of 304 prostate cancer patients were analyzed. UFM parameters were significantly worsened immediately after the treatment. However, they recovered to pretreatment levels after three months and remained stable until five years post-treatment. Notably, Average flow rate showed significant improvement after three years of treatment compared to before the treatment. Prostate volume decreased to 80% of baseline in patients treated with CIRT alone and to 60–70% of baseline in those receiving combined CIRT and either short- or long-term ADT. The logistic-binomial analysis identified post-voiding residual urine volume (PVR) as a significant factor for predicting adverse events in the acute phase. Conclusions Following CIRT treatment, the voiding parameters in PCa patients significantly deteriorated immediately. However, after three months, they returned to their pre-treatment levels and remained stable for five years.