CIRT Causes Temporary Urinary Decline, With Recovery by 3 Months
CIRT led to a short-term drop in urinary function in prostate cancer patients, with recovery starting at 3 months and continuing for 5 years.
Conceptual image for viral etiology of prostate cancer: © Dr_Microbe - stock.adobe.com
Research from a prospective study, presented at the 2025 ASCO Genitourinary Cancers Symposium and published in Radiation Oncology in 2024, found that carbon ion radiation therapy (CIRT) caused a temporary decline in urinary function in patients with prostate cancer, with recovery beginning at 3 months and continuing for 5 years.1, 2
“Following CIRT treatment, the voiding parameters in patients [with prostate cancer] significantly deteriorated immediately,” first author Yoshiyuki Miyazawa MD, PhD and colleagues concluded in a poster presentation of the study’s fundings at the symposium. “However, after 3 months, they returned to their pre-treatment levels and remained stable for 5 years. Without [androgen deprivation therapy (ADT)], the prostate volume reduced -20% after 2 years and remained reduced for 5 years.”
Miyazawa is an assistant professor with the Department of Urology, Gunma University Graduate School of Medicine, in Gunma, Japan.
Researchers enrolled 309 patients with localized prostate cancer who were classified as T1-T3N0M0 onto the trial. The median age of eligible patients was 66.5 years (range, 48-80) who underwent CIRT between 2010 and 2013. Of these eligible participants, patients with T1c-T2bN0M0, an initial PSA of less than 10 ng/ml, and a Gleason score of 6 or less were classified as the low-risk group (n = 16), with none receiving ADT. Patients with at least T3, an initial PSA of 20 ng/ml or greater, or a Gleason Score of at least 8 were categorized as the high-risk group (n = 146), with 6 months of neoadjuvant ADT and 1.5 years of adjuvant ADT. Any patients falling outside of these parameters were classified into the intermediate-risk group (n = 142), with 6 months of neoadjuvant ADT, according to the poster presentation.
CIRT, researchers explained, was administered at 57.6 Gy (RBE) in 16 fractions, with pre- and post-treatment evaluations including uroflowmetry (UFM), transrectal ultrasound, and residual urine tests performed and data collected over a 5-year period.
Patients’ maximum flow rate was found to significantly worsen at 1-month post-treatment compared with pre-treatment levels, but returned to pre-treatment levels by 3 months post-treatment. Researchers reported flow rates of 20.0 ± 10.6 ml/s pre-treatment, 14.5 ± 7.3 ml/s, post-treatment, and 18.7 ± 8.9 ml/s 3 months after treatment. The mean flow rate was found to have significantly worsened 1 month after treatment but was shown to return to pre-treatment levels by 3 months later, and was maintained for up to 5 years, with rates of 8.3 ± 4.0 ml/s pre-treatment, 6.0 ± 3.2 ml/s post-treatment, 7.7 ± 4.3 ml/s at 3 months, and 10.5 ± 4.9 ml/s at 3 years.
Prostate volume in cases without ADT was found to significantly decrease 1 year after treatment and reached approximately 80% of initial volume by 3 years and remained stable up to 5 years, researchers reported in the poster, also noting that multivariate analysis identified T classification (T1 vs at least T2, P < .001) and prostate volume (P = .014) as significant predictive factors for late genitourinary tract complications.
The 5-year PSA biochemical non-recurrence rate was 92.7%, researchers noted in Radiation Oncology, explaining that results broken down by risk criteria were 91.7% for low-risk cases, 93.4% for intermediate-risk cases, and 92.0% for high-risk cases, while the overall survival rate during the follow-up period was 96.6%.
“The long-term prospective study conducted over five years has elucidated the changes in urinary function and prostate volume in patients with prostate cancer following CIRT. Based on these data, it was suggested that complications in CIRT patients might be predictable through pre-treatment evaluations,” Miyazawa and authors concluded in the abstract of the poster presentation.
