Carbon ion radiotherapy for locally advanced prostate cancer with bladder invasion: A case series report
Abstract Background: The optimal management of clinical T4 (cT4) prostate cancer (PC) is still uncertain. At our institution, carbon ion radiotherapy (CIRT) with or without androgen-deprivation therapy (ADT) for nonmetastatic PC, including tumors invading the bladder, has been performed since 2010. Since carbon ion beams provide a sharp dose distribution with minimal penumbra and have biological advantages over photon radiotherapy, CIRT may provide a therapeutic benefit for PC with bladder invasion. Hence, we evaluated CIRT for locally advanced PC with bladder invasion in terms of the safety and efficacy.Methods: Between March 2010 and December 2016, a total of 1,337 patients with nonmetastatic PC received CIRT at a total dose of 57.6 Gy (RBE) in 16 fractions over 4 weeks at our institution. Among them, 7 patients who had locally advanced PC with bladder invasion were identified. Long-term ADT was also administered to these patients. Adverse events were graded according to the Common Terminology Criteria for Adverse Event (CTCAE) version 5.0.Results: At the conclusion of our study, all the patients with cT4 PC were alive with a median follow-up period of 78 months. Grade 2 acute urinary disorders were observed in only 1 patient. Regarding late toxicities, only 1 patient developed grade 2 hematuria and urinary urgency. There was no grade 3 or worse toxicity. Gastrointestinal toxicity was not observed. As for efficacy, 6 (85.7%) patients had no recurrence or metastasis. One patient had biochemical and local failures 42 and 45 months after CIRT, respectively. However, the recurrent disease has been well controlled by salvage ADT.Conclusions: Seven patients with locally advanced PC invading the bladder were treated with CIRT. There was no severe toxicity, and only 1 patient had clinical relapse, suggesting a positive safety profile for CIRT. Therefore, there is scope for future research among larger cohorts to ascertain the safety and effectiveness of CIRT for PC with bladder invasion.