Assessment of Clinicopathological Characteristics and Clinical Outcomes of Patients Who Developed Non-Muscle-Invasive Bladder Cancer After Radiotherapy for Prostate Cancer: A Retrospective Multicenter Study

Takuma Sato,^1,12 Takeshi Sano,² Hisanobu Adachi,^3,12 Yoshihiro Ikeda,^4,12 Jun Takemoto,^5,12 Shingo Myoen,^6,12 Koji Mitsuzuka,^7,12 Atsushi Kyan,^8,12 Hiroshi Aoki,^9,12 Satoru Tokuyama,^10,12 Hideo Saito,^11,12 Shinichi Yamashita,^1,12 Yoichi Arai,^1,12 Takashi Kobayashi² and Akihiro Ito^1,12

¹Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
²Department of Urology, Kyoto University Graduate School of Medicine, Kyoto, Japan
³Department of Urology, Miyagi Cancer Center, Natori, Miyagi, Japan
⁴Department of Urology, Osaki Citizen Hospital, Osaki, Miyagi, Japan
⁵Department of Urology, Kesennuma City Hospital, Kesennuma, Miyagi, Japan
⁶Department of Urology, Hachinohe City Hospital, Hachinohe, Aomori, Japan
⁷Department of Urology, Japan Community Health Care Organization Sendai Hospital, Sendai, Miyagi, Japan
⁸Department of Urology, Shirakawa Kosei General Hospital, Shirakawa, Fukushima, Japan
⁹Department of Urology, Sendai Red Cross Hospital, Sendai, Miyagi, Japan
¹⁰Department of Urology, Iwaki City Medical Center, Iwaki, Fukushima, Japan
¹¹Department of Urology, National Hospital Organization Sendai Medical Center, Sendai, Miyagi, Japan
¹²Tohoku Urological Evidence-Based Medicine Study Group, Sendai, Miyagi, Japan

Radiotherapy for prostate cancer may induce the development of secondary bladder cancer. However, the clinicopathological characteristics and clinical outcomes of this entity have not been fully elucidated. Therefore, this study compared the clinicopathological characteristics and clinical outcomes of patients who developed secondary bladder cancer after radiotherapy with those of controls. The medical records of patients newly diagnosed with non-muscle-invasive bladder cancer were retrospectively analyzed. Newly diagnosed non-muscle-invasive bladder cancer that developed ≥ 5 years after radiotherapy for prostate cancer was defined as secondary non-muscle-invasive bladder cancer during this study. Patients with newly diagnosed non-muscle-invasive bladder cancer who did not meet this criterion were included in the control group. The clinicopathological characteristics and recurrence-free survival rates of patients with secondary non-muscle-invasive bladder cancer were compared with those of controls. A total of 26 (2.6%) of the 1,019 patients from the Tohoku Urological Evidence-Based Medicine Study Group and Kyoto University Hospital who were screened met this criterion for secondary non-muscle-invasive bladder cancer. Clinicopathological characteristics were similar between the secondary non-muscle-invasive bladder cancer and control groups, except for sex and age. Propensity score-matched analysis revealed that the recurrence-free survival rates of patients with secondary non-muscle-invasive bladder cancer may not be poorer than those of control patients. Tumor characteristics and recurrence-free survival rates of patients with secondary non-muscle invasive bladder cancer were comparable with those of controls. Further large-scale studies should be conducted to clarify the tumor characteristics and clinical outcomes of these patients after radiotherapy.

Key words —— clinical outcome; non-muscle-invasive bladder cancer; prostate cancer; radiation-induced malignancy; secondary bladder cancer

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Tohoku J. Exp. Med., 2025 May, 266(1), 37-46.

Correspondence: Takuma Sato, Department of Urology, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.

e-mail: takuma.sato.a4@tohoku.ac.jp