Tomoki Tanaka1, Atsunori Yorozu2, Shinya Sutani2, Yasuto Yagi3, Toru Nishiyama3, Yutaka Shiraishi4, Toshio Ohashi4, Takashi Hanada4, Shiro Saito3, Kazuhito Toya5, Naoyuki Shigematsu4. 1. Department of Radiology, Tokyo Medical Center, National Hospital Organization, Meguro-ku, Tokyo, Japan; Department of Radiology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan. Electronic address: tanakatomo@rad.med.keio.ac.jp. 2. Department of Radiology, Tokyo Medical Center, National Hospital Organization, Meguro-ku, Tokyo, Japan. 3. Department of Urology, Tokyo Medical Center, National Hospital Organization, Meguro-ku, Tokyo, Japan. 4. Department of Radiology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan. 5. Department of Radiology, Tokyo Medical Center, National Hospital Organization, Meguro-ku, Tokyo, Japan; Department of Radiology, International University of Health and Welfare Mita Hospital, Minato-ku, Tokyo, Japan.
Abstract
PURPOSE: We analyzed factors associated with rectal toxicity after iodine-125 prostate brachytherapy (BT) with or without external beam radiation therapy (EBRT). METHODS AND MATERIALS: In total, 2216 prostate cancer patients underwent iodine-125 BT with or without EBRT between 2003 and 2013. The median followup was 6.9 years. Cox proportional hazards modeling was used for univariate and multivariate analyses to assess clinical and dosimetric factors associated with rectal toxicity. Dosimetric parameters from 1 day after implantation (Day 1) and 1 month after implantation (Day 30) were included in the analyses. RESULTS: The 7-year cumulative incidence of Grade 2 or higher rectal toxicity was 5.7% in all patients. The multivariate analysis revealed that antiplatelet or anticoagulant therapy, neoadjuvant androgen deprivation therapy, treatment modality, Day 1 rectal volume receiving 100% of the prescribed dose (RV100), and the Day 30 minimal percent of the prescribed dose delivered to 30% of the rectum (RD30) were associated with rectal toxicity. Day 1 RV100 was a common predictor in both BT-alone and the BT + EBRT groups. The 5-year cumulative incidence of Grade 2 or higher rectal toxicity was 12.6%, 5.9%, and 1.7% for BT + 3-dimensional conformal radiation therapy, BT + intensity-modulated radiation therapy, and the BT-alone groups, respectively (p < 0.001). CONCLUSIONS: Rectal dosimetric parameters in BT were associated with late rectal toxicity. Although the risk of rectal toxicity was higher when EBRT was combined with BT, with proper and achievable rectal dose constraints intensity-modulated radiation therapy yielded less toxicity than 3-dimensional conformal radiation therapy.
PURPOSE: We analyzed factors associated with rectal toxicity after iodine-125 prostate brachytherapy (BT) with or without external beam radiation therapy (EBRT). METHODS AND MATERIALS: In total, 2216 prostate cancerpatients underwent iodine-125 BT with or without EBRT between 2003 and 2013. The median followup was 6.9 years. Cox proportional hazards modeling was used for univariate and multivariate analyses to assess clinical and dosimetric factors associated with rectal toxicity. Dosimetric parameters from 1 day after implantation (Day 1) and 1 month after implantation (Day 30) were included in the analyses. RESULTS: The 7-year cumulative incidence of Grade 2 or higher rectal toxicity was 5.7% in all patients. The multivariate analysis revealed that antiplatelet or anticoagulant therapy, neoadjuvant androgen deprivation therapy, treatment modality, Day 1 rectal volume receiving 100% of the prescribed dose (RV100), and the Day 30 minimal percent of the prescribed dose delivered to 30% of the rectum (RD30) were associated with rectal toxicity. Day 1 RV100 was a common predictor in both BT-alone and the BT + EBRT groups. The 5-year cumulative incidence of Grade 2 or higher rectal toxicity was 12.6%, 5.9%, and 1.7% for BT + 3-dimensional conformal radiation therapy, BT + intensity-modulated radiation therapy, and the BT-alone groups, respectively (p < 0.001). CONCLUSIONS: Rectal dosimetric parameters in BT were associated with late rectal toxicity. Although the risk of rectal toxicity was higher when EBRT was combined with BT, with proper and achievable rectal dose constraints intensity-modulated radiation therapy yielded less toxicity than 3-dimensional conformal radiation therapy.