Influence of transitioning of planning techniques in high-dose-rate brachytherapy monotherapy for clinically localized prostate cancer from two- to three-dimensional planning.

The purpose of this study was to examine the influence of transitioning treatment planning techniques in high-dose-rate interstitial brachytherapy monotherapy for localized prostate cancer.

We compared 113 patients treated with initial two-dimensional treatment planning (2D: 74% received 54 Gy/nine fractions) to 240 patients treated with three-dimensional planning (3D: 70 CT image-guided 3D [CT-3D]: 84% 45. 5 Gy/seven fractions and 170 MRI image-guided [MRI-3D]: 87% received 49 Gy/nine fractions).

The actuarial 5-year biochemical failure-free survival rates for 2D and 3D planning were 88.4% and 95.1% (p = 0.0285 between 2D and 3D) (89.4% in CT-3D and 97.5% in MRI-3D), respectively; the rates for 2D and 3D planning were not available and 100% in the low-risk group (100% and 100%), 97.7% and 94.5% (p = 0.7626) (85.1% and 100%) in the intermediate-risk group, and 82.5% and 94.4% (p = 0.0507) (93.8% and 94.7%) for the high-risk group. Late gastrointestinal (GI) toxicity Grade 1, Grade 2, and Grade 3 was found in 13%, 4%, and 1% in 2D, whereas 8%, 2%, and 0% in 3D group (p = 0.0699), respectively. 3D decreased GI toxicity Grade 2 ≤ than 2D (19% and 10%, p = 0.0169). Late genitourinary toxicity Grade 1, Grade 2, and Grade 3 was 21%, 12%, and 3% for 2D and 32%, 18%, and 3% for 3D, respectively (p = 0.0217).

The 3D technique has the potential to reduce GI toxicity and improve biochemical control rate compared to 2D planning, whereas 3D resulted in increased mild genitourinary toxicity.

Brachytherapy. 2019 Jun 19 [Epub ahead of print]

Hideya Yamazaki, Koji Masui, Gen Suzuki, Satoaki Nakamura, Ken Yoshida, Tadayuki Kotsuma, Eiichi Tanaka, Keisuke Otani, Yasuo Yoshioka, Kazuhiko Ogawa

Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan. Electronic address: ., Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan., Department of Radiation Oncology, National Hospital Organization Osaka National Hospital, Osaka, Osaka, Japan., Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.