Sasaki Naomi, Yamazaki Hideya, Shimizu Daisuke, Suzuki Gen, Masui Koji, Nakamura Satoaki, Okabe Haruumi, Nishikawa Tatsuyuki, Yoshida Ken
Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
Anticancer Res. 2018 Jan;38(1):385-391. doi: 10.21873/anticanres.12234.
BACKGROUND/AIM: We experienced an unexpected high incidence of gastrointestinal (GI) toxicity in patients undergoing image-guided intensity-modulated radiotherapy (IG-IMRT) using helical tomotherapy in our initial 2.2 Gy/fraction schedule for prostate cancer; hence, a dose-reduction trial from 2.2 Gy to 2 Gy/fraction was conducted using modified planning target volume (PTV) contouring.
We compared 130 patients treated using 2.2 Gy/fraction (Group A) and 144 treated using the 2 Gy/fraction (Group B) with modified PTV (excluding rectal volume) with a median follow-up period of 62 months. Prescribed dose was 72.6-74.8 Gy in 33-34 fractions (Group A) and 72-74 Gy in 36-37 fractions (Group B).
Patients in Group B had a reduced rectal and bladder V10-V70 and were irradiated at the maximal dose. Their cumulative incidence of grade ≤2 GI toxicity at 5 years improved from 10.1% [95% confidence interval (CI), 4.9-15.3%] to 1.4% (0-3.3%). Grade 2≤ urinary toxicity also decreased from 5.5% (1.5-9.4%) in Group A to 1.4% (0-3.3%, p=0.0167) in Group B. The biochemical failure-free 5-year survival rate was 89.1% (95%CI=83.6-95.4%) and 87.5% (82.0-92.9%, p=0.75) in groups A and B, respectively.
The reduced dose fraction schedule decreased the incidence of late GI toxicity without compromising prostate-specific antigen control. Careful target volume definition and fraction size are important even for IG-IMRT.
背景/目的：在我们最初采用螺旋断层放疗进行图像引导调强放疗（IG-IMRT）治疗前列腺癌的2.2 Gy/分次方案中，我们发现胃肠道（GI）毒性的发生率意外地高；因此，我们采用改良的计划靶区（PTV）轮廓勾画方法进行了从2.2 Gy降至2 Gy/分次的剂量降低试验。
我们比较了130例采用2.2 Gy/分次治疗的患者（A组）和144例采用2 Gy/分次治疗的患者（B组），两组均采用改良PTV（不包括直肠体积），中位随访期为62个月。A组的处方剂量为72.6 - 74.8 Gy，分33 - 34次照射；B组的处方剂量为72 - 74 Gy，分36 - 37次照射。
B组患者的直肠和膀胱V10 - V70降低，且接受的是最大剂量照射。B组5年时≤2级GI毒性的累积发生率从10.1%[95%置信区间（CI），4.9 - 15.3%]降至1.4%（0 - 3.3%）。2级及以上泌尿毒性也从A组的5.5%（1.5 - 9.4%）降至B组的1.4%（0 - 3.3%，p = 0.0167）。A组和B组的5年无生化失败生存率分别为89.1%（95%CI = 83.6 - 95.4%）和87.5%（82.0 - 92.9%，p = 0.75）。
降低分次剂量方案降低了晚期GI毒性的发生率，且不影响前列腺特异性抗原的控制。即使对于IG-IMRT，仔细的靶区定义和分次剂量也很重要。
