Tho Lye Mun, Glegg Martin, Paterson Jennifer, Yap Christina, MacLeod Alice, McCabe Marie, McDonald Alexander C
Colorectal Cancer Team, Beatson Oncology Centre, Western Infirmary, University of Glasgow, United Kingdom.
Int J Radiat Oncol Biol Phys. 2006 Oct 1;66(2):505-13. doi: 10.1016/j.ijrobp.2006.05.005. Epub 2006 Jul 31.
The relationship between volume of irradiated small bowel (VSB) and acute toxicity in rectal cancer radiotherapy is poorly quantified, particularly in patients receiving concurrent preoperative chemoradiotherapy. Using treatment planning data, we studied a series of such patients.
Details of 41 patients with locally advanced rectal cancer were reviewed. All received 45 Gy in 25 fractions over 5 weeks, 3-4 fields three-dimensional conformal radiotherapy with daily 5-fluorouracil and folinic acid during Weeks 1 and 5. Toxicity was assessed prospectively in a weekly clinic. Using computed tomography planning software, the VSB was determined at 5 Gy dose intervals (V5, V10, etc.). Eight patients with maximal VSB had dosimetry and radiobiological modeling outcomes compared between inverse and conformal three-dimensional planning.
VSB correlated strongly with diarrheal severity at every dose level (p<0.03), with strongest correlation at lowest doses. Median VSB differed significantly between patients experiencing Grade 0-1 and Grade 2-4 diarrhea (p<or=0.05). No correlation was found with anorexia, nausea, vomiting, abdominal cramps, age, body mass index, sex, tumor position, or number of fields. Analysis of 8 patients showed that inverse planning reduced median dose to small bowel by 5.1 Gy (p=0.008) and calculated late normal tissue complication probability (NTCP) by 67% (p=0.016). We constructed a model using mathematical analysis to predict for acute diarrhea occurring at V5 and V15.
A strong dose-volume relationship exists between VSB and acute diarrhea at all dose levels during preoperative chemoradiotherapy. Our constructed model may be useful in predicting toxicity, and this has been derived without the confounding influence of surgical excision on bowel function. Inverse planning can reduce calculated dose to small bowel and late NTCP, and its clinical role warrants further investigation.
在直肠癌放疗中，照射小肠体积（VSB）与急性毒性之间的关系尚未得到充分量化，尤其是在接受术前同步放化疗的患者中。我们利用治疗计划数据研究了一系列此类患者。
回顾了41例局部晚期直肠癌患者的详细资料。所有患者在5周内分25次接受45 Gy照射，在第1周和第5周采用3 - 4野三维适形放疗，并每日给予5 - 氟尿嘧啶和亚叶酸。每周在门诊对毒性进行前瞻性评估。使用计算机断层扫描计划软件，以5 Gy剂量间隔（V5、V10等）确定VSB。对8例VSB最大的患者，比较了逆向和适形三维计划之间的剂量测定和放射生物学建模结果。
在每个剂量水平，VSB与腹泻严重程度密切相关（p<0.03），在最低剂量时相关性最强。0 - 1级和2 - 4级腹泻患者的VSB中位数差异显著（p≤0.05）。未发现与厌食、恶心、呕吐、腹部绞痛、年龄、体重指数、性别、肿瘤位置或野数相关。对8例患者的分析表明，逆向计划使小肠的中位剂量降低了5.1 Gy（p = 0.008），并使计算出的晚期正常组织并发症概率（NTCP）降低了67%（p = 0.016）。我们使用数学分析构建了一个模型，以预测V5和V15时发生的急性腹泻。
在术前放化疗期间，所有剂量水平下VSB与急性腹泻之间均存在强烈的剂量 - 体积关系。我们构建的模型可能有助于预测毒性，并且该模型是在没有手术切除对肠功能的混杂影响的情况下得出的。逆向计划可以降低计算出的小肠剂量和晚期NTCP，其临床作用值得进一步研究。
