Academic Urology Unit, Institute of Cancer Research and The Royal Marsden Hospital, London and Sutton, United Kingdom.
Int J Radiat Oncol Biol Phys. 2012 Dec 1;84(5):e601-6. doi: 10.1016/j.ijrobp.2012.07.2368. Epub 2012 Sep 18.
Intensity modulated radiation therapy (IMRT) is a significant therapeutic advance in prostate cancer, allowing increased tumor dose delivery and increased sparing of normal tissues. IMRT planning uses strict dose constraints to nearby organs to limit toxicity. Bile acid malabsorption (BAM) is a treatable disorder of the terminal ileum (TI) that presents with symptoms similar to radiation therapy toxicity. It has not been described in patients receiving RT for prostate cancer in the contemporary era. We describe new-onset BAM in men after IMRT for prostate cancer.
Diagnosis of new-onset BAM was established after typical symptoms developed, selenium-75 homocholic acid taurine (SeHCAT) scanning showed 7-day retention of <15%, and patients' symptoms unequivocally responded to a bile acid sequestrant. The TI was identified on the original radiation therapy plan, and the radiation dose delivered was calculated and compared with accepted dose-volume constraints.
Five of 423 men treated in a prospective series of high-dose prostate and pelvic IMRT were identified with new onset BAM (median age, 65 years old). All reported having normal bowel habits before RT. The volume of TI ranged from 26-141 cc. The radiation dose received by the TI varied between 11.4 Gy and 62.1 Gy (uncorrected). Three of 5 patients had TI treated in excess of 45 Gy (equivalent dose calculated in 2-Gy fractions, using an α/β ratio of 3) with volumes ranging from 1.6 cc-49.0 cc. One patient had mild BAM (SeHCAT retention, 10%-15%), 2 had moderate BAM (SeHCAT retention, 5%-10%), and 2 had severe BAM (SeHCAT retention, <5%). The 3 patients whose TI received ≥45 Gy developed moderate to severe BAM, whereas those whose TI received <45 Gy had only mild to moderate BAM.
Radiation delivered to the TI during IMRT may cause BAM. Identification of the TI from unenhanced RT planning computed tomography scans is difficult and may impede accurate dosimetric evaluation. Thorough toxicity assessment and close liaison between oncologist and gastroenterologist allow timely diagnosis and treatment.
调强放射治疗（IMRT）是前列腺癌治疗的重大进展，它可以提高肿瘤的剂量输送，并减少对正常组织的损伤。IMRT 计划使用严格的剂量限制来保护附近的器官，以限制毒性。胆汁酸吸收不良（BAM）是回肠末端（TI）的一种可治疗的疾病，其症状与放射治疗毒性相似。在当代接受前列腺癌放射治疗的患者中尚未描述过这种情况。我们描述了接受 IMRT 治疗前列腺癌后的男性中出现的新发病例胆汁酸吸收不良。
在出现典型症状后，通过硒-75 同型胆酸牛磺酸（SeHCAT）扫描显示 7 天内保留率<15%，并且患者的症状明确对胆汁酸螯合剂有反应，从而确诊新发病例胆汁酸吸收不良。在原始放射治疗计划上确定 TI 的位置，并计算并比较接受的剂量-体积限制所给予的 TI 剂量。
在一项前瞻性高剂量前列腺和盆腔 IMRT 治疗的 423 名男性患者中，有 5 名被发现患有新发病例胆汁酸吸收不良（中位年龄 65 岁）。所有患者在接受放射治疗前均报告有正常的肠道习惯。TI 的体积范围为 26-141 cc。TI 接受的放射剂量范围为 11.4 Gy 至 62.1 Gy（未校正）。5 名患者中有 3 名的 TI 接受了超过 45 Gy 的照射（在 2-Gy 分次中计算等效剂量，使用α/β 比为 3），其体积范围为 1.6 cc-49.0 cc。1 名患者患有轻度胆汁酸吸收不良（SeHCAT 保留率为 10%-15%），2 名患者患有中度胆汁酸吸收不良（SeHCAT 保留率为 5%-10%），2 名患者患有严重胆汁酸吸收不良（SeHCAT 保留率<5%）。TI 接受≥45 Gy 的 3 名患者发展为中重度胆汁酸吸收不良，而 TI 接受<45 Gy 的患者仅为轻度至中度胆汁酸吸收不良。
在 IMRT 期间给予 TI 的放射治疗可能会导致胆汁酸吸收不良。在未增强的放射治疗计划 CT 扫描中识别 TI 较为困难，这可能会阻碍准确的剂量评估。彻底的毒性评估和肿瘤学家与胃肠病学家之间的密切联系可实现及时诊断和治疗。
