Pharmacotherapy. 2010 Feb;30(2):217. doi: 10.1592/phco.30.2.217.
Roux-en-Y gastric bypass is a gastric reduction duodenal switch with a combination of restrictive and malabsorptive procedures. It is the most common gastric bypass procedure performed in the United States. Malabsorption causing nutritional deficiencies does occur, yet a PubMed literature search (1955-2009) returned no reports of malabsorption of anticancer agents after gastric bypass. To our knowledge, this is the first report of three cases of malabsorption of the anticancer agent tamoxifen after this procedure. The first patient was a 58-year-old woman who underwent Roux-en-Y bypass for morbid obesity. Two years later, she developed estrogen receptor-positive ductal carcinoma in situ of the breast, underwent lumpectomy and irradiation, and tamoxifen was started. Two years after that, she presented with concerns of potential malabsorption of the drug. Her plasma tamoxifen level was 28 ng/ml, which was below the lower limit of the therapeutic range (77-274 ng/ml for 10-30-mg/day regimens). The second patient was a 51-year-old woman who sought medical advice on risk reduction for breast cancer after receiving a diagnosis of atypical ductal hyperplasia of the breast. She also had a history of morbid obesity and underwent Roux-en-Y bypass. Tamoxifen was started to reduce her risk of breast cancer; her plasma tamoxifen level was subtherapeutic at 14 ng/ml. The third patient was a 53-year-old woman with estrogen receptor-positive breast cancer who underwent lumpectomy and was prescribed anastrozole, an aromatase inhibitor. She also underwent Roux-en-Y bypass for morbid obesity. As she experienced adverse effects while receiving anastrozole, the drug was discontinued, and tamoxifen 20 mg/day was started. Her tamoxifen plasma level was 52 ng/ml. Therefore, her tamoxifen dosage was increased to 20 mg twice/day. Six weeks later, her tamoxifen level was 120 ng/ml (therapeutic range 95-520 ng/ml for the increased dosage). These three cases suggest that steady-state serum tamoxifen levels should be evaluated in patients who have undergone Roux-en-Y gastric bypass. Until adequate data suggest otherwise, parenteral anticancer alternatives should be considered when systemic therapy is needed in a patient with malabsorption.
胃旁路术（Roux-en-Y gastric bypass）是一种胃缩小十二指肠转位术，结合了限制和吸收不良程序。它是美国最常见的胃旁路手术。虽然确实会发生导致营养缺乏的吸收不良，但 PubMed 文献检索（1955-2009 年）未报告胃旁路术后抗癌药物吸收不良的报告。据我们所知，这是首例报告胃旁路术后三种抗癌药物他莫昔芬吸收不良的病例。第一例患者是一名 58 岁女性，因病态肥胖接受 Roux-en-Y 旁路手术。两年后，她患有雌激素受体阳性的乳腺导管原位癌，接受了乳房切除术和放疗，并开始服用他莫昔芬。两年后，她出现了对药物潜在吸收不良的担忧。她的血浆他莫昔芬水平为 28ng/ml，低于治疗范围下限（77-274ng/ml，用于 10-30mg/天方案）。第二位患者是一位 51 岁女性，在被诊断为乳腺非典型导管增生后寻求降低乳腺癌风险的咨询。她也有病态肥胖史，并接受了 Roux-en-Y 旁路手术。为降低患乳腺癌的风险，她开始服用他莫昔芬；她的血浆他莫昔芬水平为 14ng/ml，低于治疗范围下限。第三位患者是一位 53 岁女性，患有雌激素受体阳性乳腺癌，接受了乳房切除术，并被开处芳香酶抑制剂阿那曲唑。她还因病态肥胖接受了 Roux-en-Y 旁路手术。由于她在服用阿那曲唑时出现不良反应，因此停止了该药的使用，并开始服用他莫昔芬 20mg/天。她的他莫昔芬血浆水平为 52ng/ml。因此，她的他莫昔芬剂量增加到 20mg，每天两次。六周后，她的他莫昔芬水平为 120ng/ml（增加剂量的治疗范围为 95-520ng/ml）。这三个病例表明，接受 Roux-en-Y 胃旁路手术的患者应评估稳态血清他莫昔芬水平。在吸收不良的患者需要全身治疗时，应考虑使用其他静脉内抗癌药物，直到有足够的数据表明可以使用其他药物为止。
