Intensity-modulated radiation therapy (IMRT) combined with chemotherapy followed by surgery is the standard treatment for locally advanced rectal cancer (LARC). IMRT, however, uses a larger number of monitor units (MU) to achieve a highly conformal radiation distribution while causing spillage of radiation to the surrounding normal soft tissues of the body, this phenomenon has led to concerns of increased risk of secondary radiation-induced malignancies for patients with long life expectancies.

中文翻译：

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VMAT 和 IMRT 治疗直肠癌的整体剂量比较：剂量分析

调强放射治疗（IMRT）联合化疗和手术是局部晚期直肠癌（LARC）的标准治疗方法。然而，IMRT使用更多的监测单元（MU）来实现高度适形的辐射分布，同时导致辐射溢出到身体周围的正常软组织，这种现象引起了人们对二次辐射风险增加的担忧。恶性肿瘤患者的预期寿命较长。