Radiation therapy (RT) is an effective treatment for stage IIA and select stage IIB seminomas. However, given the long life expectancy of seminoma patients, there are concerns about the risk of secondary cancers from RT. This study assessed differences in secondary cancer risk for stage II seminoma patients following proton pencil-beam scanning (PBS) and photon VMAT, compared to 3D conformal photon RT. Ten seminoma patients, five with a IIA staging who received 30 GyRBE and five with a IIB staging who received 36 GyRBE, had three RT plans generated. Doses to organs at risk (OAR) were evaluated, and secondary cancer risks were calculated as the Excess Absolute Risk (EAR) and Lifetime Attributable Risk (LAR). PBS reduced the mean OAR dose by 60% on average compared to 3D, and reduced the EAR and LAR for all OAR, with the greatest reductions seen for the bowel, liver, and stomach. VMAT reduced high doses but increased the low-dose bath, leading to an increased EAR and LAR for some OAR. PBS provided superior dosimetric sparing of OAR compared to 3D and VMAT in stage II seminoma cases, with models demonstrating that this may reduce secondary cancer risk. Therefore, proton therapy shows the potential to reduce acute and late side effects of RT for this population.
放射治疗（RT）是治疗IIA期及部分IIB期精原细胞瘤的有效方法。然而，考虑到精原细胞瘤患者预期寿命较长，放疗引发继发性癌症的风险备受关注。本研究评估了II期精原细胞瘤患者在接受质子笔形束扫描（PBS）和光子容积旋转调强放疗（VMAT）后，与三维适形光子放疗（3D-CRT）相比，继发性癌症风险的差异。研究纳入10例精原细胞瘤患者（5例IIA期接受30 GyRBE照射，5例IIB期接受36 GyRBE照射），为每例患者制定三种放疗计划。通过评估危及器官（OAR）的受照剂量，并采用超额绝对风险（EAR）和终生归因风险（LAR）计算继发性癌症风险。结果显示，与3D-CRT相比，PBS使OAR平均剂量降低60%，所有OAR的EAR和LAR均显著下降，其中肠道、肝脏和胃的风险降低最为明显。VMAT虽能降低高剂量照射，但增加了低剂量照射范围，导致部分OAR的EAR和LAR升高。在II期精原细胞瘤治疗中，PBS相较于3D-CRT和VMAT能更优地保护OAR，模型分析表明这可能降低继发性癌症风险。因此，质子治疗显示出降低该人群放疗急性和远期副作用的潜力。
肿瘤(癌症)患者之家