Radiation therapy (RT) is a standard treatment for the local control of primary pelvic cancers (PPC), yet the risk of second corpus uteri cancer (SCUC) in PPC patients undergoing RT is still controversial. This study investigated the impact of RT on the risk of SCUC and assessed the survival outcome.

We queried nine cancer registries for PPC cases in the Surveillance, Epidemiology, and End Results (SEER) database. The cumulative incidence of SCUC was analyzed using Cox regression and Fine–Gray competing risk regression analysis. The Poisson regression analysis was employed to assess the standardized incidence ratios (SIRs) and radiation-attributed risk (RR) for SCUC. We evaluated the overall survival of patients with SCUC using the Kaplan–Meier method.

Receiving radiotherapy was strongly associated with a higher risk of developing SCUC for PPC patients in Fine–Gray competing risk regression (No-RT vs. RT: adjusted HR = 1.77; 95% CI, 1.40–2.28; p < 0.001). The incidence of SCUC in PPC patients who received RT was higher than in the US general population (SIR, 1.66; 95% CI, 1.41–1.93; p < 0.05), but the incidence of SCUC in patients who did not receive RT was lower than with the US general population (SIR, 0.68; 95% CI, 0.61–0.75; p < 0.05). The dynamic SIR and RR for SCUC decreased with decreasing age at PPC diagnosis and decreased with time progress. In terms of overall survival, 10-year survival rates with SCUC after No-RT (NRT) and SCUC after RT were 45.9% and 25.9% (HR = 1.82; 95% CI, 1.46–2.29; p < 0.001), respectively.

Radiotherapy for primary pelvic cancers is associated with a higher risk of developing SCUC than patients unexposed to radiotherapy. We suggest that patients with pelvic RT, especially young patients, should receive long-term monitoring for the risk of developing SCUC.

放射治疗 (RT) 是局部控制原发性盆腔癌 (PPC) 的标准治疗方法，但在接受放疗的 PPC 患者中第二次子宫体癌 (SCUC) 的风险仍存在争议。本研究调查了放疗对 SCUC 风险的影响并评估了生存结果。

我们在监测、流行病学和最终结果 (SEER) 数据库中查询了 9 个癌症登记处的 PPC 病例。使用 Cox 回归和 Fine-Gray 竞争风险回归分析分析 SCUC 的累积发病率。泊松回归分析用于评估 SCUC 的标准化发病率 (SIR) 和辐射归因风险 (RR)。我们使用 Kaplan-Meier 方法评估了 SCUC 患者的总生存期。

在 Fine-Gray 竞争风险回归中，接受放疗与 PPC 患者发生 SCUC 的较高风险密切相关（无放疗与放疗：调整后 HR = 1.77；95% CI，1.40-2.28；p< 0.001)。接受 RT 的 PPC 患者的 SCUC 发生率高于美国普通人群（SIR，1.66；95% CI，1.41-1.93；p< 0.05），但未接受放疗的患者的 SCUC 发生率低于美国普通人群（SIR，0.68；95% CI，0.61-0.75；p< 0.05)。SCUC 的动态 SIR 和 RR 随着 PPC 诊断年龄的降低而降低，并随着时间的推移而降低。在总生存率方面，非放疗后 SCUC (NRT) 和放疗后 SCUC 的 10 年生存率分别为 45.9% 和 25.9% (HR = 1.82; 95% CI, 1.46–2.29;p< 0.001)，分别。

与未接受放射治疗的患者相比，原发性盆腔癌的放射治疗与发生 SCUC 的风险更高有关。我们建议盆腔放疗患者，尤其是年轻患者，应接受长期监测，以了解发生 SCUC 的风险。