Background

Radiotherapy (RT) following breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS) reduces ipsilateral breast event rates in clinical trials. This study assessed the impact of DCIS treatment on a 20-year risk of ipsilateral DCIS (iDCIS) and ipsilateral invasive breast cancer (iIBC) in a population-based cohort.

Methods

The cohort comprised all women diagnosed with DCIS in the Netherlands during 1989–2004 with follow-up until 2017. Cumulative incidence of iDCIS and iIBC following BCS and BCS + RT were assessed. Associations of DCIS treatment with iDCIS and iIBC risk were estimated in multivariable Cox models.

Results

The 20-year cumulative incidence of any ipsilateral breast event was 30.6% (95% confidence interval (CI): 28.9–32.6) after BCS compared to 18.2% (95% CI 16.3–20.3) following BCS + RT. Women treated with BCS compared to BCS + RT had higher risk of developing iDCIS and iIBC within 5 years after DCIS diagnosis (for iDCIS: hazard ratio (HR)_age < 50 3.2 (95% CI 1.6–6.6); HR_{age ≥ 50} 3.6 (95% CI 2.6–4.8) and for iIBC: HR_age<50 2.1 (95% CI 1.4–3.2); HR_{age ≥ 50} 4.3 (95% CI 3.0–6.0)). After 10 years, the risk of iDCIS and iIBC no longer differed for BCS versus BCS + RT (for iDCIS: HR_age < 50 0.7 (95% CI 0.3–1.5); HR_{age ≥ 50} 0.7 (95% CI 0.4–1.3) and for iIBC: HR_age < 50 0.6 (95% CI 0.4–0.9); HR_{age ≥ 50} 1.2 (95% CI 0.9–1.6)).

Conclusion

RT is associated with lower iDCIS and iIBC risk up to 10 years after BCS, but this effect wanes thereafter.

中文翻译：

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乳腺导管原位癌手术加或不加放疗后后续同侧病变的长期风险

背景

在临床试验中，导管原位癌 (DCIS) 保乳手术 (BCS) 后的放疗 (RT) 可降低同侧乳房事件发生率。本研究评估了基于人群的队列中 DCIS 治疗对同侧 DCIS (iDCIS) 和同侧浸润性乳腺癌 (iIBC) 20 年风险的影响。

方法

该队列包括 1989-2004 年在荷兰被诊断患有 DCIS 并随访至 2017 年的所有女性。评估了 BCS 和 BCS + RT 后 iDCIS 和 iIBC 的累积发生率。在多变量 Cox 模型中估计了 DCIS 治疗与 iDCIS 和 iIBC 风险的关联。

结果

BCS 后任何同侧乳房事件的 20 年累积发生率为 30.6%（95% 置信区间 (CI)：28.9-32.6），而 BCS + RT 后为 18.2%（95% CI 16.3-20.3）。与 BCS + RT 相比，接受 BCS 治疗的女性在 DCIS 诊断后 5 年内发生 iDCIS 和 iIBC 的风险更高（对于 iDCIS：风险比 (HR)_{年龄 < 50} 3.2（95% CI 1.6–6.6）；HR_{年龄 ≥ 50} 3.6 (95% CI 2.6–4.8) 和 iIBC：HR_年龄<50 2.1 (95% CI 1.4–3.2)；HR_{年龄≥ 50} 4.3 (95% CI 3.0–6.0))。10 年后，BCS 与 BCS + RT 的 iDCIS 和 iIBC 风险不再存在差异（对于 iDCIS：HR_{年龄 < 50} ± 0.7 (95% CI 0.3–1.5)；HR_{年龄 ≥ 50} ±0.7 (95% CI 0.4–1.3)对于 iIBC：HR_{年龄 < 50}0.6（95% CI 0.4–0.9）；HR_{年龄 ≥ 50} 1.2 (95% CI 0.9–1.6))。

结论

RT 与 BCS 后长达 10 年的较低 iDCIS 和 iIBC 风险相关，但此后这种影响减弱。