Dess Robert T, Liss Adam L, Griffith Kent A, Marsh Robin B, Moran Jean M, Mayo Charles, Koelling Todd M, Jagsi Reshma, Hayman James A, Pierce Lori J
Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
Center for Cancer Biostatistics, University of Michigan, Ann Arbor, Michigan.
Int J Radiat Oncol Biol Phys. 2017 Dec 1;99(5):1146-1153. doi: 10.1016/j.ijrobp.2017.06.2459. Epub 2017 Jun 27.
Regional nodal irradiation, including radiation therapy (RT) to the internal mammary node (IMN) region, improves oncologic outcomes in patients with node-positive breast cancer. Concern remains, however, given the proximity of the IMNs to the heart and the association between cardiac RT exposure and toxicity. The objective of the study was to evaluate rates of ischemic cardiac events (ICEs) and associated risk with treatment of the IMN region.
The cardiac outcomes of 2126 patients treated with adjuvant breast RT or breast and nodal RT from 1984 to 2007 at a single institution were reviewed. The primary endpoint was an ICE following RT initiation. The association between IMN RT and ICEs was assessed using Cox proportional hazards models. Treatment with both IMN RT and 3-dimensional (3D) conformal radiation therapy (CRT) began in 1997; therefore, subset analyses of patients with only 3D CRT were performed to minimize bias associated with improved treatment technique.
The median follow-up period was 9.3 years. An ICE occurred in 87 patients (4.1%). No increased 10-year rate of ICEs was observed with IMN RT compared with no IMN RT in the total cohort (3.2% [95% confidence interval (CI), 2.4%-4.3%] vs 3.4% [95% CI, 1.5%-7.5%]; hazard ratio [HR], 0.88; P=.73). Similarly, no statistically significant difference was noted in the 3D CRT-planned, left-sided disease subset (5.1% [95% CI, 1.8%-14.1%] vs 4.0% [95% CI, 2.0%-8.0%]; HR, 1.18, P=.76). On multivariate analysis, adjusting for cardiac risk factor imbalances, no significantly increased hazard was noted with IMN RT (HR, 1.84; P=.28) in the 3D CRT-planned, left-sided disease subset.
No statistically significant association between IMN RT and ICEs was demonstrated in a review of patients treated at a single institution from 1984 to 2007. Given the long natural history and low overall rate of ICEs, continued follow-up of this study, as well as additional studies in the 3D CRT era, is warranted to confirm these results. Minimizing cardiac exposure, when treating a limited IMN field, is critical to limit excess risk of ICEs.
区域淋巴结照射，包括对内乳淋巴结（IMN）区域进行放射治疗（RT），可改善淋巴结阳性乳腺癌患者的肿瘤学结局。然而，鉴于IMN与心脏的距离以及心脏接受放疗与毒性之间的关联，人们仍存在担忧。本研究的目的是评估缺血性心脏事件（ICEs）的发生率以及IMN区域治疗相关的风险。
回顾了1984年至2007年在一家机构接受辅助性乳腺放疗或乳腺及淋巴结放疗的2126例患者的心脏结局。主要终点是放疗开始后的ICE。使用Cox比例风险模型评估IMN放疗与ICEs之间的关联。IMN放疗和三维（3D）适形放疗（CRT）均始于1997年；因此，对仅接受3D CRT的患者进行亚组分析，以尽量减少与治疗技术改进相关的偏差。
中位随访期为9.3年。87例患者（4.1%）发生了ICE。在整个队列中，与未进行IMN放疗相比，IMN放疗未观察到ICE的10年发生率增加（3.2%[95%置信区间（CI），2.4%-4.3%]对3.4%[95%CI，1.5%-7.5%]；风险比[HR]，0.88；P = 0.73）。同样，在3D CRT计划的左侧疾病亚组中也未发现统计学上的显著差异（5.1%[95%CI，1.8%-14.1%]对4.0%[95%CI，2.0%-8.0%]；HR，1.18，P = 0.76）。在多变量分析中，对心脏危险因素不平衡进行调整后，在3D CRT计划的左侧疾病亚组中，IMN放疗未观察到显著增加的风险（HR，1.84；P = 0.28）。
在对1984年至2007年在一家机构接受治疗的患者进行的回顾中，未证明IMN放疗与ICEs之间存在统计学上的显著关联。鉴于ICEs的自然病程较长且总体发生率较低，有必要继续对本研究进行随访，并在3D CRT时代开展更多研究以证实这些结果。在治疗有限的IMN区域时，尽量减少心脏照射对于限制ICEs的额外风险至关重要。
