br The development of an NR and DM
The development of an NR and DM are often inextri-cably linked, making it difficult to discern which event comes first.16 The most compelling rationale for preventing regional nodal failures was provided by the NCIC MA20 and EORTC 22922 trials, in which RNI was associated with an absolute POM 1 in DM of 4%.2,3 Our study excluded patients with DM identified before NR, but 56% of patients still had DM detected concurrently (within 1 month of diagnosis of NR). Furthermore, among 30 patients with lateral or posterior SCV NR, 26 patients (86%) had sites of concurrent DM, suggesting that SCV NR in these locations might be markers of other regional nodal and distant
involvement. Larger-scale, independent data sets are obvi-ously required to confirm this hypothesis.
Patients with isolated IMN NR had inferior survival compared with SCV or axillary NR and were also more likely to develop DM. These survival outcomes should be interpreted in context of the potential selection bias intro-duced by the inclusion of patients with isolated NR or concurrent DM, or both. Consistent with other reports, the vast majority (94%) of IMN NR were located within the first 1 to 3 intercostal spaces, with no IMN NRs occurring caudal to the fourth rib.22 Unlike other studies that have examined patterns of IMN NRs, we did not examine the
association between IMN NR events and the quadrant of the primary lesion,2,3,15,23 although we did observe IMN
NRs abutting the sternum >5 mm medial to the internal mammary vessels (2.5%; 2/79), suggesting CTV coverage should extend all the way to the sternal border.
In conclusion, in this large, 3D imageebased analysis of NR patterns in patients with breast cancer treated with contemporary therapies, the lateral and posterior SCVs represented a distinct site of NR not routinely included within current breast cancer contouring atlases. Grade 3 breast cancer and LVI were most commonly associated with the development of NR in these regions. Modifying the CTV to encompass the lateral and posterior SCV in patients with breast cancer patients with these features might be justified.
1. Early Breast Cancer Trialists’ Collaborative G, Darby S, McGale P, Correa C, et al. Effect of radiotherapy after breast-conserving surgery on 10-year recurrence and 15-year breast cancer death: Meta-analysis of individual patient data for 10,801 women in 17 randomised trials. Lancet 2011;378:1707-1716.
4. White J, Tai A, Arthur D, et al. RTOG breast cancer atlas; 2009. Available at: https://www.rtog.org/LinkClick.aspx?fileticketZvzJFh PaBipE%3d&tabidZ236.
5. Kirova YM, Castro Pena P, Dendale R, et al. Simplified rules for everyday delineation of lymph node areas for breast cancer radio-therapy. Br J Radiol 2010;83:683-686.
6. Nielsen MH, Berg M, Pedersen AN, et al. Delineation of target vol-umes and organs at risk in adjuvant radiotherapy of early breast cancer: National guidelines and contouring atlas by the danish breast cancer cooperative group. Acta Oncol 2013;52:703-710.
7. Offersen BV, Boersma LJ, Kirkove C, et al. Estro consensus guideline on target volume delineation for elective radiation therapy of early stage breast cancer. Radiother Oncol 2015;114:3-10.
8. Verhoeven K, Weltens C, Remouchamps V, et al. Vessel based delineation guidelines for the elective lymph node regions in breast cancer radiation therapyeprocab guidelines. Radiother Oncol 2015; 114:11-16.
9. MacDonald SaC O. Breast contouring radcomp consortium I; 2016. Available at: https://www.rtog.org/LinkClick.aspx?fileticketZeVB 451KQ83M%3d&tabidZ429.
10. Ohri N, Sittig MP, Tsai CJ, et al. Trends and variations in post-mastectomy radiation therapy for breast cancer in patients with 1 to 3 positive lymph nodes: A national cancer data base analysis. Cancer 2018;124:482-490.