Internal Mammary Node Irradiation in Patients With Node-Positive Early Breast Cancer: Fifteen-Year Results From the Danish Breast Cancer Group Internal Mammary Node Study.

PURPOSE: The Danish Breast Cancer Group Internal Mammary Node study demonstrated improved 8-year overall survival (OS) with internal mammary node irradiation (IMNI) in patients with node-positive early breast cancer. Here, we present long-term results from the Danish Breast Cancer Group Internal Mammary Node study cohort. PATIENTS AND METHODS: This nationwide, prospective cohort study allocated patients with node-positive early breast cancer to adjuvant radiotherapy with or without IMNI depending on cancer laterality. Patients with right-sided cancer received IMNI. Patients with left-sided cancer were treated without IMNI because of risk of radiation-induced heart disease. Other treatment was independent of laterality. The primary study end point was OS. Secondary end points were distant recurrence and breast cancer mortality. Analyses were by intention to treat. RESULTS: During 2003-2007, 3,089 women were allocated to IMNI (right-sided, n = 1,491) or no IMNI (left-sided, n = 1,598). With a median follow-up of 14.8 years, 589 patients with and 701 patients without IMNI had died. The corresponding 15-year OS rates were 60.1% and 55.4%. The adjusted hazard ratio (HR) for death was 0.86 (95% CI, 0.77 to 0.96; P = .007) in favor of IMNI. The 15-year risk of developing distant recurrence was 35.6% (523 recurrences) and 38.6% (602 recurrences) with vs. without IMNI (adjusted HR, 0.88 [95% CI, 0.79 to 0.99; P = .04]). The 15-year breast cancer mortality with IMNI was 31.7% (467 deaths) compared with 33.9% (537 deaths) without IMNI (adjusted HR, 0.88 [95% CI, 0.78 to 1.00; P = .05]). The distribution of other deaths was similar across groups. CONCLUSION: In patients with node-positive early breast cancer treated with IMNI or without IMNI depending on breast cancer laterality, IMNI reduced the risk of distant recurrence and death from breast cancer, thereby improving long-term survival.

CT-planned internal mammary node radiotherapy in the DBCG-IMN study: benefit versus potentially harmful effects.

BACKGROUND: The DBCG-IMN is a nationwide population-based cohort study on the effect of internal mammary node radiotherapy (IMN-RT) in patients with node positive early breast cancer. Due to the risk of RT-induced heart disease, only patients with right-sided breast cancer received IMN-RT, whereas patients with left-sided breast cancer did not. At seven-year median follow-up, a 3% gain in overall survival with IMN-RT has been reported. This study estimates IMN doses and doses to organs at risk (OAR) in patients from the DBCG-IMN. Numbers needed to harm (NNH) if patients with left-sided breast cancer had received IMN-RT are compared to the number needed to treat (NNT). MATERIAL AND METHODS: Ten percent of CT-guided treatment plans from the DBCG-IMN patients were selected randomly. IMNs and OAR were contoured in 68 planning CT scans. Dose distributions were re-calculated. IMNs and OAR dose estimates were compared in right-sided versus left-sided breast cancer patients. In six left-sided patients, IMN-RT was simulated, and OAR doses were compared to those in the original plan. The NNH resulting from the change in mean heart dose (MHD) was calculated using a published model for risk of RT-related ischemic heart death. RESULTS: In original plans, the absolute difference between right- and left-sided V90% to the IMNs was 38.0% [95% confidence interval (5.5%; 70.5%), p < 0.05]. Heart doses were higher in left-sided plans. With IMN-RT simulation without regard to OAR constraints, MHD increased 4.8 Gy (0.9 Gy; 8.7 Gy), p < 0.05. Resulting NNHs from ischemic heart death were consistently larger than the NNT with IMN-RT. CONCLUSION: Refraining from IMN-RT on the left side may have spared some ischemic heart deaths. Assuming left-sided patients benefit as much from IMN-RT as right-sided patients, the benefits from IMN-RT outweigh the costs in terms of ischemic heart death.

Quality assurance of conventional non-CT-based internal mammary lymph node irradiation in a prospective Danish Breast Cancer Cooperative Group trial: the DBCG-IMN study.

UNLABELLED: In 2003, the Danish Breast Cancer Cooperative Group (DBCG) initiated DBCG-IMN, a prospective study on the effect of adjuvant internal mammary lymph node radiotherapy (IMN-RT) in patients with early lymph node positive breast cancer (BC). In the study, standard DBCG IMN-RT was provided only to patients with right-sided BC. We provide estimates of doses to IMNs and organs at risk (OARs) in patients treated with the non-CT-based RT techniques used during the DBCG-IMN study. MATERIAL AND METHODS: Five DBCG RT regimens were simulated on planning CT scans from 50 consecutively scanned BC patients, 10 in each group. Intended target volumes were chest wall or breast and regional lymph nodes ± IMNs. Field planning was conducted in the Eclipse(TM) RT treatment planning system. Subsequently, IMN clinical target volumes (CTVs) and OARs were delineated. Estimates on doses to the IMN-CTV and OARs were made. RESULTS: IMN dose coverage estimates were consistently higher in right-sided techniques where IMN treatment was intended (p < 0.0001). Estimated doses to cardiac structures were low regardless of whether IMNs were treated or not. Post-lumpectomy patients had the highest estimated lung doses. CONCLUSION: Overall, simulator-based treatment using the DBCG RT techniques resulted in satisfactory coverage of IMNs and acceptable levels of OAR irradiation.