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

Abstract

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.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.

This work was supported by Aarhus University Hospital, the Danish Cancer Society, Breast Friends and CIRRO – the Lundbeck Foundation Center for Interventional Research in Radiation Oncology.