Individual case review in a phase 3 randomized trial to investigate the role of internal mammary lymph node irradiation for breast cancer: Korean Radiation Oncology Group 08-06 study

Abstract

Purpose/objective: This study aimed to assess protocol compliance based on an individual case review (ICR) of the Korean Radiation Oncology Group-0806 trial.

Methods and materials: For the ICR, 747 participants were divided into eight subgroups based on internal mammary node irradiation (IMNI), tumor laterality, and surgery type. Next, 15% of patients were randomly selected within each subgroup, and corresponding hospitals were subsequently requested to upload information related to radiation therapy (RT) planning. We reviewed the dose distributions of targets and organs at risk to determine protocol compliance.

Results: Data of 102 patients were collected. Overall, RT plans were found to be mostly protocol compliant, with acceptability rates of 60-80% despite deviations in the ipsilateral lung in Arm 2 (IMNI group). However, despite few deviations, a subgroup analysis revealed significant differences in protocol compliance. Among RT techniques, plans using standard and partial wide tangents were most compliant in both Arms. In this ICR, the estimated survival benefits based on IMN doses were 7.7%, 8.4%, and 7.2% for all, breast-conserving surgery, and mastectomy cases, respectively.

Conclusion: This ICR demonstrated overall protocol compliance, despite significant differences with regard to IMN irradiation and organs at risk according to subgroups and adopted field arrangements.