Dummy Run of Quality Assurance Program in a Phase 3 Randomized Trial Investigating the Role of Internal Mammary Lymph Node Irradiation in Breast Cancer Patients: Korean Radiation Oncology Group 08-06 Study
- Affiliated Author(s)
- Alternative Author(s)
- Kim, Jin Hee
- Journal Title
- International Journal of Radiation Oncology*Biology*Physics
- Issued Date
- Purpose: The Korean Radiation Oncology Group (KROG) 08-06 study protocol
allowed radiation therapy (RT) technique to include or exclude breast cancer patients
from receiving radiation therapy to the internal mammary lymph node (IMN). The
purpose of this study was to assess dosimetric differences between the 2 groups and
potential influence on clinical outcome by a dummy run procedure.
Methods and Materials: All participating institutions were asked to produce RT plans
without irradiation (Arm 1) and with irradiation to the IMN (Arm 2) for 1 breastconservation
treatment case (breast-conserving surgery [BCS]) and 1 mastectomy case
(modified radical mastectomy [MRM]) whose computed tomography images were
provided. We assessed interinstitutional variations in IMN delineation and evaluated
the dose-volume histograms of the IMN and normal organs. A reference IMN was
delineated by an expert panel group based on the study guidelines. Also, we analyzed
the potential influence of actual dose variation observed in this study on patient survival.
Results: Although physicians intended to exclude the IMN within the RT field, the
data showed almost 59.0% of the prescribed dose was delivered to the IMN in Arm
1. However, the mean doses covering the IMN in Arm 1 and Arm 2 were significantly
different for both cases (P<.001). Due to the probability of overdose in Arm 1, the
estimated gain in 7-year disease-free survival rate would be reduced from 10% to
7.9% for BCS cases and 7.1% for MRM cases. The radiation doses to the ipsilateral
lung, heart, and coronary artery were lower in Arm 1 than in Arm 2.
Conclusions: Although this dummy run study indicated that a substantial dose was
delivered to the IMN, even in the nonirradiation group, the dose differences between
the 2 groups were statistically significant. However, this dosimetric profile should be
studied further with actual patient samples and be taken into consideration when
analyzing clinical outcomes according to IMN irradiation. 2015 Elsevier Inc.
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