The Likelihood of Unacceptable Normal Tissue Doses in Breast Cancer Patients Undergoing Regional Nodal Irradiation in Routine Clinical Practice

Publication date: Available online 19 October 2016
Source:Practical Radiation Oncology
Author(s): Jose Bazan, Dominic DiCostanzo, Karla Kuhn, Lonika Majithia, Allison Quick, Nilendu Gupta, Julia White
PurposeAs indications for regional nodal irradiation (RNI) for breast cancer have expanded, so too has scrutiny over potential late toxicity from radiotherapy. This emphasizes the need for careful radiation treatment planning to maximize the therapeutic ratio. We sought to evaluate how often unacceptable dosing (UD) to organs-at-risk (OAR) occurs and what factors were associated with this for patients receiving RNI in daily practice.Materials and MethodsTreatment records of patients who received RNI from 2/2012–5/2015 were studied. The NSABP B51/RTOG 1304 clinical dose-volume constraints for targets/OAR receiving RNI were used as the benchmark. Dose volume histograms (DVH) were analyzed for the rate of ≥1 UD to the following: Heart mean>5Gy; ipsilateral lung (IL): V20>35%, V10>60%, V5>70%; contralateral lung (CL) V5>15%; contralateral breast (CB) V4.1>5%. Logistic regression was used to test the association between UD to OAR and key variables.Results203 consecutive cases received RNI (105 left, 98 right). RT was to CW in 171 (84%). Internal mammary nodes (IMN) were included in 170 (84%). 77.4% of cases met all OAR constraints. The most common OAR UD were to the CB (n=32, 15.7%) and IL V5 (n=22, 10.8%). On multivariate analysis, use of IMRT (OR=64.7, 95% CI 20.8–201.5, p<0.001) and use of nodal boost (OR=5.5, 95% CI 1.1–27.1, p=0.04) but not IMN irradiation (OR=2.7, p=0.35) or reconstruction (OR=0.62, p=0.33) were independently associated with higher OAR UD rate. For 3DCRT plans, 7.9% had OAR UD.ConclusionThe OAR UD rate with 3DCRT+/−DIBH in routine clinical practice is low and not independently associated with IMN irradiation or reconstruction presence. Women treated with IMRT had a significantly higher overall OAR UD rate, and clinicians should be aware of this as they initiate RNI treatment planning.



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