title: Likelihood of unacceptable normal tissue doses in breast cancer patients undergoing regional nodal irradiation in routine clinical practice.
abstract: OBJECTIVE
  As 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 doses (UDs) to organs at risk (OARs) occur and the associated factors for patients receiving RNI in daily practice.
  
  
  METHODS
  Treatment records of patients who received RNI from February 2012 to May 2015 were studied. The NSABP B51/RTOG 1304 clinical dose-volume constraints for targets/OARs receiving RNI were used as the benchmark. Dose-volume histograms were analyzed for the rate of ≥1 UD delivered to the following organs: heart, mean >5 Gy; ipsilateral lung, V20 >35%, V10 >60%, V5 >70%; contralateral lung (CL), V5 >15%; and contralateral breast, V4.1 >5%. Logistic regression was used to test the association between UDs to OAR and key variables.
  
  
  RESULTS
  Two hundred three consecutive cases received RNI (105 left, 98 right), to the chest wall in 171 (84%) and to the internal mammary nodes in 170 (84%); 77.4% of cases met all OAR constraints. The most common OAR UDs were delivered to the contralateral breast (n = 32, 15.7%) and ipsilateral lung V5 (n = 22, 10.8%). On multivariate analysis, use of intensity modulated radiation therapy (odds ratio [OR], 64.7; 95% confidence interval, 20.8-201.5; P < .001) and use of nodal boost (OR, 5.5; 95% confidence interval, 1.1-27.1; P = .04), but not internal mammary node irradiation (OR, 2.7; P = .35) or reconstruction (OR, 0.62; P = .33), were independently associated with higher OAR UD rate. For 3-dimensional conformal radiation therapy plans, 7.9% had OAR UDs.
  
  
  CONCLUSIONS
  The OAR UD rate with 3-dimensional conformal radiation therapy ± deep inspiration breath-hold in routine clinical practice is low and not independently associated with internal mammary node irradiation or reconstruction presence. Women treated with intensity modulated radiation therapy had a significantly higher overall OAR UD rate, and clinicians should be aware of this as they initiate RNI treatment planning.
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio. Electronic address: jose.bazan2@osumc.edu.
authors.forename: Jose
authors.initials: J
authors.lastname: Bazan
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio.
authors.forename: Dominic
authors.initials: D
authors.lastname: DiCostanzo
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio.
authors.forename: Karla
authors.initials: K
authors.lastname: Kuhn
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio.
authors.forename: Lonika
authors.initials: L
authors.lastname: Majithia
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio.
authors.forename: Allison
authors.initials: A
authors.lastname: Quick
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio.
authors.forename: Nilendu
authors.initials: N
authors.lastname: Gupta
authors.affiliation: Department of Radiation Oncology, Ohio State University, Columbus, Ohio.
authors.forename: Julia
authors.initials: J
authors.lastname: White
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D062485:Breath Holding; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology / Q000528:radiation effects; D008875:Middle Aged; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods