Session Item

The esophagus lies in close proximity to the supraclavicular nodal region, a target volume in regional nodal irradiation (RNI)/postmastectomy radiation therapy (PMRT). However, acute esophagitis rates are often not reported. We use a planning target volume (PTV)-based, dose volume analysis (DVA)-driven approach to RNI/PMRT using 3D conformal radiation therapy (3DCRT) or inverse-planned intensity modulated radiation therapy (IMRT) as needed to meet planning objectives. We set to determine the rate of Grade 2 (symptomatic) esophagitis (G2E) with a goal of identifying potential dose constraints to minimize this toxicity.

We identified patients that received RNI/PMRT from 1/2013-6/2019. Patients received conventional fractionation (2 Gy/day to 50 Gy) to the breast/chestwall, axillary, supraclavicular, and internal mammary chain PTVs as per the RTOG Breast Atlas. We divided the patients into training (1/2013-12/2016) and validation (1/2017-6/2019) cohorts. Our primary endpoint was the G2E rate, which we verified by identifying patients that received sucralfate and/or a viscous lidocaine/diphenhydramine/magnesium&aluminum hydroxide mixture during radiation.  We retrospectively contoured the esophagus from the caudal edge of the cricoid cartilage to the carina and recorded the mean esophageal dose and V10, V20, V30, V40, and V50. Patients in the training cohort were dichotomized by the median value for the esophageal parameters and logistic regression analysis was used to test for associations between esophageal dose and G2E. Parameters identified as associated with G2E (p<0.05) in the training cohort were then tested in the validation cohort. We report odds ratios (OR) and 95% confidence intervals (CI) adjusted for technique (IMRT v. 3DCRT) and laterality (left v. right).

The training cohort consisted of 248 patients (52% left-sided;28% IMRT). The overall G2E rate=13% and was significantly higher in IMRT vs. 3DCRT patients (20% vs. 10%,p=0.03) but not for left-side vs. right-side (15% vs. 11%,p=0.40). Median  dosimetric values were:  esophageal mean dose-9.3 Gy, V10-27%,  V20-16%, V30-8%,  V40-3% and  V50-0%. All dosimetric parameters were significantly associated with increased odds of G2E.  The validation cohort consisted of 268 patients (51% IMRT;48% left-sided) with G2E rate=17.9%. Esophageal mean dose≥9.3 Gy(OR=6.8,95% CI 2.1-21.5,p=0.001), V10≥27%(OR=11.4,95% CI 3.2-40.8,p=0.0002), V20≥16%(OR=2.5,95% CI 1.2-5.2,p=0.01), V30≥8%(OR=2.6,95% CI 1.1-5.9,p=0.02), V40≥3%(OR=3.7,95% CI 1.4-10.3,p=0.011) and V50>0%(OR=3.7,95% CI 1.0-13.2,p=0.04) were all significantly associated with G2E.

We found that G2E~15% in patients receiving RNI/PMRT with a PTV-based, DVA-driven approach and we found associations between G2E and esophageal dose. These data strongly support the routine contouring of the esophagus in RNI/PMRT planning. Our constraints are now implemented at our center and should be incorporated in future prospective protocols of RNI/PMRT to limit G2E.