Lung Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_26_3574 - Predictors of radiation esophagitis in locally advanced non-small cell lung cancer with modern radiation therapy planning

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Predictors of radiation esophagitis in locally advanced non-small cell lung cancer with modern radiation therapy planning
D. S. Bitterman1, B. Rawal2, K. M. Atkins1, T. L. Chaunzwa3, K. Diao4, P. S. Catalano2, E. H. Baldini5, A. B. Chen5, D. E. Kozono5, and R. H. Mak5; 1Harvard Radiation Oncology Program, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, 2Department of Biostatistics & Computational Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 3Yale School of Medicine, New Haven, CT, 4Harvard Medical School, Boston, MA, 5Dana-Farber Cancer Institute, Brigham and Women's Hospital, Harvard Medical School, Boston, MA

Purpose/Objective(s): Radiation esophagitis (RE) is major side effect of concurrent chemoradiation (cCRT) for locally advanced non-small cell lung cancer (NSCLC). Advances in radiation technology allow for better esophageal sparing, potentially affording opportunities to reduce RE without compromising outcomes. Existing studies on RE largely do not include patients treated using intensity modulated radiation therapy (IMRT). In this study, we aimed to determine RE frequency and predictors with modern radiation planning.

Materials/Methods: We retrospectively analyzed 594 NSCLC patients treated with definitive intent with cCRT using 3D-conformal RT (3D-CRT) or IMRT at one institution from 2001-2014. A mean esophageal dose constraint of 34 Gy was used in most cases. RE events were graded with the Radiation Therapy Oncology Group (RTOG) system. Predictors of RTOG grade ≥3 RE were analyzed with multivariable logistic regression using backward selection. Overall survival (OS) and progression free survival (PFS) were calculated with the Kaplan-Meier method.

Results: Median follow-up was 22.8 months (mo), median OS was 25.2 mo, and median PFS was 10.8 mo. Median age was 65.2 years and 49.8% of patients were male. At presentation, 8.4% were Stage II, 55.9% Stage IIIA, and 35.7% Stage IIIB. Adenocarcinoma made up 46.0% of cases, squamous cell carcinoma 30.0%, and NSCLC-NOS 24.1%. 3D-CRT was used in 75.1% of cases, and IMRT in 24.9%. Median prescribed dose was 66 Gy (range, 36-74 Gy) and median dose per fraction was 2 Gy (range, 1.8-3 Gy). Median maximum and mean esophageal doses were 64.7 Gy (range, 0.9-78.8 Gy) and 24.0 Gy (range, 0.4-56.8 Gy), respectively. Mean esophageal dose was >34 Gy in 95 (16.0%) of patients. Median esophageal V45, V55, and V60 were 28.7% (range, 0-82.7%), 17.0% (range, 0-73.7%), and 8.4% (range, 0-66.8%), respectively, and these values were higher in patients treated with IMRT (Table 1). Grade ≥3 RE was observed in 113 (19%) patients. On multivariable analysis, NSCLC-NOS histology (OR 2.08, 95% CI 1.23-3.53, p=0.006), IMRT (OR 0.36, 95% CI 0.20-0.63, p<0.001), and mean esophageal dose per Gy (OR 1.10, 95% CI 1.07-1.13, p<0.001) were associated with grade ≥3 RE.
Table 1. 3D-CRT and IMRT dose-volume metrics
3D-CRT (n=446) IMRT (n=148) p-value
Prescribed dose, Gy (median, range) 66 (36-74) 66 (40-72) 0.65
Maximum esophageal dose, Gy 63.2 (0.9-78.8) 66.9 (7.5-77.5) 0.0001
Mean esophageal dose, Gy 22.7 (0.4-56.8) 27.5 (1.6-55.4) <0.0001
Esophageal V45, % 28.1 (0-77.8) 33.2 (0-82.7) 0.0002
Esophageal V55, % 16.0 (0-71.2) 21.0 (0-73.7) 0.0005
Esophageal V60, % 5.8 (0-66.8) 16.0 (0-66.6) 0.0003

Conclusion: Mean esophageal dose was the strongest dosimetric predictor of grade ≥3 RE. Even after controlling for higher mean esophageal dose, IMRT was associated with lower RE risk. This suggests that different dose-volume constraints may be important in 3D-CRT and IMRT plans.

Author Disclosure: D.S. Bitterman: None. B. Rawal: None. K.M. Atkins: None. T.L. Chaunzwa: None. E.H. Baldini: None. A.B. Chen: None. D.E. Kozono: Research Grant; NCI. R.H. Mak: Consultant; Boehringer-Ingelheim, Inc. Stock; Celgene.

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