2084 - Reduced Frequency and Severity of Radiation Esophagitis without Marginal Failure Risk By Contralateral Esophagus Sparing IMRT in Stage III Non-Small Cell Lung Cancer Patients Undergoing Definitive Con

H. Lim¹, K. Yang¹, J. M. Noh¹, H. Pyo¹, J. M. Kim², D. Y. Kwon¹, S. G. Ju¹, and Y. C. Ahn¹; ¹Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea, Republic of (South), ²Department of Radiation Oncology, Samsung Medical Center, Seoul, Korea, Republic of (South)

Purpose/Objective(s): Radiation esophagitis is frequent and annoying toxicity in high dose thoracic radiation therapy. Contralateral esophagus sparing intensity modulated radiation therapy (CES-IMRT) has been proposed to mitigate this problem, and this is to report impact of CES-IMRT in definitive concurrent chemoradiotherapy (dCCRT) for lung cancer patients. Materials/

Methods: From January 2021 till May 2023, 183 stage III non-small cell lung cancer patients underwent dCCRT. Esophagus was located within 1 cm from internal target volume in 159 patients. We comparatively evaluated frequency and severity of esophagitis by pain-killer usage, analgesic quantification algorithm (AQA) score, and failure patterns in 159 CES-necessary patients.
Results: All patients underwent dCCRT (66 Gy in 30 fractions with concurrent chemotherapy). Actual CES-IMRT application was determined based on discretion of responsible radiation oncologists: CES-applied in 41 patients; and CES-unapplied in 118. CES-applied patients experienced pain events less frequently (pain-killer usage: 53.7% vs. 77.1%, p=0.008) and less severely (AQA score of 2-3: 39.0% vs. 68.6%, p=0.002). On multivariate analyses, overlapping volume of esophagus and planning target (HR = 1.32, 95% CI 1.12~1.55, p=0.001) and CES-IMRT application (HR = 0.31, 95% CI 0.13~0.76, p=0.010) were associated with AQA score of 2-3 less frequently. There were no differences in failure pattern, progression-free survival, and overall survival.
Conclusion: CES-IMRT application resulted in less frequent and less severe pain events without compromising oncologic outcomes. Further studies, preferably in a randomized fashion, would be desired. Abstract 2084 – Table 1

	Total (N=159)	CES-applied (N=41)	CES-unapplied (N=118)	p	CES-applied
					CE constraints fully satisfied (N=18)	CE constraints partly satisfied (N=23)	p
Median Dshort (range)	0.4 mm (-8.0~9.0)	0 mm (-8.0~7.0)	0.6 mm (-5.0~9.0)	0.146	1.0 mm (0~7.0)	0 mm (-8.0~3.0)	0.001
Median VEOP (range)	3.4 cc (0.0~32.7)	3.1 cc (0.1~13.6)	3.6 cc (0~32.7)	0.634	1.7 cc (0.1~5.7)	3.9 cc (0.1~13.6)	0.004
Median PTV length (range)	14.5 mm (4.8~26.0)	13.6 mm (4.8~24.0)	14.8 mm (6.0~26.0)	0.086	13.1 mm (8.0~19.5)	14.0 mm (4.8~24.0)	0.53
Pain killer usage				0.008			0.046
No	46 (28.9%)	19 (46.3%)	27 (22.9%)		7 (30.4%)	12 (66.7%)
Yes	113 (71.1%)	22 (53.7%)	91 (77.1%)		16 (69.6%)	6 (33.3%)
AQA score				0.002			0.735
0~1	62 (39.0%)	25 (61.0%)	37 (31.4%)		13 (56.5%)	12 (66.7%)
2~3	97 (61.0%)	16 (39.0%)	81 (68.6%)		10 (43.5%)	6 (33.3%)