Lung Cancer

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TU_34_3652 - Ultra-Central Radiation of Sixty-Two Thoracic Tumors Using 10 Fraction Stereotactic Body Radiation Therapy(SBRT): Outcome and Toxicity Analysis

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

Ultra-Central Radiation of Sixty-Two Thoracic Tumors Using 10 Fraction Stereotactic Body Radiation Therapy(SBRT): Outcome and Toxicity Analysis
S. S. Sood1, R. G. Ganju1, M. J. Tennapel2, X. Shen3, A. M. Chen1, and F. Wang1; 1Department of Radiation Oncology, University of Kansas School of Medicine, Kansas City, KS, 2Department of Radiation Oncology, University of Kansas Medical Center, Kansas City, KS, 3University of Kansas School of Medicine, Department of Radiation Oncology, Kansas City, KS

Purpose/Objective(s): Treatment of ultra-central thoracic tumors, where the planning target volume (PTV) overlaps the mediastinal structures (trachea, primary bronchial tree, great vessels, and esophagus) with ablative doses delivered by SBRT remains controversial and challenging due to concern for normal tissue toxicity. We report our clinical outcomes of patients with ultra-centrally located primary or recurrent/metastatic tumors treated with 10 fractions SBRT.

Materials/Methods: Sixty-two patients with ultra-centrally located lung tumors treated at our institution with 10 fractions SBRT from November 2009 to March 2017 were included in this IRB approved retrospective analysis. Patients included in the study had either primary (34%), recurrent (37%), or limited volume metastatic disease (29%). Twenty-three (37%) patients had a prior a history of previous in field thoracic radiation. Treated tumor location included the mediastinum (n=13, 21%), hilum (n=29, 47%), mediastinum and hilum (n=9, 14%), and lung parenchyma (n=11, 18%). Endpoints evaluated included tumor local control, progression free survival, overall survival and toxicity.

Results: Median follow up time was 12 months (1 to 82 months). Median fraction size and biologically effective dose (BED) were 6.5 Gy (5 to 7 Gy) and 107 (56 to 119) respectively. Median PTV was 66 cc (4 to 591 cc). In the re-irradiation cohort, median time from previous treatment was 15 months (3 to 101 months). The 1-year local control (LC) rates, progression free survival (PFS) and overall survival (OS) were 84 %, 39% and 62%, respectively. Higher LC rates were observed in tumors with adenocarcinoma histology when compared to squamous cell histology (p=0.033). There were no significant correlations between LC rate and total dose, target size, or tumor location (p>0.05). The 1 year PFS (66% vs. 26%, p<0.0001) and OS (73% vs. 57%, p=0.004) significantly differed between the primary and non-primary (metastatic/recurrent) cohorts. However, there was no significant difference between the 1 year LC rates between these two cohorts (89% vs. 82%, p=0.268). Overall, ≥ grade 2 and ≥ grade 3 toxicities were observed in fifteen (24%) and three patients (6%) respectively. Observed ≥ grade 2 toxicity in the re-irradiation vs. no re-irradiation group were 34% vs. 18% (p=0.261). The most common toxicity was ≥ grade 2 pneumonitis (19%). One patient, in which tumor was abutting the esophagus, experienced grade 3 esophagitis. Three (4%) patients experienced hemoptysis at time of death. On detailed review, these three deaths were felt to be related to tumor progression and scored as having an “unlikely” treatment-related death between 9 and 24 months after treatment. No definite grade 4 or 5 toxicities were observed.

Conclusion: Our results demonstrate that hypofractionated SBRT is a feasible treatment option for either primary or recurrent ultra-central thoracic tumors. Our results are limited by our relatively shorter follow up interval.

Author Disclosure: S.S. Sood: None. R.G. Ganju: None. M.J. Tennapel: None. X. Shen: None.

Sumit Sood, MD

University of Kansas Medical Center

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