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C. Reddy
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MA 09 - The Current Status of Radiation Oncology (ID 666)
- Event: WCLC 2017
- Type: Mini Oral
- Track: Locally Advanced NSCLC
- Presentations: 1
- Moderators:Tomoki Kimura, Yong Chan Ahn
- Coordinates: 10/17/2017, 11:00 - 12:30, Room 316
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MA 09.04 - Increasingly Abnormal Pre-Treatment Diffusion Capacity Is Associated with Greater Local Failure After Lung SBRT (ID 7391)
11:00 - 12:30 | Author(s): C. Reddy
- Abstract
- Presentation
Background:
We hypothesized that impaired pulmonary functions tests might predict for altered lung density which would interfere with the efficacy of radiotherapy. We therefore sought to determine if there are associations between pre-treatment [preTx] forced expiratory volume in 1 second (FEV1, in L and as % predicted [%p]) and diffusion capacity (DLCO, as %p) with local failure (LF) rates seen with lung stereotactic body radiotherapy (SBRT) for medically inoperable lung cancer.
Method:
From an IRB-approved institutional prospective SBRT registry of 1330 patients, we identified 557 treated definitively for medically inoperable early stage T1-T3N0M0 non-small cell lung cancer (NSCLC) between 2003 and 2016 for whom both preTx FEV1 and DLCO were available. Lung SBRT dose/fractionation for a given pt was at the discretion of the treating physician. LF was defined as progressive and increasing CT scan abnormalities confirmed by progressive and incremental increases in lesion SUVs on serial PET imaging, with or without biopsy. Predictors of LF were determined using competing risks regression and rates of local control were determined from cumulative incidence analysis.
Result:
Pt characteristics included: female gender (52.6%); median age 74 years (range 42-95); median KPS 80 (range 50-100); median preTx FEV1 and DLCO: 1.39L (range 0.26-3.87), 60 %p (range 13-151) and 52 %p (range 10-143), respectively. Tumor characteristics included: median diameter 2.2 cm (range 0.7-7.2); median PET SUVmax 7.7 (range 0.8-56); % as T stage 1a, 1b, 2a, 2b, 3: 40.2; 35.5; 18.9; 4.5; 0.9, respectively; “central” location (per RTOG 0813) 22.6%. Median follow up was 18.3 months. At analysis, 46.9% pts were alive. Treatment characteristics included 50 Gy/5 fractions (fx) for 235 pts (42.2%), 60 Gy/3 fx for 167 pts (30%), and other schedules for 155 pts (27.8%), with the latter excluded from analysis due to variability in schedules, leaving 402 pts (72.2%). Only dose was significantly associated with LF on multivariable analysis [p=0.0057; HR =3.416, 95% CI 1.429-8.166]. Three-year cumulative incidence of LF post-SBRT for 50 Gy/5fx and 60 Gy/3 fx was 15.2% and 2.3% [p=0.024], respectively. In subset analysis of the 50 Gy/5 fx, DLCO was significant for LF both as a continuous variable and as a categorical variable. The significant cut-off for DLCO was 45%p, such that 3-year LF at <45 was 24.7% (95% CI 13.6-35.8) and at > 45 was 10.6% (95% CI 5.3-16.0), [p=0.0234; HR =0.441, %95 CI 0.217-0.895[CR1] ]. There were no significant associations between LF and pulmonary functions tests for 60 Gy/3 fx.
Conclusion:
As preTx DLCO drops below 45 %p, our findings suggest local failure increases when lung SBRT is delivered as 50 Gy/5 fx for early stage NSCLC. This warrants validation in prospective series.
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