3419 - Safety and Outcomes of Lung SBRT in Severely Pulmonary Impaired Patients with FEV1 or DLCO =25% Predicted

05:45pm - 05:50pm ET

Room 258

Presenter(s)

Katherine Amarell, MD, BS - Cleveland Clinic Foundation, Cleveland, OH

K. Amarell¹, C. A. Reddy², G. M. Videtic³, and K. L. Stephans⁴; ¹Cleveland Clinic Foundation, Cleveland, OH, ²Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic Foundation, Cleveland, OH, ³Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, ⁴Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH

Purpose/Objective(s):

Clinicians may question the safety and appropriateness of lung stereotactic body radiation therapy (SBRT) for inoperable patients with severely impaired pulmonary function testing (PFTs), particularly when pre-treatment Forced Expiratory Volume in 1 second (FEV1) or diffusion capacity for Carbon Monoxide (DLCO) are =25% predicted. Published data describing tolerance, toxicity, morbidity, and cancer outcomes in this population remain limited. We analyzed our single-institution database to report relevant cancer- and treatment-related outcomes following lung SBRT in this high-risk cohort.

Materials/Methods:

An IRB-approved database was queried for patients treated with SBRT for primary lung cancers with baseline [defined institutionally as measured within 6 months prior to treatment] FEV1 or DLCO as % predicted =25. Post-SBRT PFTs were grouped at 6, 12, and 24 months using the closest assessment. OS, rates of local failure (LF), distant failure (DF), and toxicity were assessed. Factors associated with PFT decline at 6 months post SBRT were identified using logistic regression.

Results:

A total of 144 of 3060 (4.7%) patients met inclusion criteria. Median follow up was 14 months. Median age was 69.9 years, median KPS 70, 74 (51.4%) were male, and 37 (25.7%) were actively smoking at treatment. Median (range) baseline PFTs were: FEV1% 26.8 (10-102) and DLCO 22 (8.6-67). Median tumor size was 2.2 cm (0.9-6.8). Of 101 biopsied patients (70.1%), histology included 25.7% adenocarcinoma, 52.5% squamous, 7.9% small cell, and 13.9% nondiagnostic. Tumor location was central in 32 (22.2%), 10 of which were ultracentral (6.9%), and 47.2% were located in the upper lobes. Dose schedules were: 50 Gy/5 fractions (fx) (37.5%), 34 Gy/1 fx (28.5%), and 60 Gy/3 fx (23.6%).

There were eight (5.6%) G1 and G2 pulmonary toxicity events which included pneumonitis (6) and pleural effusion (2). There were three (2%) G3 toxicities (acute pneumonia, pleural effusion, pneumonitis), one (0.7%) G4 pleural effusion, and zero G5 events.

Median PFT change for the population was: at 6 months FEV1% +1.0% (n=72) and DLCO +3% (n=63); at 12 months FEV1% 0% (n=34) and DLCO -1% (n=23); at 24 months FEV1% -3% (n=23) and DLCO +5% (n=16). On univariate analysis, larger tumor size (p=0.03) was associated with FEV1% decline >10% at 6 months. No factors predicted DLCO decline >10%.

One- and three-year cumulative incidence of LF was 5.6% (95% CI 2.6–10.2%) and 7.8% (4.1–13%); DF was 9.1% (5.1–14.5%) and 13.6% (8.5–19.9%). One- and three-year OS was 67.2% (59.5–74.9%) and 33.4% (25.5–41.3%).

Conclusion:

In patients with PFTs <25% predicted, SBRT was associated with toxicity rates, minimal PFT decline, and tumor control consistent with historic lung SBRT outcomes, supporting its use in high-risk patients. OS however was lower than expected, suggesting increased mortality due to severe lung disease.