Pulmonary Function Test Results for Patients Treated on a Two-Institution, 4DCT-Ventilation Functional Avoidance Prospective Clinical Trial

Abstract

<h3>Purpose/Objective(s)</h3> Functional imaging has been developed that uses 4DCT images along with image processing to generate lung ventilation maps (4DCT-ventilation). 4DCT-ventilation based functional avoidance uses 4DCT-images to generate plans that avoid functional regions of the lung with the goal of reducing pulmonary toxicity for lung cancer patients. A phase II, multi-center, prospective study was completed to evaluate 4DCT-ventilation functional avoidance radiotherapy. As part of the trial, pulmonary function tests (PFTs) were acquired at baseline and 3 months following radiotherapy in order to quantitatively assess pulmonary function decline. The purpose of this study is to report the results for pre- to post-treatment PFT changes for patients treated with functional avoidance radiotherapy. <h3>Materials/Methods</h3> Patients with locally advanced lung cancer receiving curative intent radiotherapy (prescription 45-75 Gy) and curative intent chemotherapy were accrued from two institutions. Each patient had a 4DCT-ventilation image generated using 4DCT scans and image processing techniques. Favorable arc geometry and optimization techniques were used to generate functional avoidance plans based on the 4DCT-ventilation images. PFTs were obtained at baseline and 3 months (median 3.4 months) following radiotherapy and included measurements of diffusing capacity for carbon monoxide (DLCO), forced expiratory volume (FEV1), and forced vital capacity (FVC). Pre- to post-treatment PFT changes are reported as mean ± standard deviation. PFT metrics were compared for patients who did/did not experience grade 2+ pneumonitis. <h3>Results</h3> 56 patients enrolled on the study had baseline and post-treatment PFTs evaluable for analysis. The median age was 65 years, 43 (76.8%) patients had stage III disease, and 29 (51.8%) had pre-existing COPD. The mean change in DLCO, FEV1, and FVC was -11.6% ± 14.2%, -5.6% ± 16.9%, and -9.0% ± 20.1%, respectively. Mean DLCO and FEV1 change were higher for patients with grade 2+ pneumonitis than for patients with < grade 2 pneumonitis (-15.4 versus -10.8% and -14.3 versus -3.9%, respectively). <h3>Conclusion</h3> The current work is the first to quantitatively characterize PFT changes for lung cancer patients treated on a prospective functional avoidance radiotherapy study. Large review studies show mean DLCO reductions of -15.3% (range -10% to -26%) and mean FEV1 reductions of -5.5% (range -1% to -24%) for lung cancer patients treated with standard chemoradiation. In comparison to patients treated with standard thoracic chemoradiation, our data qualitatively show that functional avoidance resulted in less of a decline in DLCO and similar declines of FEV1. The presented data can help elucidate the potential pulmonary function improvement with functional avoidance radiotherapy using a quantitative, PFT-based, pulmonary function end-point.