Clinical Investigation
Pulmonary Function Testing After Stereotactic Body Radiotherapy to the Lung

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Purpose

Surgical resection remains the standard of care for operable early-stage non–small-cell lung cancer (NSCLC). However, some patients are not fit for surgery because of comorbidites such as chronic obstructive pulmonary disease (COPD) and other medical conditions. We aimed to evaluate pulmonary function and tumor volume before and after stereotactic body radiotherapy (SBRT) for patients with and without COPD in early-stage lung cancer.

Methods and Materials

A review of prospectively collected data of Stage I and II lung cancers, all treated with SBRT, was performed. The total SBRT treatment was 60 Gy administered in three 20 Gy fractions. The patients were analyzed based on their COPD status, using their pretreatment pulmonary function test cutoffs as established by the American Thoracic Society guidelines (forced expiratory volume [FEV]% ≤50% predicted, FEV%/forced vital capacity [FVC]% ≤70%). Changes in tumor volume were also assessed by computed tomography.

Results

Of a total of 30 patients with Stage I and II lung cancer, there were 7 patients in the COPD group (4 men, 3 women), and 23 in t he No-COPD group (9 men, 14 women). At a mean follow-up time of 4 months, for the COPD and No-COPD patients, pretreatment and posttreatment FEV% was similar: 39 ± 5 vs. 40 ± 9 (p = 0.4) and 77 ± 0.5 vs. 73 ± 24 (p = 0.9), respectively. The diffusing capacity of the lungs for carbon monoxide (DLCO) did significantly increase for the No-COPD group after SBRT treatment: 60 ± 24 vs. 69 ± 22 (p = 0.022); however, DLCO was unchanged for the COPD group: 49 ± 13 vs. 50 ± 14 (p = 0.8). Although pretreatment tumor volume was comparable for both groups, tumor volume significantly shrank in the No-COPD group from 19 ± 24 to 9 ± 16 (p < 0.001), and there was a trend in the COPD patients from 12 ± 9 to 6 ± 5 (p = 0.06).

Conclusion

SBRT did not seem to have an effect on FEV1 and FVC, but it shrank tumor volume and improved DLCO for patients without COPD.

Introduction

Although surgical resection remains the standard of care for operable early-stage non–small-cell lung cancer (NSCLC), a promising alternative, especially for patients unfit for the operating room, is stereotactic body radiotherapy (SBRT). The technique involves the delivery of high-dose radiation precisely to the area of the lung where the tumor is located. Multiple studies have found SBRT feasible at different doses, with tumor control rates up to 90% 1, 2, 3, 4, 5. In a Phase II study, comorbidities such as cardiovascular disease and chronic obstructive pulmonary disease (COPD) for patients undergoing SBRT were examined (6). The authors found good local control of the cancer with low overall toxicity. That same group, in 2009, reported very favorable tumor control rates after 3 years of initial SBRT (7). As SBRT continues to become more popular as both an option for patients unfit for surgery and even an alternative for surgical treatment, a better understanding of the implications of its effect on lung function for patients with and without COPD is necessary. We set out to compare patients’ pulmonary function before and after SBRT and to stratify these patients based on their baseline COPD status.

Section snippets

Patients

All patients were evaluated in a university hospital multidisciplinary lung cancer evaluation center and were diagnosed with Stage I biopsy-proven NSCLC. All patients were considered unfit for surgical treatment according to the consensus of a tumor board according to the criteria of the American College of Surgeons Oncology Group (https://www.acosog.org/). Staging of the cancer was accomplished by positron emission tomography/computed tomography and bronchoscopy with biopsy of the

Results

A total of 30 patients had a complete set of PFTs before and after SBRT. Of those, 7 had COPD (4 men, 3 women) and 23 did not have COPD (9 men, 14 women). The mean age for the COPD vs. the No-COPD group was 75 ± 7.8 vs. 77 ± 8.7 years, respectively (Table 1, Table 2, Table 3). The time between SBRT and follow-up PFT was similar in both groups: 112 ± 67.5 days for the COPD group and 112 ± 53 days for the No-COPD group. Using the Mann-Whitney U test, pretreatment FEV1 and FVC percent of predicted

Discussion

The use of SBRT in North America has been limited to medically inoperable patients. These patients present with a higher number of comorbidities, and that has a direct impact on their long-term survival. Inoue et al. (8) reported that for tumors ≤20 mm in diameter, SBRT had safe outcomes, with a 3-year survival rate of 89.9%. Several studies have been made of inoperable patients with 2- to 3-year local control rates of more than 80% 1, 2, 3, 4, 5. Despite their overall poor health, more than

Conclusion

The literature now contains several studies showing either a slight improvement or a slight decline in pulmonary function (10–15%) up to a year after SBRT. Interestingly, no study, as far as we are aware, has yet shown a crossover (i.e., an initial gain resulting in a loss or vice versa). In our data, SBRT did not seem to have a deleterious effect on FEV1 and FVC with an average follow-up time of 4 months. For patients without COPD, there was a notable improvement in DLCO, which was not

Acknowledgment

The authors thank Dr. Zhigang Xu, Ph.D., and Matthew Worth in the Medical Physics Department for help in data collection of tumor volume.

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Conflict of interest: none.

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