Registry Data Reveals Sustained Local Control With Minimal Side Effects for Medically Inoperable, Early-Stage Lung Cancer Patients Receiving SBRT
Analysis of data from an institutional patient registry on stereotactic body radiotherapy (SBRT) indicates excellent long-term, local control in 79% of tumors for medically inoperable, early-stage lung cancer patients treated with the procedure from 2003 to 2012, according to research presented at the 2014 Chicago Multidisciplinary Symposium in Thoracic Oncology. (Abstract 116)
The 300 patients in the study had 340 lesions and were treated from October 1, 2003, through December 31, 2012, at the Cleveland Clinic, one of the early adopters of SBRT technology for lung cancer patients in the United States. Patients in the study had a median age of 74 years (range = 37–97 years), a median Karnofsky performance status of 80 (range = 40–100), and were not candidates for surgery because of associated medical conditions, of which chronic obstructive pulmonary disease was the most common (62%).
Median follow-up was 17.4 months (range = 0.3–112.2 months), with 46.7% (n = 140) alive at the time of follow-up. Median tumor diameter was 2.4 cm (range = 0.1–10 cm), and 36.3% of tumors (n = 123) had either no biopsy or a nondiagnostic biopsy. Approximately 15% of patients (n = 45) received two or more SBRT treatments.
Procedural Technique
SBRT for lung cancer necessitates accurate and custom mapping of the individual patient’s anatomy and a way of accounting for breathing motion to optimally target tumors while sparing as much of the surrounding healthy tissue as possible. In this study, all patients were uniformly treated using a vacuum-bag immobilization system and abdominal compression to limit breathing effects. Then, CT images were acquired to record tumor motion when at rest, full inhalation, and full exhalation.
These three images merged together generated the internal target volume of the tumors, essentially representing a virtual map of tumor motion. Radiation doses were calculated to deliver ≥ 95% of the planning target volume, defined as the internal target volume plus 5 mm “safety” margin. All patients received 50 Gy in five fractions delivered during 1 week by seven to nine highly targeted radiation beams.
Major Data
At 5 years post-treatment, the local control rates were 79.0% vs 75.4% for patients with central tumors vs noncentral tumors, respectively. The distant metastasis–free rates were 49.5% vs 56.7%, and disease failure–free rates were 37.3% vs 34.3%. Overall survival rates were 18.3% vs 20.3%.
The failure rates of the central vs noncentral tumors utilizing all parameters had no statistically significant differences. Rates of local, lobar, and regional node failure for lesions were 11.2%, 4.1%, and 13.5%, respectively.
Early and late toxicity, as defined by the Common Terminology Criteria for Adverse Events, version 3.0, was measured for all patients. The overall rate of any toxicity was 13.0% (n = 45), with most patients having minimal toxicities (grade 2 or less), and no grade 4 or 5 toxicity events were recorded.
The most common occurrences were chest wall toxicity (7.7%), and pneumonitis (4.1%). The toxicity rate for the 115 lesions classified as “central” tumors, according to the RTOG 0813 definition of “within or touching the zone of the proximal bronchial tree or adjacent to mediastinal or pericardial pleura,” vs noncentral tumors (225 lesions) was 15.5% (18 lesions) vs 11.7% (27 lesions).
Study Ramifications
“We have been privileged in demonstrating that lung SBRT can now be considered the standard of care for medically inoperable patients with early-stage lung cancer,” said Gregory M.M. Videtic, MD, lead study author, radiation oncologist at the Cleveland Clinic Foundation, and Associate Professor of Radiation Oncology at the Cleveland Clinic Lerner College of Medicine, Case Western Reserve University.
“Since our results indicate no unusual long-term side effects, we are hoping to extend the potential uses of this therapy to more-fit, operable lung cancer patients whose cancer has not spread outside of the lung and to collaborate with other institutions on conducting such a clinical trial. SBRT could provide a more minimally invasive procedure than surgery, with fewer side effects and improved patient outcomes,” he said.
The Symposium is sponsored by the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), the International Association for the Study of Lung Cancer (IASLC) and The University of Chicago Medicine.
The authors reported no potential conflicts of interest.
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