ASTRO 2016: Advances in Radiation Therapy Have Improved Survival Rates for Patients With Early-Stage Lung Cancer
A new analysis of records in the Veterans Affairs Central Cancer Registry demonstrates a clear positive impact of the increased use of stereotactic body radiation therapy (SBRT) to treat patients with stage I non–small cell lung cancer (NSCLC) in recent years, according to research presented by Boyer et al at the 58th Annual Meeting of the American Society for Radiation Oncology (ASTRO). Escalated adoption of this advanced form of radiation therapy from 2001 to 2010 was associated with substantial increases in overall survival rates and lung cancer–specific survival rates.
“Lung cancer causes more than one million deaths each year worldwide,” said Matthew Boyer, MD, PhD, lead author of the study and a resident in radiation oncology at Duke University. “Moreover, an increasing number of localized, or stage I, lung cancer diagnoses are occurring, due to an aging population and advanced screening techniques.”
While the majority of patients with stage I NSCLC underwent surgery, radiation therapy is recommended for patients who cannot tolerate surgery or desire nonsurgical management. SBRT, which was developed in the 1990s, uses advanced imaging techniques to deliver highly-targeted radiation to a tumor and limit damage to surrounding tissue. Preserving healthy tissue is particularly important for NSCLC patients, whose tumors are located near or in essential organs, including the heart and lungs.
Study Background
Researchers sought to determine whether the increased use of SBRT in recent years had a subsequent impact on the outcomes of patients with NSCLC. Using the Veteran’s Affairs Central Cancer Registry, they identified more than 14,000 patients diagnosed with stage I NSCLC from 2001 to 2010, including 3,012 records of patients who received radiation therapy as their primary treatment. From this cohort, 468 patients were identified who had SBRT and 1,203 patients who received conventional radiation therapy (ie, the CRT group). Data regarding fractionation, comorbidities, treatment toxicity, positron emission tomography (PET) utilization, and vital status were obtained from the VA Corporate Data Warehouse.
Primary outcomes included rates of overall survival and lung cancer–specific survival measured at 4 years following radiation therapy. Researchers computed hazard ratios (HR) to compare overall survival and lung cancer–specific survival rates and changes in survival rates between the SBRT and CRT groups, as well as employed multivariate analysis to assess the influence of participant characteristics on survival outcomes.
The average age of study participants was 72, and 98.6% of patients were male. At the time of diagnosis, nearly 9 in 10 patients (89.4%) were current or former smokers. In terms of disease type, 50.5% of patients were diagnosed with stage IA NSCLC, and 41.5% were diagnosed with squamous cell carcinoma.
Findings
Average survival rates for all patients increased over the study period, as did the use of SBRT. Four-year overall survival for study participants as a whole who underwent radiation rose from 12.7% to 28.5%, and 4-year lung cancer–specific survival rose from 33.9% to 50.4%, concurrent with increased utilization of SBRT from 4.7% to 60.3%.
At 4 years’ follow-up, both overall survival and lung cancer–specific survival rates were significantly higher for SBRT patients than for CRT patients. By Kaplan Meier analysis, 4-year overall survival was 37.0% for SBRT patients, which was significantly higher than the 18.8% overall survival rate for CRT patients (HR = 0.60; P < .001). This improvement in overall survival was largely due to an increase in lung cancer–specific survival which, at 4 years, was 53.2% for patients treated with SBRT as compared to 28.3% for patients treated with CRT (HR = 0.39; P < .001).
On multivariate analysis, treatment with SBRT vs CRT was associated with a nearly 30% reduction in the risk of death (HR = 0.72; P < .001). In addition, older age (HR = 1.01 per year; P = .022), higher Charlson comorbidity score (HR = 1.52 for a score of 2 vs 0; P < .001), and higher stage (HR = 1.39 for Stage IB vs IA; P < .001) were associated with improved survival. Notably, there was no significant difference in survival on multivariate analysis based on receipt of PET scans for staging (HR = 0.88; P = .084) or treatment era (HR = 0.93 for 2006–2010 vs 2001–2005; P = .317), indicating that the doubling in survival for patients receiving radiation was strongly correlated with increased utilization of SBRT, and not with improved staging with PET scans or other improvements in treatment and care over the same time period.
“It is very rare for a study to show that double the number of patients were likely to be alive at 4 years due to the introduction of a new treatment,” said Dr. Boyer. “We identified that this doubling was due to the introduction of these advanced radiation techniques collectively termed [as] SBRT. These findings of improved survival in stage I lung cancer patients in general, and those undergoing radiation specifically, are generalizable to patients outside the VHA. Although a number of studies are underway to define the best treatment for stage I non–small cell lung cancer, our study, and others, indicate that advances in radiation treatment and delivery can improve patient survival and that SBRT should be the standard treatment for patients treated with radiation for stage I NSCLC.”
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
