(P142) Older Patients Derive Greater Benefit From Adjuvant and Neoadjuvant Radiotherapy in Diverse Solid Malignancies

April 30, 2015
Oncology, Oncology Vol 29 No 4_Suppl_1, Volume 29, Issue 4_Suppl_1

This is the largest analysis to date examining the effects of RT in a broad population of solid tumor patients. Although we were unable to control for chemotherapy use in this cohort, RT was associated with superior oncologic outcome compared with surgery alone among patients with multiple solid malignancies. This positive effect was most pronounced in older patients with breast and rectal cancer, suggesting age-dependent effects of RT.

Noah K. Yuen, MD, Arta Monjazeb, MD, PhD, Chin-Shang Li, PhD, Dariusz Borys, MD, Richard Bold, MD, Robert Canter, MD; University of California, Davis Medical Center

BACKGROUND: Radiation therapy (RT) is a standard component in the contemporary multimodality management of numerous solid malignancies. Increasing studies have shown that age-related immunologic changes may impact the bioactivity of RT. We hypothesized that outcomes of RT would be influenced by age across various solid cancers.

METHODS: Using Surveillance, Epidemiology, and End Results (SEER) data (1990–2011), we identified 959,731 adult patients (aged > 18 yr) with common nonmetastatic solid malignancies, including breast, lung, and rectal cancer, undergoing surgery ± RT. We compared patient demographics, tumor characteristics, and treatments by age. Multivariable analyses were used to examine the effect of these variables on overall survival (OS) and disease-specific survival (DSS). Hazard ratios were calculated based on multivariable Cox proportional hazards models and logistic regression analysis.

RESULTS: The study cohort consisted of 70.0% breast, 13.5% lung, 11.9% rectal, 3.4% sarcoma, and 1.2% esophageal cancer. Mean age at diagnosis was 61.1 ± 13.8 years, and 42% of patients were aged ≥ 65 years. A total of 43.2% received either adjuvant (39.0%) or neoadjuvant (4.2%) RT. With the exception of lung cancer (OS hazard ratio [HR] = 1.21; 1.19–1.23), RT was associated with improved survival in patients of all ages: breast (OS HR = 0.72; 0.71–0.73), rectal (OS HR = 0.81; 0.79–0.83), esophageal (OS HR = 0.83; 0.75–0.91), and sarcoma (OS HR = 0.63; 0.56–0.70). These positive effects were amplified in elderly patients (aged ≥ 65 yr), with breast (OS HR = 0.66; 0.65–0.66) and rectal cancers (OS HR = 0.74; 0.72–0.76) having the most benefit. On logistic regression, the HR for risk of death per year of age was lower in patients receiving RT vs those not receiving RT: breast (1.057–1.060 vs 1.072–1.074), rectal (1.043–1.048 vs 1.081–1.085), esophageal (1.006–1.023 vs 1.026–1.046), and lung cancer (1.039–1.047 vs 1.050–1.054).

CONCLUSIONS: This is the largest analysis to date examining the effects of RT in a broad population of solid tumor patients. Although we were unable to control for chemotherapy use in this cohort, RT was associated with superior oncologic outcome compared with surgery alone among patients with multiple solid malignancies. This positive effect was most pronounced in older patients with breast and rectal cancer, suggesting age-dependent effects of RT. Further investigation into the mechanism of these age-related effects is indicated.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org