Older women with early-stage, low-risk breast cancer who were treated with radiation therapy (RT) after breast-conserving surgery (BCS) showed higher cause- specific (CSS) and overall survival (OS) rates than those who did not undergo radiation, according to research presented at the American Society for Radiation Oncology’s (ASTRO’s) 54th Annual Meeting.

The study also found a six percent decrease in the use of radiation after 2004 in this population of patients, suggesting that treatment guidelines, which allow for omission of radiation therapy, may need to be re-examined.

The study evaluated the patient records of 27,559 women from the Surveillance, Epidemiology and End Results (SEER) database from 2000 to 2008 who were over the age of 70, who had early-stage (≤ 5 cm), estrogen receptor positive (ER+), node negative breast cancer and who had completed BCS with a minimum follow-up of three months.

Patients who received radiation had a higher OS rate than those who did not, accounting for 87 percent and 73 percent at the five- and eight-year follow-up point, respectively, and 69 percent and 49 percent for those who only underwent BCS.

Radiation was also shown to improve CSS rates, which were 97 percent and 95 percent for patients who received radiation at the five- and eight-year follow-up point, compared to 95 percent and 91 percent for those who did not.

A total of 4,573 deaths were recorded, 17 percent (790) of which were attributed to breast cancer.

The purpose of the study was to assess changes in patterns of care and to determine CSS and OS outcomes with and without RT after BCS in a large, population-based group of older women.

The study separated patients into two groups: BCS or BCS plus RT, and clinical covariates were compared between the groups using the Chi-square test. Cox multivariable regression analyses were performed to determine predictors of CSS and OS.

Survival curves were calculated using the Kaplan-Meier method and compared using the log-rank test. Within the study group, 70 percent of patients received RT after BCS. From 2000 to 2004, 72 percent of patients received RT, which decreased to 66 percent from 2005 to 2008.

The study found that patients were statistically more likely to undergo RT if they were younger than 80 years old, received a diagnosis from 2000 to 2004 or if re-excision of the biopsy site was required for residual disease.

“Our research shows that older breast cancer patients who undergo radiation therapy after breast-conserving surgery have a higher cause-specific survival rate than those who do not.

In practice, however, we also found that the use of breast radiation has declined by six percent since the National Comprehensive Cancer Network treatment guidelines were revised in 2005,” said Mariam P. Korah, MD, lead author of the study and a radiation oncologist at the University of Southern California Keck School of Medicine in Los Angeles. “The large number of patients and breast cancer-specific events in this study highlighted clinically meaningful survival advantages among patients who received radiation in conjunction with breast-conserving surgery as compared to those who received breast-conserving surgery alone, which may not have been detected in earlier studies. In advancing the care of our patients, treatment recommendations should be guided by a synthesis of the best available aggregate evidence.”

Source: ASTRO