Radiation After Breast-Conserving Surgery Increases Cause-Specific Survival Rate for Older Women With Early-Stage Breast Cancer

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| Source: American Society for Radiation Oncology

BOSTON, Oct. 29, 2012 (GLOBE NEWSWIRE) -- 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 today 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."

The abstract, "Implications of Omitting Radiation after Breast Conserving Surgery in Elderly Women with Low Risk Invasive Breast Cancer," will be presented in detail during a scientific session at ASTRO's Annual Meeting at 11:00 a.m. Eastern time, on Monday, October 29, 2012. To speak with Dr. Korah, call Michelle Kirkwood on October 28 – 31, 2012, in the ASTRO Press Office at the Boston Convention and Exhibition Center at 617-954-3461 or 617-954-3462, or email michellek@astro.org.

ASTRO's 54th Annual Meeting, held in Boston, October 28 – 31, 2012, is the premier scientific meeting in radiation oncology and brings together more than 11,000 attendees including oncologists from all disciplines, medical physicists, dosimetrists, radiation therapists, radiation oncology nurses and nurse practitioners, biologists, physician assistants, practice administrators, industry representatives and other health care professionals from around the world. The theme of the 2012 Annual Meeting is "Advancing Patient Care through Innovation" and examines how innovation in technology and patient care delivery can lead to improved patient outcomes. The four-day scientific meeting includes six plenary papers and 410 oral presentations in 63 oral scientific sessions, and 1,724 posters and 130 digital posters in 18 tracks/topic areas.

ABOUT ASTRO

ASTRO is the largest radiation oncology society in the world, with more than 10,000 members who specialize in treating patients with radiation therapies. As the leading organization in radiation oncology, biology and physics, the Society is dedicated to improving patient care through education, clinical practice, advancement of science and advocacy. For more information on radiation therapy, visit www.rtanswers.org. To learn more about ASTRO, visit www.astro.org.

2012 American Society for Radiation Oncology (ASTRO) 54th Annual Meeting

News Briefing, Tuesday, October 30, 2012, 7:00 a.m. – 7:45 a.m. Eastern time

Scientific Session: Monday, October 29, 2012, 11:00 a.m. – 12:30 p.m. ET, Boston Convention & Exhibition Center

84 Implications of Omitting Radiation after Breast Conserving Surgery in Elderly Women with Low Risk Invasive Breast Cancer
M. P. Korah, S. F. Sener, D. Tripathy, USC Keck School of Medicine, Los Angeles, CA

Purpose/Objectives: Following the publication of the CALGB 9343 and Fyles et al trials in 2004, opinions have varied regarding the benefit of radiation therapy (RT) after breast conserving surgery (BCS) in elderly women with early stage, ER+ breast cancer. The randomized controlled trials (RCTs) failed to show a survival advantage despite lower rates of local relapse with RT after BCS in women that received tamoxifen, with a small number of breast cancer specific deaths observed. The specific aims of this analysis are to assess changes in patterns of care and to determine cancer specific (CSS) and overall survival (OS) outcomes with and without RT after BCS in a large population based cohort.

Materials/Methods: The Surveillance, Epidemiology, and End Results (SEER) database was queried for women =age 70 diagnosed with T1 or T2, N0 M0 ER+ breast cancer that underwent BCS from 2000-2008, with a minimum follow-up of 3 months. The cohort was stratified by type of treatment into two groups: BCS or BCS + RT. 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.

Results: The study cohort is comprised of 27,559 women. One third of the women were =80 years. Most tumors were =2cm (85%), grade 1 or 2 (81%), and PR+ (81%). Seventy percent of patients received RT after BCS; the proportion of patients receiving RT was 72% from 2000-2004 and 66% from 2005-2008. Patients were statistically more likely to undergo RT if they met one of the following criteria: age less than 80 years, diagnosis from 2000-2004, or if re-excision of the biopsy site was required for residual disease. A total of 4,573 deaths were recorded among which 790 were attributed to breast cancer. CSS at 5/8 years was 95%/91% (BCS) vs. 97%/95% (BCS + RT), p less than 0.001. OS at 5/8 years was 69%/49% (BCS) vs. 87%/73% (BCS + RT), p less than 0.001. Radiation use was associated with improved CSS (HR: 0.61) and OS (HR: 0.51), p less than 0.001. Age =80 years and grade 3 tumors were associated with worse CSS and OS, p less than 0.001

Conclusions: In this analysis of more than 25,000 elderly women with small, ER+, N0 breast cancers, RT delivery after BCS appeared to be associated with a reduction in the risk of death. An evolution in the patterns of care was noted after 2004 with a 6% drop in RT utilization. The perceptible shift in practice paradigm dovetailed the publication of the aforementioned RCTs. The SEER database did not provide information pertaining to comorbidities, surgical margin status, and use of endocrine therapy, which may have contributed to selection bias. The large number of patients and breast cancer specific events in this analysis highlight survival differences between the BCS and BCS + RT groups, which may not have been detected in earlier studies.

Author Disclosure Block:

M.P. Korah: None. S.F. Sener: None. D. Tripathy: None.

Michelle Kirkwood, 703-286-1600,