(ChemotherapyAdvisor) –  An increasing proportion of US women have been treated with breast-conserving surgery (BCS) instead of mastectomy for stage I breast cancer over recent decades, but rates of adjuvant radiotherapy have not improved — and not receiving radiotherapy has been associated with poorer survival rates, according to a population-based study published in the Annals of Surgical Oncology.

“There was a progressive decline in the proportion of patients with stage I breast cancer who were treated with mastectomy from 1998 to 2007,” reported lead author Shayna L. Showalter, MD, of the Department of Surgery at the University of Pennsylvania, Philadelphia, PA, and coauthors. “We found that 20% of the patients treated with BCS did not receive radiotherapy, and that this proportion was constant throughout the 20 years of the study.”

The authors assessed trends in treatment and survival rates using NCI Surveillance, Epidemiology, and End Results (SEER) data for 194,860 women diagnosed with stage I breast cancer. Mastectomy was more common among single and divorced women (P=0.007), women diagnosed during earlier years, with smaller tumor sizes or estrogen receptor negativity, and white race (all Ps<0.001), the authors reported.

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“African American women were less likely than white women to be treated with a mastectomy (OR 0.86, 95% CI 0.83-0.90; P<0.001),” the authors noted.

Radiotherapy is recommended after BCS, but SEER data suggests many women, particularly African Americans and women living in the eastern and southern/Midwestern US, did not receive radiotherapy after BCS. African American women were less likely to undergo radiotherapy than white women (OR 0.78, 95% CI, 0.84-0.83; P<0.001). Patients in the eastern US, South and Midwest were significantly less likely to receive radiotherapy than women in the western US (for east, OR 0.54, 95% CI, 0.52-0.57;  P<0.001; for South/Midwest, OR 0.77, 95% CI, 0.74-0.80; P<0.001).

Among patients undergoing BCS, survival rates were significantly higher among patients who did receive radiotherapy than among those who did not (HR 0.61, 95% CI, 0.58-0.65; P<0.001).  

It is possible that the SEER database suffers from a systematic under-ascertainment of radiotherapy, the authors cautioned; other registry studies have suggested >90% of women undergoing BCS for stage I breast cancer also undergo radiotherapy. SEER data suggest only 80% received radiotherapy.

The authors called for further research to “identify strategies to reduce racial and other demographic disparities in the receipt of radiotherapy after BCS.”

Full PDF Reprint of Study