Premenopausal women with cancer who were previously treated with radiation for a primary childhood, adolescent, or young adult cancer had worse breast cancer-specific survival, according to a new study published in Cancer Epidemiology, Biomarkers & Prevention.

These findings extended to patients who had early-stage breast cancer and other characteristics that are typically considered good prognostic factors, according to a statement from researcher Candice A. Sauder, MD.

“We traditionally use similar therapies for primary breast cancer and second primary breast cancer, and base our treatment approaches on specific prognostic factors,” Sauder said in a press release. “Our results suggest that breast cancer-related survival is significantly decreased among all survivors of childhood, adolescent, and young adult cancer who were treated with radiation therapy and then develop breast cancer.”

Treatments for many common childhood and adolescent cancers involve radiation therapy, which has been established as a risk factor for a second primary breast cancer. Second primary breast malignancies in younger patients who had received radiation therapy have unique clinical characteristics, but researchers do not know whether those characteristics are related to prior radiation or to their premenopausal status, according to the study.

To better understand this issue, investigators used the California Cancer Registry to analyze data from women aged 12 to 50 years diagnosed with primary or second primary breast cancer between January 1, 1988, and December 31, 2014. Patients with second primary breast cancer were limited to those who had a first primary cancer that had been treated with radiation between ages 12 and 39.

When compared with premenopausal women with primary breast cancer, patients with second primary breast cancer previously treated with radiation were more likely to be Hispanic or Black, had earlier stage tumors, had higher grade tumors, had cancer without lymph node involvement, and had tumors that were hormone receptor-negative. The investigators also found that women with second primary breast cancer in this cohort had approximately twice as much risk of breast cancer-specific death compared to women with primary breast cancer.

Notably, the researchers found that breast cancer-specific survival among women with a second primary breast cancer previously treated with radiation was significantly worse for all analyzed subgroups. Even women who typically have a better prognosis in the primary breast cancer setting experienced worse survival after a second primary breast cancer.

“We found that the negative impact of second primary breast cancer among women previously treated with radiation was particularly strong in subgroups of patients that have superior survival after primary breast cancer,” Sauder said in the release. “It will be important to prospectively evaluate how certain treatments, such as specific radiation fields or chemotherapeutic agents, can affect second primary breast cancer outcomes.”

REFERENCE
Radiation Treatment for Childhood or Young Adult Primary Cancer Linked to Worse Breast Cancer-specific Survival In Premenopausal Women [news release]. American Association for Cancer Research; August 26, 2020. https://www.aacr.org/about-the-aacr/newsroom/news-releases/radiation-treatment-for-childhood-or-young-adult-primary-cancer-linked-to-worse-breast-cancer-specific-survival-in-premenopausal-women/. Accessed August 27, 2020.