Higher breast cancer risk for childhood cancer survivors

Higher breast cancer risk for childhood cancer survivors

4 Jun 2014


According to researchers, women who have survived a childhood cancer have 4x higher breast cancer risk, even if they were not exposed to chest radiation then.

This was according to Tara Henderson, MD, MPH, of the University of Chicago.

Also, they tended to get the disease at a much younger age and were also more likely to get bilateral breast cancer, Henderson said at the American Society of Clinical Oncology annual meeting.

The latter two characteristics were similar to what is seen among women who had been exposed to chest radiation, where the increased risk of later breast cancer has been well established, Henderson said.

Study analyzed 3,768 women of whom 47 developed breast cancer

The findings come from an analysis of 3,768 women in the Childhood Cancer Survivor Study, a cohort of people who survived at least 5 years after an initial diagnosis of cancer between 1970 and 1986.

Of those, Henderson said, 47 developed breast cancer at a median of 24 years after their first diagnosis.

Analysis showed that the women with breast cancer were older at the time first diagnosis and were more likely to have died of the disease than those who did not get breast cancer -- 26% versus 6% of the cohort as a whole.

In the general population, according to data from the Surveillance, Epidemiology, and End Results (SEER) program, the median age for a breast cancer diagnosis is 61, Henderson noted.

In this cohort, the median age was 38, comparable with the 39 seen among women exposed as children to chest radiation.

The proportion of women who develop bilateral disease in the SEER database is 3% to 5%, she said, compared with 15% in her study and 13% to 17% among women exposed to early chest radiation.

Higher breast cancer risk for some groups of women

Over the whole group, the standardized incidence ratio (SIR) for breast cancer was 3.8 times what is seen in the general population. But the risk was elevated:

  • For women between ages 10 to 20 at initial diagnosis (SIR 4.8 versus 1.7 among women whose initial cancers occurred earlier)
  • For women whose primary diagnosis was leukemia (SIR 3.9 versus general population for all such disorders, 3.2 for acute lymphoblastic leukemia, and 9.3 for acute myeloid leukemia)
  • For women whose first cancer was a sarcoma (SIR 5.3 overall, 9.5 for Ewing's sarcoma, 4.6 for soft tissue sarcoma, and 4.3 for bone sarcoma)

The leukemias and sarcomas are part of the Li-Fraumeni syndrome, which raises the possibility that other diseases linked to mutations in the p53 gene might also increase the risk for later breast cancer, Henderson noted.

A multivariate risk factor analysis found that treatment of the primary tumor with anthracycline drugs or high-dose alkylating agents was also associated with increased risk of breast cancer.

Henderson noted that the study had a small number of events, which limits the ability to separate the associations with primary diagnosis and treatment, since many sarcoma patients are treated with anthracyclines or high-dose alkylators.

The study is both interesting and useful, commented Torunn Yock, MD, of Massachusetts General Hospital in Boston.

"It's useful in that it serves to highlight that the risks for childhood cancer survivors are multifaceted," she told MedPage Today. "It's not just radiation exposure that predisposes one to have a second cancer."

She noted that people with diseases associated with mutations in the p53 gene (leukemias and sarcomas) were at higher risk, as were those who were treated with some common chemotherapeutics.

"We don't classically think of these as causing secondary tumors," she said, and physicians might want to keep future risks in mind when designing a treatment plan for younger patients.

But the finding also has implications for later breast cancer screening, since breast cancer is a disease that -- when caught early -- has a higher rate of cure.

It might also lower the bar for genetic screening for p53 mutations, she said, which might have implications for watching for other tumors.


Source: MedPage Today

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