Study examines OC-breast cancer risk
A recent study that examined 426 families of breast cancer patients suggests that women who have ever used earlier formulations of oral contraceptives (OCs) and also have a first-degree relative with breast cancer may be at particularly high risk for the disease.1 The increased risk associated with OC use was seen only among women who used pills marketed before 1975.
Thomas Sellers, PhD, MPH, associate director at the Mayo Clinic Cancer Center in Rochester and co-author of the study, says that the results should be encouraging for most women.
"Our findings are consistent with the 50-plus studies that show the use of oral contraceptives does not significantly increase risk of breast cancer for most women," he states. "For those with a strong family history — our results were most apparent for those with at least three relatives with cancer — oral contraceptives appear to increase risk, but only the early formulations." (The journal Contraception published a comprehensive overview and analysis of the 50-plus studies [1996; 54(suppl):1S-106S].)
Based on the current data, there is no reason for physicians to decline prescription of OCs for their patients at high familial risk, although it would seem prudent to use the lowest dose formulations possible, Sellers says.
The results of this intergenerational Minnesota study provide clinicians and average-risk women with reassurance that use of OCs does not impact breast cancer risk, notes Andrew Kaunitz, MD, professor and assistant chair in the obstetrics and gynecology department at the University of Florida Health Science Center/Jacksonville. However, the study does not exclude the possibility that OC use by high-risk women might amplify breast cancer risk. "Clinicians counseling high-risk women regarding contraceptive options will need to factor these observations into their individualized counseling," he states.
It is important to provide women who are at a high risk for breast cancer with all the information they need to make a sound decision about use of OCs, says Susan Wysocki, RNC, NP, president and CEO of the Washington, DC-based National Association of Nurse Practitioners in Women’s Health.
In talking with women about the new study, clinicians should clarify the recently published information by noting that the highest risk was among women using higher dose OCs pre-1975, Wysocki explains. Also, it is important to explain that the risk declines after OCs are discontinued.
The recently published report is one in a series, based on a long-term follow-up study of families originally identified through a patient with breast cancer at the University of Minnesota between 1944 and 1952, Sellers explains.
"We followed the sisters, daughters, granddaughters, and nieces for occurrence of cancer through 1996 and had recently reported that their risk of breast cancer was elevated compared to a control group of women who married into the families," he notes. "The most recent report in JAMA attempted to identify factors that influenced this risk further."
Because of the link between estrogens and breast cancer, it was logical to examine risks associated with oral contraceptive use, says Sellers. Although a number of studies have examined whether or not OCs were a more important risk factor among women with a family history of disease, because of the documented medical histories in up to five generations, the one published by Sellers’ group was the first to focus on those women with the strongest apparent predisposition to breast or ovarian cancer.
The elevated risk among women with a first-degree family history of breast cancer was most evident for OC use during or prior to 1975, when formulations were likely to contain higher dosages of estrogen and progestins, the study concludes. A small number of breast cancer cases limited the statistical power to detect risk among women with a first-degree relative with breast cancer and OC use after 1975.
Does the research group plan to take a second look at women with strong family histories of breast cancer in regards to use of today’s lower-dose oral contraceptives?
"Although we found no evidence that oral contraceptives introduced in the U.S. after 1975 increased risk, we recognize that this result is based on few cases of breast cancer, and the women — on average — are still young," says Sellers. "Thus, we are continuing to follow these families."
The new research also raises the question whether the effect of OCs is specific to certain genetic risk states, such as those women with BRCA1 or BRCA2 mutations or applicable to all women with an increased risk based on family history, wrote Wylie Burke, MD, PhD, associate professor in the department of medical history and ethics, University of Washington, in a companion editorial to the study.2 "Oral contraceptives cannot be viewed as an established measure to reduce ovarian cancer risk, nor can they be considered contraindicated in women with a family history of breast cancer. Rather, the use of OCs needs to be considered on an individual basis, taking into account baseline risk for breast and ovarian cancer, alternative strategies for cancer risk reduction, and other benefits OCs may provide."
References
1. Grabnick DM, Hartmann LC, Cerhan JR, et al. Risk of breast cancer with oral contraceptive use in women with a family history of breast cancer. JAMA 2000; 284:1,791-1,798.
2. Burke W. Oral contraceptives and breast cancer. A note of caution for high-risk women. JAMA 2000; 284:1,837-1,838.
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