Prophylactic surgery greatly reduces cancer risk, but by how much is unclear

July 01, 2003

The risk reductions suggested by studies examining the value of prophylactic surgery for the prevention of breast and ovarian cancer in high-risk women may be over- or underestimated because of potentially unrecognized biases in study design, according to a commentary in the July 2 issue of the Journal of the National Cancer Institute. Understanding these biases might help researchers better evaluate past studies and improve the design of future studies.

Women who carry germline mutations in the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 are at increased risk of breast and ovarian cancer. In studies, prophylactic bilateral mastectomy has been associated with an 85% to 100% reduction of breast cancer risk. Prophylactic oophorectomy (surgery to remove the ovaries) has been associated with a similar risk reduction in ovarian cancer and in breast cancer.

Hester M. Klaren, M.D., Matti A. Rookus, Ph.D., and their colleagues from the Netherlands Cancer Institute in Amsterdam, caution that such studies contain a number of potential biases. One such bias is confounding by indication, which occurs when comparing surgery and nonsurgery patients who are from families with a different baseline risk of breast and ovarian cancer. This form of bias may lead to an underestimation of risk reduction after prophylactic oophorectomy.

Familial-event bias may occur when a woman's decision to undergo prophylactic surgery for a certain cancer is influenced by events involving a family member who was recently diagnosed with that cancer or died from that cancer. If this familial event is also included in the study, this may result in bias. As a consequence, cancer risk among women in the nonsurgery group may be overestimated, and this will result in an overestimation of the risk reduction after prophylactic surgery.

Other potential biases include survival bias, detection bias, testing bias, and confounding by other risk factors for breast and ovarian cancer.

The authors say that such biases need to be considered seriously, particularly because most biases seem to result in a misestimation of the benefit from prophylactic surgery. They say that a more critical discussion about potential biases, including an estimation of their direction and quantitative impact, is needed.

"Only in this way can BRCA1/2 mutation carriers, clinical geneticists, and treating physicians obtain more accurate information about the true extent of cancer risk reduction from prophylactic surgery," they say. "This valid estimate of risk reduction may become even more crucial in the future when data become available regarding the efficacy of new surveillance methods, such as magnetic resonance imaging, and new chemoprevention agents, such as raloxifene."
-end-
Contact: Netherlands Cancer Institute
Department of Communications
31-20-5122999
l.kuipers@nki.nl.

Klaren HM, van't Veer LJ, van Leeuwen FE, Rookus MA. Potential for bias in studies on efficacy of prophylactic surgery for BRCA1 and BRCA2 mutation. J Natl Cancer Inst 2003;95:941-7.

Note: The Journal of the National Cancer Institute is published by Oxford University Press and is not affiliated with the National Cancer Institute. Attribution to the Journal of the National Cancer Institute is requested in all news coverage.

Journal of the National Cancer Institute

Related Breast Cancer Articles from Brightsurf:

Oncotarget: IGF2 expression in breast cancer tumors and in breast cancer cells
The Oncotarget authors propose that methylation of DVDMR represents a novel epigenetic biomarker that determines the levels of IGF2 protein expression in breast cancer.

Breast cancer: AI predicts which pre-malignant breast lesions will progress to advanced cancer
New research at Case Western Reserve University in Cleveland, Ohio, could help better determine which patients diagnosed with the pre-malignant breast cancer commonly as stage 0 are likely to progress to invasive breast cancer and therefore might benefit from additional therapy over and above surgery alone.

Partial breast irradiation effective treatment option for low-risk breast cancer
Partial breast irradiation produces similar long-term survival rates and risk for recurrence compared with whole breast irradiation for many women with low-risk, early stage breast cancer, according to new clinical data from a national clinical trial involving researchers from The Ohio State University Comprehensive Cancer Center - Arthur G.

Breast screening linked to 60 per cent lower risk of breast cancer death in first 10 years
Women who take part in breast screening have a significantly greater benefit from treatments than those who are not screened, according to a study of more than 50,000 women.

More clues revealed in link between normal breast changes and invasive breast cancer
A research team, led by investigators from Georgetown Lombardi Comprehensive Cancer Center, details how a natural and dramatic process -- changes in mammary glands to accommodate breastfeeding -- uses a molecular process believed to contribute to survival of pre-malignant breast cells.

Breast tissue tumor suppressor PTEN: A potential Achilles heel for breast cancer cells
A highly collaborative team of researchers at the Medical University of South Carolina and Ohio State University report in Nature Communications that they have identified a novel pathway for connective tissue PTEN in breast cancer cell response to radiotherapy.

Computers equal radiologists in assessing breast density and associated breast cancer risk
Automated breast-density evaluation was just as accurate in predicting women's risk of breast cancer, found and not found by mammography, as subjective evaluation done by radiologists, in a study led by researchers at UC San Francisco and Mayo Clinic.

Blood test can effectively rule out breast cancer, regardless of breast density
A new study published in PLOS ONE demonstrates that Videssa® Breast, a multi-protein biomarker blood test for breast cancer, is unaffected by breast density and can reliably rule out breast cancer in women with both dense and non-dense breast tissue.

Study shows influence of surgeons on likelihood of removal of healthy breast after breast cancer dia
Attending surgeons can have a strong influence on whether a patient undergoes contralateral prophylactic mastectomy after a diagnosis of breast cancer, according to a study published by JAMA Surgery.

Young breast cancer patients undergoing breast conserving surgery see improved prognosis
A new analysis indicates that breast cancer prognoses have improved over time in young women treated with breast conserving surgery.

Read More: Breast Cancer News and Breast Cancer Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.