2014 SABCS, Part Four: Breast Cancer Screening and Prevention

While breast cancer outcomes have continued to improve and women are living longer after a breast cancer diagnosis, the goal of research has to be no diagnosis at all — preventing cancer from occurring in the first place. Mammography continues to be the standard screening tool, but for women with moderate to high risk, supplemental screening with ultrasound, MRI or genetic screening is often recommended.

Assessing breast density as a marker of breast cancer risk

Breast density is a known risk factor for breast cancer, and women with dense breasts detected by mammography may be referred to additional screening such as ultrasound or MRI, because dense breast tissue limits the ability of mammography to detect small potential cancers.

In 2009, Connecticut became the first state to require that radiologists inform women when their mammogram indicates a high breast density. The state legislation further mandated coverage for supplemental ultrasound screening in women with dense breasts, but limited data have been available to assess the benefit of additional ultrasound (US) screening.

Dr. Jean Weigert, a radiologist at Connecticut Central Hospital, was skeptical about the benefit of supplemental US screening in this scenario. At SABCS, she discussed results from a study she called the Connecticut Experiment, which was conducted to assess the benefit of US in detecting breast cancers in women with dense breasts. She evaluated four years of data from five ultrasound screening sites in the state and, to her surprise, found that US did improve the detection rate of breast cancer.

In spite of these findings, Dr. Weigert does not believe that US is a panacea for predicting risk in women with dense breasts. She recommends that a complete risk assessment be considered and that doctors discuss the benefits and potential harms (such as increased cost and anxiety associated with additional screening) with the patients. She and others agree that US in this scenario does not solve the potential problem of over diagnosis, or not knowing whether a small lesion detected on US is, or eventually will become, cancer.

Tamoxifen shows extended breast cancer prevention benefit

The Breast Cancer Intervention Study (IBIS-1) was a long-term study to test the benefits and risk of tamoxifen for prevention of breast cancer in high risk women. Study investigator and BCRF grantee, Jack Cuzick reported new study findings after a median follow up of 16 years. Importantly, Dr. Cuzick and colleagues (including BCRF co-investigator John Forbes) found that the five years of tamoxifen reduced the risk of breast cancer out to 20 years, though there were concerns about the increases in endometrial cancers and in estrogen receptor-negative breast cancers. Read more about the study here.

A healthy lifestyle may improve survival in some breast cancers

Observational studies have suggested that dietary fat intake may affect breast cancer outcomes. Many other studies have shown that being overweight or obesity increases the risk of breast cancer after menopause and is associated with poor breast cancer outcomes at any age. The Women’s Intervention Nutrition Study (WINS) was a randomized clinical trial to assess whether reduced fat intake influences outcomes in women with early stage breast cancer and was supported by BCRF.

The study recruited 2,437 postmenopausal women between 1994 and 2001 who received standard chemotherapy and were randomized to either a five-year low-fat diet intervention or a control group. Previously reported results of the study showed a 24 percent improvement in relapse-free survival in women in the intervention group. The women on the low-fat diet significantly reduced fat intake as well as body weight.

Lead study investigator, Rowan Chlebowski, MD, Los Angeles Biomedical Research Institute, Harbor UCLA Medical Center reported final results after more than 19 years of follow-up. While women in the low-fat diet intervention group had better survival rates than the women in the non-intervention (control) group, there was not a significant difference in deaths between the two groups (13.6 percent in the intervention group vs. 17 percent in the control group).

When breast cancer subtypes were analyzed separately, however, the low-fat diet intervention resulted in a 36 percent decrease in deaths in women whose breast cancers were ER- (did not have the estrogen receptor) and in women with neither the estrogen receptor nor progesterone receptor (which accounts for approximately 73 percent of triple negative breast cancers), the effect of the low fat diet was a 54 percent reduction in death. Given the current data on obesity and the risk of breast and other cancers, Dr. Chlebowski believes that these findings support recommendations for lifestyle interventions that target weight loss, maintenance and increased physical activity, especially during treatment. Here, BCRF grantee Hope Rugo comments on these findings.

We hope you enjoyed this series on the highlights from the 37th San Antonio Breast Cancer Symposium. Did you miss our previous coverage? Read parts one, two and three.