The breast cancer chemoprevention debate

Acceptance and adherence to chemoprevention among women at increased risk of breast cancer

BACKGROUND

Chemoprevention is an option for women who are at increased risk of breast cancer (five year risk ≥1.7%). It is uncertain, however, how often women accept and complete five years of therapy and whether clinical or demographic factors predict completion.

METHODS

Medical records were abstracted for 219 women whose five year risk of breast cancer was ≥1.7% and who were offered chemoprevention while attending a high risk breast clinic at the Moffitt Cancer Center. We examined the likelihood of accepting chemoprevention and completing five years of therapy, and potential clinical and demographic predictors of these outcomes, using multivariable logistic regression and survival analysis models.

RESULTS

There were 118/219 women (54.4%) who accepted a recommendation for chemoprevention and began therapy. The likelihood of accepting chemoprevention was associated with lifetime breast cancer risk and was higher for women with specific high risk conditions (lobular carcinoma in situ and atypical ductal hyperplasia). Women with osteoporosis and those that consumed alcohol were also more likely to accept medication. There were 58/118 (49.2%) women who stopped medication at least temporarily after starting therapy. Based on survival curves, an estimated 60% of women who begin chemoprevention will complete five years of therapy.

CONCLUSIONS

A substantial percentage of women at increased risk of breast cancer will decline chemoprevention and among those that accept therapy, approximately 40% will not be able to complete five years of therapy because of side effects.

Chemoprevention of Breast Cancer: The Paradox of Evidence versus Advocacy Inaction

Women who are at high risk of breast cancer can be offered chemoprevention. Chemoprevention strategies have expanded over the past decade and include selective receptor modulator inhibitors and aromatase inhibitors. Physicians are expected to provide individualized risk assessments to identify high risk women who may be eligible for chemoprevention. It is prudent that physicians utilize a shared decision approach when counseling high risk women about their preventive options. Barriers and misperceptions however exist with patient and physician acceptance of chemoprevention and continue to impede uptake of chemoprevention as a strategy to reduce breast cancer risk. Programs to increase awareness and elucidate the barriers are critical for women to engage in cancer prevention and promote chemoprevention adherence.

Human cancer chemoprevention: hurdles and challenges

Cancer is considered a disease of aging since the risk for developing the disease considerably increases with age. It is estimated that 77% of all cancers are diagnosed in people who fall within the age group of 55 or older. Also, it takes several years from initiation to the development of detectable cancer. One advantage of the long latency is that it provides numerous opportunities for intervention. While intervention approaches cannot be geared towards a whole population, they can nevertheless be directed towards a defined group of people who have a greater relative risk for developing the disease. The idea of cancer prevention through the use of nontoxic agents, preferably from dietary sources, has therefore emerged as an appropriate strategy for controlling the disease. An important aspect of chemoprevention is that agents can be designed for intervention at any stage during the multistage process of carcinogenesis. This process of slowing the progression of cancer is applicable to many cancers with long latency, including prostate cancer. Over the past two decades we have put considerable effort into identifying dietary substances in the form of extracts and pure compounds that can be used for the prevention of prostate and other cancers. Although cancer chemoprevention has proven to be a successful strategy in animals and, to some extent, we can say that the mission has been accomplished, its application to humans has met with limited success. This chapter will discuss various challenges associated with chemoprevention of cancer with the focus on studies with green tea and prostate cancer.