Risk of Death From Breast Cancer Higher Among Older Patients
Among postmenopausal women with hormone receptor-positive breast cancer, increasing age was associated with a higher risk of death from breast cancer, according to a study in the February 8 issue of JAMA.
“Breast cancer is the leading contributor to cancer incidence and cancer mortality in women worldwide, with 1,383,500 new cases in 2008. In the United States in 2008, 41 percent of these women were aged 65 years or older at diagnosis. Because breast cancer incidence increases with increasing age, changing demographics and continuously increasing life expectancy will further enlarge the number of older women confronted with breast cancer,” according to background information in the article. “In addition to classic tumor-related prognostic factors, patient characteristics may be associated with breast cancer outcome.”
Willemien van de Water, M.D., of the Leiden University Medical Center, Leiden, the Netherlands, and colleagues conducted a study to assess disease-specific mortality among age groups in postmenopausal patients with hormone receptor-positive breast cancer. The study consisted of an analysis of 9,766 patients enrolled in the TEAM (Tamoxifen Exemestane Adjuvant Multinational) randomized clinical trial between January 2001 and January 2006. Age at diagnosis was categorized as younger than 65 years (n = 5,349), 65 to 74 years (n = 3,060), and 75 years or older (n = 1,357).
During median (midpoint) follow-up of approximately 5.1 years, there were a total of 1,043 deaths. The number of deaths was 391 (7.3 percent) in patients younger than 65 years, 341(11.2 percent) in patients ages 65 to 74 years, and 311 (22.9 percent) in patients ages 75 years or older. Cumulative incidence of death due to breast cancer increased from 5.7 percent in patients younger than 65 years, 6.3 percent in patients 65 to 74 years of age, to 8.3 percent in patients 75 years or older.
Increasing age was associated with a lower number of deaths due to breast cancer as a proportion of all-cause mortality (less than 65 years, 77.5 percent; 65-74 years, 56.3 percent; 75 years or older, 36.3 percent). Additional analysis indicated that compared with patients younger than 65 years, disease-specific mortality increased with age for patients ages 65 to 74 years and patients 75 years or older.
Risk Factors for Breast Cancer in Older Women
Family history appears to be a risk factor even for older women. However, familial prevalence does not necessarily imply inheritance, because environmental conditions in the same household (e.g., dietary habits, substances in the air) hypothetically may cause a cluster of cancers in a family. Only a negligible proportion of breast cancers in older women are associated with known genetic mutations.
Risk Factors for Breast Cancer
Age
Family history
Endocrine history
-Early menarche and late menopause
-Late age of first completed pregnancy
-Number of pregnancies
-Android obesity
-Hormone replacement therapy
Alcohol use
Nutritional factors (e.g., dietary fat)
Ionizing radiation
Pathophysiology in Older Women
According to both clinical observations and laboratory studies, breast cancer becomes more indolent in the aged. Thus, as women age, the prevalence of non–life-threatening metastases appears to increase, while the incidence of life-threatening metastases tends to decrease. The risk of death due to metastatic disease also decreases with advancing age.
One explanation for the more indolent course of breast cancer in older women is that the prevalence of hormone-receptor–rich, well-differentiated and slowly proliferating neoplasms increases with age. The ability of the host to support tumor growth may also decrease with age.
The researchers also found that mortality from other causes increased with age, and that increasing age was associated with a higher risk of breast cancer relapse.
The authors speculate that a possible underlying mechanism that may help explain the age-specific outcome in this relatively healthy population is that older patients may experience undertreatment, and in particular undertreatment of either chemotherapy or radiotherapy.
“In conclusion, regardless of a higher risk of other-cause mortality and independent of tumor and treatment characteristics, disease-specific mortality increases with age among postmenopausal women with hormone receptor-positive breast cancer. These data underline the need for age-specific breast cancer studies in order to improve breast cancer outcome in patients of all ages. Moreover, future detailed population-based and translational studies may increase insight into causal factors of higher disease-specific mortality and breast cancer relapse with increasing age,” the researchers write.