Chemotherapy prolongs life for older adults with most types of cancer, but for women older than 80 years with breast cancer, the chances of improved survival due to chemotherapy are significantly lower, according to a study published in the Journal of American Geriatrics Society (2015; doi:10.1111/jgs.13523).

“Chemotherapy’s reduced effect on the risk of mortality in older breast cancer patients could be due to several factors: tumors being less sensitive to chemotherapy, a decrease in dosage as the body gets weaker with age, or chemotherapy killing healthy cells in addition to cancer cells,” said lead author Xianglin Du, MD, PhD, professor in the Department of Epidemiology, Human Genetics and Environmental Sciences at The University of Texas School of Public Health in Houston.

Du and fellow researchers examined data from Surveillance, Epidemiology, and End Results (SEER), a Medicare-linked database. The database held information on 14,440 women with Stage I to IIIA hormone receptor-negative breast cancer and 26,893 men and women with Stage III colon cancer diagnosed from 1992-2009. All subjects were older than 65 years.

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Among the women who had breast cancer, chemotherapy treatment reduced the risk of death from all causes by 30% for women ages 65 to 69 years, 26% for women ages 70 to 74 years, and 24% for women ages 75 to 79 years. For women older than 80 years, chemotherapy did not significantly reduce the risk of mortality.

However, when chemotherapy was combined with an additional treatment of doxorubicin and cyclophosphamide in women older than 80 years with breast cancer, mortality risk was reduced by 29% for these patients.

Although the benefit of chemotherapy in reducing the risk of mortality decreased with age for females with breast cancer, men and women with colon cancer did not experience the same trend. Chemotherapy remained effective for patients with colon cancer patients until age 89 years.

“Previous clinical trial research has shown that chemotherapy is inefficient for breast cancer patients [older than 70 years], but the trials have been considered to have small sample sizes. This study, using large sample sizes, shows that there’s strong evidence to this finding,” said Du.