HOUSTON - (Aug. 11, 2015) - Chemotherapy prolongs life for older adults with most types of cancer, but for women over the age of 80 with breast cancer, the chances of survival due to chemotherapy are significantly lower, according to a study led by researchers from The University of Texas Health Science Center at Houston (UTHealth).
The results were published this month in the print edition of the Journal of American Geriatrics Society.
"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 Xianglin Du, M.D., Ph.D., lead author and professor in the Department of Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of Public Health.
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 diagnosed with Stage I to IIIA hormone receptor-negative breast cancer and 26,893 men and women diagnosed with Stage III colon cancer from 1992-2009. All subjects were over the age of 65.
Among the women who had breast cancer, chemotherapy treatment reduced the risk of death from all causes by 30 percent for women ages 65 to 69, 26 percent for women ages 70 to 74 and 24 percent for women ages 75 to 79. For women over the age of 80, chemotherapy did not significantly reduce the risk of mortality.
However, when women over the age of 80 with breast cancer combined chemotherapy and an additional treatment, Adriamycin and cyclophosphamide, they experienced a 29 percent reduced mortality risk.
While the benefit of chemotherapy in reducing the risk of mortality decreased with age for female breast cancer patients, men and women with colon cancer did not experience the same trend. Chemotherapy remained effective for colon cancer patients until the age of 89.
"Previous clinical trial research has shown that chemotherapy is inefficient for breast cancer patients over the age of 70, 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.
Additional co-authors of the study from the School of Public Health include Yefei Zhang, M.S., Rohan Parikh, M.S., David Lairson, Ph.D., and Yi Cai, M.D. Funding for the study was supported by a grant from Agency for Healthcare Research and Quality (R01-HS018956) and in part by a grant from the Cancer Prevention Research Institute of Texas (RP130051).