Progressive telomere shortening with cell division is a hallmark of aging. Short telomeres are associated with increased cancer risk, but there are conflicting reports about telomere length and mortality in breast cancer survivors.
We measured peripheral blood leukocyte telomere length at two time points in women enrolled in a multiethnic, prospective cohort of stage I to stage IIIA breast cancer survivors diagnosed between 1995 and 1999 with a median follow-up of 11.2 years. We evaluated associations between telomere length measured at mean 6 (baseline; LTL0; n = 611) and 30 months (LTL30; n = 478) after diagnosis and the change between those time points (n = 478), with breast cancer-specific and all-cause mortality using Cox proportional hazards models adjusted for possible confounders. Statistical tests were two-sided.
There were 135 deaths, of which 74 were due to breast cancer. Neither baseline nor 30-month telomere length was associated with either all-cause or breast cancer-specific mortality (LTL0: hazard ratio [HR] = 0.83, 95% confidence interval [CI] = 0.67 to 1.02; HR = 0.88; 95% CI = 0.67 to 1.15; LTL30: HR = 0.78, 95% CI = 0.59 to 1.05; HR = 0.86; 95% = CI = 0.58 to 1.26, respectively). However, participants whose telomeres shortened between baseline and 30 months were at a statistically significantly increased risk of breast cancer-specific (HR = 3.03; 95% CI = 1.11 to 8.18) and all-cause mortality (HR = 2.38; 95% CI = 1.28 to 4.39) compared with participants whose telomeres lengthened. When follow-up was censored at 5-years after diagnosis, LTL0 (HR = 0.66; 95% CI = 0.45 to 0.96), LTL30 (HR = 0.51; 95% CI = 0.29 to 0.92), and change in telomere length (HR = 3.45; 95% CI = 1.11 to 10.75) were statistically significantly associated with all-cause mortality.
Telomere shortening was associated with increased risk of breast cancer-specific and all-cause mortality, suggesting that change in blood telomere length over time could be a biomarker of prognosis. Research on determinants of telomere length and change is needed.