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Breast cancer survivors do not face increased chronic disease mortality
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Women with breast cancer who achieved 5-year survival demonstrated a comparable risk for mortality from new chronic diseases as women without cancer in the general population, according to study results.
However, patients with breast cancer who received chemotherapy and radiotherapy demonstrated greater risks for death from new chronic diseases.
“Increasing life expectancy and improved breast cancer prognosis have resulted in growing numbers of breast cancer survivors at risk of other chronic diseases,” Anne Gulbech Ording, PhD, of the department of clinical epidemiology at Aarhus University Hospital, Denmark, and colleagues wrote. “It remains unknown … if specific chronic diseases diagnosed during long-term follow-up are more often fatal in breast cancer survivors than in women free of breast cancer.”
Ording and colleagues evaluated data from 32,403 Danish patients with breast cancer who achieved 5-year survival and an age-matched comparison cohort of 162,015 women without cancer from the general population. The median age of the entire population was 66.4 years (range, 58.9-74.7).
All patients in the breast cancer cohort had undergone at least one prior treatment. Most patients (97%) underwent surgery; an additional 29% underwent radiotherapy, 27% received hormone therapy and 15% underwent chemotherapy.
Researchers examined all-cause mortality associated with incident chronic diseases among the two cohorts separately for 14 years to inform preventive strategies for long-term breast cancer survivors.
Median follow-up was 4.6 years from the index date 5 years after diagnosis for the breast cancer cohort, and 5.3 years from the index date for the cohort without cancer.
Thirty percent of breast cancer survivors and 26% of the comparison cohort were diagnosed with an incident chronic disease. A greater proportion of breast cancer survivors compared with women in the comparison cohort demonstrated a Charlson comorbidity index (CCI) of 4 or worse during follow-up (9.4% vs. 4%). Researchers noted median age at diagnosis and types of diagnoses were similar among both cohorts.
Fifty-one percent of the breast cancer cohort died during 14 years of follow-up compared with 39% of the comparison cohort. However, analyses adjusted for age and prevalent CCI score at index indicated the mortality rate ratios (MRRs) associating any incident CCI disease compared with the absence of incidence disease were comparable in the breast cancer survivor cohort (MRR = 7.1; 95% CI, 6.7-7.4) and comparison cohort (MRR = 7.5; 95% CI, 7.3-7.7).
Mortality was greater among breast cancer survivors who received chemotherapy (MRR = 10; 95% CI, 8.7-12) or radiotherapy (MRR = 9.8; 95% CI, 8.8-11) compared with women treated with surgery (MRR = 7; 95% CI, 6.7-7.4) and hormone therapy (MRR = 6.3; 95% CI, 5.8-6.9).
Mortality from incident diseases other than breast cancer was highest among women younger than 60 years (MRR = 14; 95% CI, 12-15) and lowest among those aged at least 80 years (MRR = 3.8; 95% CI, 3.5-4.1).
The researchers acknowledged several limitations, including the inability to examine whether the breast cancer survivor cohort had diseases diagnosed at less severe stages than the comparison cohort, and that the analysis was restricted to patients with breast cancer who received treatment between 1994 and 2003, which may not account for more recently developed treatment options.
“Previous investigations demonstrated that 5-year breast cancer survivors have a similar frequency of prevalent and incident diseases as women from the general population, in agreement with our study,” Ording and colleagues concluded. “The initial breast cancer may therefore play a minor role in the association between new chronic diseases other than cancer and death in long-term survivors.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures.
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