The prevalence of coexistent diseases in addition to breast cancer becomes increasingly important in an ageing population. However, the clinical implications are unclear. The age-specific prevalence of serious comorbidity among all new breast cancer patients diagnosed from 1995 to 2001 (n=8966) in the South of the Netherlands was analysed in relation to age, stage and treatment. Independent prognostic effects of age and comorbidity were evaluated (follow-up was continued until 1 January 2004). The prevalence of comorbidity increased from 9% for those aged <50 years to 56% for patients aged 80+ years. The most frequent conditions were cardiovascular disease (7%), diabetes mellitus (7%), and previous cancer (6%). In the presence of comorbidity, fewer patients received radiotherapy (51% vs. 66%, P<0.0001) and fewer patients who underwent breast-conserving surgery also had axillary dissection (P<0.0001). Relative 5-year survival rates for patients without comorbidity (87%) were significantly higher (P<0.01) than those for patients with previous cancer (77%), diabetes mellitus (78%), and for patients with 2+ coexistent diseases (59%). Relative survival of patients without comorbidity increased with age to 93% for patients older than 70 years. Comorbidity negatively affected prognosis, independent of age, stage of disease, and treatment (Hazard Ratio (HR)=1.3, P=0.0001 for one coexistent disease and HR=1.4, P=0.0001 for 2+ coexistent diseases). The most important effects were found for previous cancer (HR=1.4, P=0.003), cerebrovascular disease (HR=1.6, P<0.004) or dementia (HR=2.3, P<0.0001). Elderly breast cancer patients can be divided in those without other diseases, who have a relatively good prognosis, and those who have at least one other serious coexistent disease and significantly poorer prognosis.
Louwman, W. J., Janssen Heijnen, M. L., Houterman, S., Voogd, A. C., Van der Sangen, M. J. C., Nieuwenhuijzen, G. A. P., & Coebergh, J. W. W. (2005). Less extensive treatment and inferior prognosis for breast cancer patient with comorbidity: a population-based study. European Journal of Cancer, 41(5), 779-785. https://doi.org/10.1016/j.ejca.2004.12.025