Background: It has been observed in some settings that cancer patients with other chronic diseases (comorbidities) are less likely to receive definitive treatment for their cancer, and in general have a poorer prognosis than those patients without comorbidity. The Cancer, Comorbidity and Care (‘C3’) projects aim to investigate the impact of comorbidity and ethnicity on cancer care and outcomes in New Zealand.
Methods: Patients included in the study were diagnosed with colorectal, breast, gynaecological, upper gastrointestinal, or urological cancers identified from the national Cancer Registry between 1 July 2006 and 30 June 2008 (n=14096). Age-standardised prevalence of comorbid conditions was determined for each cancer. In addition, the influence of comorbidity on likelihood of treatment receipt and mortality was determined using regression methods.
Results: In general comorbidity was common among cancer patients. Patients with liver and stomach cancers tended to have higher comorbidity, and those with breast cancer lower comorbidity than other cancer patients. Of the 50 comorbid conditions investigated, the most common were hypertension (prevalence 8.0 to 20.9%); cardiac conditions (2.1-13.5%); and diabetes with (2.3-13.3%) and without (2.9-12.9%) complications. Conditions most consistently associated with adverse outcomes across all cancer sites were renal disease, coagulopathies and congestive heart failure. Comorbidity was associated with lower likelihood receipt of treatment and higher all-cause mortality in most cases, but this impact varied by condition and across cancer site with less impact for cancers with poor prognoses.
Conclusions: Comorbidity is common among cancer patients and associated with lower likelihood of treatment and poor patient prognosis, with the magnitude of this association varying by cancer.