Influence of comorbidity on chemotherapy use for early breast cancer: systematic review and meta-analysis

Patients with early breast cancer and coexistent comorbidities generally experience worse prognosis which may be in part related to inferior treatment. Randomised data on chemotherapy use and tolerance in comorbid patients are limited. We aimed to review the available literature regarding the use of chemotherapy in such patients.

A systematic search of databases was performed for English-language articles evaluating the impact of comorbidity on chemotherapy use for early breast cancer. Comorbidity was assessed as a specific condition, summary count or index. Outcomes of interest were receipt of chemotherapy, change in chemotherapy delivery and occurrence of toxicity.

Sixty studies met inclusion criteria for systematic review. Thirty-three studies evaluated receipt of chemotherapy, with 19 reporting reduced treatment, particularly with higher levels of comorbidity. Meta-analysis of 10 eligible studies returned odds ratios (OR's) of 0.88 [95% confidence interval (CI) 0.80-0.96] and 0.63 (95% CI 0.49-0.80) for receipt of chemotherapy by patients with comorbidity scores of 1 and ≥2, respectively, compared with no comorbidity. Comorbidity had a generally adverse impact on the quality of chemotherapy delivery, although outcomes were heterogeneous. Toxicity was greater in patients with comorbidity, with 10 out of 13 studies reporting greater odds of toxicity or hospitalisation during chemotherapy. Meta-analysis of three studies addressing chemotherapy-associated hospitalisation produced OR's of 1.42 (95% CI 1.20-1.67) and 2.23 (95% CI 1.46-3.39) for comorbidity scores of 1 and ≥2, respectively.

Compared with their non-comorbid counterparts, comorbid patients with early breast cancer receive less quality adjuvant chemotherapy and experience greater toxicity.