Background: Patients with early breast cancer and co-existent comorbidities generally receive less guideline concordant curative treatment and experience worse prognosis. Depending on disease stage and subtype, chemotherapy can be an important treatment modality to reduce risk of recurrence and improve survival. Randomised trial data on chemotherapy use and tolerance in comorbid patients is limited.
Methods: A systematic search of databases was performed for English-language articles evaluating the impact of comorbidity on chemotherapy use in early breast cancer. Comorbidity was assessed as a specific condition, summary count or index. Outcomes of interest were receipt of chemotherapy, quality of chemotherapy delivery and occurrence of toxicity. Odds ratio’s (OR’s) stratified by level of comorbidity severity were derived where possible and results presented by narrative synthesis and meta-analysis.
Results: Sixty studies met inclusion criteria for systematic review. Most were observational cohorts and study populations were heterogeneous. Thirty-three studies evaluated receipt of chemotherapy, with 58% reporting reduced treatment, particularly with higher levels of comorbidity. Meta-analysis of 10 eligible studies returned OR’s of 0.88 (95% CI: 0.81-0.96) and 0.62 (95% CI: 0.50-0.78) for receipt of chemotherapy in 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 the 23 studies reported on greatly heterogeneous outcomes. Toxicity was also greater in patients with comorbidity, with two out of seven studies demonstrating higher non-completion of treatment and 10 out of 13 studies reporting greater odds of toxicity/hospitalisation during chemotherapy. Meta-analysis of three eligible studies reporting on chemotherapy-associated hospitalisation resulted in 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.
Conclusions: Compared with their non-comorbid counterparts, patients with early breast cancer and comorbidity receive less adjuvant chemotherapy. Furthermore, if chemotherapy is received, treatment is of lower quality and greater levels of toxicity are incurred.