Chemotherapy Dose Intensity and Overall Survival Among Patients With Advanced Breast or Ovarian Cancer

Background: The effects of chemotherapy dose intensity on patient outcomes in advanced cancer are not well understood. We studied the association between chemotherapy relative dose intensity (RDI) and overall survival (OS) among patients with advanced breast or ovarian cancer.

Patients and methods: This retrospective cohort study included adults with advanced breast or ovarian cancer who received first-line myelosuppressive chemotherapy (January 2007 to December 2010) in US Oncology Network community practices. Dose delays ≥ 7 days, dose reductions ≥ 15%, and RDI relative to standard regimens were described. OS was measured by the Kaplan-Meier method and Cox proportional hazards models.

Results: Among 874 patients with advanced breast cancer, 33.2% experienced dose delays ≥ 7 days, 48.7% experienced dose reductions ≥ 15%, and 38.9% had RDI < 85%. In the multivariable Cox proportional hazards model, Eastern Cooperative Oncology Group performance status 1/2 versus 0 (hazard ratio [HR] = 1.45; 95% confidence interval [CI], 1.15-1.82) and triple-negative status (HR = 3.14; 95% CI, 1.15-8.62) were significantly associated with mortality. Among 170 patients with advanced ovarian cancer, 43.5% experienced dose delays ≥ 7 days, 48.2% experienced dose reductions ≥ 15%, and 46.5% had RDI < 85%. In the multivariable Cox proportional hazards model, dose reductions ≥ 15% (HR = 1.94; 95% CI, 1.09-3.46) and other tumor histology (vs. nonserous adenocarcinoma; HR = 3.55; 95% CI, 1.38-9.09) were significantly associated with mortality.

Conclusion: Dose delays, dose reductions, and reduced RDI were common. In advanced breast cancer, health status and triple-negative disease were significantly associated with mortality. In advanced ovarian cancer, dose reductions and tumor histology were significantly associated with mortality. These results can help identify potential risk factors and characterize the effect of chemotherapy dose modification strategies on mortality.