PhD Student University of North Carolina Chapel Hill Chapel Hill, United States
Background: Delivery of cancer treatments, like chemotherapy, require a complex set of decisions on the part of patients and healthcare providers that can change over time. Traditional measures of chemotherapy delivery, such as relative-dose intensity, measure the amount of chemotherapy received by the end of treatment, but mask the timing of dose reductions, delays, and omissions. These events may be important for delivering timely interventions to support adherence and lower the risk of recurrence.
Objectives: To quantify chemotherapy delivery among women with early-stage breast cancer treated in the University of North Carolina (UNC) Health System using a novel measure, longitudinal cumulative dose (LCD), for all patients and by age group.
Methods: We used an institutional database to identify women diagnosed with stage I-III breast cancer receiving adjuvant chemotherapy with a standard 4-cycle regimen of docetaxel + cyclophosphamide (TC, every 21 days) or doxorubicin + cyclophosphamide (AC, every 14 days) within the UNC Health System from April 2014 to December 2019. Data on the delivery of each chemotherapy agent was abstracted from the EHR including the dose (in mg/m2) and date of treatment administration. LCD was calculated as the amount of a given chemotherapy agent delivered at a specified time, t, divided by the total planned standard chemotherapy dose at time t. We visualized LCD curves for each chemotherapy agent and reported the median LCD and interquartile range (IQR) at the end of the regimen (day 51 for AC and day 72 for TC), overall and by age group ( < 65 years vs. 65+ years).
Results: The study population included 122 women, 79 (65%) treated with TC and 43 (35%) treated with AC. Women treated with AC were younger than those with TC (mean age 53.2 vs. 58.2), had a higher percentage of stage III disease (30% vs. 3%), and more often self-identified as Black race (26% vs. 18%). Overall, both TC and AC were well-tolerated, with only slight delays observed between the third and fourth cycles. At the end of treatment, overall median LCDs for cyclophosphamide were 100% (IQR: 99.6%, 100%) and 100% (IQR: 99.2%, 100%) for TC and AC, respectively. However, the lower quartile LCD for cyclophosphamide was 98.7% in older women treated with TC compared with 99.7% in younger women. Similar results were not observed for women treated with AC.
Conclusions: Within a cohort of women with stage I-III breast cancer treated at UNC Health System, adjuvant TC and AC were well-tolerated with LCD curves showing largely on-time and full-dose administration. Subgroup analyses showed only slight decreases in adjuvant TC LCD for patients age 65+ versus < 65 years, providing further evidence that these regimens are broadly well-tolerated.
