Dr. Lu Zhang, postdoctoral fellow, Louisiana State University Health Sciences Center-New Orleans, School of Public Health, is the lead author of an article entitled “Impact of chemotherapy relative dose intensity on cause-specific and overall survival for stage I–III breast cancer: ER+/PR+, HER2- vs. triple-negative”. The study, published in Breast Cancer Research and Treatment, examined the various chemotherapy relative dose intensity (RDI) cut-off points by breast cancer subtype.
[Photo: Dr. Lu Zhang (left) and Dr. Tekeda Ferguson]
Chemotherapy has greatly improved breast cancer survival. A quality indicator of cancer chemotherapy implementation is RDI, a ratio of the dose intensity a patient receives over the dose intensity a standard regimen requires. Clinicians are recommended to maintain RDI at 85 percent or higher for survival benefit. In recent decades, despite different subtypes of breast cancer being identified with various prognoses and treatment options, breast chemotherapy implementation has remained identical for each subtype. The research team investigated whether maintaining high RDI is associated with better survival for each subtype and whether the optimal RDI cut-off point remains the same for each subtype.
Utilizing data from the Louisiana Tumor Registry, Centers for Disease Control and Prevention (CDC) funded “Enhancing Cancer Registry Data for Comparative Effectiveness Research” project and “Patient Centered Outcomes Research” project, all breast cancer patients diagnosed in Louisiana in 2011 were identified and five-year follow-up data collected in addition to their detailed first course of treatment information. Based on the data of 494 stage I-III female patients with estrogen receptor positive and/or progesterone receptor positive and human epidermal growth factor 2 receptor negative (ER+/PR+, HER2-), and 180 patients with all the three receptors negative, known as triple-negative breast cancer (TNBC), the researchers found that higher chemotherapy RDI is associated with better survival for both patient populations. This data suggests that to optimize survival benefits, RDI should be maintained ≥85 percent in ER+/PR+, HER2- patients, and ≥75 percent in TNBC patients. For the first time, this study evaluated the impact of chemotherapy RDI on survival for different breast cancer subtypes. More importantly, given the high toxicity associated with high RDI, this study provided a starting point for considering the possibility of tailoring chemotherapy RDI by breast cancer subtype.