Impact of Treatment Delay on Clinical Outcomes in Breast Cancer Patients

SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately, 246,660 new cases of invasive breast cancer will be diagnosed in 2016 and 40,450 women will die of the disease. Patients with early stage breast cancer often receive adjuvant chemotherapy and this is even more so true for HER positive and triple negative (ER, PR and HER negative) breast cancer patients, who are at an increased risk to develop recurrent disease. Even though majority of the patients start their adjuvant chemotherapy within 4-6 weeks following surgery, the impact of delay in the initiation of adjuvant therapy on outcomes, has remained unclear. Preclinical models have suggested that there is phase of increased angiogenesis and accelerated growth of micrometastases, as well as development of drug resistant clones, following removal of the primary tumor. Previously published data from a large meta-analysis had suggested that a four week delay in the initiation of adjuvant chemotherapy resulted in a 6% increase in the risk of death and an 8% increase in the risk of relapse. Nonetheless, over the past 2 decades, there has been increasing delay for both surgery and adjuvant chemotherapy treatment intervention, following diagnosis of breast cancer. These delays have been attributed to the increasing use of prognostic tools prior to treatment intervention, in order to optimize breast cancer care, germ-line genetic testing to plan appropriate surgical intervention, as well as patients seeking immediate reconstructive surgical options. Two studies addressed the impact of delay in treatment intervention following diagnosis of breast cancer, by investigating outcomes, in a very large group of patients with breast cancer.

In the study by Bleicher, et al., the relationship between the time from diagnosis to breast cancer surgery and survival was investigated, by collecting data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database and the National Cancer Database (NCDB). The SEER-Medicare cohort had 94,544 patients 66 years or older, diagnosed between 1992 and 2009 and the NCDB cohort included 115,790 patients 18 years or older, diagnosed between 2003 and 2005. Patients included in this analysis underwent surgery as initial treatment and had a diagnosis of non-inflammatory, non-metastatic, invasive breast cancer. The primary outcome was Overall and Disease-Specific Survival, as a function of time between diagnosis and surgery, measured in 30 day increments. They noted that with each interval of treatment delay increase, Overall Survival was lower (HR=1.09; P<0.001 in the SEER-Medicare cohort and HR=1.10; P<0.001 in the NCDB cohort). This relationship was statistically significant only in stages I and II breast cancer. The authors in this study concluded that longer time to surgery is associated with lower Overall and Disease-Specific Survival.

Chavez-MacGregor et al. analyzed the outcomes of 24, 843 patients in the California Cancer Registry with stage I-III invasive breast cancer, diagnosed between January 2005 and December 2010, and treated with adjuvant chemotherapy. Time to chemotherapy was defined as the number of days between surgery and the first dose of chemotherapy, and delayed treatment was defined as 91 or more days from surgery to the first dose of adjuvant chemotherapy. Median age at the time of diagnosis was 53 years, and median time to adjuvant chemotherapy was 46 days. Patients were evaluated for Overall Survival and Breast Cancer-Specific Survival. They noted that patients receiving adjuvant chemotherapy 91 or more days following surgery experienced worse Overall Survival (HR=1.34) and worse Breast Cancer-Specific Survival (HR=1.27) compared with patients receiving adjuvant chemotherapy within 31 days from surgery and these adverse outcomes were even more so, among patients with triple negative breast cancer (HR=1.53). Factors associated with adjuvant therapy delays included, low socioeconomic status, breast reconstruction, non-private insurance, and Hispanic or African American ethnicity. The authors in this study concluded that delaying initiation of adjuvant chemotherapy 91 days or more, results in adverse outcomes and this may be even more detrimental, in patients with triple negative breast cancer.

These two studies strongly suggest that treatment delays should be avoided in patients with early stage breast cancer and if surgery is to be delayed, neoadjuvant treatment approach may be reasonable, to avoid adverse outcomes.

Time to Surgery and Breast Cancer Survival in the United States. Bleicher RJ, Ruth K, Sigurdson ER, et al. JAMA Oncol. 2016;2:330-339.

Delayed Initiation of Adjuvant Chemotherapy Among Patients With Breast Cancer. Chavez-MacGregor M, Clarke CA, Lichtensztajn DY, et al. JAMA Oncol. 2016;2:322-329.