Abstract P3-15-01: Metastatic breast cancer: A retrospective study of clinical trials versus standard therapy
Authors: Sritharan N , Tuft M , Rosenzweig MQ , Jankowitz RC 
Published: May 2019

Background: Breast cancer is a leading cause of death in women. Metastatic breast cancer (MBC) was the leading cause of death among the 41,000 patients with breast cancer who died this year. The number of available clinical trials for breast cancer patients has dramatically increased over the last two decades, yet recruitment to trials remains low.

To better understand the characteristics of women with MBC who agree to participate in clinical trials (CT) as compared to those who do not, control (C), we:

1. Compared the characteristics (age, race, tumor characteristics, and disease course) of women with MBC in the groups CT and C.

2. Compared the outcomes of women with MBC (metastatic survival), who enrolled in a clinical trial vs those who did not.

3. Noted the predictors for poor MBC survival overall

Methods: Patients with MBC, from the year 2000 to 2017, were analysed retrospectively from an established metastatic database at our institution. Characteristics and outcomes were compared for patients enrolled in clinical trials (CT) with patients who were not enrolled in any trials (C). Characteristics included race, receptor status (ER/Her2), site of initial metastasis, presence of visceral and/ or CNS metastasis, number of chemotherapy and metastatic hormonal therapy cycles. Comparison of groups utilized the Chi-square test for proportions and Student's T test for means. Univariable and multivariable associations with survival were analysed using Cox regression.

Results: Of the 660 patients, 249 enrolled in clinical trial (CT) and 411 served as controls (C). Demographic analysis showed that the age at first metastasis was identical in both the groups (52.8 ± 11.4 in CT and 53.8 ± 11.2 in C). Racial distribution was predominantly Caucasian, n= 92% (CT) vs n= 89% (C), with African Americans forming 4.5% (n=11) and 8.3% (n=34) in the respective non-Caucasians in the CT and C groups (p= 0.13). No significant differences were noted between CT and C groups in the proportion of CNS metastasis, receptor status (ER/ Her2), initial site of metastasis (visceral/ non-visceral), number of cycles of chemotherapy or a diagnosis of de novo metastatic disease. The proportion of patients with visceral metastases was higher in the CT patients (82.3%) vs. (71.3%) (p &lt; 0.012). Mortality was noted to be higher in the CT group (85.9%), when compared to C (73.2%), measured over the study duration.

Survival from the diagnosis of metastatic disease was not significantly different between CT and C patients. Worse survival outcome overall was noted in patients with triple negative disease (HR 1.7, p &lt; 0.0001), presence of visceral metastases (HR 1.6, 2.0 and 1.9 for 1, 2 and 3+ visceral metastases respectively (p &lt; 0.0001) and CNS metastases (HR 1.5, p &lt; 0.0001) in the CT group.

Conclusion: No significant demographic differences were identified between the patients enrolled in CT vs C. Higher mortality was noted in the CT group over the study duration of 17 years. The CT group had a higher number of patients with visceral metastases, but lower CNS metastases as expected for clinical trial enrolment. Although no survival difference was identified based on trial enrolment, worse outcomes were seen in patients with triple negative disease, presence of visceral or CNS metastases.

Citation Format: Sritharan N, Tuft M, Rosenzweig MQ, Jankowitz RC. Metastatic breast cancer: A retrospective study of clinical trials versus standard therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-15-01.