Abstract PO4-02-11: Optimizing Taxane-based Chemotherapy in Breast Cancer: Retrospective study comparing 4 cycles of TC to 6 cycles of TC
Authors: Ahluwalia Amith , Koifman Michelle , Nannar Jaspreet , Vachhani Bhavya , Ashraf Kanwal , Shulimovich Maxim 
Published: May 2024

Breast cancer remains one of the most prevalent cancers among women worldwide. First-line chemotherapy options include anthracycline (AC-T) and Taxane (TC) based regimens. While anthracycline-based chemotherapy is most commonly used, the use of anthracycline-sparing regimens is also approved. The US Oncology 9735 trial conducted in the mid 2000s showed that four cycles of docetaxel and cyclophosphamide (TC4) were superior to four cycles of Doxorubicin and cyclophosphamide (AC). The follow-up ABC trials compared six cycles of TC(TC6) to AC-T. This trial showed that while AC-T was superior to TC, the difference was modest. AC-T has remained the standard of care, but TC is an acceptable option. One retrospective analysis involving 143 patients showed TC4 was non-inferior to TC6, and suggested that TC4 had fewer adverse events; however, statistical significance was not reached. The question remains whether six cycles of TC is required, or if four cycles is adequate.

Methods:

Patient information was retrieved from the EMR of a large private oncology group. The EMR was screened for all breast cancer patients who began treatment with TC between 1/1/2011 and 12/31/2021. Patients were required to have continuous follow-up, documented up to at least 6/30/2022. Only patients receiving TC as the first-line setting were included, while patients with metastatic disease were excluded.

Adjusted Kaplan Meier curves for overall survival (OS) and disease-free survival (DFS) were generated. A log-rank test was used to determine the statistical difference between the two curves. OS was defined from the date of the last chemotherapy given to death. DFS is defined from the date of the last chemotherapy given to disease recurrence. The Chi-square analysis test of homogeneity was conducted to evaluate the differences in reported symptoms. Statistical analysis was completed with IBM SPSS version 29. Ethical approval was obtained from The Brooklyn Hospital Center Institutional Review Board.

Results:

A total of 376 charts were reviewed, out of which 224 met the criteria for inclusion. Of these 191 patients received TC4 and 33 received TC6. TC4 patients were noted to be older than TC6 patients. There were a higher percentage of hormone-positive cancers in the TC4 group while the TC6 group had a larger proportion of triple-negative breast cancers. There was a larger proportion of stage III patients that received TC6 than in TC4. TC6 patients were also noted to receive neo-adjuvant chemotherapy at a substantially higher rate. A greater proportion of patients in the TC4 group received breast-conserving surgery, with radiation than the TC6 group. TC6 had a completion rate of 76 % (Table 1). There was a significant difference in DFS noted between TC4 and TC6 (p = 0.016) with TC6 patients having a higher rate of relapse. No difference was noted in the overall survival. No differences were seen in side effects between TC4 and TC6, however, there was a trend toward high rates of neutropenia, anemia, and neuropathy seen in the TC6 group (Table 2).

Conclusions:

This real-world retrospective study reviewed patients who received TC in a large community oncology practice. The study reaffirms conclusions seen in previous retrospective studies conducted in the academic setting that there is no difference in overall survival when using six cycles of TC compared to four cycles of TC. Slight detriment was seen in the DFS setting when using TC6 however the small sample size along with the larger proportion of patients with stage III disease make it challenging to interpret this finding. There was a trend towards higher toxicities with TC6 that did not reach significance. Until a prospective randomized study comparing four vs six cycles of TC is conducted no definitive conclusions can be drawn, however, this study contributes to the current body of evidence that four cycles of TC is adequate and could potentially improve the quality of life of patients with early breast cancer.

Table. Patient characteristics Patient characteristics including age, hormone status, stage, type of surgery, radiation, and treatment setting.

Table. Adverse effects Adverse effect information obtained from physician documentation, and CBC reports documented at time of treatment with TC.

Citation Format: Amith Ahluwalia, Michelle Koifman, Jaspreet Nannar, Bhavya Vachhani, Kanwal Ashraf, Maxim Shulimovich. Optimizing Taxane-based Chemotherapy in Breast Cancer: Retrospective study comparing 4 cycles of TC to 6 cycles of TC [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-02-11.