Abstract P4-07-60: Identification of Optimal Carboplatin Containing Regimen for Triple Negative Breast Cancer
Authors: Rempel Geoffrey J. , Rim Claire S. , Hussein Abdulkadir , Bocicariu Alina , Kulkarni Swati , Gupta Rasna , Matthews John , Kay Amin , Porter Lisa , Hamm Caroline 
Published: March 2023

Background: Current management for triple negative breast cancer (TNBC) involves chemotherapy and immunotherapy systemic treatments. TNBC treatment remains a challenge, with up to 40% of those treated using standard methods for stage I to III TNBC experiencing recurrence. Currently, the optimal carboplatin regimen for TNBC is yet to be defined. In our previous study, we identified an optimal carboplatin containing chemotherapy regimen that improved patient outcomes. In this study, we expanded the cohort as an extension of the previous prospective study to further verify these promising results.

Patients and Methods: We performed a retrospective review of 37 TNBC patients who had &lt; 10% estrogen and progesterone receptor positivity and were human epidermal growth factor receptor-2 (HER2) negative. This study was originally done in an adjuvant setting, but patients with locally advanced tumors received neoadjuvant chemotherapy. Patients received dose-dense Adriamycin, cyclophosphamide, and paclitaxel every two weeks for sixteen weeks. Adriamycin (60 mg/m^2) and cyclophosphamide (600 mg/m^2) were given intravenously every two weeks for four cycles, followed by paclitaxel (175 mg/m^2) every two weeks for four cycles. Carboplatin with an area under the curve of 6 was added to cycles two and four of paclitaxel. Last, we changed the parameters of continuing chemotherapy to allow platelet counts &gt; 70,000 × 10^9. Only paclitaxel could be modified for neuropathy.

Results: Of 37 patients enrolled in this trial, 35 patients survived without recurrence, one required a dose reduction in paclitaxel, and one has incomplete staging as grade is still pending. The two patients that did experience recurrence died. Of these two patients, the first had American Joint Committee on Cancer (AJCC) 7 stage IIIC cancer, and the second had two separate TNBCs at presentation – AJCC-7 IIB cancer of the right breast and AJCC-7 IIA cancer of the left breast. Under the AJCC-8 system, the first patient had AJCC-8 IIIB cancer, while the second patient had AJCC-8 IIIB cancer of the right and left breasts. These data suggest a completion rate of 97%, overall survival (OS) rates of 95% (AJCC-7 & 8), and progression free survival (PFS) rates of 95% and 94% (AJCC-7 & 8, respectively; Table 1). Additional stage-specific survival metrics and patient staging information are available in Table 1. Median follow-up in this study was 3.14 years. This is consistent with data from our previous study with significant PFS benefit over historic chemotherapy. All patients completed this regimen with no dose reductions of carboplatin and a 32% dose reduction in paclitaxel due to neuropathy. Toxicity was established in our previous study. The favourable toxicity profiling of the regimen allowed maximal tolerance for patients.

Conclusion: Although administration of carboplatin with chemotherapy for TNBC is known to be beneficial, the ideal carboplatin containing regimen has not been identified because of concerns regarding toxicity and low completion rates. Here, an optimal carboplatin-containing regimen identified in our previous clinical trial led to 95% overall survival rates (AJCC-7 & 8), 95% and 94% progression free survival rates (AJCC-7 & 8, respectively), and a 97% completion rate for 37 TNBC patients. A limitation is that this is a small single center trial, and plans are underway to test this regimen with immunotherapy in a larger randomized control trial.

Table 1: Patient Staging and Survival Metrics.

Citation Format: Geoffrey J. Rempel, Claire S. Rim, Abdulkadir Hussein, Alina Bocicariu, Swati Kulkarni, Rasna Gupta, John Matthews, Amin Kay, Lisa Porter, Caroline Hamm. Identification of Optimal Carboplatin Containing Regimen for Triple Negative Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-60.