Results of two Chinese phase 3 trials presented at this year’s San Antonio Breast Cancer Symposium (SABCS) 2025 provide strong support for adjuvant carboplatin in early-stage triple-negative breast cancer (TNBC).

The RJBC 1501 and CITRINE trials both demonstrated superior survival outcomes when adding adjuvant carboplatin to standard adjuvant anthracycline/taxane-based chemotherapy in early-stage TNBC.

In both trials, patients receiving carboplatin alongside standard of care demonstrated a significant disease-free survival (DFS) and overall survival benefit at 3 years. In the CITRINE trial, these patients also demonstrated a significant 3-year recurrence-free survival benefit.

The findings help clarify the long-debated role of platinum therapy in the adjuvant setting, particularly for patients who receive upfront surgery, experts said.

“Accumulating data now shows that carboplatin, when incorporated in [a] curative chemotherapy regimen, improves long-term outcomes for triple-negative breast cancer,” discussant for the studies Priyanka Sharma, MD, with The University of Kansas Cancer Center, Westwood, Kansas, told attendees.

Debate Settled?

TNBC, which makes up about 15%-20% of breast cancers, is characterized by aggressive biology and a high risk for early recurrence.

Anthracycline/taxane-based regimens have formed the backbone of adjuvant therapy, but outcomes remain suboptimal, particularly for patients with high-risk disease, leaving a need for more effective adjuvant regimens.

Several trials and meta-analyses have shown that adding carboplatin to standard anthracycline/taxane regimens can improve pathologic complete response rates in the neoadjuvant setting for high-risk, early-stage TNBC. However, the evidence for routine use of carboplatin in the adjuvant setting has been limited and inconsistent, leading to debate on whether to include it.

To help clarify the use of adjuvant carboplatin, researchers conducted the RJBC 1501 trial — an open-label, multicenter, randomized phase 3 trial that enrolled 786 Chinese women with node-positive or node-negative early-stage TNBC (tumor size ≥ 1 cm) who had undergone definitive surgery.

Patients were randomly allocated (1:1) to receive four cycles of standard epirubicin and cyclophosphamide followed by four cycles of a taxane or standard anthracycline/taxane plus carboplatin between March 2016 and March 2023. Randomization was stratified by lymph node status and baseline characteristics. The primary endpoint was DFS; distant DFS and overall survival were the key secondary endpoints.

At a median follow-up of 4.5 years, 103 DFS events occurred — 41 in the carboplatin group and 62 in the standard group. At the data cutoff date (March 2025), seven patients in the carboplatin had died vs 18 in the standard therapy group.

Adding carboplatin to standard therapy was associated with a significant DFS benefit (hazard ratio [HR], 0.66; P = .034). At 3 years, the DFS rate was 93.1% with carboplatin vs 89.8% without. At 5 years, the DFS rate was 89.5% with carboplatin and 82.6% without.

Adjuvant carboplatin also led to a significant improvement in distant DFS (HR, 0.61; P = .040) and overall survival (HR, 0.39; P = .029), reported lead author Xiaosong Chen, MD, with the Comprehensive Breast Health Center, Ruijin Hospital, Shanghai, China.

In exploratory subgroup analyses, the benefit of carboplatin was generally consistent across clinicopathologic subgroups, except for age and HER2 status. Larger relative benefits were observed in patients older than 50 years and in those with HER2 low (vs HER2 negative) disease.

Grade 3-4 adverse events were more common with carboplatin (49.9% vs 38.7%), mostly due to the higher incidence of neutropenia (47.0% vs 37.8%) and thrombocytopenia (4.5% vs 0%). Febrile neutropenia rates were similar between groups (about 2%).

Chen cautioned that the RJBC 1501 trial was conducted exclusively in a Chinese population, which may limit generalizability to other ethnic groups. In addition, only a minority of patients underwent germline or homologous recombination repair (HRR) testing, restricting insights into biologic predictors of platinum sensitivity.

Chen also cautioned that the findings should be considered in the context of the evolving standard of care incorporating neoadjuvant immunotherapy. None of the patients had received neoadjuvant therapy or a PD-1 inhibitor, such as pembrolizumab.

Results of the RJBC 1501 trial were also published online in the Journal of Clinical Oncology to coincide with presentation at SABCS.

The CITRINE Study

Results of the CITRINE trial, presented by Jun-Jie Li, MD, with Fudan University Shanghai Cancer Center, Shanghai, China, also found improved survival outcomes when adding adjuvant carboplatin to adjuvant chemotherapy.

This study enrolled 808 women who had undergone surgery for high-risk, early-stage TNBC (defined as node positive or node negative with Ki-67 labeling index of ≥ 50%).

Patients were randomly allocated (1:1) to the standard-of-care group (2- or 3-week epirubicin and cyclophosphamide followed by weekly paclitaxel) or to the carboplatin group (2-week epirubicin plus cyclophosphamide followed by weekly paclitaxel combined with carboplatin).

At a median follow-up of 44.7 months, the 3-year DFS rate was 92.3% in the carboplatin group vs 85.8% in the control group (HR, 0.64; P = .03). 

Adjuvant carboplatin also led to a significant improvement in 3-year recurrence-free survival (93.8% vs 88.3%; HR, 0.59; P = .021), 3-year distant DFS (94.8% vs 89.8%; HR, 0.61; P = .039), and 3-year overall survival (98.0% vs 94.0%; HR, 0.41; P = .011).

Subgroup analyses suggested a “consistent” treatment effect across all subgroups including pathologic stage, histological grade, BRCA1/2 mutation status, and HRR-related gene alterations.

Grade 3-4 adverse events were more common with the addition of carboplatin (66.7% vs 55.0%), with neutropenia, thrombocytopenia, anemia, and infusion-related reactions being among the most common.

As in RJBC 1501, safety data were consistent with the known safety profile of carboplatin in early TNBC, with more adverse events observed in the carboplatin arm, Li said.

Overall, the CITRINE data suggest that “the addition of carboplatin to adjuvant anthracycline/taxane-based chemotherapy significantly improves survival outcomes in patients with high-risk, early-stage TNBC, driven by reducing early recurrence risk,” Li concluded.

Based on these findings, “perhaps the more important question in the contemporary era of chemo-immunotherapy is not who should get carboplatin, but rather, can carboplatin-based regimens be used to spare anthracyclines?” asked Sharma, the study discussant.

Given that availability of immunotherapy is uneven worldwide, Sharma said she would “recommend including carboplatin in an adjuvant chemotherapy regimen for patients who do not have access to immunotherapy.”

Li had no financial relationships to disclose. Disclosure for RJBC 1501 trial authors can be found in the Journal of Clinical Oncologyarticle.