Platinum-based chemotherapy for early triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer associated with shorter survival and a higher likelihood of the cancer returning. In early TNBC, platinum-based chemotherapy has been shown to improve pathological complete response (pCR); however, its effect on long-term survival outcomes has not been fully elucidated and recommendations to include platinum chemotherapy are not consistent in international guidelines.

OBJECTIVES

To evaluate the benefits and harms of platinum-based chemotherapy as adjuvant and neoadjuvant treatment in people with early triple-negative breast cancer.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 4 April 2022.

SELECTION CRITERIA

We included randomised controlled trials examining neoadjuvant or adjuvant platinum chemotherapy for early TNBC.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were disease-free survival (DFS) and overall survival (OS). Our secondary outcomes were pCR, treatment adherence, grade III or IV toxicity related to chemotherapy, and quality of life. Prespecified subgroups included BRCA mutation status, homologous recombination deficiency (HRD) status, frequency of chemotherapy, type of platinum agent used, and the presence or absence of anthracycline chemotherapy. We assessed risk of bias using Cochrane's RoB 1 tool and certainty of evidence using the GRADE approach.

MAIN RESULTS

From 3972 records, we included 20 published studies involving 21 treatment comparisons, and 25 ongoing studies. For most domains, risk of bias was low across studies. There were 16 neoadjuvant chemotherapy studies (one of which combined neoadjuvant and adjuvant therapy) and four adjuvant chemotherapy trials. Most studies used carboplatin (17 studies) followed by cisplatin (two), and lobaplatin (one). Eight studies had an anthracycline-free intervention arm, five of which had a carboplatin-taxane intervention compared to an anthracycline-taxane control. All studies reporting DFS and OS used carboplatin. Inclusion of platinum chemotherapy improved DFS in neoadjuvant and adjuvant settings (neoadjuvant: hazard ratio (HR) 0.63, 95% confidence interval (CI) 0.53 to 0.75; 7 studies, 8 treatment comparisons, 1966 participants; high-certainty evidence; adjuvant: HR 0.69, 95% CI 0.54 to 0.88; 4 studies, 1256 participants; high-certainty evidence). Platinum chemotherapy in the regimen improved OS (neoadjuvant: HR 0.69, 95% CI 0.55 to 0.86; 7 studies, 8 treatment comparisons, 1973 participants; high-certainty evidence; adjuvant: 0.70, 95% CI 0.50 to 0.96; 4 studies, 1256 participants; high-certainty evidence). Median follow-up for survival outcomes ranged from 36 to 97.6 months. Our analysis confirmed platinum chemotherapy increased pCR rates (risk ratio (RR) 1.44, 95% CI 1.31 to 1.59; 15 studies, 16 treatment comparisons, 3083 participants; high-certainty evidence). Subgroup analyses showed no evidence of differences in DFS according to BRCA mutation status, HRD status, lymph node status, or whether the intervention arm contained anthracycline chemotherapy or not. Platinum chemotherapy was associated with reduced dose intensity, with participants more likely to require chemotherapy delays (RR 2.23, 95% CI 1.70 to 2.94; 4 studies, 5 treatment comparisons, 1053 participants; moderate-certainty evidence), dose reductions (RR 1.77, 95% CI 1.56 to 2.02; 7 studies, 8 treatment comparisons, 2055 participants; moderate-certainty evidence) and early cessation of treatment (RR 1.20, 95% CI 1.04 to 1.38; 16 studies, 17 treatment comparisons, 4178 participants; moderate-certainty evidence). Increased haematological toxicity occurred in the platinum group who were more likely to experience grade III/IV neutropenia (RR 1.53, 95% CI 1.43 to 1.63; 19 studies, 20 treatment comparisons, 4849 participants; moderate-certainty evidence), anaemia (RR 8.20, 95% CI 5.66 to 11.89; 18 studies, 19 treatment comparisons, 4757 participants; moderate-certainty evidence) and thrombocytopenia (RR 7.59, 95% CI 5.10 to 11.29; 18 studies, 19 treatment comparisons, 4731 participants; moderate-certainty evidence). There was no evidence of a difference between chemotherapy groups in febrile neutropenia (RR 1.16, 95% CI 0.89 to 1.49; 11 studies, 3771 participants; moderate-certainty evidence). Renal impairment was very rare (0.4%, 2 events in 463 participants; note 3 studies reported 0 events in both arms; 4 studies; high-certainty evidence). Treatment-related death was very rare (0.2%, 7 events in 3176 participants and similar across treatment groups; RR 0.58, 95% 0.14 to 2.33; 10 studies, 11 treatment comparisons; note 8 studies reported treatment-related deaths but recorded 0 events in both groups. Thus, the RR and CIs were calculated from 3 studies rather than 11; 3176 participants; high-certainty evidence). Five studies collected quality of life data but did not report them.

AUTHORS' CONCLUSIONS

Platinum-based chemotherapy using carboplatin in the adjuvant or neoadjuvant setting improves long-term outcomes of DFS and OS in early TNBC, with no evidence of differences by subgroup. This was at the cost of more frequent chemotherapy delays and dose reductions, and greater haematological toxicity, though serious adverse events including neuropathy, febrile neutropenia or treatment-related death were not increased. These findings support the use of platinum-based chemotherapy for people with early TNBC. The optimal dose and regimen are not defined by this analysis, but there is a suggestion that similar relative benefits result from the addition of carboplatin to either anthracycline-free regimens or those containing anthracycline agents.

Systemic Treatment Strategies for Patients with Hereditary Breast Cancer Syndromes

Hereditary breast cancer syndromes are associated with an increased risk of breast cancer and constitute a unique patient population, making up approximately 5%-10% of breast cancer cases in the United States. By virtue of the germline mutations that define these syndromes, invasive breast cancers in these patients have unique mechanisms that can be rationally targeted for therapeutic opportunities distinct from standard of care treatments in nongermline mutation associated breast cancers. This review intends to describe existing data on several of the most common hereditary breast cancer syndromes, including BRCA-related breast cancer syndrome, Li-Fraumeni syndrome, Cowden syndrome, Peutz-Jeghers syndrome, and hereditary diffuse gastric cancer syndrome, specifically focusing on rational therapeutics utilized in these distinct patient subgroups and completed or ongoing clinical trials evaluating their efficacy. By exploiting the distinct biologic features associated with these syndromes, tailored treatment strategies have the potential for improved efficacy and lower toxicity. Knowledge of the emergence of these targeted cancer therapies is critical for appropriate management in these patients, extending beyond treatment to highlight the need for appropriate genetic screening to allow for early recognition of these patients and therefore appropriate treatment.

IMPLICATIONS FOR PRACTICE

Molecular testing allows for identification of germline mutations that place individuals at high risk for breast cancer and that are associated with distinct histopathology and molecular characteristics that define the invasive breast cancer cases that these patients develop. These unique characteristics may ultimately provide rational targets for systemic treatments with improvements in both morbidity and efficacy. Identification of patients with these germline mutations is important for not only appropriate screening and prophylaxis, but knowledge of therapies specifically targeting several of the most common hereditary breast cancer syndromes is essential to ensure appropriate treatment of invasive breast cancers in these patients.