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Trastuzumab-dkst Shows Promising Results in Real-World Setting for HER2+ Breast Cancer


A Brazilian real-world study found trastuzumab-dkst to be an effective and safe adjuvant therapy for HER2-positive (HER2+) breast cancer, with clinical outcomes comparable to reference trastuzumab.

Trastuzumab-dkst was found to be an effective and safe treatment option as adjuvant therapy in HER2-positive (HER2+) breast cancer, with comparable clinical outcomes to the reference product (Herceptin), according to a Brazilian study published in Oncology and Therapy.1

doctor with breast cancer ribbon | Image credit: Romolo Tavani - stock.adobe.com

Female breast cancer has consistently been a major health concern, as evidenced by its status as the most commonly diagnosed cancer worldwide in 2020, with 2.3 million new cases | Image credit: Romolo Tavani - stock.adobe.com

Female breast cancer has consistently been a major health concern, as evidenced by its status as the most commonly diagnosed cancer worldwide in 2020, with 2.3 million new cases. In Brazil, it is anticipated that 73,610 new breast cancer cases will occur annually between 2023 and 2025, corresponding to an adjusted incidence rate of 41.89 cases per 100,000 women.2 Data from 14 population-based registries in Brazil showed a stable breast cancer incidence from 2000 to 2010.

Trastuzumab improves survival in HER2+ breast cancer but can be very costly. The present multicentric, observational, prospective real-world study assessed the biosimilar trastuzumab-dkst in 59 Brazilian patients with early-stage HER2+ breast cancer.

“While randomized clinical trials play a crucial role, they often have limitations, such as strict eligibility criteria and potential underestimation of real-world issues such as compliance and tolerability. As a result, the effectiveness of a treatment in clinical practice may differ from trial expectations. Real-world evidence studies are thus increasingly important in oncology, offering insights into the long-term safety and effectiveness of treatments in broader patient populations,” the authors explained.

In the present study (NCT03892655), female participants aged 18 or older were included; those with cardiac dysfunction or improper use of trastuzumab-dkst were excluded. Data on demographics, medical history, and treatment were collected, with effectiveness assessed via invasive disease-free survival (IDFS) and overall survival (OS). Safety was evaluated using the Eastern Cooperative Oncology Group (ECOG) performance scale and monitoring adverse events (AEs) and left ventricular ejection fraction (LVEF). Partial results from participants who completed treatment by February 2022 across 11 institutions were included.

Of 176 enrolled patients, data from the first 59 who met inclusion criteria and completed treatment with trastuzumab-dkst by February 2022 were presented. These participants (mean [SD] age, 51.7 [12.9] years) represented the initial cohort of an ongoing study. All patients underwent surgery, with 67.8% having conservative breast surgery and 32.2% undergoing mastectomy. The mean time from diagnosis to the first adjuvant treatment with trastuzumab-dkst was 5.5 months. The median age at diagnosis was 50 (range, 29-83) years, with 98.3% having invasive ductal breast cancer and 84.7% showing a HER2 score of 3 or higher in immunohistochemistry tests.

Most participants (74.6%) received adjuvant treatment with trastuzumab-dkst, 18.6% received it with pertuzumab, and 3.4% switched from reference trastuzumab to trastuzumab-dkst. The average duration of anti-HER2 therapy was 10.2 months, covering around 14 cycles of 21 days each. The shorter duration than the recommended 12 months was due to prior neoadjuvant therapy. Overall, 61% of patients received adjuvant chemotherapy, with most (77.8%) treated with taxane, and 62.7% of participants used adjuvant endocrine therapy for an average of 7.8 months.

The median follow-up was 31.7 months, with 59% of patients reaching at least 30 months. The IDFS rate was 94.5% at 24 and 31.7 months. Only 3 patients had disease recurrence, all with distant metastasis. The OS rate was 100%, so the median OS was not reached.

On trastuzumab-dkst administration days, 63.8% of patients were fully active, 34.0% had restricted activity, and 1 was unable to work but could self-care. Regarding safety, 78.0% experienced AEs, mostly during monotherapy (67.8%). Four serious AEs were noted, with 2 during and 2 after treatment. Two patients had infusion reactions. LVEF reductions of at least 10% occurred in 16.9%, but none fell below 50%. Two had reduced doses, and there were no treatment interruptions.

The authors concluded, “Our study bolsters the existing pivotal data concerning the biosimilar trastuzumab-dkst, underscoring its real-world efficacy and safety in the adjuvant treatment of early HER2-positive [breast cancer]. The comprehensive long-term efficacy and safety data we provide further establish trastuzumab-dkst as a cost-saving alternative in oncological care. These findings carry important implications for enhancing patient access to essential therapies and optimizing the efficiency of health care resource utilization.”


1. Gagliato D, Reinert T, Rocha C, et al. Real-World Study of Adjuvant Biosimilar Trastuzumab-dkst for HER2-Positive Breast Cancer Treatment in a Brazilian Population. Oncol Ther. Published online June 5, 2024. doi:10.1007/s40487-024-00284-5

2. Lemos LLP, Souza MC, Guerra AAG, Piazza T, Araújo RM, Cherchiglia ML. Racial disparities in breast cancer survival after treatment initiation in Brazil: a nationwide cohort study. Lancet Glob Health. 2024;12(2):E292-E305. doi:10.1016/S2214-109X(23)00521-1

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