A real-world retrospective study (Canadian population) showed that patients with HER2-positive neoadjuvant early breast cancer treated with trastuzumab-dkst versus trastuzumab achieved similar pCR rates.
Clinical studies have demonstrated biosimilarity of the biosimilar trastuzumab-dkst to trastuzumab originator in the metastatic setting. In the real-world setting, a retrospective study compared the pathologic complete response (pCR) rates achieved with neoadjuvant use of trastuzumab-dkst with trastuzumab neoadjuvant treatment in patients with HER2-positive early breast cancer (EBC).
The study included patients with HER2-positive EBC treated with neoadjuvant trastuzumab from November 2018 to October 2019 and trastuzumab-dkst from December 2019 to September 2020 in Alberta, Canada. A logistic regression model was applied by trastuzumab product (trastuzumab vs trastuzumab-dkst), age (<40 years vs ≥40 years), preoperative T (T1/2 vs T3/4) and N stage (negative vs positive), grade (I/II vs III), hormone receptor status (estrogen receptor and/or progesterone receptor positive vs estrogen receptor/progesterone receptor negative), HER2 (3+ vs silver in situ hybridization+), chemotherapy (anthracycline containing vs not), and chemotherapy completion (yes vs no).
A total of 136 patients were identified, of which 56% of patients received trastuzumab and 43% received trastuzumab-dkst. Baseline characteristics were mostly comparable between the 2 groups, except a higher proportion of patients in the trastuzumab-dkst group were clinically N-negative (39% vs 14.3%; P = .001). The pCR rates were comparable between trastuzumab-dkst and trastuzumab (35.6% vs 40.3%; P = .598). In the logistic regression model, the odds of a pCR were not different between treatment with trastuzumab-dkst and trastuzumab (odds ratio, 1.1; 95% confidence interval, 0.5-2.4; P = .850). Anthracycline use was associated with a trend for decreased odds of pCR (odds ratio, 0.72; 95% confidence interval, 0.3-1.6; P = .417). Moreover, the estimated cost-savings of trastuzumab-dkst therapy was $22,000 (for a 65-kg patient).
Based on the results of this real-world analysis, the authors concluded that patients with HER2-positive EBC treated with trastuzumab-dkst versus trastuzumab in the neoadjuvant setting achieved similar pCR rates, which were comparable with results obtained in pivotal phase 3 trials.
Source: Yang C, Khwaja R, King K, et al. Trastuzumab-dkst versus trastuzumab: real-world pCR rates in patients with HER2>+ breast cancer treated with neoadjuvant chemotherapy plus trastuzumab from Alberta, Canada. J Clin Oncol. 2021;39(suppl_15):e12569.