The American Society of Clinical Oncology (ASCO) develops and disseminates clinical practice guidelines and other guidance documents to assist providers in their clinical decision-making. It uses a signals approach to determine when clinical guidelines need to be updated.

ASCO recently published a focused update of its 2018 guidelines on the selection of optimal adjuvant chemotherapy and targeted therapy for early breast cancer (BC).

The original guidelines were an adaptation of the Cancer Care Ontario guidelines on the same topic. The guidelines were recently updated in response to results of the phase III clinical trial, the KATHERINE trial, which had found that the risk of recurrence of invasive BC or death was 50% lower in patients who had received adjuvant trastuzumab emtansine compared with trastuzumab alone in women with HER2-positive early BC who had residual invasive disease after finishing their course of neoadjuvant therapy. Relevant data from FDA labeling of trastuzumab biosimilars also helped to inform the clinical decision-making process associated with these recommendations.

In this focused update, ASCO made two recommendations. The first recommendation, which was a strong recommendation based on high-quality evidence, stated that “patients with HER2- positive BC with pathologic invasive residual disease at surgery after standard preoperative chemotherapy and HER2-targeted therapy should be offered 14 cycles of adjuvant trastuzumab emtansine, unless there is disease recurrence or unmanageable toxicity.”

The KATHERINE trial had found that the estimated percentage of patients free of invasive disease at 3 years and those with invasive disease-free survival were significantly higher in the trastuzumab emtansine group than in the trastuzumab group for patients with stage I or II HER2-positive BC who had residual invasive disease in the breast or axilla after completion of neoadjuvant chemotherapy along with HER2-targeted therapy.

The risk of distant recurrence was significantly less in the trastuzumab emtansine group than in the trastuzumab group. The occurrence of invasive disease or death was also lower in the trastuzumab biosimilar group than with the originator product. However, it should be kept in mind that the percentage of patients who had experienced adverse events was higher in the trastuzumab emtansine group, including the occurrence of more grade 3 or higher adverse events than in the trastuzumab group. There were also more discontinuations in the biosimilar group compared with the original biologic agent. When these patients were switched to trastuzumab, they were able to complete 14 total postoperative cycles of HER2-targeted therapy.

The second recommendation, which was also a strong recommendation based on high-quality evidence, suggested that “clinicians may offer any of the available and approved formulations of trastuzumab, including trastuzumab, trastuzumab and hyaluronidase-oysk, and available biosimilars.” There are currently five trastuzumab biosimilar formulations approved by the FDA: trastuzumab-dkst, trastuzumab-pkrb, trastuzumab-anns, trastuzumab-dttb, and trastuzumab-qyyp. The guidelines support the use of these products as cost-effective options, especially given that high patient out-of-pocket expenses for pharmaceuticals is a barrier to care. The recommendation encourages shared decision-making with patients in which cost is addressed.

Pharmacists can utilize these recommendations to help optimize adjuvant therapies in patients with HER2-positive early BC and to encourage the use of biosimilars in this population as cost-effective alternatives.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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