The following article features coverage from the American Society of Clinical Oncology 2019 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

According to results of a phase 2 PREDIX HER2 study (ClinicalTrials.gov Identifier #: NCT02568839), patients with HER2-positive, hormone receptor-positive stage II/III breast cancer had similar rates of pathologic complete response (pCR) and less toxicity when treated with neoadjuvant trastuzumab emtansine (T-DM1) compared with a neoadjuvant chemotherapy-based regimen containing both pertuzumab and trastuzumab,. The findings from this study were presented at the 2019 American Society of Clinical Oncology Annual Meeting in Chicago, IL.

Neoadjuvant therapy is a standard of care in patients with HER2-positive, stage II/III operable  breast cancer.  While neoadjuvant regimens including 2 anti-HER2 targeted agents in combination with chemotherapy have achieved high pathologic complete response (pCR) rates, toxicity due to chemotherapy can be considerable. A regimen including trastuzumab emtansine (T-DM1) may represent an effective alternative treatment in this setting, although the possible existence of tumor HER2 heterogeneity could mitigate its potential benefits.

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This randomized, open-label clinical trial randomly assigned (1:1) 202 patients with operable HER2-positive breast cancer characterized by tumors >20 mm or verified lymph node metastasis to receive neoadjuvant therapy with 6 cycles of either T-DM1 or the regimen of docetaxel, trastuzumab and pertuzumab. Crossover was allowed for nonresponding patients or those experiencing severe treatment-related toxicity. Adjuvant chemotherapy consisted of epirubicin/cyclophosphamide followed by trastuzumab (2 cycles in the arm receiving neoadjuvant docetaxel/trastuzumab/pertuzumab and 4 cycles in the neoadjuvant T-DM1 arm), radiotherapy, and endocrine therapy, when appropriate.

The median age of the study population was 52 years, and 62.6% of the tumors were classified as hormone receptor- (HR-) positive. Clinicopathologic characteristics related to menopausal status, and tumor stage were well balanced between the 2 study arms.

The rate of pathologic complete response (pCR) were 47% and 45% for patients receiving T-DM1 and docetaxel/trastuzmab/pertuzumab, respectively (P = .359).

Of note, lower pCR rates were observed for patients with HR-positive tumors; these were 36%, and 36% in the T-DM1,and docetaxel/trastuzmab/pertuzumab arms, respectively (P =.929).

In contrast, the corresponding pCR rates for patients with HR-negative tumors were 57%, and 67% for the groups receiving T-DM1 and docetaxel/trastuzmab/pertuzumab, respectively (P =.502).

The pCR rate was independent of tumor size for both regimens, and rates of breast-conserving therapy were 47% and 48% in patients receiving T-DM1-based therapy compared with chemotherapy-based treatment.

Regarding rates of grade 3/4 adverse events, febrile neutropenia (23% versus 3%), infection (11% versus 1%), and diarrhea (14% versus 0%) were substantially higher in patients receiving the docetaxel-containing regimen.

In his concluding comments, Dr Jonas Bergh, the study presenter, stated that “there were no statistically significant differences in pCR rates between docetaxel/trastuzumab/pertuzumab versus T-DM1.“

Read more of Cancer Therapy Advisor‘s coverage of ASCO’s annual meeting by visiting the conference page.

Reference

  1. Bergh JCS, Andersson A, Bjohle J, et al. Docetaxel, trastuzumab, pertuzumab versus trastuzumab emtansine as neoadjuvant treatment of HER2-positive breast cancer: Results from the Swedish PREDIX HER2 trial identifying a new potential de-escalation standard? Presented at: 2019 American Society of Clinical Oncology. May 31-June 4, 2019; Chicago, IL: Abstract 501.