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Endocrine Therapy Noninferior to Chemotherapy as First-Line Treatment for Patients with MBC

Combined treatment with trastuzumab and endocrine therapy proved noninferior to trastuzumab plus chemotherapy as a first-line option for patients with HR–positive, HER2–positive metastatic breast cancer, according to the results of a phase 3 study presented at the 2021 ASCO Annual Meeting. 

However, patients assigned to trastuzumab plus endocrine therapy experienced fewer toxicities than those treated with chemotherapy. 

Both endocrine therapy and chemotherapy are routinely administered with anti–HER2 therapy as a first-line treatment for HR–positive, HER2–positive metastatic breast cancer.  

Zhongyu Yuan, MD, medical oncologist at Sun Yat-sen University Cancer Center (Guangzhou, China), and colleagues sought to determine whether trastuzumab plus endocrine therapy could decrease toxicities in the first line while remaining as effective as chemotherapy. 

The researchers randomly assigned 392 patients to treatment with trastuzumab plus endocrine therapy or chemotherapy (n = 196 for both). Progression-free survival (PFS) served as the primary endpoint. 

Patients assigned to treatment with trastuzumab plus endocrine therapy achieved a median PFS of 19.2 months (95% CI, 16.7-21.7), compared with 14.8 months (95% CI, 12.8-16.8) for those assigned chemotherapy.  

The outcomes met the noninferiority upper margin of 1.35 established by the researchers (hazard ratio, 0.88; 95% CI, 0.71-1.09; P < .0001 for noninferiority). 

A significantly greater proportion of patients assigned chemotherapy reported toxicities than those assigned endocrine therapy, including leucopenia (50% vs. 6.6%), nausea (47% vs. 12%), fatigue (24% vs. 16%), vomiting (23% vs. 6%), headache (33% vs. 12%) and alopecia (64% vs. 4%). 

No patient in either cohort died of treatment-related complications. 

“Trastuzumab plus endocrine therapy could provide more convenient treatment and allow better treatment tolerance,” Yuan and colleagues concluded. 

 
By Cameron Kelsall, /alert Contributor 

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