BERLIN — Patients with a highly aggressive form of breast cancer will likely have new treatment options for the first time in years after AstraZeneca and Gilead Sciences both presented successful trial results here Sunday, dual achievements that will also leave clinicians having to figure out which drug to choose when treating triple-negative tumors.

Both studies tested what’s known as an antibody-drug conjugate — essentially, a next-generation type of chemotherapy — versus traditional chemotherapy regimens as a first-line medicine in patients with metastatic triple-negative breast cancer who couldn’t receive an immunotherapy. The women largely weren’t eligible for treatments like checkpoint inhibitors because their tumors did not express the protein that the drugs target. For these pat

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