A pill has been shown to help keep certain early-stage, hard-to-treat breast cancers at bay after initial treatment. Study results were released Thursday by the American Society of Clinical Oncology ahead of its annual meeting and published in the New England Journal of Medicine. Lynparza, a pill marketed by AstraZeneca and Merck, is already sold in the United States and elsewhere for treating some widely spread breast cancers. The new study tested it in patients with earlier-stage disease after standard surgery and chemotherapy. Independent monitors advised releasing the results early after seeing clear benefit from Lynparza.