Thousands of women with breast cancer may now be able to skip chemotherapy, according to a new study.

The majority of women diagnosed with a common form of early-stage breast cancer should be able to avoid chemo and its side effects. Up to 70 percent of women with HR-positive, HER2-negative, and node-negative breast cancer can safely skip the treatment, a gene study has proven. The study involved over 10,000 women with early-stage breast cancer from the US, Ireland, New Zealand, Australia, Canada, and Peru. Research was conducted over the course of 15 years and showed that the vast majority of women with this form of cancer could alleviate their uncertainty about undergoing chemotherapy. The study was described as the largest breast cancer trial in the world and has since been hailed as a "breakthrough." Almost 700 Irish women took part in the decade and a half long study. One in nine women will develop breast cancer over the course of their lifetimes. It is most common in women between 45 and 64 years old. 15 percent of cases occur in women under the age of 44. The results of the trial were released this week at the American Society of Clinical Oncology annual meeting.