The POSITIVE trial was designed to address the clinical conundrum that many of our young patients face, which is the desire to have the best breast cancer treatment possible, which in the setting of hormone receptor-positive breast cancer is somewhere between five to 10 years of adjuvant endocrine therapy for the most part. And to also be able to have the full life that they desire, which for many young women that's having a future biologic child. The majority of women diagnosed premenopausaly have hormone receptor-positive breast cancer. When we think about women who want to have a pregnancy after a diagnosis of breast cancer, we're usually thinking about women who are 40 to 45 and under the majority of those women have ER positive breast cancer. When we've looked at this in cohort studies, somewhere between 40 to 60% of patients 40 and under desire future fertility at diagnosis.
The important eligibility criteria for the POSITIVE trial included the desire to become pregnant, being 42 or younger at diagnosis and premenopausal, and no evidence of clinical recurrence at that time. And of course, all the women had ER positive breast cancer that had been treated for cure. All women who enrolled in the POSITIVE trial were required to have completed at least 18 months and no more than 30 months of endocrine therapy. When we looked at the pregnancy outcomes and the majority of women, 74% had become pregnant by the time we locked the database, which was a 41 month medium follow up, there didn't appear to be any negative impact in terms of the pregnancy outcomes on the prior endocrine therapy.
The POSITIVE trial entailed a planned interruption of endocrine therapy. After 18 to 30 months of endocrine therapy, women with early stage hormone receptor-positive breast cancer took a break. They had a three month washout, and then they were encouraged to get pregnant because they went on because they desired pregnancy, carry that pregnancy if they were able to get pregnant, and they were allowed to use assisted reproductive technologies if they wanted to or needed to. Carry the pregnancy, deliver, breastfeed if that was something that was desired. And then ideally, they would get back on endocrine therapy within a two year period. The majority of women got pregnant and 70 plus percent were pregnant by two years. The majority of women also got back on endocrine therapy. Over 70% were back on endocrine therapy by the data lock at 41 months.
The good news about the POSITIVE trial results, at least on our preliminary analysis at 41 months median follow up, is that not only did the vast majority of women achieve a pregnancy and a live birth if they became pregnant, but the women who went on to POSITIVE appeared to have disease recurrence risks that were similar to women in a matched control population in terms of both relapse-free interval as well as distant recurrence. So that's really reassuring news. The numbers were actually fairly low. There was an 8.9% relapse-free interval rate that equated to 44 events, and about half of those were distant recurrences. And that's similar to the match control group.
So we're absolutely following the mothers on POSITIVE in terms of their disease outcomes and their psychological outcomes, and we're also following the infants in short-term with regard to their early outcomes, birth defects, birth weight, Apgars, and other things around the infant. The next steps in the POSITIVE trial are to follow these women long term for resumption of endocrine therapy and disease outcomes in particular. Short term outcomes look really good. At 41 months median follow up, women in the POSITIVE trial appear to do just as well as women in an age and other parameter matched controlled cohort. Long term is what we really need to look at in light of the fact that patients with hormone receptor-positive breast cancer also are at risk for late recurrence.
