Day One: International Summit on Breast Cancer

A 34-year-old woman finishes treatment, interrupts her endocrine therapy to try for a baby, and two years later still cannot get pregnant. Dr. Hee Jeong Kim opened with that case because it is the one too many clinics reach only after the window has closed. Her argument is simple and hard to ignore: the conversation about fertility has to start on the day of diagnosis, not years into treatment.

Dr. Kim, a breast surgeon at Asan Medical Center speaking on behalf of the Korean Breast Cancer Society, lays out why young women are a distinct clinical population and what it takes to protect both their survival and their chance at a family. Young women under 45 make up about 19 percent of breast cancer worldwide and roughly 30 percent in the Korean registry, and they have historically carried worse survival. Adding ovarian function suppression to endocrine therapy has narrowed that gap, but longer and more intensive treatment collides with the years these women would be building families. The talk moves from that tension to concrete practice: fertility preservation before treatment, ovarian function suppression during chemotherapy, safe interruption of endocrine therapy, and the real-world barriers that keep good options from ever being offered.

Key points for clinicians:

• Young women under 45 are about 19 percent of breast cancer cases worldwide and about 30 percent in the Korean breast cancer registry, with historically higher mortality on SEER data. Because amenorrhea is associated with improved survival, ovarian function suppression added to tamoxifen (studied since 2003 in Europe and 2009 in Korea) has consistently shown a survival benefit.

• Breast cancer survivors report a 60 percent lower chance of getting pregnant, driven by chemotherapy, extended endocrine therapy, and fear of recurrence. Yet in the POSITIVE trial population, 36 percent of young patients reported interest in pregnancy within five years of diagnosis.

• The POSITIVE trial showed that interrupting endocrine therapy after two to three years to attempt pregnancy did not compromise safety, and that fertility preservation at the time of diagnosis raised the pregnancy rate roughly 2.4 times. The practice lesson is to start fertility and pregnancy counseling at diagnosis, not later.

• Ovarian function suppression given concurrently with chemotherapy roughly doubled ovarian preservation and pregnancy rates versus controls, without a survival penalty. Random-start ovarian stimulation with an aromatase inhibitor to limit estrogen exposure, followed by a GnRH agonist, allows egg retrieval without delaying chemotherapy.

• The barriers are as much systemic as biological. In a US survey of oncologists willing to enroll patients on these trials, more than half still felt uncomfortable recommending that women stop endocrine therapy, and across Asian and Latin American surveys the top barriers were time constraints, no referral system, treatment delay, and cost. Among BRCA carriers, the 10-year pregnancy rate was 22 percent in one series and only 10 percent at Asan, partly because prenatal diagnosis is not permitted in Korea.

• Dr. Kim's myBC study, a shared-decision-making program for young women with breast cancer, has enrolled 11,000 patients prospectively plus 5,500 retrospectively, using decision aids, patient-partner research, and even a metaverse symposium for women who cannot easily leave work. It has since expanded into myHOP for young people with all cancers, reframing the goal as life course oncology: fertility, pregnancy, parenting, survivorship, and return to work as one continuous journey.

The most useful thing about a tumor board is watching experts disagree in good faith. In this session, an international panel takes two early-stage breast cancer cases and works them the way a real team would, out loud, with the tension left in.

Moderated by Professor William Gradishar, the panel walks a 35-year-old with BRCA1-associated triple-negative breast cancer and a 50-year-old with HER2-positive, hormone-receptor-positive breast cancer from diagnosis through surgery, systemic therapy, and the decisions in between. What comes through is how much thoughtful practice varies across the United States, Europe, and Asia, and how often the right answer is a shared decision rather than a protocol.

Key points for clinicians:

• Case 1 covers nodal clipping, neoadjuvant KEYNOTE-522 chemoimmunotherapy, PARP inhibition for BRCA carriers, and de-escalation of axillary surgery after an excellent response.

• Fertility preservation is treated as part of the plan, with egg or embryo harvesting and GnRH agonists during chemotherapy in a young patient.

• The panel openly disagrees on prophylactic bilateral mastectomy in a BRCA1 carrier, weighing contralateral risk against the limits of the survival evidence.

• Case 2 examines neoadjuvant therapy thresholds for HER2-positive disease, THP versus more intensive regimens, and where antibody-drug conjugates such as T-DXd are indicated before or after after surgery.

• Regional differences in mastectomy rates and de-escalation, across the US, South Korea, and China, show how the same case is managed differently around the world.