Background: In step with the aging of the Japanese population, late recurrence of hormone receptor positive (HR+) breast cancer occurring especially beyond 20 years after the initial diagnosis has been recognized as not rare anymore, as it has been occurring at a constant rate lately. The administration of an aromatase inhibitor with a CDK4/6 inhibitor has become the gold standard in Japan for cases of recurring HR+ breast cancer without severe visceral metastasis.
Case: A 73- year-old woman was diagnosed by chance with late recurrence of HR+ breast cancer 21 years after undergoing radical resection followed by adjuvant anastrozole for 5 years for stage Ⅲb right breast cancer. Asymptomatic multiple bone metastases on her ribs and sternum with bilateral lung metastasis and malignant effusion all disappeared while she was on a year- long administration of anastrozole and an optimal dose of abemaciclib(100 mg bid). However, because of the Grade 3 digestive adverse event that occurred at approximately 1 year of treatment, she could only maintain the treatment for up to 13 months. After then, no recurrence has been detectable for 6 months so far.
Conclusion: CDK4/6 inhibitors, in combination with anastrozole, will play a pivotal role in the initial approach to elderly patients with HR+ late recurrence as a chemotherapy- free strategy.