Long-Term Outcome Of Breast Cancer Patients Diagnosed <= 40 Years According To Breast Cancer Subtype In The Absence Of Adjuvant Systemic Therapy: The Paradigm Initiative.

535Background: Young age at breast cancer diagnosis is considered a poor prognostic factor. As a result, many treatment guidelines advice adjuvant systemic treatment for young patients. Answering prognostic questions on young patients has therefore become a challenge. The PARADIGM (PAtients with bReast cAncer DIaGnosed preMenopausally) project aims to assess the long-term outcome of women diagnosed with breast cancer ≤40 years in the absence of adjuvant systemic therapy, using real world data from the nationwide Netherlands Cancer Registry (NCR) coupled with tissue biobanking. Methods: All women ≤40 years, diagnosed in the Netherlands between 1989-2000 with a primary invasive, histologically proven, TanyN0M0 breast cancer, without adjuvant systemic treatment were identified through the NCR. Back then N0 patients were considered low risk and did not receive adjuvant systemic treatment. Tissue specimens were revised by a team of dedicated breast pathologists. Cox regression was performed to estimate hazard ...