Stage I Breast Cancer in the Modern Era: A Retrospective Cohort Study of 328 Patients Diagnosed from 2002 to 2006 with a 14-Year Median Follow-Up.

Introduction: This study aimed to evaluate the long-term outcomes of stage I breast cancer (BC) patients diagnosed during the current era of screening mammography, immunohistochemistry receptor testing, and systemic adjuvant therapy.

Methods: A retrospective cohort study was conducted on 328 stage I BC patients treated consecutively in a single referral center with a follow-up period of at least 12 years. The primary endpoints were invasive disease-free survival (IDFS) and overall survival (OS). The influence of tumor size, grade, and subtype on the outcomes was analyzed.

Results: Most patients were treated by lumpectomy, sentinel node biopsy, and adjuvant endocrine therapy, and most (82%) were of subtype luminal A. Adjuvant chemotherapy was administered to 25.6% of our cohort. Only 24 patients underwent gene expression testing, which was introduced toward the end of the study period. Mean IDFS was 14.64 years, with a 15-year IDFS of 75.6%. Mean OS was 15.28 years with a 15-year OS of 74.9%. In a Cox multivariate analysis, no clinical or pathologic variable impacted on OS and only tumor size (<1 cm vs. 1-2 cm) impacted significantly on IDFS. During follow-up, 20.1% of the cohort developed second primary cancers, including BC. The median time to diagnosis of a second BC was 6.49 years.

Conclusion: The study results emphasize the importance of long-term follow-up and screening for subsequent malignancies of patients with stage I BC and support the need for using prognostic and predictive indicators beyond the routine clinicopathological characteristics in luminal A patients.