Stage at diagnosis and tumor characteristics among screen-detected breast cancer cases in Cartagena, Colombia

INTRODUCTION: The implementation of breast cancer screening programs aims for an early diagnosis and timely management. In Colombia, national regulations recommend biennial mammography for women aged 50 - 69 years. Patients with mammographic findings suggestive of malignancy are referred for biopsy. Limited data exists on screening performance and stage distribution in Cartagena. OBJECTIVE: To characterize the stage at diagnosis and clinical and pathological features of women participating in a breast cancer screening program in Cartagena, Colombia. METHODS: A retrospective study which included women screened for breast cancer between January 2019 and February 2023 with BIRADS 4A, 4B, 4C, and 5 mammographic results. Data were collected from mammography and biopsy reports and medical records. Associations between clinical and pathological variables were evaluated, including age, BI-RADS category, histological type and grade, ER, PR, and HER2 status, Ki-67 index, tumor size, multifocality, axillary lymph node involvement, metastatic disease, and TNM stage. A p-value < 0.05 was considered statistically significant. RESULTS: 211 women were included (mean age=58.9, SD=11.3). 39,8% (n=84) mammograms were reported as BI-RADS-5, 97.5% had a histopathological diagnosis of cancer, compared to 81.8%, 47% and 40% of patients classified as BI-RADS 4C, 4B and 4A, respectively. Women with malignant diagnoses were significantly older than those with benign findings (p = 0.021, t test). At the time of diagnosis, tumor size was predominantly between 2 and 5 cm (T2), most tumors were unicentric, 42.9% had lymph node involvement and 8.2% had metastases. Most patients (50%) were diagnosed at intermediate stages (IIA-IIB), a significant proportion (20%) at stage III, and 7% at stage IV. Invasive ductal carcinoma represented 76.2% of cases, followed by invasive lobular carcinoma. The predominant subtype was HR+/HER2- (62%), and a high proportion of triple-negative breast cancer (HR-/HER2-) was observed (23%). The Ki67 index greater than 20% was observed in 51.7% of the cases and there was a significant association between histological type and Ki67 index (p=0.014, Fisher test).CONCLUSION: Stage at diagnosis of screen-detected breast cancers in this program cannot be considered neither very early nor very late. This suggests that while the screening program has improved, opportunities remain to strengthen early detection and screening efforts. The higher-than-expected malignancy rate in the BI-RADS 4A category may indicate a population with more aggressive disease biology. Although the predominant histological subtype is associated with better prognosis and effective therapies, the relatively high incidence of triple-negative breast cancer may be related to population-specific risk factors and carries therapeutic and prognostic implications that should be further investigated.