Late Breast Cancer Recurrence Prediction: The Role of CTS5 and Progesterone Receptor Status.

Purpose: The current study aimed to assess the recurrence rate in hormone-receptor positive, HER2 negative (HR-positive/HER2-negative) breast cancer patients from a single center in Brazil and compare it with estimates provided by the Clinical Treatment Score post-five years (CTS5).

Methods: This study comprised a retrospective analysis of patients from a national cancer center database, which began treatment between 2007 and 2008 and had no evidence of recurrence after five years of follow-up. All patients had confirmed diagnosis of HR-positive/HER2-negative early breast cancer. Disease Free-Survival (DFS) according to each CTS5 risk subgroup was the main outcome.

Results: A total of 162 patients were enrolled, 26.5% being premenopausal. The mean age at diagnosis was 60.1 years (49.8─71.6). Tumor stage: I (43.8%) and II (56.2%). Endocrine therapy consisted mainly of tamoxifen (88.0%). About 39.5%, 39.5%, and 21.0% of patients were in the low, intermediate, and high-risk (L/I/H) subgroups according to CTS5, respectively. Progesterone-receptor (PR) was ≥20% in 71.0% of tumors and 77.0%, 69.0%, and 65.0% in the L/I/H subgroups, respectively. The median follow-up was 88.9 months. DFS at 5 years (10 years since the beginning of endocrine therapy) was 100%, 96.3% (95% CI, 89.4%─100%) and 68.2% (95% CI, 48.7%─95.5%) in the L/I/H subgroups, respectively. PR was an independent prognostic factor for late recurrence in intermediate- (p=0.022) and high-risk (p=0.003) subgroup patients according to CTS5.

Conclusion: CTS5 performed well in the high-risk subset of patients from a wider population, including premenopausal women. The progesterone receptor was an independent prognostic factor for DFS in intermediate- and high-risk populations and should be further investigated in prospective multicenter studies.