Predicting invasive disease-free survival in ER-positive, HER2-negative early breast cancer using the PAM50 risk-of-recurrence score: a retrospective analysis using single-center long-term follow-up data of postmenopausal Japanese patients

BackgroundThe prognostic value of the risk-of-recurrence (ROR) score calculated using PAM50 has been validated using clinical trials and patient cohorts. This study aimed to investigate the prognostic value of the PAM50 ROR score in Japanese patients with early breast cancer using long-term follow-up data.MethodsWe enrolled postmenopausal patients with ER-positive, HER2-negative, stage I-II breast cancer who had undergone surgery at the Kyoto University Hospital between 2008 and 2014. The intrinsic subtype and ROR score were calculated using PAM50. The primary endpoint was invasive disease-free survival (IDFS).ResultsWe enrolled 146 patients, of whom 47 (32%) patients had node-positive disease, and 36 (25%) had received neoadjuvant or adjuvant chemotherapy. The proportions of intrinsic subtypes for luminal A, luminal B, HER2-enriched, and basal-like subtypes were 67%, 27%, 3%, and 2%, respectively. The median follow-up duration was 8.4 (range 6.3-10.0) years, and 21 IDFS events were observed. Based on the ROR score, 37%, 33%, and 30% of the patients were classified as low, intermediate, and high risks, respectively. Patients in the high-risk group had a significantly worse 8-year IDFS rate than those in the low-to-intermediate-risk groups (75.1% vs. 91.6%, p = 0.04). The same trend was observed in patients with and without neoadjuvant or adjuvant chemotherapy.ConclusionsUsing long-term follow-up data, this study showed that the ROR score can predict the prognosis of ER-positive, HER2-negative early breast cancer in Japanese postmenopausal patients. Further investigations are required to confirm the prognostic value of the ROR score in Asian populations.