Background: Indication for chemotherapy in estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancers is determined on the basis of Ki67 expression level. However, since Ki67-high cancers are not necessarily sensitive to chemotherapy, identification of such patients who do not need chemotherapy is an important issue.
Patients and methods: We used immunohistochemical staining to examine the expression levels of ER, progesterone receptor (PgR), Ki67, and geminin, a marker of S to G2/M phases, in 80 ER-positive/HER2-negative breast cancers. The labeling indices of Ki67 and geminin were determined and cutoff values were set at 15 and 6 %, respectively.
Results: Ki67 and geminin expression levels were significantly associated with nuclear grade. In the Ki67-low subset, 26 out of 28 (92.9 %) cancers were geminin low and in the Ki67-high subset, 31 out of 52 (59.6 %) were geminin high. Distant disease-free survival (DDFS) of the geminin-high subset was significantly poorer than that of the geminin-low subset (P = 0.009). In the Ki67-low subset, only one patient showed recurrence. Metastasis was detected in eight out of 31 (25.8 %) patients in the geminin-high group of the Ki67-high subset, but no recurrence was observed in the geminin-low group of the Ki67-high subset.
Conclusion: Geminin-high breast cancers are significantly associated with worse prognosis. Since poorer prognosis was recognized only in the geminin-high group in Ki67-high cancers, we speculate that geminin may be useful for identifying patients in the Ki67-high subset who can avoid unnecessary chemotherapy.
Keywords: Breast cancer; Geminin; Ki67; Luminal subtype; Prognosis.