Proliferation (Ki-67 and phosphohistone H3) and oncotype DX recurrence score in estrogen receptor-positive breast cancer.

The Oncotype DX Recurrence Score (RS) is often used in lymph node-negative, estrogen receptor-positive breast cancer to refine prognosis and direct therapy. Its utility is limited by its cost, proprietary nature, and turnaround time. Markers of proliferation factor heavily into determination of RS. Our aim is to correlate expression of proliferation markers Ki-67 and phosphohistone H3 (PPH3) with RS and other prognostic indicators. Estrogen receptor-positive invasive breast carcinomas from 133 patients with Oncotype DX testing were selected. Representative tumor sections were stained with MIB1, a monoclonal antibody that reacts against Ki-67, and antibody to PPH3. Nuclear staining was quantitated through an automated imaging system. The percentage of positive cells was scored as low (<10%), intermediate (10% to 20%), or high (>20%) for Ki-67, and low (<2%), intermediate (2% to 5%), or high (>5%) for PPH3. Expression of both markers was compared with RS and clinicopathologic parameters including grade, tumor size, lymph node metastasis, and angiolymphatic invasion. Ki-67 and PPH3 expression were both significantly associated with RS (P=0.02 and P=0.027, respectively) and grade (P<0.001 and P=0.002, respectively). Ki-67 expression correlated with angiolymphatic invasion (P=0.01) but not with tumor size or lymph node metastasis; PPH3 expression showed no association with any of these 3 parameters. Expression of proliferation markers Ki-67 and PPH3 by immunohistochemistry is significantly correlated with RS and tumor grade. This observation suggests that immunohistochemical assessment of markers of proliferation may provide useful prognostic information, at lower cost than RS testing.