The relationship of the neo-angiogenic marker, endoglin, with response to neoadjuvant chemotherapy in breast cancer

Endoglin (CD105) is upregulated in endothelial cells of tissues undergoing neovascularisation. A greater number of CD105-positive vessels predicts poor survival in breast cancer. We examine whether CD105 expression predicts response to neoadjuvant chemotherapy. Fifty-seven women (median age 50 years, range 29–70) received neoadjuvant chemotherapy for operable breast cancer. Immunohistochemical staining using monoclonal antibodies to CD105 and CD34 was performed on pretreatment biopsies and post-treatment surgical specimens. Individual microvessels were counted in 10 random fields at × 200 magnification. Median counts were correlated with clinical and pathological response using the Mann–Whitney U-test. Forty-five out of fifty-seven patients (79%) responded clinically, 22 (39%) responded pathologically. On pretreatment biopsies, clinical responders had significantly lower median CD105-positive vessel counts than nonresponders (median counts 5 and 9.3/high-power field (hpf), median difference=4.0/hpf, 95% CI 0.5–8.0/hpf, P=0.02). For pathological responders and nonresponders, median counts were 4.8 and 5.5/hpf (median difference –0.5/hpf, 95% CI=−2.5–2.0/hpf, P=0.77). CD34 expression (total microvessel density) did not correlate with response. Pretreatment CD105 expression predicts for clinical response to chemotherapy, with a lower initial count being favourable. Patients with high baseline new vessel counts or increased counts after conventional therapy may benefit from additional antiangiogenic therapy.