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Vascular endothelial growth factor (VEGF-A) is considered a prognostic indicator for clinical outcome in breast cancer. Conflicting results nevertheless exist and there is a need for larger studies including untreated patients in order to clarify the importance of tumor-specific VEGF-A regarding prognosis as well as potential links to predictive treatment information. VEGF-A and its receptor, vascular endothelial growth receptor 2 (VEGFR2), were therefore analyzed by immunohistochemistry in postmenopausal breast cancers enrolled in a clinical trial where patients were randomized to adjuvant tamoxifen treatment (n=124) for 2 years or no treatment (n=127) with a median follow-up of 18 years. The tumors were arranged in a tumor tissue microarray system enabling parallell analysis of the angiogenic factors and hormone receptor status. Tumor-specific expression of VEGFR2 correlated strongly with expression of VEGF-A and progesterone receptor (PR) negativity, whereas VEGF-A was not associated with hormone receptor status. Among patients with estrogen receptor (ER) positive (fraction > 10%) tumors, there was a statistically significant tamoxifen response in VEGF-A negative tumors at both 10-year and 18-year disease-free survival (DFS), contrasting to VEGF-A positive tumors who had no beneficial effect of tamoxifen. A treatment-interaction variable indicated a marked difference in tamoxifen response depending on VEGFA-status in terms of DFS at 10 and 18 years of follow-up, p=0.046 and p=0.039, respectively. VEGFR2 status did not yield significant predicitve information for tamoxifen response in patients with ER fraction > 10%, whereas in patients with ER fraction > 90% both VEGF-A and VEGFR2 status were associated with tamoxifen treatment effect.

Antioestrogen treatment by tamoxifen is a well-established adjuvant therapy for oestrogen receptor-alpha (ERalpha) positive breast cancer. Despite ERalpha expression some tumours do not respond to tamoxifen and we therefore delineated the potential link between the cell cycle regulator and ERalpha co-factor, cyclin D1, and tamoxifen response in a material of 167 postmenopausal breast cancers arranged in a tissue array. The patients had been randomised to 2 years of tamoxifen treatment or no treatment and the median follow-up time was 18 years. Interestingly in the 55 strongly ERalpha positive samples with moderate or low cyclin D1 levels, patients responded to tamoxifen treatment whereas the 46 patients with highly ERalpha positive and cyclin D1 overexpressing tumours did not show any difference in survival between tamoxifen and no treatment. Survival in untreated patients with cyclin D1 high tumours was slightly better than for patients with cyclin D1 low/moderate tumours. However, there was a clearly increased risk of death in the cyclin D1 high group compared to an age-matched control population. Our results suggest that cyclin D1 overexpression predicts for tamoxifen treatment resistance in breast cancer, which is line with recent experimental data using breast cancer cell lines and overexpression systems.