Magnetic resonance imaging and spectroscopy of MCF7 human breast cancer: pathophysiology and monitoring of treatment.

Magnetic resonance imaging at high spatial resolution, dynamic-contrast enhanced imaging, and localized 31P magnetic resonance spectroscopy were applied to monitor in vivo growth and tamoxifen treatment of MCF7 human breast tumors implanted in athymic mice. Correlation of the imaging data with histological findings demonstrated significant differences between viable carcinoma, fibrous, and necrotic regions on T2 weighted images. At an early stage after tamoxifen treatment rapid necrosis preceded tumor regression suggesting tamoxifen inhibition of angiogenesis. The necrosis was followed by growth of reperative fibrous tissue at the boundary of the viable cancer cells and the necrotic regions. The dynamic of contrast enhancement after tamoxifen treatment revealed high permeability of microvessels at this boundary cord. In parallel to the induction of the repair process the tumor energy profile changed, showing a significant increase in the ratio of ATP to inorganic phosphate. Initial attempts to use MRI for evaluating the response of breast cancer patients to treatment are also described.