CONTRAST-ENHANCED MR-IMAGING ASSESSMENT OF TUMOR CAPILLARY-PERMEABILITY - EFFECT OF IRRADIATION ON DELIVERY OF CHEMOTHERAPY

PURPOSE: To assess the effect of x rays on tumor capillary permeabilit y with macromolecular contrast medium (MMCM)-enhanced magnetic resonan ce (MR) imaging.MATERIALS AND METHODS: One of paired R3230 mammary ade nocarcinomas implanted in the flanks of 48 Fischer rats was treated wi th a single 5- or 15-Gy dose of x rays. After 1 or 3 days, MR imaging in 30 rats was performed unenhanced and enhanced with albumin-(gadolin ium diethylenetriaminepent aacetic acid)(30) (0.02 mmol gadolinium per kilogram body weight). Signal intensity enhancement was analyzed to e stimate fractional blood volume and permeability-surface area product (PS). In 18 irradiated rats, 2.5 mg/kg cisplatin was injected intraven ously, and fractional tumor platinum concentrations were measured spec trometrically. RESULTS: MR imaging showed highest capillary permeabili ty 1 day after 15 Gy (PS 110% above control [P <.001]); PS was elevate d 57% 1 day after 5 Gy and 63% 3 days after 15 Gy (P <.05). The larges t mean tumor platinum fraction occurred 1 day after 15 Gy: 48% versus 20% (control) (P <.05). CONCLUSION: Transient irradiation-induced incr ease in tumor capillary permeability to cisplatin can be quantified wi th MMCM-enhanced MR imaging.