Tumor angiogenesis of low-grade astrocytomas measured by dynamic susceptibility contrast-enhanced MRI (DSC-MRI) is predictive of local tumor control after radiation therapy

Purpose: To assess regional cerebral blood volume (rCBV) as a surrogate mar ker of angiogenesis in patients with low-grade fibrillary astrocytoma befor e radiation therapy and to correlate measured values with clinical outcome after fractionated stereotactic radiotherapy (FSRT). Methods: Twenty-five patients with histologically proven fibrillary astrocy tomas were examined using dynamic susceptibility contrast-enhanced MRI befo re radiotherapy. Radiotherapy was delivered to mean and median total doses of 60.9 and 60 Gy, respectively (range 55.8-66 Gy). During MRI for treatmen t planning, 55 T2*-weighted gradient echo images were acquired before, duri ng, and after i.v. contrast-bolus injection. The acquired signal-time curve s were converted into concentration-time curves. By normalization to an art erial input function, absolute and relative rCBV values were calculated. Me asured pretherapeutic rCBV data were correlated to outcome in terms of loca l control after FSRT. Results: Mean pretherapeutic rCBV for astrocytomas was 6.5 +/- 3.7 ml/100 g tissue. Mean and median follow-up times were 47.8 and 52 months. respectiv ely. Fifteen tumors recurred during the period. with a mean and median late ncy of 39.1 and 42 months, respectively. Tumors recurring earlier than 42 m onths after FSRT showed a higher pretreatment rCBV than tumors recurring la ter and tumors in continued local control (8.12 +/- 4.48 ml/100 g vs. 6.0 /- 2.3 ml/100 g and 4.73 +/- 2.47 ml/100 g; p = 0.02 and p = 0.03). The res pective ratios of tumor rCBV in early recurrent tumors to gray matter and w hite matter rCBV were 0.98 +/- 0.38 and 2.17 +/- 1.36 as compared with 0.79 +/- 0.14 and 1.44 +/- 0.29 in locally controlled tumors (p = 0.074 and p = 0.056). Conclusions: In fibrillary low-grade astrocytomas, a noninvasive assessment of angiogenesis as indicated by rCBV measurement was feasible. The present data suggest that high pretherapeutic angiogenic activity in low-grade ast rocytomas indicates a subgroup of tumors at higher risk for early local rec urrence or malignant transformation after FSRT. (C) 2001 Elsevier Science I nc.