Inter- and intrapatients comparison of WHO grade II glioma kinetics before and after surgical resection

Grade II gliomas grow slowly and linearly (at rates about 4 mm/year) before undergoing anaplastic transformation. In order to analyze how surgery may affect radiological grade II glioma kinetics, we restrospectively reviewed our national database searching for patients operated on for a supratentorial grade II glioma between 1997 and 2007. We selected patients with at least two postoperative MRI with a minimal delay of 6 months. For each patient, postoperative residues were segmented on successive MRIs. Velocities of diameter expansion were estimated by linear regression of mean diameter evolution for each patient. Fifty-four patients fulfilled inclusion criteria. Median postoperative follow-up was 1.6 years with, on average, 3.4 MRI examinations per patient. Postoperative growth rates of mean diameter were normally distributed, around a mean value of 4.3 mm/year (SD = 3.2 mm/year). Statistical analysis showed no difference between this distribution and the distribution of preoperative growth rates in a previous series of 143 grade II gliomas. For a subset of 23 patients, delay between first MRI and surgery made it possible to estimate also preoperative growth rates. Intrapatient comparison revealed that growth rates were grossly unchanged for 80% of cases. In summary, inter- and intrapatient comparison of pre- and postoperative growth rates proves that surgery does not change grade II glioma dynamics, thus, acting as a cytoreduction.