The fate of spinal schwannomas following subtotal resection: a retrospective multicenter study by the Korea spinal oncology research group.

The fate of residual spinal schwannomas needs to be estimated in order to plan further management after subtotal removal. Our aim was to evaluate the growth rate of residual spinal schwannomas and compare results in regrowth and no regrowth groups by using data collected from the Korea Spinal Oncology Research Group database. From January 1989 to August 2011, 27 patients with residual spinal schwannomas were selected. Patients with at least two follow-up magnetic resonance image (MRI) studies after subtotal resection were included. The mean period of MRI follow-up was 62.4 months. A tumor size increase of over 2 mm in the maximal diameter was considered indicative of regrowth. Age, sex, size at initial diagnosis, postoperative tumor size, and Ki-67 labeling index were compared between regrowth and no regrowth groups. Eight residual schwannomas regrew (29.6 %), and 19 (70.4 %) did not regrow. Average growth rate of the regrowing tumors was 1.0 ± 4.4 mm/year. The mean percentage increase in tumor size during follow-up was 10.0 ± 28.8 %. The Ki-67 labeling indices were significantly different between regrowth and no regrowth groups (P = 0.014). Two patients underwent a revision operation for significant tumor regrowth. Nineteen cases (70.4 %) among 27 residual spinal schwannomas did not regrow significantly, but further surgical treatments were necessary in 2 patients due to significant regrowth. The Ki-67 labeling index was higher in the regrowth group. Earlier follow-up MRI is recommended for patients whose tumors have higher Ki-67.