The role of radical microsurgical resection in multimodal treatment for skull base meningioma

Abstract

Because resection followed by timely stereotactic radiosurgery (SRS) is becoming a standard strategy for skull base meningiomas, the role of initial surgical tumor reduction in this combined treatment should be clarified. This study examined 161 patients with benign skull base meningiomas surgically treated at Osaka City University between January 1985 and December 2005. The mean follow-up period was 95.3 months. Patients were categorized into 3 groups based on the operative period and into 4 groups based on tumor location. Maximal resection was performed as first therapy throughout all periods. In the early period (1985-1994), in the absence of SRS, total excision of the tumor was intentionally performed for surgical cure of the disease. In the mid and late periods (1995-2000 and 2001-2005), small parts of the tumor invading critical neurovascular structures were left untouched to obtain good functional results. Residual tumors with high proliferation potential (Ki 67 index > 4%) or with progressive tendencies were treated with SRS. The extent of initial tumor resection, recurrence rate, Karnofsky Performance Scale score, and complication rate were investigated in each group. The mean tumor equivalent diameter of residual tumors was 3.67 mm in the no-recurrence group and 11.7 mm in the recurrence group. The mean tumor resection rate (TRR) was 98.5% in the no-recurrence group and 90.1% in the recurrence group. A significant relationship was seen between postoperative tumor size, TRR, and recurrence rate (p < 0.001), but the recurrence rate showed no significant relationship with any other factors such as operative period (p = 0.48), tumor location (p = 0.76), or preoperative tumor size (p = 0.067). The mean TRR was maintained throughout all operative periods, but the complication rate was lowest and postoperative Karnofsky Performance Scale score was best in the late period (p < 0.001 each). Late-period results were as follows: mean TRR, 97.9%; mortality rate, 0%; and severe morbidity rate, 0%. Stereotactic radiosurgery procedures were added in 27 cases (16.8%) across all periods. Throughout all follow-up periods, 158 tumors were satisfactorily controlled by maximal possible excision alone or in combination with adequate SRS. The combination of maximal possible resection and additional SRS improves functional outcomes in patients with skull base meningioma. A TRR greater than 97% in volume can be achieved with satisfactory functional preservation and will lead to excellent tumor control in combined treatment of skull base meningioma.