Importance and accuracy of intraoperative frozen section diagnosis of the resection margin for effective carmustine wafer implantation

For effective implantation of carmustine (BCNU) wafers, it is important to determine the order of priority with reference to the intraoperative frozen section diagnosis of the resection margin (IOFM). The accuracy of IOFM and patterns of tumor recurrence with implantation of BCNU wafers were studied retrospectively. Forty-six cases of newly diagnosed malignant glioma were evaluated. Tumors were resected after intraoperative frozen section diagnosis (IOFD). IOFM was performed for resection walls and evaluated on a three-level scale (-, no tumor invasion; 1+, minor cell invasion; 2+, evident cell invasion). The results were used for effective BCNU wafer implantation. The IOFM sections were then thawed, frozen-paraffin marginal (FPM) sections were prepared, and IOFM was evaluated with FPM sections. The accuracy of IOFD grading was compared to that of the formalin fixed paraffin-embedded section and was 76.1%. The accuracy of IOFM was compared with the FPM section in 148 specimens from 42 patients. The IOFM accuracy was 80.4%. BCNU wafers were implanted in 25 patients and there was recurrence in 15. Local recurrence was seen in 40% (6 patients). However, there was no recurrence immediately below the BCNU wafers. With properly performed IOFM, BCNU wafers can be efficiently implanted, and local recurrence immediately below the BCNU wafers can be inhibited.