Quantitative spectroscopic analysis of talaporfin sodium fluorescence: Utility in fluorescence-guided surgery and detection of invasive tumor cells in glioblastoma.

Background: Talaporfin sodium (TS) has been widely used as photodynamic therapy (PDT) for glioblastoma (GB), but its sensitivity and selectivity in fluorescence-guided surgery are not fully understood. This study aimed to elucidate whether quantitative analysis of spectroscopic TS fluorescence intensity could evaluate the degrees of glioma cell infiltration in the peritumoral area. Methods: The study included 12 patients with recurrent GB who underwent surgical resection and PDT with TS. Primary tumors were classified into high-invasive (HI) and low-invasive (LI) subtypes based on magnetic resonance imaging. TS-fluorescence intensities were analyzed using fluorescence spectroscopy. A relationship between TS-fluorescence intensities that were measured in four subareas divided according to the signal intensity and degrees of tumor activity evaluated by Ki-67 staining index (SI) was investigated. Results: Five tumors were HI type and seven were LI type. Both progression-free survival after surgical reresection and PDT with TS and overall survival were significantly longer in patients with the LI-type GB compared to the HI-type. The median Ki-67 SI in the area with a signal intensity >5000 arbitrary units (a.u.) was 23.5%, 3000-5000 a.u. was 10.0%, and 1000-3000 a.u. was 2.70%. When the TS signal intensity was <1000 a.u., almost no tumor cells were detected in the peritumoral tissue. Conclusion: Tumor invasiveness was assessed by quantitative analysis of TS-fluorescence spectroscopy during GB surgery. They correlated with tumor density assessed by Ki-67 SI. Aggressive surgical resection, including regions with TS fluorescence intensity >1000 a.u., should be considered for maximum resection of GBs.