CASP3 and neoplasm: Quantifying the extent of cellular damage using quantitative pathologic image analysis similarly confirmed significant apoptosis with cleaved caspase-3 staining in 65.7% ± 17.3% of tumor cells treated with PS-PDT versus only 3.9% ± 5.0% and 8.9% ± 3.7% apoptotic tumor cells in the light and drug treatment tumors, respectively (Fig. 4E, P value <0.001; see statistics in Supplementary Table S8).