Criteria for evaluation of therapeutic efficacy Grade 0: Ineffective There is no discernible therapeutic effect on cancer tissue or cells. Grade 1: Slightly effective Apparently “viable” cancer cells (including cells having eosinophilic cytoplasm with vacuolation and swollen nuclei) account for 1/3 or more of tumor tissue, but there is some evidence of degeneration of cancer tissue or cells. Gra..