Long-term response of CT-26 murine colon carcinomas to low-dose DMXAA, HPPH-sensitized PDT and PDT–DMXAA combination therapy. Kaplan–Meier survival curves of BALB/c mice bearing subcutaneous CT-26 tumors treated with low-dose DMXAA (D; 25 mg kg−1, n = 9) alone, HPPH-PDT alone (48 at 112, n = 21 and 128 at 14, n = 21), HPPH-PDT in combination with DMXAA (48 at 112 + D, n = 15) or no treatment (control, n = 10). Log rank test P < 0.001 between 48 at 112 + D vs controls, D and 48 at 112.