Intratumoral hypericin and KTP laser therapy for transplanted squamous cell carcinoma

Objectives/Hypothesis: To test intratumoral pho todynamic therapy (IPDT) as a new treatment for squamous cell carcinoma in a preclinical tumor model. Study Design and Methods: Human P3 squamous carcinoma cells were transplant ed subcutaneously in athymic nude mice and allowed to grow into 300- to 500 -mm(3) tumors. Hypericin dye at 1 mu g/gm of body weight was injected intra tumorally (IT) or intravenously (IV), After 4 hours hypericin biodistributi on was assessed in ethanol extracts from tissues by fluorescence spectrosco py. IPDT also was tested by KTP laser fiberoptic insertion in tumors 4 hour s after rr dye injection compared to KTP532 laser therapy alone (532 nm, 1W , 40-60 J, 0,6-mm fiber), Results: Hypericin concentration in tissues was a s follows: (FT vs, IV) for tumors (3660 vs. 135 ng dye/gm tissue), lung (76 0 vs, 6345), liver (75 vs. 935), blood (65 vs. 480) com pared to shin (465 vs, 110) or muscle (335 vs. 80) adjacent to the squamous cell tumors. Four hours after dye injection, the tumor exhibited bright orange fluorescence w hen excited by KTP 532-nm green laser light. The IPDT-treated tumors had a 3.32 +/- 0,32-mm radius of cell destruction when H&E-stained sections were examined compared with 2.5 +/- 0.38 mm for the laser only control group (n = 10, P = .003), Conclusions: This pilot study indicates laser IPDT with hy pericin induces a significant increase in tumor necrosis compared with lase r alone and may be useful as a less invasive adjuvant treatment for recurre nt or inoperable human squamous cell cancers of the head and neck.