Photodynamic therapy (
PDT) may be an attractive option for treatment of early stage
prostate cancer.
Aminolevulinic acid (ALA) acts as a
prodrug leading to a selective accumulation of a
photosensitizer,
protoporphyrin IX (
PpIX), in epithelial cells. We investigated the efficacy of ALA-mediated
PDT for rat R3327-H
prostate cancer, compared with the AY-27
bladder tumor. Rats bearing either AY-27 or R3327-H
tumors were randomized to different groups when their
tumors reached approximately 1000 mm3. At the day of
PDT, animals were administered 500 mg/kg ALA intravenously 4 hours prior to
laser therapy. The
argon-pumped
dye laser light (630 nm) was coupled to multiple
quartz fibers with cylindrical diffusing
tips, which were inserted into the
tumor in icosahedral pattern. Light exposure was varied to yield doses of 1000 to 3000 J/
tumor. Animals bearing R3327-H
tumors were imaged with
99mTc-HMPAO scintigraphy to evaluate
tumor perfusion changes induced by
PDT. There was a light-dose dependent
tumor response in both
tumor models. The mean time for R3327-H
tumor to re-grow to 4 x treatment volume was 79.7 days in the control group (light only), 159 days in 1000 J group, and 169 days in 2000 J group (P < 0.05).
Tumors treated with 3000 J were clinically cured (P < 0.01). Likewise, for AY-27
tumors, the average time to re-grow to 4 x treatment volume was 13.7 days in the control group, 179.3, 183.3, and 185.7 days in groups of 1000, 1500, and 2000 J (P < 0.05), respectively.
Tumors treated with 3000 J were clinically cured (P < 0.01).
99mTc-HMPAO scintigraphy demonstrated a mild perfusion impairment following
PDT. Interstitial
PDT with ALA/
PpIX is equally effective in treating
prostate cancer and TCC in these heterotopic rat models.