IN-VIVO LASER-LIGHT DISTRIBUTION IN HUMAN PROSTATIC-CARCINOMA

The extent of laser light diffusion within prostatic tumor is of major importance in the treatment of localized prostatic cancer with photod ynamic therapy (PDT). The penetration of 633 nm. wavelength red light was studied in eleven patients with suspected prostatic cancer using a novel method suitable for in situ measurements. Light delivery and de tector fiber, placed interstitially within the gland, determined light attenuation at different interfiber separations. Of 11 patients, 10 h ad bilateral and 1 had single lobe studies. The mean +/- the standard error of the mean attenuation coefficients (($) over bar Sigma(eff)) f or benign and malignant prostate tissue were 0.35 +/- 0.02 mm.(-1) and 0.36 +/- 0.02 mm.(-1), respectively, indicating similar optical densi ties (p =.58). Patients with bilateral lobe mm. involvement showed lit tle intraglandular variation in Sigma(eff) (p = 0.23). However, there was interpatient variation (Sigma(eff) = 0.28 to 0.48 mm.(-1)) reflect ing biological differences which, though therapeutically important, we re not statistically significant (p = 0.057). This study showed that t reatment requires individualization and predicted that 4 cylindrical d iffusers are expected to destroy 25 ml. of prostatic tumor with PDT.