Spectral grading and Gleason grading of malignant prostate tissue using Stokes shift spectra

Abstract

ABSTRACT Gleason score is the most common method of grading the virulence of prostate malignancy and is based on the pathological assessment of morphology of cellular matrix. Si nce this involves the excision of the tissue, we are working on a new, minimally invasive, non contact, procedure of spectral diagnosis of prostate malignancy. In this preliminary in vitro study reported here, we have analyzed 27 tissue sample s (normal control =7: benign=8: malignant =12) by Stokes’ shift spectra (SSS) to establish a one- to- one corre lation between spectral grading and Gleason grading. Key Words: Spectral grading and Gleason grading, maligna nt prostate tissue, Stokes' shift spectra. 1.INTRODUCTION Gleason Score (GS) is the most common method of grading the prostate cancer tissue in order to understand how much and how fast the malignancy is spreading. This kind of scor ing, though subjective and varies considerably between two professional pathologists, has been a useful tool for long term prognosis of the afflicted patients. This score is based on the microscopic appearance of the tissue a nd greater the score the more aggressive the disease and worse the prognosis. The pathologist assign a score 1 for the normal well differen tiated tissue which has small, well formed uniform glands; he assigns a score of 5 for the poorly differentiated, irregular mesh of cells with few glands. Most often the tissues do not have such well defined structure, but exhibit a mix of two patterns: A primary or the most prominent pattern and a secondary, less prominent pattern, say 3 and 4 or 4 and 3. Though for both cases the total score is 7, the former one has better prognosis than the latter. The primary pattern determines the Gleason grade, which runs from 1 to 5; the combination of grades of two important patterns is called Gleason Score.[1] The objective of this paper is to establish a parallelism between the Gleason score of microscopic cellular morphology and the spectral features of fluorescencent bio markers of the malignant prostate tissues. For men above sixty, benign prostate hyperplasia (BPH) is common; and cancer of prostate (CaP) is rare. Optical techniques were recently used in differentiating BPH from Ca P. Raman spectroscopy has been employed to detect and grade prostatic adeno carcinoma [2]. This study showed discrimination between BPH and CaP based on increase in concentration of nucleic acid and decrease in glycogen for CaP, as compared to BPH. This reduced level of glycogen has also been reported with independent FTIR (Fourier transform – infra red) study [3]. Magnetic resonance spectroscopy (MRS) has also been used to delineate citrate levels [4] and the ratio of creatine and myo-inositol [5], as parameters for BPH and CaP discrimination. Recently, research based on native fluorescence and Raman si gnals of malignant tissues, a technique known as optical biopsy, is gaining importance [6-8]. In spite of extensive work done on native fluorescence of malignant tissues of many cancers, significant results of endogenous fluorescence analysis in discrimination of BPH and CaP has been reported only very recently [9] A few biomolecules in the human body have endogenous fluorescence, with unique combination of excitation and emission maxima, which taken together can serve as a fingerprint for the molecule. Native fluorescence analysis of