Mid-infrared imaging in breast cancer tissue: an objective measure of grading breast cancer biopsies

Abstract

Introduction : - The majority of cancers are diagnosed using excised biopsy specimens. These are graded, using a g old - standard histopathology protocol based on haemotoxylin and eosin ( “H+E” ) chemical staining . However the grading is done by eye and i f the same biopsy is graded by different practitioners, they typic ally only agree ~70% of the time. The resulting overtreatment problem constitutes a massive unmet need worldwide. Objective: - Our new ‘Digistain ’ technology, uses mid - infrared imaging to map the fractional concentration of nucleic acids, i.e. the n uclea r - to - cytoplasmic chemical ratio (NCR) across an unstained biopsy section. It allows a quantitative “Digistain index” (DI) score, corresponding to the NCR, to be reproducibly extracted from an objective p hysical measurement of a cancer. O ur objective here i s to evaluate its potential for aiding cancer diagnosis for the first time. We correlate the DI scores with H+E grades in a double - blind clinical pilot trial. Methods: - T wo adjacent slices were taken from 75 breast cancer FFPE blocks; one was graded with the standard H+E protocol, and also used to define a “Region of Int erest” (RoI). Digistain was then used to acquire a DI value averaged over the corresponding RoI on the other (unstained) slice and the r esults were statistically analysed. Results : - We find the DI score correlates significantly (p=0.0007) with tumor grade in a way that promises to significantly reduce the inherent subjectivity and variability in biopsy grading. Discussion: The NCR is elevated by increased mitotic activity because cells divide when they are younger and , on average, become smaller as the di sease progresses. Also, extra DNA and RNA is generated as the nuclear transcription machinery goes awry and nuclear pleomorphism occurs . Both effects make the NCR a recognized biomarker for a wide range of tumors, so we expect Digistain will find application in a very wide range of cancers.