Optical reflectance spectroscopy to differentiate renal tumor from normal parenchyma

Optical spectroscopy has been evaluated as an innovative technique for the ex vivo study of renal and prostate tumors. In this pilot study we assessed the ability of optical reflectance spectroscopy to reliably differentiate tumor and normal tissue in renal specimens.

From January to April 2007 we completed optical reflectance spectroscopy measurements at several standardized tumor and normal parenchymal locations immediately after kidney tumor removal. The slopes of the optical reflectance spectroscopy curves were compared, and the correlation between tumor and normal parenchyma reflectance was assessed.

Reliable measurements were obtained from 13 radical and 8 partial nephrectomy specimens. Histology was malignant in 15 cases (clear cell in 14 and papillary in 1) and benign in 6 cases of oncocytoma. Overall we found a significant difference between the average optical reflectance spectroscopy slopes of tumor and normal parenchyma (p = 0.03). In individual radical nephrectomy specimens optical reflectance spectroscopy measurements at different locations in the tumor showed an excellent correlation (r = 0.968). Normal parenchymal measurements also correlated well (r = 0.88), although there was poor correlation between tumor and nontumor tissue in the specimen (r = 0.07). In the partial nephrectomy subset we also found a close correlation among measurements made on the normal parenchymal margin of the tumor (r = 0.94) except in 1 case of a positive margin (oncocytoma), in which the measurement from the positive margin site did not correlate with that of the adjacent parenchymal margin (r = 0.48).

Optical reflectance spectroscopy can help distinguish tumor from normal renal tissue in specimens immediately removed at surgery. Optical reflectance spectroscopy may allow real-time assessment of positive margins during partial nephrectomy.