Magnetic resonance spectroscopy of the malignant prostate gland after radiotherapy: a histopathologic study of diagnostic validity

Menard, Cynthia; Smith, Ian C.P; Somorjai, Ray L; Leboldus, Leonard; Patel, Rakesh; Littman, Charles; Robertson, Susan J; Bezabeh, Tedros

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Volume 50, Issue 2 , Pages 317-323, 1 June 2001

Magnetic resonance spectroscopy of the malignant prostate gland after radiotherapy: a histopathologic study of diagnostic validity

This work was presented in part at the following meetings: International Society of Magnetic Resonance in Medicine (Denver, Colorado, April 2000); Canadian Association of Radiation Oncologists (Edmonton, Alberta, September 2000); American Society for Therapeutic Radiology and Oncology (Boston, Massachusetts, October 2000).

Cynthia Menard, M.D.
- Department of Radiation Oncology, CancerCare Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada
Ian C.P Smith, Ph.D.
- Institute for Biodiagnostics, National Research Council, Winnipeg, Manitoba, Canada
Ray L Somorjai, Ph.D.
- Institute for Biodiagnostics, National Research Council, Winnipeg, Manitoba, Canada
Leonard Leboldus, M.D.
- Winnipeg Clinic, Winnipeg, Manitoba, Canada
Rakesh Patel (M.Sc.)
- Institute for Biodiagnostics, National Research Council, Winnipeg, Manitoba, Canada
Charles Littman (M.B.Ch.B.)
- Department of Pathology, University of Manitoba, Winnipeg, Manitoba, Canada
Susan J Robertson, M.D.
- Department of Pathology, Ottawa Hospital, Ottawa, Ontario, Canada
Tedros Bezabeh, Ph.D.
- Institute for Biodiagnostics, National Research Council, Winnipeg, Manitoba, Canada
- Reprint requests to: Dr. Tedros Bezabeh, Institute for Biodiagnostics, National Research Council, 435 Ellice Ave., Winnipeg, Manitoba, R3B 1Y6 Canada. Tel: (204) 983-0994; Fax: (204) 984-7036

Accepted 12 January 2001.

Abstract

Purpose: Accurate spatial representation of tumor clearance after conformal radiotherapy is an endpoint of clinical importance. Magnetic resonance spectroscopy (MRS) can diagnose malignancy in the untreated prostate gland through measurements of cellular metabolites. In this study we sought to describe spectral metabolic changes in prostatic tissue after radiotherapy and validate a multivariate analytic strategy (based on MRS) that could identify viable tumor.

Methods and Materials: Transrectal ultrasound–guided prostate biopsies from 35 patients were obtained 18–36 months after external beam radiotherapy. One hundred sixteen tissue specimens were subjected to ¹H MRS, submitted to histopathology, and analyzed for correlation with a multivariate strategy specifically developed for biomedical spectra.

Results: The sensitivity and specificity of MRS in identifying a malignant biopsy were 88.9% and 92% respectively, with an overall classification accuracy of 91.4%. The diagnostic spectral regions identified by our algorithm included those due to choline, creatine, glutamine, and lipid. Citrate, an important discriminating resonance in the untreated prostate gland, was invisible in all spectra, regardless of histology.

Conclusions: Although the spectral features of prostate tissue markedly change after radiotherapy, MRS combined with multivariate methods of analysis can accurately identify histologically malignant biopsies. MRS shows promise as a modality that could integrate three-dimensional measures of tumor response.

Keywords: Classifier, Magnetic resonance spectroscopy, Multivariate analysis, Prostate cancer, Radiotherapy