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Grading inaccuracies in diagnostic biopsies revealing prostatic adenocarcinoma: implications for definitive radiation
P A Johnstone1, R Riffenburgh, E L Saunders
1Radiation Oncology Division, Naval Medical Center, San Diego, CA 92134-5000, USA.
Purpose:
A critical determinant of prognosis in prostate cancer is grade of disease. Historically, this has been determined by biopsy of the prostate using transperineal, transrectal, or transurethral approaches. Several reports in the literature reveal that these biopsies often underestimate the histologic grade of the tumor when compared with subsequent radical prostatectomy specimens.
Methods And Materials:
Data from the literature were analyzed to assess the magnitude of this bias towards undergrading. Grade of biopsy specimens (well-differentiated = Gleason score 2-4; moderately differentiated = Gleason 5-7; poorly differentiated = Gleason 8-10) were correlated with the ultimate prostatectomy grade. Analysis was made of tendency to undergrade specimens using strict criteria of data inclusion for needle biopsies, and more relaxed criteria for all types of prostate biopsies.
Results:
Grading accuracy from needle biopsies was 71%, with 23% undergraded and 6% overgraded. A chi-square test on equal chance of under- vs. overgrading yielded p = 0.022. Grading accuracy from needle, open perineal, and transurethral biopsies was 65%, with 23% undergraded and 12% overgraded. A similar chi-square test yielded p = 0.007. In both cases, there appears to exist a significant bias towards undergrading.
Conclusions:
In addition to other well-documented factors that confound comparisons between radiation therapy and surgical series in carcinoma of the prostate, grade migration exists as well. The equivalence of radiation therapy and surgery with respect to overall survival in this disease is accomplished despite these biases.