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In Reply: Re Endo-Rectal Coil Magnetic Resonance Imaging in Clinically Localized Prostate Cancer: Is it Accurate?
1372
LETTERS TO THE EDITOR
used by the radiologists. Some of the specific shortcomings of the techniques are described. Regarding image acquisition, the MRI technique described is identical to that used in the comparative study conducted by the Radiology Diagnostic Oncology Group between 1990 and 1992,and cited by the authors.' Subsequent improvements in MRI hardware and software have made such techniques suboptimal for current practice. The authors should specify when the images were acquired. The conventional spin-echo pulse sequences a s described would take a t least 10 minutes to acquire 1 data set. Presently, the routine and more rapid 13 to 4 minutes) pulse sequence fast spin-echo technique allows acquisition of the data in a shorter period, thus reducing artifacts that interfere with image interpretation. Another advantage to the faster sequences is the ability to have time to image in different planes. The authors limited themselves to imaging in the axial (transaxialt plane only. Most radiologists would now acquire T2-weighted sequences in the axial, sagittal and coronal planes. Many scanners now allow for the combination of an endo-rectal coil with an external multi-coil to improve signal-to-noise, particularly in the anterior aspect of the gland. In regard to image analysis, the description of the MRI criteria for the diagnosis of capsular penetration is limited. The only feature mentioned is a "focal contour bulge," which has been shown to have a positive predictive value of 30 to 60% depending on the characteristics of the bulge.2 The authors apparently did not use some of the more recently developed features proved to enhance MRI with a n area under the receiver operating characteristics curve of 0.81. The authors did not identify who interpreted the images in the study and whether they were blinded to clinical information, such as biopsy results and serum PSA values a s well as the extent of their experience and training regarding prostate MRI. The Radiology Diagnostic Oncology Group study and other large reader studies have detected significant interobserver variability. The authors suggest that the main limitation of MRI is its inability to detect reliably microscopic extracapsular extension. However, relatively low sensitivity need not limit its clinical use. Achieving high specificity (that is a low rate of false-positive readings) at the expense of some sensitivity is a desirable goal that increases the clinical use of the technique. We would have liked to see these discrepancies mentioned in the discussion and references made to the extensive discussion of these issues in the radiology literature.3 In conclusion, we believe that the techniques described by the authors have several limitations and do not represent current radiological practice. While its precise clinical role in the staging of prostate cancer has not been determined, MRI can provide important data in specific patient subgroups? Respectfully, Clare M. C. Tempany Department of Radiology Brigham & Women's Hospital Boston, Massachusetts 021 15 and Curtis P. Langlotz Department of Radiology 3600 Market Street, Suite 370 Philadelphia, Pennsylvania 19104 1. Tempany, C. M.,Zhou, X., Zerhouni, E. A., Ritkin, M. D., Quint, L. E., Piccoli, C. W., Ellis, J. H. and Mc Neil, B. J.: Staging of prostate cancer: results of Radiology Diagnostic Oncology Group project comparison of three MR imaging techniques. Radiology, 192:47, 1994. 2. Langlotz, C. P.,Schnall, M. D. and Pollack, H.: Staging of prostatic cancer: Accuracy of MR imaging. Radiology, 194: 645,1995. 3. Langlotz. C. P.:Benefits and costs of MR imaging of prostate cancer. MR Clin. N. Amer., pp. 533-544, 1996. 4. DAmico, A. V.,Whittington, R., Schnall, M. D., Malkowicz, S. B., Tomaszewski, J. E., Schultz, D. and Wein, A.: The impact of the inclusion of endorectal coil magnetic resonance imaging in a multivariate analysis to predict clinically unsuspected extraprostatic cancer. Cancer, 7 5 2368,1995. Reply 6yAuthors. Of our 12 patients with a PSA of 10 to 20 ng./ml. 5 also had a biopsy Gleason score of less than or equal to 7 and at least 5 0 9 positive biopsies. The sensitivity, specificity and overall
accuracy of endo-rectal coil MRI for predicting pathological stage T3 disease in this subset were 50% (1 of 2 cases), 100%(3of 3)and 80% (4of 6), respectively. Although the sample size is small, the results
are similar to those of DAmico et al, and the overall accuracy is improved compared to the group as a whole. D ' h i c o et al clarified the anticipated role of endo-rectal coil MRI in the challenging task of accurately staging prostate cancer cases. Similar to our prospective study, these investigators concluded that endo-rectal coil MRI should not be used routinely for preoperative staging of prostate cancer. However, a select subset of patients has been identified in whom use of endo-rectal coil MRI warrants further study. Such critical evaluation continues to be essential for the development of practical guidelines for this procedure. In response to Tempany and Langlotz, our investigation, which was conducted during the 1993 academic year and used state of the art technology, is not the first to find the main limitation of endorectal coil MRI to be its inability to detect microscopic extracapsular disease spread. Harris et al had similar results despite the incorporation of fast spin-echo technique into image acquisition. 1 Our study was specifically designed to determine whether endo-rectal coil MRI could offer information that might influence the treatment of patients considered clinically to be ideal candidates for radical prostatectomy. As clearly stated in the article, our conclusions refer to this select population only. Might endo-rectal coil MRI be useful in confirming t h e presence of seminal vesicle invasion by tumor in a patient clinically believed to have stage T3b disease and obviate the need for biopsy? Possibly, and this concept is presently being investigated. Also under investigation is the concept that classification of patients according to a combination of PSA, biopsy Gleason score and the percent of core biopsies positive may identify a subset for whom endo-rectal coil MRI may be helpful.* Presently there is no evidence to support the routine use of endo-rectal coil MRI in the staging of newly-diagnosed prostate cancer. 1. Harris, R. D., Schned, A. R. and Heaney, J. A.: Staging of prostate cancer with endorectal MR imaging: lessons from a learning curve. Radiographics, 15: 813,1995. 2. DAmico, A. V., Whittington, R., Malkowicz, S. B., Schultz, D., Schnall, M. D., Tomaszewski, J. E. and Wein, A.: Multivariate analysis evaluatin the role of the percent of positive biopsies, and endorectal c o j MRI in predicting extraprostatic disease and postoperative PSA failure in intermediate risk prostate cancer patients. In: Proceedings of the Annual Meeting of the American Radium Society, Abstract 31,p. 26, 1996.
RE: LE'ITERS TO THE EDITOR ON LONG-TERM SURVIVAL AND MORTALITY IN PROSTATE CANCER TREATED WITH NONCURATIVE INTENT T.
Y. Chun, G. W. Chodak a n d R. A. Thisted J. Urol., 165 2039-2041, 1996
To the Editor. The exchange of Letters to the Editor on the results of watchful waiting is a n education in medical statistics. To the unlearned clinician the 3 Letters emphasize the dictum t h a t complex statistical computation is a poor substitute for actual patient numbers and analysis. In the United States in no other area of medicine would one adopt a standard "do nothing" approach for a n illness that is the cause of 40,000 deaths a year. This seems to be a strong recommendation of the National Comprehensive Cancer Network. Much of t h e controversy in prostate cancer management, including watchful waiting or benign neglect, could be decreased if the end points for benefits were standardized. While some end points may improve with 1 approach others may not. However, to expect a n approach to improve all parameters in all patients for a long time may be demanding and unattainable. The end points include tumor control (clinical and biochemical), local tumor control (clinical and pathological ), disease free survival (clinical and biochemical), freedom from relapse (time and percentage), disease progression-free survival (time and percentage), symptom-free survival (time and percentage 1, cancer specific mortality (deaths from prostate cancer a t 10 years) and patient overall survival. The change in end points reported together could help patients, clinicians and academicians to compare the benefits of various a p proaches. Considering the age group of the patient population, one cannot watch a tumor progress to incurability and patient death. Neither can major benefit be obtained by controlling clinical disease for significantly longer periods than actuarial patient sunrival. Over. all survival, a commonly used end point, is impacted more by life expectancy of the patient population, tumor selection and the behav-
LETTERS TO THE EDITOR
used by the radiologists. Some of the specific shortcomings of the techniques are described. Regarding image acquisition, the MRI technique described is identical to that used in the comparative study conducted by the Radiology Diagnostic Oncology Group between 1990 and 1992,and cited by the authors.' Subsequent improvements in MRI hardware and software have made such techniques suboptimal for current practice. The authors should specify when the images were acquired. The conventional spin-echo pulse sequences a s described would take a t least 10 minutes to acquire 1 data set. Presently, the routine and more rapid 13 to 4 minutes) pulse sequence fast spin-echo technique allows acquisition of the data in a shorter period, thus reducing artifacts that interfere with image interpretation. Another advantage to the faster sequences is the ability to have time to image in different planes. The authors limited themselves to imaging in the axial (transaxialt plane only. Most radiologists would now acquire T2-weighted sequences in the axial, sagittal and coronal planes. Many scanners now allow for the combination of an endo-rectal coil with an external multi-coil to improve signal-to-noise, particularly in the anterior aspect of the gland. In regard to image analysis, the description of the MRI criteria for the diagnosis of capsular penetration is limited. The only feature mentioned is a "focal contour bulge," which has been shown to have a positive predictive value of 30 to 60% depending on the characteristics of the bulge.2 The authors apparently did not use some of the more recently developed features proved to enhance MRI with a n area under the receiver operating characteristics curve of 0.81. The authors did not identify who interpreted the images in the study and whether they were blinded to clinical information, such as biopsy results and serum PSA values a s well as the extent of their experience and training regarding prostate MRI. The Radiology Diagnostic Oncology Group study and other large reader studies have detected significant interobserver variability. The authors suggest that the main limitation of MRI is its inability to detect reliably microscopic extracapsular extension. However, relatively low sensitivity need not limit its clinical use. Achieving high specificity (that is a low rate of false-positive readings) at the expense of some sensitivity is a desirable goal that increases the clinical use of the technique. We would have liked to see these discrepancies mentioned in the discussion and references made to the extensive discussion of these issues in the radiology literature.3 In conclusion, we believe that the techniques described by the authors have several limitations and do not represent current radiological practice. While its precise clinical role in the staging of prostate cancer has not been determined, MRI can provide important data in specific patient subgroups? Respectfully, Clare M. C. Tempany Department of Radiology Brigham & Women's Hospital Boston, Massachusetts 021 15 and Curtis P. Langlotz Department of Radiology 3600 Market Street, Suite 370 Philadelphia, Pennsylvania 19104 1. Tempany, C. M.,Zhou, X., Zerhouni, E. A., Ritkin, M. D., Quint, L. E., Piccoli, C. W., Ellis, J. H. and Mc Neil, B. J.: Staging of prostate cancer: results of Radiology Diagnostic Oncology Group project comparison of three MR imaging techniques. Radiology, 192:47, 1994. 2. Langlotz, C. P.,Schnall, M. D. and Pollack, H.: Staging of prostatic cancer: Accuracy of MR imaging. Radiology, 194: 645,1995. 3. Langlotz. C. P.:Benefits and costs of MR imaging of prostate cancer. MR Clin. N. Amer., pp. 533-544, 1996. 4. DAmico, A. V.,Whittington, R., Schnall, M. D., Malkowicz, S. B., Tomaszewski, J. E., Schultz, D. and Wein, A.: The impact of the inclusion of endorectal coil magnetic resonance imaging in a multivariate analysis to predict clinically unsuspected extraprostatic cancer. Cancer, 7 5 2368,1995. Reply 6yAuthors. Of our 12 patients with a PSA of 10 to 20 ng./ml. 5 also had a biopsy Gleason score of less than or equal to 7 and at least 5 0 9 positive biopsies. The sensitivity, specificity and overall
accuracy of endo-rectal coil MRI for predicting pathological stage T3 disease in this subset were 50% (1 of 2 cases), 100%(3of 3)and 80% (4of 6), respectively. Although the sample size is small, the results
are similar to those of DAmico et al, and the overall accuracy is improved compared to the group as a whole. D ' h i c o et al clarified the anticipated role of endo-rectal coil MRI in the challenging task of accurately staging prostate cancer cases. Similar to our prospective study, these investigators concluded that endo-rectal coil MRI should not be used routinely for preoperative staging of prostate cancer. However, a select subset of patients has been identified in whom use of endo-rectal coil MRI warrants further study. Such critical evaluation continues to be essential for the development of practical guidelines for this procedure. In response to Tempany and Langlotz, our investigation, which was conducted during the 1993 academic year and used state of the art technology, is not the first to find the main limitation of endorectal coil MRI to be its inability to detect microscopic extracapsular disease spread. Harris et al had similar results despite the incorporation of fast spin-echo technique into image acquisition. 1 Our study was specifically designed to determine whether endo-rectal coil MRI could offer information that might influence the treatment of patients considered clinically to be ideal candidates for radical prostatectomy. As clearly stated in the article, our conclusions refer to this select population only. Might endo-rectal coil MRI be useful in confirming t h e presence of seminal vesicle invasion by tumor in a patient clinically believed to have stage T3b disease and obviate the need for biopsy? Possibly, and this concept is presently being investigated. Also under investigation is the concept that classification of patients according to a combination of PSA, biopsy Gleason score and the percent of core biopsies positive may identify a subset for whom endo-rectal coil MRI may be helpful.* Presently there is no evidence to support the routine use of endo-rectal coil MRI in the staging of newly-diagnosed prostate cancer. 1. Harris, R. D., Schned, A. R. and Heaney, J. A.: Staging of prostate cancer with endorectal MR imaging: lessons from a learning curve. Radiographics, 15: 813,1995. 2. DAmico, A. V., Whittington, R., Malkowicz, S. B., Schultz, D., Schnall, M. D., Tomaszewski, J. E. and Wein, A.: Multivariate analysis evaluatin the role of the percent of positive biopsies, and endorectal c o j MRI in predicting extraprostatic disease and postoperative PSA failure in intermediate risk prostate cancer patients. In: Proceedings of the Annual Meeting of the American Radium Society, Abstract 31,p. 26, 1996.
RE: LE'ITERS TO THE EDITOR ON LONG-TERM SURVIVAL AND MORTALITY IN PROSTATE CANCER TREATED WITH NONCURATIVE INTENT T.
Y. Chun, G. W. Chodak a n d R. A. Thisted J. Urol., 165 2039-2041, 1996
To the Editor. The exchange of Letters to the Editor on the results of watchful waiting is a n education in medical statistics. To the unlearned clinician the 3 Letters emphasize the dictum t h a t complex statistical computation is a poor substitute for actual patient numbers and analysis. In the United States in no other area of medicine would one adopt a standard "do nothing" approach for a n illness that is the cause of 40,000 deaths a year. This seems to be a strong recommendation of the National Comprehensive Cancer Network. Much of t h e controversy in prostate cancer management, including watchful waiting or benign neglect, could be decreased if the end points for benefits were standardized. While some end points may improve with 1 approach others may not. However, to expect a n approach to improve all parameters in all patients for a long time may be demanding and unattainable. The end points include tumor control (clinical and biochemical), local tumor control (clinical and pathological ), disease free survival (clinical and biochemical), freedom from relapse (time and percentage), disease progression-free survival (time and percentage), symptom-free survival (time and percentage 1, cancer specific mortality (deaths from prostate cancer a t 10 years) and patient overall survival. The change in end points reported together could help patients, clinicians and academicians to compare the benefits of various a p proaches. Considering the age group of the patient population, one cannot watch a tumor progress to incurability and patient death. Neither can major benefit be obtained by controlling clinical disease for significantly longer periods than actuarial patient sunrival. Over. all survival, a commonly used end point, is impacted more by life expectancy of the patient population, tumor selection and the behav-