© 2001 by Oxford University Press
Journal of the National Cancer Institute, Vol. 93, No. 5, 401-402,
March 7, 2001
© 2001 Oxford University Press
CORRESPONDENCE |
RESPONSE: Re: Health Outcomes After Prostatectomy or Radiotherapy for Prostate Cancer: Results From the Prostate Cancer Outcomes Study
Affiliations of authors: A. L. Potosky, J. Legler, Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD; R. M. Hoffman, Albuquerque Department of Veterans Affairs Medical Center, NM; F. D. Gilliland, Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles.
Correspondence to: Arnold L. Potosky, Ph.D., National Institutes of Health, EPN, Rm. 4005, 6130 Executive Blvd., MSC 7344, Bethesda, MD 20892–7344 (e-mail: potosky{at}nih.gov).
We appreciate the time that Dr. Dalkin has taken to review and comment on our article. However, we disagree with his assessment that there are significant flaws in the study.
First, we have previously addressed the issue of the mode of questionnaire administration in an article that described the methods, rationale, and objectives of the Prostate Cancer Outcomes Study (PCOS) (1). There, we noted that 91% of all PCOS participants completed a mailed self-administered questionnaire, with the rest completing surveys by phone or in-person. We found that the mode of survey administration had no statistically significant effects on reported outcomes.
Second, we carefully noted throughout the article that the baseline measurements were obtained retrospectively at approximately 6 months after diagnosis because of the practical difficulty of surveying newly diagnosed cancer patients in a large, community-based study prior to initiation of treatment. We agree that it is important to verify the accuracy of using such recall for estimating baseline status. We, therefore, conducted our own validation study to assess recall and found that it was, in fact, reasonably accurate (2). Furthermore, we found no strong biases that would favor either underestimation or overestimation of baseline functioning. The median time of recall in the study by Litwin et al. (3) that was cited by Dr. Dalkin was 21 months, whereas in our study it was approximately 6 months. While we do not claim that recall is without error, it is unlikely that biased recall over a 6-month period would invalidate our comparisons of post-treatment outcomes.
Third, we agree with Dr. Dalkin that postsurgical results should be assessed relative to pretreatment erectile function. Our article reports (on page 1588) that, among men who were potent prior to treatment, 76% receiving prostatectomy compared with 45% of men receiving beam radiotherapy were impotent after 2 years. In Fig. 3 of our article, we showed trends in sexual function by treatment approach in men with better pretreatment function and in men with poorer function.
We did not specifically examine the technical aspects of prostatectomy in our study because we wanted to maintain the focus on a comparison between surgery and radiotherapy. An earlier study by Stanford et al. (4), also using PCOS data, compared prostatectomy patients for whom the details of their surgery were recorded in their medical records. The levels of impotence were 65.6% in men who had a non-nerve-sparing procedure, 57.0% in men who had a unilateral nerve-sparing procedure, and 56.0% in men who had a bilateral nerve-sparing procedure.
Fourth, with regard to urinary function, the difference between our study, which reported that 28.1% of men wore pads 2 years after prostatectomy, and that reported by Gralnek et al. (5) may be due to differences in patient selection, health care setting, and the skill of the surgeons. The lower rates of incontinence and impotence reported by Gralnek et al. (5) and other investigators at major academic centers highlight one of the important reasons for initiating the PCOS. The better outcomes reported by academic centers reflect the experiences of carefully selected patients who were treated by skilled surgeons. Whether these same outcomes are achievable in the general population is unknown because patients, surgical practices, and the health care system are much more heterogeneous in the general population. While case series from academic centers may tell us about patient outcomes under optimal circumstances, population-based studies, such as PCOS, tell us what most men in the community might expect after treatment. Clearly, there is value in both types of studies.
REFERENCES
1
Potosky AL, Harlan LC, Stanford JL, Gilliland FD, Hamilton AS, Albertsen PC, et al. Prostate cancer practice patterns and quality of life: the Prostate Cancer Outcomes Study. J Natl Cancer Inst 1999;91:1719–24.
2 Legler J, Potosky AL, Gilliland FD, Eley JW, Stanford JL. Validation study of retrospective recall of disease-targeted function: results from the Prostate Cancer Outcomes Study. Med Care 2000;38:847–57.[CrossRef][Web of Science][Medline]cancerlit;20383821
3
Litwin MS, McGuigan KA. Accuracy of recall in health-related quality-of-life assessment among men treated for prostate cancer. J Clin Oncol 1999;17:2882–8.
4
Stanford JL, Feng Z, Hamilton AS, Gilliland FD, Stephenson RA, Eley JW, et al. Urinary and sexual function after radical prostatectomy for clinically localized prostate cancer: the Prostate Cancer Outcomes Study. JAMA 2000;283:354–60.
5 Gralnek D, Wessells H, Cui H, Dalkin BL. Differences in sexual function and quality of life after nerve sparing and nonnerve sparing radical retropubic prostatectomy. J Urol 2000;163:1166–9; discussion 1169–70.[CrossRef][Web of Science][Medline]
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