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© 2001 American Society for Clinical Oncology Health-Related Quality-of-Life Effects of Radical Prostatectomy and Primary Radiotherapy for Screen-Detected or Clinically Diagnosed Localized Prostate CancerFrom the Departments of Public Health, Erasmus University, and Department of Urology, Erasmus University Rotterdam and Academic Hospital Rotterdam, the Netherlands. Address reprint requests to Joanna B. Madalinska, MA, MSc Department of Public Health, Erasmus University Rotterdam, PO Box 1738, 3000 DR Rotterdam, the Netherlands; email: madalinska{at}mgz.fgg.eur.nl
PURPOSE: The current study was undertaken within the framework of a screening trial to compare the health-related quality-of-life (HRQOL) outcomes of two primary treatment modalities for localized prostate cancer: radical prostatectomy and external-beam radiotherapy. PATIENTS AND METHODS: We conducted a prospective longitudinal cohort study among 278 patients with early screen-detected (59%) or clinically diagnosed (41%) prostate cancer using both generic and disease-specific HRQOL measures (SF-36, UCLA Prostate Cancer Index [urinary and bowel modules] and items relating to sexual functioning) at three points in time: t1 (baseline), t2 (6 months later), and t3 (12 months after t1). RESULTS: Questionnaires were completed by 88% to 93% of all initially enrolled patients. Patients referred for primary radiotherapy were significantly older than prostatectomy patients (63 v 68 years, P < .01). Analyses (adjusted for age and pretreatment level of functioning) revealed poorer levels of generic HRQOL after radiotherapy. Prostatectomy patients reported significantly higher (P < .01) posttreatment incidences of urinary incontinence (39% to 49%) and erectile dysfunction (80% to 91%) than radiotherapy patients (respectively, 6% to 7% and 41% to 55%). Bowel problems (urgency) affected 30% to 35% of the radiotherapy group versus 6% to 7% of the prostatectomy group (P < .01). Patients with screen-detected and clinically diagnosed cancer reported similar posttreatment HRQOL. CONCLUSION: Prostatectomy and radiotherapy differed in the type of HRQOL impairment. Because the HRQOL effects may be valued differently at the individual level, patients should be made fully aware of the potential benefits and adverse consequences of therapies for early prostate cancer. Differences in posttreatment HRQOL were not related to the method of cancer detection.
IN 1995, 6,367 CASES of prostate cancer were diagnosed in the Netherlands.1,2 The incidence has climbed in recent years, mainly because of improved diagnostic techniques.3 Questions about the potential benefits of screening for prostate cancer have been raised in the United States and Europe.4,5 Reduction in disease-specific mortality is the primary outcome measure when evaluating screening for prostate cancer. If the reduction in mortality should prove to be moderate to small, health-related quality-of-life (HRQOL, defined as patient functioning in physical, psychological, and social domains) effects may play a crucial role in the overall balance between the benefits and drawbacks of prostate cancer screening. There is no evidence for HRQOL impairment after the screening (biopsy) procedure itself,6 but possible detriment to HRQOL may result from side effects of primary treatment additionally induced by screening.7 However, if screening prevents death from prostate cancer, it will also prevent metastatic prostate cancer. Consequently, the decrease in life-years lived with poor HRQOL associated with advanced disease is a favorable effect of prostate cancer screening at the population level. The standard treatment options for locally confined prostate cancer in the Netherlands include radical prostatectomy and external-beam radiotherapy. Radical prostatectomy can result in urinary incontinence and impotence because of surgical damage to the urinary sphincter and penile nerves. Radiotherapy is associated with bladder irritation (urgency, pain, and frequency), rectal irritation (diarrhea, urgency, tenesmus, and bleeding), and impotence.8 In recent years, several studies on the clinical and HRQOL outcomes of primary treatments for localized prostate cancer have been published, indicating substantial posttreatment decrement in functioning.9,10 Some of these studies were restricted to cross-sectional designs, assessing only (posttreatment) HRQOL in long-term survivors. Other studies solely addressed disease-specific problems of one type of primary treatment (surgery or radiotherapy), not including generic HRQOL measures. So far, no studies on HRQOL have distinguished between screen-detected cases of prostate cancer and clinically diagnosed prostate cancer. The current study was undertaken within the framework of a screening trial4 to compare the HRQOL outcomes of two primary treatment modalities: radical prostatectomy and external-beam radiotherapy. We conducted a prospective longitudinal cohort study, including pretreatment assessments of generic and disease-specific HRQOL in patients with early, locally confined prostate cancer. We also investigated whether the HRQOL effects of primary treatment were different in patients with screen-detected prostate cancer compared with those with clinically diagnosed prostate cancer.
The Rotterdam Trial Within the Framework of the European Randomized Trial of Screening for Prostate Cancer The European Randomized Trial of Screening for Prostate Cancer, with seven participating European centers, will provide an empirical answer to the question of whether screening in men between 55 and 69 years of age reduces prostate cancer mortality. The ongoing trial at the Rotterdam center started in 1994. Cost-effectiveness studies, including empirical HRQOL studies of the screening procedure itself and of the phases of primary treatment and advanced disease, were conducted alongside. The current study was approved by the Medical Ethical Committees of four Rotterdam hospitals: the Academic Hospital Rotterdam, St. Franciscus Gasthuis, St. Clara Hospital, and the Zuiderziekenhuis. In accordance with regulations, written informed consent was obtained from every participant who enrolled in the study. Approval for the prostate screening program and the screening trial was obtained from the Minister of Health and the Health Council, as required by the Population Screening Act (the Netherlands, 1992).
Study Group
Patient Inclusion Procedure
Because of the method of patient inclusion, ie, before the stage of the disease was known, it was inevitable that patients with nonlocalized prostate cancer also were included in the study. However, the data on these patients were left out of the present report. Whether or not cancer was screen-detected was unknown at the moment of patient inclusion. The method of cancer detection (screening versus nonscreening) was determined from hindsight on the basis of medical records. Details on characteristics of the screened population can be found in Essink-Bot et al.6
Assessments as a Function of Time
Health-Related Quality-of-Life Measures The Medical Outcomes Study 36-Item Short Form (SF-36)11 is a generic HRQOL measure designed for use with both the general population and a wide range of populations with chronic diseases. The items are organized into eight scales: Physical Functioning, Role-Physical, Role-Emotional, Bodily Pain, General Health, Vitality, Social Functioning, and Mental Health. After linear transformation, scores range from 0 to 100, with higher values indicating better levels of functioning.12 The items can be reduced to two summary scale scores: the Physical Component Summary and Mental Component Summary,13 with the mean norm score of 50 and an SD of 10. The UCLA Prostate Cancer Index was originally developed by Litwin et al.14 For the purpose of this study, two modules comprising urinary and bowel functions were adopted. The four scales assess the level of urinary and bowel functioning (eg, frequency of urinary leakage, number of pads worn to control urinary leakage, frequency of diarrhea or abdominal cramps) and the degree of urinary and bowel bother. Like the SF-36, all scores were linearly transformed and ranged from 0 to 100. A score of 100 described the best level of functioning or no bother. To assess the patient’s sexual functioning, use was made of a battery of items designed for and previously applied to the Dutch situation by Slob et al.15 We found the sexual functioning module of the UCLA Prostate Cancer Index insufficiently detailed for the purpose of the study, especially as regards the level and causes of sexual dysfunction before the disease. We consequently decided to use the existing Dutch items to obtain more specific information on this topic. Apart from generic and disease-specific HRQOL measures, the questionnaire contained items on background characteristics, such as sociodemographic variables (age, marital status, and educational level), and comorbidity, assessed by the list of chronic conditions (Dutch Health Interview Survey, Statistics Netherlands). Tumor stage (tumor-node-metastasis clinical classification16), histopathologic tumor (biopsy) grade, and urologic treatment history were obtained from the Rotterdam Cancer Registry. For a small group of patients, information on clinical variables was collected from patients’ medical records in the hospitals. Possible postoperative adjustments to staging in the prostatectomy group were not included to maintain comparability with the radiotherapy group.
Statistical Methods
Differences in distributions of the background variables (sociodemographic data, selected comorbidity conditions, prostate-specific antigen levels, and clinical tumor characteristics) were evaluated by nonparametric procedures ( To evaluate posttreatment differences in generic (SF-36) and disease-specific HRQOL (UCLA Prostate Cancer Index) between the treatment groups, two by two analyses of covariance were applied for t2 and t3 assessments separately (main effects, the therapy type and the method of cancer detection). The covariates included in the analysis were patient’s age and pretreatment level of functioning or bother (the scale included as a covariate was identical to the one used as a dependent variable). All statistical tests were conducted with a significance level of 0.01. Chi-square tests were used to test the difference in incidence of specific problems in urinary, bowel, and sexual functioning. Inasmuch as the level of patients’ sexual functioning was not described by a single scale, a stratification was made into two age categories, 65 years or younger and older than 65 years, to eliminate a possible confounding effect of age. All P values resulted from the use of two-sided statistical tests. The data analyses were performed using SPSS (SPSS 8.02 for Windows; SPSS Inc., Chicago, IL) or SAS (SAS 6.12 for Windows; SAS Institute Inc., Cary, NC).
Background Characteristics of the Study Group Figure 1 shows the study profile. In the period from June 1996 till May 1998, 368 consecutive patients with newly diagnosed prostate cancer from four Rotterdam hospitals were approached for participation in the study. Of 368, 299 men underwent primary treatment by surgery (n = 119) or external-beam radiotherapy (n = 180), 22 patients chose watchful waiting, and 47 patients received treatments for advanced prostate cancer. The current study includes results from the prostatectomy and radiotherapy groups. The questionnaire submission rates among these patients were 93% (n = 278) at baseline, 91% (n = 271) 6 months later, and 87% (n = 261) 1 year after baseline. Before baseline, a total of 21 patients dropped out for various reasons: 13 patients had no interest in the study, five found the questions on sexual functioning too intimate and therefore refused to fill out the questionnaire, one patient reported feeling too ill to participate, and two patients moved abroad and were treated outside the Netherlands. Dropping out at t2 was caused either by lack of motivation (n = 4) or by poor psychological well-being (n = 3). At t3, reasons for dropping out were lack of motivation (n = 5), poor general well-being (n = 4), and death from cardiovascular disease (n = 1).
Table 1 presents information on the background characteristics of patients with localized (screen-detected or clinically diagnosed) prostate cancer who subsequently underwent radical prostatectomy or primary radiotherapy (33 irradiation sessions, each of 66 to 68 Gy, during 7 weeks). Patients from the prostatectomy group were significantly younger than those from the radiotherapy group, ie, 62 v 68 years of age (P < .01), in both patients with screen-detected and with clinically diagnosed cancer. No significant differences were found in distributions across categories of marital status and education. Prostatectomy patients from screening had less comorbidity than did radiotherapy patients. Screen-detected and clinically diagnosed patients showed similar levels of comorbidity. Fewer patients diagnosed by screening had prostate-specific antigen values greater than 10 ng/mL compared with those from a clinical setting (33% v 55%). Tumor characteristics differed significantly in their distributions among patients with clinically diagnosed or screen-detected cancer, with the latter group having significantly more well-differentiated tumors, and also more nonpalpable tumors, which were subsequently treated by radical prostatectomy rather than primary radiotherapy. In clinically diagnosed patients, tumor stage distributions were similar regardless of the type of therapy they were referred to.
Generic Health-Related Quality of Life: Prostatectomy Versus Radiotherapy The mean scores on generic HRQOL (SF-36 scales) at 6 (t2) and 12 months (t3) after baseline are listed in Table 2. In the short term, at t2, none of the differences were statistically significant at a 1% level, although radiotherapy patients tended to score lower for bodily pain (ie, more pain; mean scores, 83 v 92; P = .034) and general health perceptions (mean scores, 63 v 75; P = .02) than did prostatectomy patients. In the longer run, at t3, significant differences were found on two of eight SF-36 scales. Radiotherapy patients reported more limitations because of physical (mean scores, 72 v 89; P = .005) and emotional problems (mean scores, 83 v 93; P = .009). Regarding bodily pain and general health perceptions, the similar tendency was observed as at t2.
Comparisons of the SF-36 scale scores at the 12-month follow-up (t3) with the reference scores of the general Dutch population revealed no significant differences among radiotherapy patients. However, prostatectomy patients had significantly higher scores on all SF-36 scales than did the general population group (P < .01).
Generic Health-Related Quality of Life: Screen-Detected Versus Clinically Diagnosed
Urinary Symptoms
Regular (on a daily basis) or incidental (a few days a week) urinary leakage was indicated by 10% (n = 107) of prostatectomy patients versus 7% (n = 171) of radiotherapy patients at baseline. At t2 and t3 (5 and 11 months after prostatectomy, respectively), 31 (30%) of 104 patients and 34 (33%) of 102 patients reported total urinary control after prostatectomy. Regular or incidental urinary leakage was experienced by 49% (n = 104) of patients at t2, and by 39% (n = 102) of patients at t3. Forty-seven percent (n = 102) of the prostatectomy group also reported much improvement in urinary function with time (t3 versus t2). After radiotherapy at both t2 and t3 (respectively, 3 and 9 months after the end of treatment), 68% (n = 167 and n = 159) of patients reported total urinary control. Regular or incidental urinary leakage was indicated by 12% (of 167 patients) and 13% (of 159 patients) of these patients at t2 and t3. Mean scores for urinary function and urinary bother revealed statistically significant posttreatment differences (both follow-up assessments, P < .01) between radical prostatectomy and primary radiotherapy patients, with the first group reporting poorer levels of urinary functioning. No significant differences (P > .45) were found between groups with screen-detected and with clinically diagnosed prostate cancer (data not shown).
Bowel Symptoms
Sexual Functioning Patient characteristics on pretreatment and posttreatment sexual functioning are summarized in Table 5. At baseline (t1), no statistically significant differences in sexual activity and erectile function were found between men who were referred for a radical prostatectomy and those undergoing radiotherapy (P > .13 for both age groups). Posttreatment erectile dysfunction (problems with getting erections) was reported by 91% of younger (< 65 years) and 80% of older (> 65 years of age) prostatectomy patients at t2 and t3. In the radiotherapy group, posttreatment erectile problems were indicated respectively by 41% (t2) and 55% (t3) of patients younger than 65 years, and by 48% and 51% of patients older than 65 years of age. Chi-square tests revealed significant differences (P < .01) between men treated by radical prostatectomy or by primary radiotherapy, with the former group having poorer sexual functioning after treatment than the latter. The method of cancer detection did not account for any statistically significant differences in erectile problems between the two primary treatment groups at t2 and t3 (data not shown).
The present study addressed HRQOL effects of primary treatment for early screen-detected or clinically diagnosed prostate cancer. By applying both generic and disease-specific HRQOL measures, we documented the impact of treatment-related side effects on the patient’s HRQOL. Radical prostatectomy appeared to affect urinary and erectile functions, whereas external-beam radiotherapy was predominantly associated with bowel problems. Patients with screen-detected or clinically diagnosed prostate cancer did not differ in their posttreatment level of functioning. Although posttreatment incontinence, impotence, and bowel symptoms were also reported by other, primarily retrospective studies,17-21 the incidences of these functional problems lacked consistency. Some recent prospective studies reported 7% to 23% for incontinence and 69% to 91% for impotence at 12 months after radical prostatectomy.22,23 At the same time, the rates for impotence and bowel problems in radiotherapy patients were 61% and 12% to 19%, respectively. In line with these findings, our data show high posttreatment incidences of urinary leakage at least a few days a week (39% to 49%) and erectile dysfunction (80% to 91%) in patients who underwent radical prostatectomy, compared with the level of their pretreatment functioning, and compared with the patients who were treated by external-beam radiotherapy. The most important postirradiation problem involved the bowel function (urgency: 30% to 35%) and, to a lesser degree, some changes in urinary and sexual functioning (posttreatment incontinence, 12% to 13%; posttreatment erectile dysfunction, 41% to 55%). However, for a proper evaluation of possible functional impairment or improvement, a longer follow-up time may be necessary. Postradiotherapy effects in particular may become manifest even after more than a year after treatment has ceased.24,25 On the other hand, prostatectomy patients may experience further improvement in functioning.24 Our posttreatment data (t2 and t3) did not allow for determination of such long-term effects, as the assessments comprised a time interval of 3 to 9 months after radiotherapy and 5 and 11 months after surgery. After adjustment for pretreatment levels of functioning, radiotherapy patients showed poorer posttreatment levels of generic HRQOL than did prostatectomy patients. However, neither group scored below the age- and sex-adjusted Dutch population norm.26 Irrespective of the difference between radiotherapy and prostatectomy patients, decrements in generic HRQOL scores do not seem to correspond to decrements in patients’ urinary, bowel, and sexual functioning after treatment. Possible explanations for this discrepancy may include the response shift27 or the lack of relevance of the SF-36 items to patients with prostate cancer. Although our data indicate decreased levels of posttreatment HRQOL, selecting the optimal treatment for early prostate cancer in terms of HRQOL is considerably complicated for two reasons. First, radical prostatectomy and external-beam radiotherapy involve different consequences, which may be valued differently by individual patients. Second, inasmuch as there was no random allocation to the treatment groups, it is conceivable that men referred for prostatectomy or radiotherapy may not come from similar populations of patients with prostate cancer. In the past, other studies3 have found pelvic lymphadenectomy to be relatively rare in radiotherapy patients, which resulted in the understaging of the disease. More advanced stages of the disease may possibly affect the level of generic HRQOL. As long as there are no results available from well-designed randomized trials comparing HRQOL effects of radical prostatectomy and external-beam radiotherapy in similar groups of patients, comparisons from nonrandomized studies will have to be used, but their validity remains limited. Despite the fact that compared with men with clinically diagnosed prostate cancer, men with screen-detected prostate cancer had a better generic HRQOL before primary treatment,7 no statistically significant cross-sectional differences (in both generic and disease-specific HRQOL) after primary treatment emerged from our data. Because the pretreatment and posttreatment levels of urinary, bowel, and sexual functioning were similar in patients with screen-detected and clinically diagnosed prostate cancer, we assume that all decrements in HRQOL revealed in our follow-up data were related to (the type of) primary treatment. Regarding the question of whether or not to screen, early detection of prostate cancer will imply earlier primary treatment. The decrements in HRQOL after treatment are justifiable only if screening results in a substantial improvement of the survival rates. Because the data on mortality in the ERSPC trial will not be available until 2008,4 HRQOL and survival outcomes cannot be weighed at the present moment. At the public health level, the benefits and drawbacks throughout all stages of screening must be thoroughly considered before a population-based screening program for prostate cancer is implemented. On an individual level, patients should be made fully aware of the potential benefits and adverse consequences of the available therapies for early prostate cancer.
Supported by grant no. EUR 95-11.43 from the Dutch Cancer Society, Amsterdam, the Netherlands. We thank the men who, by their participation in the study, have contributed to a better understanding of the impact of prostate cancer on their lives. We also thank the urologists from the Academic Hospital Rotterdam, St. Franciscus Gasthuis, St. Clara Hospital, and the Zuiderziekenhuis for the assistance in data collection from their patients and from medical records.
1. van Leer EM, Cleton FJ, van Leeuwen FE (eds): Signaleringsrapport ‘Kanker 1999’ (Report ‘Cancer 1999’) (ed 1). Amsterdam, Nederlandse Kankerbestrijding/Koningin Wilhelmina Fonds (Dutch Cancer Society/Queen Wilhelmina Foundation), 1999, pp 12, 30 2. Coebergh JW, van der Heijden LH, Janssen-Heijnen MLe (eds): Cancer Incidence and Survival in the Southeast of the Netherlands 1955-1994. Eindhoven, the Netherlands, The Eindhoven Cancer Registry, 1995, pp 66-68 3. Spapen SJ, Damhuis RA, Kirkels WJ: Trends in the curative treatment of localized prostate cancer after the introduction of prostate-specific antigen: Data from the Rotterdam Cancer Registry. Br J Urol Int 85: 474-480, 2000 4. Schröder FH, Kranse R, Rietbergen J, et al: The European Randomized Study of Screening for Prostate Cancer (ERSPC): An update—Members of the ERSPC, Section Rotterdam. Eur Urol 35: 539-543, 1999[Medline] 5. Kramer BS, Gohagan J, Prorok PC, et al: A National Cancer Institute sponsored screening trial for prostatic, lung, colorectal, and ovarian cancers. Cancer 71: 589-593, 1993[Medline]
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Essink-Bot ML, de Koning HJ, Nijs HG, et al: Short-term effects of population-based screening for prostate cancer on health-related quality of life. J Natl Cancer Inst 90: 925-931, 1998 7. Madalinska JB, Essink-Bot ML, de Koning HJ, et al: Health-related quality of life in patients with screen-detected versus clinically diagnosed prostate cancer preceding primary treatment. Prostate (in press) 8. Naitoh J, Zeiner RL, Dekernion JB: Diagnosis and treatment of prostate cancer [see comments]. Am Fam Physician 57:1531-1539, 1541-1542, 1545-1547, 1998 9. Fowler FJ Jr, Barry MJ, Lu-Yao G, et al: Outcomes of external-beam radiation therapy for prostate cancer: A study of Medicare beneficiaries in three surveillance, epidemiology, and end results areas. J Clin Oncol 14: 2258-2265, 1996[Abstract]
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Joly F, Brune D, Couette JE, et al: Health-related quality of life and sequelae in patients treated with brachytherapy and external beam irradiation for localized prostate cancer. Ann Oncol 9: 751-757, 1998 11. Ware JE Jr, Sherbourne CD: The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 30: 473-483, 1992[Medline] 12. Ware JE Jr, Snow KK, Kosinski M, et al: SF-36 health survey manual and interpretation guide. Boston, MA, New England Medical Center, The Health Institute, 1993 13. Ware JE Jr, Kosinski M, Keller SD: SF-36 physical and mental component summary measures: A user’s manual. Boston, MA, New England Medical Center, The Health Institute, 1994 14. Litwin MS, Hays RD, Fink A, et al: The UCLA Prostate Cancer Index: Development, reliability, and validity of a health-related quality of life measure. Med Care 36: 1002-1012, 1998[Medline] 15. Slob AK, Blom JH, van der Werff ten Bosch JJ: Erection problems in medical practice: Differential diagnosis with relatively simple method. J Urol 143: 46-50, 1990[Medline] 16. UICC International Union Against Cancer: TNM Classification of Malignant Tumours (ed 4, 2nd revision). Berlin, Germany, Springer-Verlag, 1992 17. Caffo O, Fellin G, Graffer U, et al: Assessment of quality of life after radical radiotherapy for prostate cancer. Br J Urol 78: 557-563, 1996[Medline] 18. Crook J, Esche B, Futter N: Effect of pelvic radiotherapy for prostate cancer on bowel, bladder, and sexual function: The patient’s perspective. Urology 47: 387-394, 1996[Medline] 19. Feneley MR, Gillatt DA, Hehir M, et al: A review of radical prostatectomy from three centres in the UK: Clinical presentation and outcome [see comments]. Br J Urol 78: 911-920, 1996[Medline] 20. Lim AJ, Brandon AH, Fiedler J, et al: Quality of life: Radical prostatectomy versus radiation therapy for prostate cancer [see comments]. J Urol 154: 1420-1425, 1995[Medline] 21. Fowler FJ Jr, Barry MJ, Lu-Yao G, et al: Patient-reported complications and follow-up treatment after radical prostatectomy. The National Medicare Experience: 1988-1990 (updated June 1993). Urology 42: 622-629, 1993[Medline]
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Talcott JA, Rieker P, Clark JA, et al: Patient-reported symptoms after primary therapy for early prostate cancer: Results of a prospective cohort study. J Clin Oncol 16: 275-283, 1998
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Stanford JL, Feng Z, Hamilton AS, et al: Urinary and sexual function after radical prostatectomy for clinically localized prostate cancer: The Prostate Cancer Outcomes Study. JAMA 283: 354-360, 2000 24. Litwin MS, Flanders SC, Pasta DJ, et al: Sexual function and bother after radical prostatectomy or radiation for prostate cancer: Multivariate quality-of-life analysis from CaPSURE—Cancer of the Prostate Strategic Urologic Research Endeavor. Urology 54: 503-508, 1999[Medline] 25. Nguyen LN, Pollack A, Zagars GK: Late effects after radiotherapy for prostate cancer in a randomized dose-response study: Results of a self-assessment questionnaire. Urology 51: 991-997, 1998[Medline] 26. Aaronson NK, Muller M, Cohen PD, et al: Translation, validation, and norming of the Dutch language version of the SF-36 Health Survey in community and chronic disease populations. J Clin Epidemiol 51: 1055-1068, 1998[Medline] 27. Sprangers MA, Schwartz CE: Integrating response shift into health-related quality of life research: A theoretical model. Soc Sci Med 48: 1507-1515, 1999 Submitted July 31, 2000; accepted December 11, 2000.
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Copyright © 2001 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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ABSTRACT
INTRODUCTION
2 or Mann-Whitney tests). Mean values are presented as the measure of central tendency in the scores for the SF-36 and UCLA Prostate Cancer Index. The observed dispersion of these scores is presented as the interval bounded by the 25th and 75th percentile scores. 
