|
|||||
|
|
||||||
Journal of Clinical Oncology, Vol 22, No 18 (September 15), 2004: pp. 3726-3732 © 2004 American Society of Clinical Oncology. DOI: 10.1200/JCO.2004.01.164 Impact of the Percentage of Positive Prostate Cores on Prostate CancerSpecific Mortality for Patients With Low or Favorable Intermediate-Risk DiseaseFrom the Department of Radiation Oncology and Pathology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA; and Department of Statistics, University of Connecticut, Storrs, CT Address reprint requests to Anthony V. D'Amico, MD, PhD, Brigham and Women's Hospital, Department of Radiation Oncology, 75 Francis St, L-2 Level, Boston, MA 02215; e-mail: adamico{at}lroc.harvard.edu
PURPOSE: We investigated whether pretreatment factors predicted time to prostate cancerspecific mortality (PCSM) after conventional-dose and conformal radiation therapy (CRT).
PATIENTS AND METHODS: Between 1988 and 2002, 421 patients with low (prostate-specific antigen [PSA] level
RESULTS: The % PC was the only significant predictor (Cox P
CONCLUSION: CRT dose-escalation techniques, the addition of hormonal therapy, or both should be considered in the management of patients with low or favorable intermediate-risk disease and
Although prostate-specific antigen (PSA) failure occurs after radical prostatectomy (RP) or external-beam radiation therapy (RT) for patients with clinically localized prostate cancer diagnosed during the PSA era, a minority (12% to 20%) of these patients subsequently experience prostate cancerspecific mortality (PCSM).1 Pretreatment risk groups based on the baseline PSA level, biopsy Gleason score, and clinical T category have been constructed and shown to predict time to PCSM after RP or RT. Specifically, in a prior study2 of 7,316 patients treated in the United States at 44 institutions with either RP (n = 4,946) or RT (n = 2,370), evidence was provided to support the prediction of time to PCSM after RP or RT based on pretreatment risk group. The percentage of positive cores (% PC) has been previously shown to provide additional information to the pretreatment risk group regarding time to PSA failure after RP3 or RT.4 However, whether the % PC also adds information to the pretreatment risk group regarding time to PCSM after RT monotherapy is unknown. High-risk (PSA > 20 ng/mL or biopsy Gleason score of 8 to 10) and more advanced intermediate-risk (PSA > 15 to 20 ng/mL and biopsy Gleason score of 7) patients are infrequently considered for RT monotherapy given the survival benefit shown in prior studies of RT plus androgen suppression therapy (AST) as compared with RT for patients with locally advanced prostate cancer.5 Therefore, the purpose of this study was to determine whether the % PC provided additional information regarding time to PCSM after RT in patients who would be offered RT as monotherapy controlling for the PSA level, biopsy Gleason score, and clinical T category at diagnosis. Therefore, the study cohort assembled to address this issue were men with low- or favorable intermediate-risk disease.
Patient Selection and Treatment Four hundred twenty-one men treated with conformal RT (CRT) between 1988 and 2002 at a Harvard community outreach Hospital (St Anne's Hospital, Fall River, MA) for clinically localized (T1c to T2) and low- (PSA 10 ng/mL and biopsy Gleason score 6) or favorable intermediate-risk (PSA > 10 to 15 ng/mL or biopsy Gleason score of 3 + 4, but not both factors) disease comprised the study cohort. Patients with a PSA level greater than 15 ng/mL, a biopsy Gleason score of 4 + 3 or higher, or evidence of perineural invasion on biopsy were excluded. In addition, patients who had fragmentation of their biopsy specimen (n = 57) were also excluded. A human investigations committeeapproved consent form was obtained for each study patient to permit the collection and analysis of de-identified baseline, treatment, and follow-up information. The median age of study cohort at the time of initial therapy was 71.9 years (range, 44.9 to 89.6 years). The pretreatment clinical characteristics of all study patients stratified by the PSA and Gleason score at diagnosis are listed in Table 1.
The RT treatment performed was a four-field CRT technique that used a multileaf collimator from 1994 to 2002 and shaped cerrobend blocks between 1988 and 1993 to achieve conformality. Before 1994, computed tomography simulation was not available, so the RT fields were created using a clinical target volume obtained by transposing the computed tomographydefined anatomy onto orthogonal plain radiographs at the time of radiation planning. Low-risk patients were defined as those with a PSA 10 ng/mL and Gleason score 6 at diagnosis; these patients received a median dose of 70.4 Gy after 95% normalization in 1.8-Gy fractions to the prostate gland with a 1.5-cm margin. The remaining favorable intermediate-risk patients had either a PSA greater than 10 to 15 ng/mL or biopsy Gleason score 3 + 4 disease; these patients received the same total median dose to the prostate gland after having received 45 Gy in 1.8-Gy fractions to the prostate gland and seminal vesicles with a 1.5-cm margin. All radiation doses reported are the minimum dose that the planning target volume (ie, prostate gland with or without the seminal vesicles plus a 1.5-cm margin) received.
Staging
Follow-Up
Determination of the Cause of Death
Statistical Methods
The relative risk of PCSM with its associated 95% CI were derived from the Cox model for each pretreatment clinical predictor and calculated for three patient groups. In addition, an evaluation for interaction effects among the pretreatment predictors, when assessable, was performed. The three patient groups were defined based on the PSA and biopsy Gleason score at diagnosis and were low-risk (PSA For all analyses, the assumptions of the Cox model were tested and satisfied. Estimates of PCSM were calculated using the cumulative incidence method.12 Comparisons of PCSM were evaluated using a two-sided log-rank P value. For the purpose of illustration, the relative contributions of PCSM and non-PCSM to all-cause mortality are displayed stratified by the pretreatment factors that were significant predictors of time to PCSM after CRT for each of the three patient groups.
Relative Risk of Cancer-Specific Mortality by % PC At a median follow-up of 4.5 years, 117 (28%) of 421 patients had died, and of the 117 deaths, 15 (13%) were from prostate cancer. The % PC was the only significant predictor (Cox P .03) of time to PCSM after RT. The results of the Cox regression multivariable analyses in which PSA was treated as a categoric variable are listed in Table 2. No significant interaction effects were noted among the pretreatment clinical predictors. The relative risk of PCSM after CRT for patients with 50% as compared with less than 50% PPB was 10.4 (95% CI, 1.2 to 87; Cox P = .03), 6.1 (95% CI, 1.3 to 28.6; Cox P = .02), and 12.5 (95% CI, 1.5 to 107; Cox P = .02) in men with a PSA 10 and Gleason score 6, PSA 10 and Gleason score 3 + 4, and PSA 15 and Gleason 6 score, respectively.
By 8 years after CRT, 5% to 9% as compared with less than 1% (log-rank P .01) of these patients experienced PCSM if they had 50% as compared with less than 50% PC, as shown in Figures 1 through 3. For the purpose of illustration, Figure 4 contains the relative contributions of PCSM and non-PCSM after treatment to all-cause mortality, stratified by the % PC (< 50% v 50%) and the PSA level and biopsy Gleason score at diagnosis.
PSA failure, although representative of treatment failure, does not imply PCSM. Given that the vast majority of men with prostate cancer are diagnosed after the age of 60 years,13 both advanced age and underlying comorbid illnesses can exist at the time of PSA failure. As a result, many patients who sustain PSA failure do not subsequently experience PCSM.1 Therefore, although the % PC has been previously shown to provide additional information to the pretreatment risk group regarding time to PSA failure after RP3 or RT,4 whether the % PC also adds information to the pretreatment risk groups regarding time to PCSM after RT monotherapy is unknown.
In this study, the prognostic significance of the PSA level, biopsy Gleason score, 2002 AJCC clinical T category, and % PC was investigated in men with low- or favorable intermediate-risk disease whose median age at the time of RT was 71.9 years. Only the % PC was found to be significantly associated with the time to PCSM after CRT (Cox P
There are two factors that may explain the increased risk of PCSM in patients with low- or favorable intermediate-risk disease and There are several points that require clarification. First, the predictions of PCSM using the % PC in this study are only applicable to patients with clinically localized low- or favorable intermediate-risk prostate cancer undergoing conventional-dose CRT and not RT plus AST. If future studies document a survival benefit for the addition of AST to RT for patients with clinically localized disease, as has been shown for patients with locally advanced prostate cancer,5 then the ability of the % PPB to predict the time to PCSM after RT plus AST would need to be evaluated. Perhaps with the addition of AST to RT, the difference in time to PCSM noted in this study may be lost, which could be due to the impact of AST on both local control and occult micrometastatic disease. Second, the impact that % PC has on the time to PCSM after surgery or dose-escalated CRT in the form or external-beam, brachytherapy, or the combination in patients with low- or favorable intermediate-risk disease remains to be studied. It is possible that approaches that improve local control for patients with high biopsy volume and low- or favorable intermediate-risk disease may eliminate or reduce the difference noted in this study in the time to PCSM after treatment when stratified by the % PC. Third, at the time of this analysis, 15 patients had experienced PCSM, and therefore, it is possible that with more events, other predictors may emerge, such as PSA greater than 10 to 15 ng/mL, for which P value was .11 in this study. Fourth, prior studies have shown a significant association with other measures of the tumor extent in the needle cores and either pathologic stage and/or the time to PSA failure after surgery. These measures include the total percentage of needle biopsy tissue involved by carcinoma,15 the greatest percentage of one core involved by carcinoma,18 and the total linear millimeters of carcinoma.18,19 Whether these measures are also associated with the time to PCSM after RT require further study. Finally, whether the specific treatment(s) individual patients received after PSA failure impacted on time to PCSM remains unknown and requires clarification in future studies.
In conclusion, there was a significant increase in relative risk (six- to 12-fold) of PCSM after CRT delivered to a median dose of 70.4 Gy for patients in this study who had
The authors indicated no potential conflicts of interest.
Authors' disclosures of potential conflicts of interest are found at the end of this article.
1. D'Amico AV, Moul J, Carroll P, et al: Surrogate marker for prostate cancer specific mortality following radical prostatectomy or radiation therapy. J Natl Cancer Inst 95:1376-1383, 2003
2. D'Amico AV, Moul J, Carroll P, et al: Cancer-specific mortality after surgery or radiation for patients with clinically localized prostate cancer managed during the prostate-specific antigen era. J Clin Oncol 21:2163-2172, 2003
3. D'Amico AV, Whittington R, Malkowicz SB, et al: The clinical utility of the percentage of positive prostate biopsies in defining biochemical outcome after radical prostatectomy for patients with clinically localized prostate cancer. J Clin Oncol 18:1164-1172, 2000 4. D'Amico AV, Schultz D, Silver B, et al: The clinical utility of the percent of positive prostate biopsies in predicting biochemical outcome following external beam radiation therapy for patients with clinically localized prostate cancer. Int J Radiat Oncol Biol Phys 49:679-684, 2001[CrossRef][Medline] 5. Bolla M, Collette L, Blank L, et al: Long-term results with immediate androgen suppression and external irradiation in patients with locally advanced prostate cancer (an EORTC study): A phase III randomised trial. Lancet 360:103-106, 2002[CrossRef][Medline] 6. Gleason DF: Histologic grading and staging of prostatic carcinoma, in Tannenbaum M (ed): Urologic Pathology. Philadelphia, PA, Lea & Febiger, 1977, pp 171-187 7. Lee CT, Oesterling JE: Using prostate-specific antigen to eliminate the staging radionuclide bone scan. Urol Clin North Am 24:389-394, 1997[CrossRef][Medline] 8. Greene FL, Page DL, Fleming ID, et al: American Joint Committee on Cancer: Manual for Staging Cancer (ed 6). New York, NY, Springer-Verlag, 2002, pp 337-346 9. Cox JD: Consensus statement: Guidelines for PSA following radiation therapyAmerican Society for Therapeutic Radiology and Oncology Consensus Panel. Int J Radiat Oncol Biol Phys 37:1035-1041, 1997[CrossRef][Medline] 10. Klein JP, Moeschberger ML (eds): Survival Analysis. New York, NY, Springer-Verlag, 1997, pp 229-263 11. Bahnson RR, Hanks GE, Huben RP, et al: NCCN practice guidelines for prostate cancer. Oncology (Huntingt) 14:111-119, 2000 12. Gaynor JJ, Feur EJ, Tan CC, et al: On the use of cause-specific failure and conditional failure probabilities: Examples from clinical oncology data. J Am Stat Assoc 88:400-409, 1993[CrossRef] 13. Crawford ED: Epidemiology of prostate cancer. Urology 62:3-12, 2003 (suppl 1)[Medline]
14. Stamey TA, McNeal JE, Yemoto CM, et al: Biological determinants of cancer progression in men with prostate cancer. JAMA 281:1395-1400, 1999 15. Freedland SJ, Aronson WJ, Terris MK, et al: Percent of prostate needle biopsy cores with cancer is significant independent predictor of prostate-specific antigen recurrence following radical prostatectomy: Results from SEARCH database. J Urol 169:2136-2141, 2003[Medline] 16. Grossfeld GD, Chang JJ, Broering JM, et al: Under staging and under grading in a contemporary series of patients undergoing radical prostatectomy: Results from the Cancer of the Prostate Strategic Urologic Research Endeavor database. J Urol 165:851-856, 2001[CrossRef][Medline]
17. Pound CR, Partin AW, Eisenberger MA, et al: Natural history of progression after PSA elevation following radical prostatectomy. JAMA 281:1591-1596, 1999 18. Bismar TA, Lewis JS Jr, Vollmer RT, et al: Multiple measures of carcinoma extent versus perineural invasion in prostate needle biopsy tissue in prediction of pathologic stage in a screening population. Am J Surg Pathol 27:432-440, 2003[CrossRef][Medline] 19. Naya Y, Slaton JW, Troncoso P, et al: Tumor length and location of cancer on biopsy predict for side specific extraprostatic extension. J Urol 171:1093-1097, 2004[Medline] Submitted January 26, 2004; accepted June 10, 2004. This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||
|
Copyright © 2004 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
|