STATISTICAL CONSIDERATIONS WHEN ASSESSING OUTCOMES FOLLOWING TREATMENT FOR PROSTATE CANCER

Impact of Robotic Technologies on Prostate Cancer Patients' Choice for Radical Treatment

Prostate cancer (PCa) surgery has a strong impact on men's social and sexual lives. For this reason, many patients ask for robotic surgery. To assess the rate of lost patients due to the lack of a robotic platform (RPl) at our center, we retrospectively selected 577 patients who underwent prostate biopsy between 2020 and 2021 who were eligible for radical prostatectomy (RP) (ISUP ≥ 2; age ≤ 70 yr). Patients eligible for surgery who decided to be operated received a phone call interview asking the reason for their choice. Overall, 230 patients (31.7%) underwent laparoscopic-assisted radical prostatectomy (LaRP) at our center, while 494 patients (68.3%) were not treated in our hospital. Finally, 347 patients were included: 87 patients (25.1%) underwent radiotherapy; 59 patients (17%) were already under another urologist's care; 113 patients (32.5%) underwent robotic surgery elsewhere; and 88 patients (25.4%) followed the suggestion of friends or relatives based on their surgical experience. Despite no surgical technique for RP having shown superiority in terms of oncological or functional outcomes, patients eligible for PCa treatment decided to be operated on elsewhere because of the lack of an RPl. Our results show how the presence of an RPl may increase the case volume of RP by 49% at our center.

Cancer-specific and other-cause mortality after radical prostatectomy versus observation in patients with prostate cancer: competing-risks analysis of a large North American population-based cohort

BACKGROUND

Initial treatment options for low-risk clinically localized prostate cancer (PCa) include radical prostatectomy (RP) or observation.

OBJECTIVE

To examine cancer-specific mortality (CSM) after accounting for other-cause mortality (OCM) in PCa patients treated with either RP or observation.

DESIGN, SETTING, AND PARTICIPANTS

Using the Surveillance Epidemiology and End Results Medicare-linked database, a total of 44 694 patients ≥65 yr with localized (T1/2) PCa were identified (1992-2005).

INTERVENTION

RP and observation.

MEASUREMENTS

Propensity-score matching was used to adjust for potential selection biases associated with treatment type. The matched cohort was randomly divided into the development and validation sets. Competing-risks regression models were fitted and a competing-risks nomogram was developed and externally validated.

RESULTS AND LIMITATIONS

Overall, 22,244 (49.8%) patients were treated with RP versus 22450 (50.2%) with observation. Propensity score-matched analyses derived 11,669 matched pairs. In the development cohort, the 10-yr CSM rate was 2.8% (2.3-3.5%) for RP versus 5.8% (5.0-6.6%) for observation (absolute risk reduction: 3.0%; relative risk reduction: 0.5%; p<0.001). In multivariable analyses, the CSM hazard ratio for RP was 0.48 (0.38-0.59) relative to observation (p<0.001). The competing-risks nomogram discrimination was 73% and 69% for prediction of CSM and OCM, respectively, in external validation. The nature of observational data may have introduced a selection bias.

CONCLUSIONS

On average RP reduces the risk of CSM by half in patients aged ≥65 yr, relative to observation. The individualized protective effect of RP relative to observation may be quantified with our nomogram.

Update of Dutch multicenter dose-escalation trial of radiotherapy for localized prostate cancer

PURPOSE

To update the analysis of the Dutch dose-escalation trial of radiotherapy for prostate cancer.

PATIENTS AND METHODS

A total of 669 patients with localized prostate cancer were randomly assigned to receive 68 or 78 Gy. The patients were stratified by age, institution, use of neoadjuvant or adjuvant hormonal therapy, and treatment group. The primary endpoint was freedom from failure (FFF), with failure defined as clinical or biochemical failure. Two definitions of biochemical failure were used: the American Society for Therapeutic Radiology and Oncology definition (three consecutive increases in prostate-specific antigen level) and the Phoenix definition (nadir plus 2 microe secondary endpoints were freedom from clinical failure, overall survival, and genitourinary and gastrointestinal toxicity.

RESULTS

After a median follow-up of 70 months, the FFF using the American Society for Therapeutic Radiology and Oncology definition was significantly better in the 78-Gy arm than in the 68-Gy arm (7-year FFF rate, 54% vs. 47%, respectively; p = 0.04). The FFF using the Phoenix definition was also significantly better in the 78-Gy arm than in the 68-Gy arm (7-year FFF rate, 56% vs. 45%, respectively; p = 0.03). However, no differences in freedom from clinical failure or overall survival were observed. The incidence of late Grade 2 or greater genitourinary toxicity was similar in both arms (40% and 41% at 7 years; p = 0.6). However, the cumulative incidence of late Grade 2 or greater gastrointestinal toxicity was increased in the 78-Gy arm compared with the 68-Gy arm (35% vs. 25% at 7 years; p = 0.04).

CONCLUSION

The results of our study have shown a statistically significant improvement in FFF in prostate cancer patients treated with 78 Gy but with a greater rate of late gastrointestinal toxicity.

13-Year Outcomes Following Treatment for Clinically Localized Prostate Cancer in a Population Based Cohort

PURPOSE

Because data from randomized trials initiated after the introduction of prostate specific antigen testing are unavailable, we performed a retrospective, population based study to estimate prostate cancer specific survival and overall survival after surgery, radiation or observation to manage clinically localized prostate cancer.

MATERIALS AND METHODS

From the Connecticut Tumor Registry we identified Connecticut residents 75 years or younger diagnosed with clinically localized prostate cancer between January 1, 1990 and December 31, 1992. We obtained information from physician offices concerning treatments received by 1,618 patients who underwent surgery (802), external beam radiation therapy (702) or no initial therapy (114) and subsequent medical outcomes. Treatment comparisons were adjusted for pretreatment Gleason score, prostate specific antigen and clinical stage along with age at diagnosis and comorbidities using 3 methods, including categorization by risk, a proportional hazards model and a propensity score.

RESULTS

At an average followup of 13.3 years 13% of patients had died of prostate cancer, 5% had died of other cancers and 24% had died other noncancer causes. Patients undergoing surgery were younger, and had more favorable histology and lower pretreatment prostate specific antigen compared to patients undergoing radiation. Patients who elected observation had significantly worse cause specific survival than those who elected surgery. They also fared worse than men who received radiation therapy but the difference was not statistically significant, possibly because of the small number of prostate cancer deaths to date.

CONCLUSIONS

Our findings suggest that patients undergoing surgery for clinically localized prostate cancer may have a cancer specific survival advantage compared to those electing radiation or observation. However, only a randomized trial can control for the many known and unknown confounding factors that can affect long-term outcomes.

Guidelines and counselling for treatment options in the management of prostate cancer

Prostate cancer is often a complex disease and one in which many aspects of the disease and the affected patient must be taken into consideration before decisions about diagnostic work-up, treatments, follow-up, etc. can be made. The current chapter reflects the current recommendations of the European Prostate Cancer Guideline Group made on the basis of criteria of evidence-based medicine after extensive review of the literature available up to December 2005.

Interpreting Statistics in the Urological Literature

PURPOSE

Knowledge of statistical terminology and the ability to critically interpret research findings are critical skills in the practice of evidence based medicine.

MATERIALS AND METHODS

We provide a series of nontechnical explanations of basic statistical concepts commonly encountered in the urological literature. In addition, we provide examples of common statistical pitfalls to increase awareness of limitations to consider when applying research findings to practice.

RESULTS

Statistical goals encountered in the urological literature can be broadly categorized as summarizing outcome variables, comparing 2 or more groups, measuring association among variables or predicting 1 variable from another. Errors frequently include the use of an inappropriate test for the data type of interest or using statistical testing in a manner that increases the likelihood of false-positive results. Such errors pose a threat to the validity of research findings and they may undermine study conclusions.

CONCLUSIONS

Editors and reviewers alike should strive for high standards of statistical analysis and reporting, and promote the publication of high quality evidence in the urological literature. The understanding of basic statistical concepts and the principles of the hypothesis testing framework is essential to the critical appraisal process and, therefore, important to all urologists. Statistical literacy should be fostered through educational materials and courses in the urological community.

Evidence-Based Medicine: A Survey of American Urological Association Members

PURPOSE

We investigated the attitudes and opinions of urologists toward evidence-based medicine.

MATERIALS AND METHODS

In April of 2005 we contacted members of the American Urological Association listed with an e-mail address to participate in a web based survey. Participants were asked to characterize their level of agreement with statements referring to the role of evidence-based medicine in urology, to indicate their level of understanding of 15 evidence-based medicine related terms and to report their familiarity with 6 evidence-based medicine related resources.

RESULTS

Of 8,100 American Urological Association members 714 (8.8%) responded to this survey. There was widespread agreement (median score 9) with the concept that evidence-based medicine improves patient care and that every urologist should be familiar with critical appraisal techniques. Select terms such as median/mean, selection bias and type I error were well understood ("understand and could explain to others") by 86%, 57% and 17%, respectively. The American Urological Association Best Practice Guidelines were the single best known resource that 91% of respondents reviewed or used regularly.

CONCLUSIONS

To our knowledge this survey represents the first evidence-based medicine survey of a large international group of urologists. Its results indicate that evidence-based medicine is viewed favorably and that the American Urological Association Best Practice Guidelines present a well accepted instrument for the dissemination of evidence-based medicine in urology. However, given the low response rate and the potential for selection bias, interpretation of these results must be performed with caution. Future efforts should be directed toward providing increased opportunities for urologists to learn the principles of critical appraisal, facilitating the application of evidence-based medicine in the community and promoting high quality research.

Association of tobacco use with hormone refractory disease and survival of patients with prostate cancer

PURPOSE

We identified time to the development of hormone refractory prostate cancer (HRPC) and survival in men with advanced prostate cancer and examined any association with cigarette smoking history.

MATERIALS AND METHODS

The study design was retrospective. A complete tobacco history was obtained in 222 patients with advanced prostate cancer. HRPC was diagnosed in 133 of these 222 patients and death occurred in 77. Standard statistical methods and software were used to analyze these data.

RESULTS

Median time to HRPC was 11, 23 and 35 months in patients with a current, former or never smoked tobacco history (p = 0.00001). Median overall survival time on androgen ablative therapy was 38, 47 and 60 months in patients with a current, former or never smoked tobacco history, respectively (p = 0.00001).

CONCLUSIONS

Tobacco use independently correlates with time to HRPC and survival in a dose dependent manner in patients with advanced prostate cancer on androgen deprivation therapy.

Prognostic significance of obstructive uropathy in advanced prostate cancer

OBJECTIVES

To report the incidence and prognostic implications of obstructive uropathy (OU) in patients with advanced prostate cancer receiving androgen deprivation therapy and to define the impact initial local therapy has on the development of OU in patients with prostate cancer who develop recurrence and begin androgen deprivation therapy.

METHODS

From a population of 260 patients with advanced prostate cancer diagnosed between 1986 and 2003, OU was identified in 51 patients. The OU treatment options included ureteral stent, percutaneous nephrostomy, transurethral resection of the prostate, Foley catheter placement, and urinary diversion. Overall survival and the factors that influenced survival were calculated using standard statistical methods.

RESULTS

OU was diagnosed in 15 (16%) of 80 patients who received local therapy with curative intent and in whom local therapy subsequently failed and in 36 (19%) of 180 patients who had never received local therapy (P = 0.7, chi-square test). Of these 51 patients, 39 had bladder neck obstruction and 16 had ureteral obstruction. Overall survival was significantly worse for the men with OU compared with those without OU (41 versus 54 months). OU was associated with tumor stage and androgen-insensitive prostate cancer.

CONCLUSIONS

OU results in significantly reduced survival in men with prostate cancer. In a select group of patients with prostate cancer with progression after local therapy (primarily radiotherapy), no statistically significant reduction in the development of OU was observed relative to patients matched for stage, grade, and pretreatment prostate-specific antigen level treated with androgen deprivation therapy alone. Aggressive advanced stage and hormone-insensitive disease are variables associated with OU.

Survival of patients with hormone refractory prostate cancer in the prostate specific antigen era

PURPOSE

The historically reported 12 to 18-month duration of survival of patients with hormone refractory prostate cancer is not consistent with current clinical experience. Furthermore, to our knowledge patient survival after serum prostate specific antigen (PSA) progressively increases from a nadir despite castrate testosterone has not been previously reported. For this reason we studied overall survival and the clinical variables that influence survival in patients with hormone refractory prostate cancer.

MATERIALS AND METHODS

The study focused on 254 patients with prostate cancer on androgen deprivation therapy. Hormone refractory prostate cancer was defined as the first in a series of PSA elevations despite castrate levels of testosterone. The duration of survival in the hormone refractory phase was calculated from the date of the first PSA elevation to the date of death.

RESULTS

Median survival after hormone refractory prostate cancer developed in patients initially staged with and without skeletal metastasis was 40 and 68 months, respectively. Six of more than 25 input variables were retained as significant in the final Cox model. Variables associated with longer survival were lower nadir PSA, younger age, higher pretreatment testosterone, no history of obstructive uropathy, no history of tobacco use (past or current) and lower alkaline phosphatase.

CONCLUSIONS

Historical reports of survival in hormone refractory prostate cancer underestimate current survival observations. The likely explanations of this observation include delayed enrollment in clinical trials from which most survival data are derived, PSA lead time in staging and improved supportive care. Models predicting survival in patients with hormone refractory prostate cancer should consider multiple variables.

Skeletal fractures negatively correlate with overall survival in men with prostate cancer

PURPOSE

We assessed the correlation of skeletal fracture with survival in men with prostate cancer on chronic androgen suppressive therapy.

MATERIALS AND METHODS

A total of 195 consecutive patients on chronic androgen suppression for prostate cancer were evaluated for the history and type of skeletal fracture. Correlation with overall survival was performed via multivariate analysis.

RESULTS

Of these 195 men 24 reported skeletal fracture since the diagnosis of prostate cancer. Median overall survival was 121 and 160 months in men without and with a history of skeletal fracture since the diagnosis of prostate cancer, respectively (p = 0.04). A history of skeletal fracture was retained as a negative predictor of survival on forward stepwise regression analysis (RR = 7.4, p = 0.007).

CONCLUSIONS

Our results suggest that skeletal fracture in patients with prostate cancer is an independent and adverse predictor of survival. Consideration for screening men at greatest risk via bone mineral density measurements and initiating empirical skeletal therapies (bisphosphonates, estrogens and so forth) may be warranted. This recommendation awaits validation through prospective randomized trials.

Cryosurgery as primary treatment for localized prostate cancer: a community hospital experience

The technique and recent experience incorporating cryosurgery into our community practice for primary treatment of localized prostate cancer is described. Between December 2000 and December 2001, a total of 93 patients underwent targeted cryoablation for localized prostate cancer. Of the 93 patients, 18 had failed radiotherapy, and cryotherapy was used as salvage therapy. The remaining 75 patients underwent targeted cryoablation of the prostate as primary therapy. A single urologist using an argon-based cryoablation system performed the procedure. Cryoprobes and thermosensors were placed under transrectal ultrasound guidance via a transperineal route. A double freeze-thaw cycle was used with anterior-to- posterior probe operation. Strategically placed thermosensors were used to monitor and control the freezing, and a warming catheter was used to protect the urethra. We achieved a nadir prostate-specific antigen level of < or =0.4 ng/mL in 84% of the entire population we studied (63 of 75 patients). Postsurgery complications were minimal. Incontinence developed in 4 patients, as did postsuprapubic catheter removal urinary retention. Erectile dysfunction developed in 28 of 34 patients who were potent preoperatively, with 6 of the 34 patients regaining potency after surgery. No rectourethral fistula formation occurred. Urethral sloughing was observed in 5 patients, 1 of whom developed a scrotal abscess during treatment of the sloughing. The use of cryoablation of the prostate for the treatment of localized adenocarcinoma of the prostate is feasible and can easily be transferred from the pioneering centers to the community hospitals without sacrificing safety or efficacy.

Clinical predictors of androgen-independent prostate cancer and survival in the prostate-specific antigen era

OBJECTIVES

To further characterize and identify novel predictors of androgen-independent prostate cancer (AIPC) and survival in the prostate-specific antigen (PSA) era.

METHODS

A total of 184 consecutive patients with prostate cancer receiving chronic androgen suppression were assessed for the development of AIPC and overall survival.

RESULTS

The median time to development of AIPC was 44 months (Stage M+ = 24 months; Stage M0 = 63 months, P = 0.000001). The 10-year overall survival rate for Stage M0 or M+ disease was 89% and 55%, respectively. AIPC developed significantly more commonly in patients with a higher nadir PSA level (greater than 1 ng/dL), a longer time to reach nadir PSA (greater than 3 months), a larger body mass index (greater than 27 kg/m2), greater pretherapy PSA level, and when evidence of metastatic disease was identified (logistic regression analysis). Overall survival was significantly associated with advanced stage (skeletal metastases), pretreatment PSA level, and history of skeletal fracture (multivariate Cox regression analysis).

CONCLUSIONS

In the PSA era, longer intervals of androgen suppression therapy in nonmetastatic, biochemically recurrent prostate cancer have translated into a change in the duration of androgen-dependent prostate cancer. Although the duration of androgen dependence remains variable, prolonged--possibly "curative"--control exists in a subset of patients. Obese men developed AIPC significantly sooner than did slender men. A skeletal fracture was a significant negative predictor of overall survival. These observations form the basis for nomogram predictions of AIPC in the PSA era.

Lessons learnt about early prostate cancer from large scale databases: population-based pearls of wisdom

Prostate cancer is one of most common solid tumors in men and poses some of the most difficult problems in clinical research. Although many clinical research hypotheses in this condition have been explored using single center cases series and multi-center clinical trials, the results of these studies have often been equivocal, leaving many questions unanswered. Recently, investigators have utilized large, administrative datasets for prostate cancer research. These databases tend to include large numbers of patients from different geographic regions increasing their generalizability and statistical power. The goal of this report is to review lessons learnt about early prostate cancer using these data sources. In particular, we focus on the application of large, population-based datasets to address issues concerning the natural history of prostate cancer, the impact of race on outcomes in prostate cancer and the effectiveness of various treatments for localized disease. Information gathered from large, administrative databases will be helpful when counseling patients regarding their treatments options for localized prostate cancer and in identifying future directions for prostate cancer research.

The role of active treatment in early prostate cancer

The dramatic increase in the number of patients diagnosed with localized prostate cancer in the last decade presents a difficult challenge for physicians. Because the window of opportunity for cure is short it is vital to begin treatment before the cancer cells invade neighbouring tissues and organs or metastasise to other sites. This pressure of increased patient numbers provided clinicians with the opportunity to investigate other treatment options. New surgical techniques including laparoscopic radical prostatectomy, improving therapeutic radiation by the introduction of conformal radiotherapy, neutron radiation, cryosurgery, high intensity focussed ultrasound (HIF) and the revival of brachytherapy with or without external beam radiation are currently being investigated. The goal of these techniques is to treat localized prostate cancer based on the endpoints of disease specific mortality, no evidence of disease, absent or low levels of prostate-specific antigen (PSA), reduced side-effects, improved quality of life and importantly increased cost-efficacy. It is important to remember however, that watchful waiting and endocrine therapy are still valid therapy options in certain patient groups. The lack of randomized, prospective trials on local treatment of prostate cancer, makes it difficult to compare the efficacy of the different treatments, especially in terms of disease-specific survival. Trials are now in progress but it will be several years before results are available. In the meantime, we need to focus on surrogate endpoints, side effects, quality of life and the cost-efficacy of each treatment. It is also important to ensure that patients are kept informed and up-to-date with any new therapeutic developments.