Michael R. Chernick

Targeted cryoablation of the prostate: 7-year outcomes in the primary treatment of prostate cancer

The efficacy and safety of the long-term experience with targeted cryoablation of prostate cancer (TCAP) at a community hospital is retrospectively reviewed. A series of 590 consecutive patients who underwent TCAP as primary therapy with curative intent for localized or locally advanced prostate cancer from March 1993 to September 2001 were identified. Patients were stratified into 3 risk groups according to clinical characteristics. Biochemical disease-free survival (bDFS), post-TCAP biopsy results, and post-TCAP morbidity were calculated and presented. The mean follow-up time for all patients was 5.43 years. The percentages of patients in the low-, medium-, and high-risk groups were 15.9%, 30.3%, and 53.7%, respectively. Using a prostate-specific antigen (PSA)-based definition of biochemical failure of 0.5 ng/mL, results were as follows: (1) the 7-year actuarial bDFS for low-, medium-, and high-risk patients were 61%, 68%, and 61%, respectively; (2) the bDFS probabilities for a PSA cutoff of 1.0 ng/mL for low-, medium-, and high-risk patients were 87%, 79%, and 71%, respectively; and (3) the bDFS probabilities for low-, medium-, and high-risk patients using the American Society for Therapeutic Radiology and Oncology (ASTRO) definition of biochemical failure (3 successive increases of PSA level) were 92%, 89%, and 89%, respectively. The rate of positive biopsy was 13%. After a positive biopsy, 32 patients underwent repeat cryoablation. For those patients who underwent repeat cryoablation, 68%, 72%, and 91% remain bDFS using definitions of 0.5 ng/mL, 1.0 ng/mL, and the ASTRO criteria, respectively, after a mean follow-up time since repeat cryoablation of 63 months. The rates of morbidity were modest, and no serious complications were observed. TCAP was shown to equal or surpass the outcome data of external-beam radiation, 3-dimensional conformal radiation, and brachytherapy. These 7-year outcome data provide compelling validation of TCAP as an efficacious treatment modality for locally confined and locally advanced prostatic carcinoma.

Introductory Biostatistics for the Health Sciences

Introductory Biostatistics for the Health Sciences , Introductory Biostatistics for the Health Sciences , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

Effects of Bias Adjustment on Actuarial Survival Curves

Medical device companies report the performance of their products through actuarial survival curves. Analyses are based on “passive” databases. For pacemakers, a significant number of explanted devices may not be reported to manufacturers. Thus, expiant information is lost. High rates of underreporting of failures could result. Therefore, performance curves could indicate better survival rates than those that are actually occurring. Samples of closely-followed patients called active samples are used to adjust survival curves for underreported failures. Through simulations, this paper shows a need for a larger sample size for active components and what degree of underreporting failures would be necessary to assure better estimates using adjustments rather than estimates that ignore adjustments. The issues in this paper have a much broader context as pharmaceutical companies increasingly rely on medical devices to monitor patients ‘ health or deliver drugs. This can also apply to survival curves for adverse events in Phase 4 clinical trials.