Six statistical suggestions for surgeons

Beyond the P IV: gain confidence in confidence intervals

This is the last in a 4-part series discussing the proper use, interpretation, and limitations of P values.

Morbidity and survival after 1,3-bis(2-chloroethyl)-1-nitrosourea wafer implantation for recurrent glioblastoma: a retrospective case-matched cohort series

OBJECTIVE

To determine the risks and survival benefit associated with implantation of an absorbable, 1,3-bis(2chloroethyl)-1-nitrosourea-impregnated polymer wafer, we prospectively studied patients with recurrent glioblastoma multiforme and compared them with a demographically matched cohort group.

METHODS

Over a 29-month period, 62 patients underwent operations. All had tumor growth despite standard treatment, a Karnofsky performance score of > or =70, and histopathological confirmation of glioblastoma. Seventeen patients underwent gross total resection with placement of 1,3-bis(2-chloroethyl)-1-nitrosourea wafers (wafer group) at a median 44 weeks from diagnosis (6 women, 11 men; median age, 56 years). A cohort group of 45 patients undergoing surgery for recurrent glioblastoma during the same time period, but not receiving wafers, was identified. Surgery was performed at a median 47 weeks from diagnosis (14 women, 31 men; median age, 54 years).

RESULTS

Within 6 weeks of surgery, 13 complications were identified in 8 patients in the wafer group. In the cohort group, 6 patients sustained 8 complications. We were unable to identify any survival advantage using Kaplan-Meier analysis. In the wafer group, median survival was 58 weeks from diagnosis and 14 weeks from wafer implantation. In the cohort group, median survival was 97 weeks from diagnosis and 50 weeks from operation.

CONCLUSION

1,3-bis(2-chloroethyl)-1-Nitrosourea wafer implantation for recurrent glioblastoma was associated with a higher risk of postoperative complications, particularly those related to infection and wound healing. No clear survival benefit associated with wafer implantation was identified.

The Clinical Cooperative Trial. Guide to a critical approach

The growing difference with regard to academic and professional accountability between neurosurgeons and neuroscience is alarming. Controlled clinical trials continue to be the most scientifically valid method of evaluating standard treatments against the risks and benefits of medical innovations. Clinical research becomes more rewarding as neurosurgeons gain familiarity with the particulars of the structure and relevance of expertly designed clinical cooperative trials. The basic principles and the significance of biometrical essentials (research hypothesis, comparability, randomized and non-randomized trials, phases of studies and planning steps) are briefly discussed. A guide to the pertinent literature is provided.

Application of statistics and frequency of statistical errors in articles in acta neurochirurgica

Out of 395 contributions in the volumes 51 to 64 of Acta Neurochirurgica 141 reported numerical data. The frequency of procedures used for describing distribution, location or variability and the frequency of analytical methods were evaluated. Critical assessment of these articles revealed a considerable rate of fundamental errors in application of statistics. Considering only papers involving analytical methods 52% of these (33 out of 64) contained simple statistical errors which can be avoided without any statistician's help. Some rules for improving statistical quality of medical articles are presented.