The illusion of the learning phase for lymphatic mapping.
BACKGROUND
We provide a statistical analysis of the learning phase for sentinel node biopsy.


METHODS
Four learning phases were analyzed: 25, 50, 75, and 150 procedures with a corresponding number of 10, 20, 30, and 60 tumor-positive cases. Critical values of nonidentification rate and false-negative rate were defined. The binomial distribution was used to calculate the probabilities of correctly or incorrectly accepting the quality of the performance, given a certain long-term nonidentification or false-negative rate.


RESULTS
The chance of incorrectly reaching a favorable false-negative rate of <10% (critical value) in 20 metastasized patients was 18% for a surgeon with a long-term probability of false-negative procedures of 15%. This chance was reduced to 10% with a learning phase of 60 tumor-positive cases. When this chance has to be further reduced to 5%, the critical value has to be lower in smaller groups of patients: 5% false-negative rate in 20 tumor-positive procedures.


CONCLUSIONS
A learning phase of at least 150 procedures with 60 tumor-positive cases is needed to draw any reliable conclusion about the quality of sentinel node biopsy. In general, a compromise has to be made between the reliability of the results and the practically achievable number of procedures.
Tanis
P J
PJ
Department of Surgery, The Netherlands Cancer Institute, Amsterdam, the Netherlands. ptanis@nki.nl
Nieweg
O E
OE
Hart
A A M
AA
Kroon
B B R
BB
D016010:Binomial Distribution; D002983:Clinical Competence; D003951:Diagnostic Errors / Q000517:prevention & control* / Q000706:statistics & numerical data; D005188:False Negative Reactions; D006801:Humans; D007858:Learning; D009426:Netherlands; D012680:Sensitivity and Specificity; D021701:Sentinel Lymph Node Biopsy / Q000193:education* / Q000592:standards