Introduction. To date, studies of breast cancer lymphatic mapping (LM) have
analyzed success with respect to individual surgeons. However, LM and sent
inel lymph node biopsy (SLNBx) are procedures that require institutional mu
ltidisciplinary cooperation between the departments of radiology, pathology
, and surgery. Thus, it is important to evaluate these procedures with resp
ect to the institution. This study examines 30 institutions to clarify the
value of the institutional volume index (IVI) (cases/month) to the outcome
of LM and SLNBx in breast cancer.
Methods. From July 1997 to July 1999, 30 institutions participated in the D
epartment of Defense national breast LM trial. All participants underwent a
2-day training course for surgeons, nuclear medicine physicians, and patho
logists. The records for each institution were prospectively accrued and su
bmitted to a database. The false negatives, failure rates, and IVI were cal
culated for each institution. A logistic regression model plots the relatio
nship between IVI and institutional failure rate. Using a multivariate anal
ysis, mapping failure was analyzed as a function of case number with respec
t to the individual surgeon and the institution as a whole.
Results. False negative results were demonstrated in only 5 (4%) cases amon
g all institutions and were excluded from further analysis due to small num
bers. Mapping failures were found in all but 7 of the 30 institutions whose
data were complete. There were 71 mapping failures among 74 surgeons over
555 cases, which yielded an overall failure rate of 12.79% (71 555). The lo
gistic regression model revealed an inverse relationship between IVI and in
stitutional failure rate. However, the multivariate analysis revealed that
the individual surgeon performance was the most significant factor in deter
mining institutional mapping success.
Conclusion. Failure to map can be a function of multiple factors including
surgical skill, surgical volume index, and injection method of the SLN pati
ent, all under the quality control of an institution. The surgical failure
rate on the other hand is a function of surgical skill, surgical volume, an
d injection methods. While differences in mapping success exist across inst
itutions, this disparity is not due to factors associated with the institut
ion as a whole, but lie with the individual surgeon. (C) 2001 Academic Pres
s.