National Cancer Data Base/Surveillance Epidemiology and End Results: potential insensitive-measure bias

Abstraction of data from National Cancer Data Base (NCDB)/Surveillance Epidemiology and End Results (SEER) for reasons other than incidence, mortality, and patterns of care has risen. A potential problem with these data is that insensitive-measure bias can exist because of possible inaccuracies in hospital tumor registry staging. The purpose of this study is to assess the accuracy of tumor registry staging from six community hospitals.

Staging of 103 consecutive cancers operated on by a gynecologic oncologist (one of the authors) as a surgical consultant to a gynecologist or surgeon was reviewed. Hospital tumor registry staging forms were arbitrarily assigned to be completed by the nongynecologic oncologist versus the gynecologic oncologist by the medical records department. The authors reassessed cancer staging by medical chart review. The tumor registry staging was compared with the actual staging as determined by the authors. Major staging violations were defined as errors that would significantly change stage enough to alter prognosis or change recommended adjuvant treatment. All other violations were defined as minor.

Twenty-eight (27%) cancers were staged by the gynecologic oncologist and 75 (73%) by nongynecologic oncologists. Eighty (78%) cancers were endometrial and 14 (13%) ovarian. Eighty-three (81%) tumors were stage I or II. Major staging violations occurred in 0% of cancers staged by the gynecologic oncologist and 22% (16/75) by a nongynecologic oncologist (P = 0.002). Minor staging violations occurred in 14% (4/28) of cancers staged by the gynecologic oncologist and 42% (32/75) by a nongynecologic oncologist (P = 0. 005). Minor violations were due to omission of histologic subtype and/or grade.

The 22% major staging violation rate represents significant insensitive-measure bias. If additional studies produce similar results, abstraction of data from NCDB/SEER for reasons other than incidence, mortality, and patterns of care cannot be accepted as evidence-based scientific medicine.