The impact of inter-observer variation in pathological assessment of node-negative breast cancer on clinical risk assessment and patient selection for adjuvant systemic treatment.
BACKGROUND
It is well known that there is considerable inter-observer variability in assessment of the pathological parameters that are used to select node-negative breast cancer patients for adjuvant systemic treatment. There are only limited data available as to in how many patients this leads to differences in treatment decisions.


METHODS
Clinical and pathological data of 694 patients <61 years with primary unilateral T1-4N0M0 breast cancer were analysed. Grade, estrogen receptor (ER) status and human epidermal growth factor receptor 2 (HER2) status were first assessed locally; subsequent central re-evaluation of these parameters was carried out. Clinicopathological low or high risk was assessed using national Dutch guidelines and the Adjuvant! Online (www.adjuvantonline.com).


RESULTS
The local pathological examination was discordant with central review for grade, ER and HER2 in 28% (kappa 0.56; grade 2 tumours 35% discordant), 5% (kappa 0.85) and 4% (kappa 0.81) of patients, respectively. If clinical risk were assessed based on Dutch guidelines or Adjuvant! Online, respectively, 15% (one of seven patients; kappa 0.70) or 8% (kappa 0.83) of patients would have been assigned to a different clinical risk group.


CONCLUSIONS
Inter-observer variation in pathological examination of breast carcinomas results in significant differences in grade, ER status, HER2 status, clinicopathological risk and subsequently in adjuvant systemic treatment advice.
Bueno-de-Mesquita
J M
JM
Department of Pathology, The Netherlands Cancer Institute, The Netherlands.
Nuyten
D S A
DS
Wesseling
J
J
van Tinteren
H
H
Linn
S C
SC
van de Vijver
M J
MJ
D000328:Adult; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology* / Q000628:therapy*; D005260:Female; D006801:Humans; D008495:Medical Oncology / Q000592:standards / Q000706:statistics & numerical data*; D008875:Middle Aged; D009367:Neoplasm Staging; D015588:Observer Variation; D010336:Pathology / Q000592:standards / Q000706:statistics & numerical data*; D017410:Practice Guidelines as Topic; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis; D011960:Receptors, Estrogen / Q000096:biosynthesis; D011980:Receptors, Progesterone / Q000096:biosynthesis; D012189:Retrospective Studies; D018570:Risk Assessment
D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone