ABSTRACT
OBJECTIVES: For patients with invasive breast cancer, management decisions are informed by tumor grade according to the Nottingham Grading System (NGS), either on its own or as part of the Nottingham Prognostic Index (NPI). A system retaining the nuclear grade element but substituting the two subjective components, mitosis count and tubule formation, of the NGS with a proliferation index based on Ki-67 (MIB-1) has been proposed (nuclear grade plus proliferation [N+P] grading). METHODS: We validated the prognostic value of this grading system on a population of 322 women. RESULTS: N+P grading resulted in more grade I tumors (47.9% vs 4.5%) and fewer grade II (32% vs 51.5%) and grade III (20.1% vs 44%) tumors compared with NGS. The NPI calculated based on N+P grade had a similar association with survival (P < .001; odds ratio, 1.729) as the NPI calculated on the basis of the NGS grade (P < .001; odds ratio, 1.668). CONCLUSIONS: The N+P system seems equivalent to the NGS system.
Subject(s)
Breast Neoplasms/pathology , Carcinoma, Ductal, Breast/pathology , Neoplasm Grading/methods , Aged , Cell Proliferation , Cohort Studies , Disease-Free Survival , Female , Humans , Immunohistochemistry , Middle Aged , Prognosis , Proportional Hazards Models , Retrospective Studies , Tertiary Care CentersABSTRACT
We extend proportional hazards frailty models for lifetime data to allow a negative binomial, Poisson, Geometric or other discrete distribution of the frailty variable. This might represent, for example, the unknown number of flaws in an item under test. Zero frailty corresponds to a limited failure model containing a proportion of units that never fail (long-term survivors). Ways of modifying the model to avoid this are discussed. The models are illustrated on a previously published set of data on failures of printed circuit boards and on new data on breaking strengths of samples of cord.
