Abstract P5-13-11: Medico-Economic Assessment of the Genomic Grade Index on Adjuvant Treatment Strategy in Elston-Ellis Grade 2, Estrogen Receptor Positive, HER2 Negative, Node Negative, Small Size Breast Carcinomas

Abstract

Abstract Background: Elston-Ellis grading (EE) is one of the key criteria for adjuvant therapy decision in ER+/HER2-/pN0/pT1 -2 tumors. The genomic grade index (GGI) is a 97-gene micro-array assay able to identify tumors of high or low genomic grade. GGI has been developed in order to improve the prognosis determination, especially in EE2 tumors which represent a significant proportion of breast carcinomas and where the inter-assessor variability is the highest. The aim of the present study was to model the influence of the GGI on adjuvant treatment decision in EE2 patients, using a cohort of ER+/HER2-/pN0/pT1-2 tumors. Methods: A randomly selected series of pT1-2, pN0 breast cancers from the Institut Curie 1995-1996 cohort was profiled using Affymetrix HGU133 Plus 2.0 gene chips. The GGI was calculated using Ipsogen Mapßuant Dx®. Treatment decisions were made for EE2 cases based on the Institut Curie adjuvant treatment guidelines (www.curie.fr). The treatment decision algorithm was firstly run using the grade as defined by Elston Ellis, and secondly using the GGI (undetermined cases were classified as grade2). Results: Out of 72 EE2 tumors, 35 were classified as GGI-1 (49%) and 13 (18%) as GGI-3. Based on EE, 7% of patients would have received adjuvant chemotherapy (ACT) alone (all were ER-/PR-), 50% adjuvant hormonal therapy (AHT) alone, and 43% both. Using the GGI, 7% (n=5) of patients would have been spared AHT and 10% (n=7) ACT. In the ER+/HER2- subgroup of 62 pts, 58% of patients would have received AHT alone and 42% AHT+ACT based on EE; GGI would have lead to a 14% reduction in AHT prescription and to a 26% reduction in ACT prescription. Conclusion: Applying the Genomic Grade Index instead of the Elston Ellis Grade to determine the adjuvant treatment strategy in a series of EE2/ER+/HER2-/pN0/pT1-2 breast carcinomas would lead to a 14% and 27% reduction in the administration of, respectively, adjuvant hormone-therapy and chemotherapy. Adjuvant treatment decision: models based on Elston-Ellis or Genomic Grading Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-13-11.