Immunohistochemical assessment of PTEN expression and itsassociation with tamoxifen resistance in ER positive breast cancers

Introduction: Although Estrogen Receptor (ER) positivity is a good prognostic factor in breast carcinoma (BC), a subset of patients experiences poor disease-free survival (DFS). Mutation in phosphatase and tensin homologue deleted on chromosome ten (PTEN) is identified as a poor prognostic feature in BC. This study was designed to find out the impact of lost or poor PTEN expression on ER positive BC, in terms of the recognized prognostic factors and survival outcome to find out its association with tamoxifen resistance.

 

Methods: This was a cross sectional study with a follow up component. BC tissue blocks submitted to our unit from 2006 to 2012 were selected. From the laboratory data, patients who had ER positive BC, undergone mastectomy, treated with tamoxifen were selected. All clinicopathological parameters, DFS and overall survival (OS) were analysed against lost or poor PTEN expression. Clinicopathological features were compared using Chi-square test. Kaplan-Meier model with log-rank test was used for the survival analysis.

 

Results: A total of 130 BC patients satisfied the inclusion criteria. PTEN expression was lost or poor in 82.3% (n=107) patients. PTEN expression had a positive association with the level of ER expression (p=0.011) and a negative association with Nottingham prognostic index (NPI) (p=0.045) and pathological stage (p<0.048). Only 12.1% (n=16) patients had recurrences and 7.69% (n=10) had died over a period of 51 months of mean follow up. There was no significant association between PTEN expression and survival.

 

Conclusions: This study showed that there is a statistically significant association between lost or poor PTEN expression and low ER expression, high NPI and stage 3 in ER positive BC. Further studies including larger study sample with a longer follow up are recommended to find out the association of PTEN with the survival in ER positive BC treated with tamoxifen.