Quantitative determination of insulin-like growth factor 1 receptor mRNA in formalin-fixed paraffin-embedded tissues of invasive breast cancer.

Background: Insulin-like growth factor 1 receptor (IGF1R) has recently received much attention due to its role in initiation and progression of breast cancer. Previously analysis of its gene expression has been restricted to fresh-frozen (FF) samples, but application of this technique to routinely processed formalin-fixed paraffin-embedded (FFPE) samples could facilitate larger retrospective studies correlating IGF1R expression with prognosis and therapeutic response.

Methods: A series of 77 paired FFPE and FF specimens of breast tumors was used to evaluate the possibility of quantifying IGF1R gene expression with FFPE samples and to compare the results obtained from FFPE and FF samples. The feasibility and prognostic value of analyzing IGF1R gene expression using FFPE samples was evaluated in a cohort of 260 primary breast tumors.

Results: Total RNA was extracted from 95.4% of the FFPE samples with concentration at least 30 ng/μL. Real-time PCR based on Taqman methodology was successful in 90% of the FFPE samples. IGF1R gene expression showed strong correlation not only between FFPE and FF (Spearman ρ = 0.74), but also with IGF1R protein expression in both types of specimen. Kaplan-Meier analysis showed that higher IGF1R mRNA expression was associated with longer recurrence-free survival (P = 0.009) and breast cancer-specific survival (P = 0.0002).

Conclusions: Quantitative analysis of IGF1R gene expression in FFPE tissues can be feasibly and reliably conducted, and provides information relevant to the characteristics and outcome of invasive breast cancer.