Upregulation of insulin-like growth factor II mRNA-binding protein 3 (IMP3) has negative prognostic impact on early invasive (pT1) adenocarcinoma of the esophagus

Purpose: Therapeutic decisions in esophageal adenocarcinomas (EAC) restricted to mucosa (pT1a) or submucosa (pT1b) depend mainly on classic histomorphology-based criteria like tumor grading or lymphovascular invasion with limited success. There is a strong need for reliable pre-therapeutical biomarker-based evaluation also applicable on endoscopically obtained biopsies. Methods: Patients who underwent esophagectomy due to EAC in a high volume center between 1999 and 2016 were included. Tissue microarrays (TMA) were retrospectively established from the formalin-fixed and paraffin-embedded material of the resected specimens and immunohistochemically stained using a monoclonal primary antibody specific for IMP3. IMP3 staining intensity was scored manually according to a 3-tier-scoring system (negative, weak and strong). Results: 371 EACs were interpretable for analysis. 109 patients (29%) had early invasive (pT1a/pT1b) and 262 patients (71%) locally advanced EAC (> pT2). 259 EACs (70%) revealed positive immunostaining for IMP3 including 167 strongly and 92 weakly positive. Early EAC had significantly lower IMP3 expression compared to advanced tumor stages (p < 0.0001). IMP3 positive pT1 EAC revealed higher levels of lymph node metastases (LNM) (p = 0.0001) and pT1b tumors showed higher rates of IMP3 positivity compared to pT1a (p = 0.007). Subdividing the submucosa in thirds, there was a significant trend for higher IMP3 expression with deeper tumor infiltration from pT1a to pT1b (sm3) (p = 0.0001). There was an association between IMP3 expression and shortened survival in pT1 EAC (p = 0.038). Conclusions: IMP3 expression correlates with depth of tumor infiltration, rate of LNM and is associated with worse outcome. Thus, IMP3 might be useful for therapeutic decisions in early-invasive EAC.