Aims To determine whether expression of Smad4, a tumour suppressor found to be absent in 10% of colorectal cancer (CRC), is associated with outcomes in patients with CRC.

Methods Tumour samples from 241 consecutive patients with CRC who underwent upfront colon resection between 2005 and 2009 were obtained. Triplicate tissue cores from resected primary colon tumours and matched normal controls were used to construct the tissue microarrays (TMAs). We examined the expression of Smad4 using immunohistochemistry. Clinicopathological records were obtained for all patients. TMAs were reviewed by two pathologists and scored as either ‘positive’ or ‘negative’ for nuclear staining. In total, 21 of 241 tumours (8.6%) were Smad4 negative.

Results Loss of Smad4 expression correlated with significantly worse overall survival (OS) (p=0.011) and disease-free survival (DFS) (p=0.024). Patients with loss of Smad4 expression had a median OS of 31 months compared with 89 months positive Smad4 expression. Loss of Smad4 remained significant on multivariate analysis for OS (p=0.0097). In patients with node-positive disease, loss of Smad4 predicts for worse DFS (p=0.012). In patients with metastatic and recurrent disease, Smad4 loss predicts for worse OS (p=0.012). Of the patients that received capecitabine over the course of their treatment, those with Smad4 loss (n=13) had significantly worse DFS (p=0.003) and OS (p=0.0007).

Conclusions Loss of Smad4 expression is associated with worse DFS and OS in multiple subsets of patients with CRC. Further studies are required to validate our findings and ascertain the role of Smad4 status in the management of this disease.