Introduction Initial radiological staging imaging frequently detects indeterminate pulmonary nodules (IPNs) in patients presenting with colorectal cancer (CRC). The discovery of such nodules creates a clinical dilemma for multidisciplinary team. We aimed to assess the outcome of initial IPNs during follow up for patients with CRC.

Method A prospectively maintained CRC database (2008–2010) at University Hospitals of Leicester NHS Trust was analysed. Clinical, pathological and radiological characteristics were studied for outcome of IPNs during CRC follow up. Nodules were characterised as malignant, benign or indeterminate). Data is expressed as number (n) and percentage (%).

Results 2008 patients were studied for IPNs. Median Follow up was 44 months. 180 (8.9%) patients were identified with pulmonary nodules on initial staging scan. In 69 (3.4%) patients, pulmonary nodules were characterised as IPNs. Follow up imaging for IPNs modality was CT chest in 65.2% (24 patients did not have follow up scans) and CT-PET in 13% patients. After follow up scans, 20 cases (30.4%) were found to have metastasis in lung and one case had primary lung cancer.

Conclusion This study shows that one third of the indeterminate lung nodule on initial staging scan were characterised as malignant in follow up radiological imaging.

Disclosure of interest None Declared.