The clinical significance of radiologically detected indeterminate pulmonary nodules in colorectal cancer

Aim Colorectal cancer patients identified with indeterminate pulmonary nodules (IPN) in the absence of other metastasis represent a clinical dilemma. This study aimed to identify characteristics that could predict which nodules truly represented a metastasis in an attempt to optimize therapy and to reduce the number of follow-up chest CT scans performed. Method All patients with colon or rectal cancer who presented between 2004 and 2008 were analysed. Patients with IPN on staging CT were identified from a dedicated prospective database and the medical records analysed and follow up recorded. Patients with obvious metastatic disease were excluded from analysis. Association of location, number and size of the nodules and metastatic disease were the primary end-points for analysis. Results Nine hundred and eight patients presenting with cancer of the colon or rectum were identified. Thirty-seven (4%) patients were diagnosed with IPN with no obvious metastatic disease on staging CT. At a median follow up of 23 months there were eight (21%) cases where nodules had progressed. No significant association was detected between nodule size and pulmonary metastasis. Half of the patients with four or more nodules showed progression on serial CT imaging suggestive of pulmonary metastasis (χ2, P ≤ 0.01). Conclusion Colorectal cancer patients with four or more indeterminate pulmonary nodules on preoperative staging CT imaging, even in the absence of metastasis elsewhere, are likely to represent pulmonary metastatic disease. These patients should be followed up with short-term interval CT imaging to enable early detection of progression so that treatment can be tailored appropriately.