Risk of metastasis in non-calcified pulmonary nodules on initial staging CT in patients with primary extra pulmonary malignancy

Author(s): Samer Abi Khalil,Celine Harmouche*,Iyad Mallak, Elias Haddad,LinaMenassa-Moussa & NoelAoun

Purpose: Detection of pulmonary nodules in patients with extra pulmonary malignancy is common. Consequently, differentiating malignant from benign lesions is important to determine adequate treatment protocol. This study aims first to detect pulmonary nodules at first staging CT for extra pulmonary malignancy; and second to evaluate the correlation between the morphological criteria of pulmonary nodules and the malignancy of nodules. By doing so, the study would be able to estimate the risk of metastasis in pulmonary nodules detected at first staging CT for extra pulmonary malignancy.

Methods: In this retrospective study, we included patients aged 18 years old and over that had a first staging CT between January 2010 and December 2012 for extra pulmonary malignancy and showed one or more pulmonary nodules, and that had been followed for more than 5 years. Each nodule detected was judged by a radiologist as suspicious or non-suspicious based on morphological characterization and confirmed on subsequent follow-up CT scans as metastatic or not metastatic.

Results: 108 patients were included with a male/female ratio of 1. The mean age at diagnosis was 58.56 years. In total, the study included 287 nodules measuring 4.54 mm ± 1.68 mm. The distance between each nodule and a pleural surface was in average 6.12 mm. 42.2% of nodules presented a septal tail, and 81.5% had regular margins. The round shape was the most frequent (35.9%). The concordance between the judgment of the nodules into suspicious and non-suspicious and their metastatic character was statistically proven (P<0.001).

The judgment showed a sensitivity of 80.2%, specificity of 68%, and positive predictive value of 67.7% and negative predictive value of 80.3%. The distance to a pleural surface of the non-suspicious nodules was significantly shorter than that of the suspicious nodules (P<0.001), the same for non-metastatic and metastatic nodules. The metastatic nodules were more common in patients with a larger number of nodules (P<0.001). The irregular margins were significantly correlated with the suspicious judgment of the nodules (P=0.001). 92.8% of oval nodules were non-suspicious whereas 74.7% were non-metastatic. 97.1% of round nodules were suspicious whereas 65% were metastatic.

Conclusion: The characterization of pulmonary nodules is essential in estimating the risk of metastasis. The nodule characteristics showed a higher capacity to exclude a metastasis than to confirm it.