Usefulness of serum interleukin-6 to discriminate between cardiac myxomas and non-myxomatous cardiac masses

Abstract

Summary Background: An elevated interleukin-6 (IL-6) serum level was described as a diagnostic marker for a myxoma. This study tried to assess the value of IL-6 determination to differentiate myxomas from non-myxomatous tumours in patients with an intracardiac mass. Methods: From 1993 to 2001, patients with an intracardiac mass by echocardiography were prospectively included. There were 32 patients: 19 consecutive patients with a cardiac myxoma (all histologically confirmed), and 13 randomly selected patients with non-myxomatous cardiac masses including seven with a cardiac tumour and six with an intracardiac thrombus. Serum IL-6 and C-reactive protein (CRP) levels were compared between groups and correlated with tumour size measured by 2D echocardiography. Additionally, two patients with relapsing myxomas were studied with serial IL-6 determinations and echocardiography. Results: There was no difference in tumour size between myxomas (57 ± 55 ml) and nonmyxomatous masses (50 ± 116 ml; p = 0.83). Average IL-6 levels were 11.6 ± 7.9 pg/ml (range: 0.3–29.5) in 19 patients with myxomas and 16.2 ± 15.5 pg/ml (range: 0–43.7) in 13 with a non-myxomatous heart tumour (p = 0.28). IL-6 levels were elevated in 15 patients with myxomas resulting in a sensitivity of 79% (95% confidence interval CI 54–94%) and in 10 with non-myxomatous tumours resulting in a specificity of 23% (95% confidence interval 5–54%; p = 0.67). There was no significant difference between CRP levels between the different groups (p = 0.77). There was no correlation between serum IL-6 or CRP with tumour size in any of the groups (p >0.05). ROC analysis showed an area under the curve for IL-6 of 0.47 (95% CI 0.24–0.70) and for CRP 0.50 (95% CI 0.26–0.74). In the two patients with relapsing myxomas, however, there was no relapse without an increase in IL-6. Conclusions: An elevated IL-6 or CRP serum level in a patient with an intracardiac mass is not specific for myxoma or another type of intracardiac tumour. The value of IL-6 as an additive marker to echocardiography in the detection and follow-up of patients with suspected or resected myxomas has yet to be proven.