We wanted to investigate the diagnostic and prognostic significance of serum CYFRA 21-1, especially in predicting the risk of recurrence in patients with operable squamous cell lung cancer. Serum levels of CYFRA 21-1 were measured using an immunoradiometric assay (CIS bio) in 76 patients with squamous cell lung cancer (64 operable and 12 with unresectable tumours), 22 with other non-small-cell type (12 with adenocarcinoma and 10 with large-cell type) and 45 with nonmalignant lung diseases. Elevated preoperative CYFRA 21-1 levels were identified in 63%, of patients with squamous cell type (SqCC), 33% with adenocarcinoma, and 30% with large-cell carcinoma type. The diagnostic specificity of the assay was 96%. Positive CYFRA 21-1 levels were observed in 33% of stage I, 52% of stage II, 76% of stage IIIa and 83% of stage ziiib patients with SqCC type. Statistically significant differences were obtained between stages I and II and between II and IIIa, but not between stages IIIa and IIIb Recurrence-free survival probability for patients with elevated serum CYFRA 21-1 levels before surgery was 63% (24/38) versus 92% (24/26) for patients with normal serum CYFRA 21-1 levels. However, the difference was not statistically significant when adjusted for the TNM stage (primary tumour, regional lymph node involvement, occurrence of distant metastasis). In 9 of the 10 patients with increased trend for CYFRA 21-1 during follow-up, elevated serum CYFRA 21-1 levels preceded (7) or coincided (2) with the clinical detection of tumour recurrence, providing a predictive value of an increased trend of 90%. In the multivariate analysis, the association of the increase of CYFRA 21-1 level with a higher risk of recurrence was statistically significant. Our results indicate that CYFRA 21-1 may be a useful marker in SqCC. Serial determination of CYFRA 21-1 was consistent with the treatment results and the serum CYFRA 21-1 levels were shown to reflect the disease process during followup. Rising serum CYFRA 21-1 levels in patients after tumour resection were an early indicator of tumour recurrence.
