Differences in the prognostic implications of vascular invasion between lung adenocarcinoma and squamous cell carcinoma.

Objectives: Vascular invasion (VI) has been accepted as a universally important prognostic factor for patients with lung carcinoma. However, the clinical significance of VI in each of the histological subtypes has been unclear. The aim of the present study was to investigate differences in the clinicopathological implications of VI between adenocarcinoma and squamous cell carcinoma.

Method: A total of 336 patients were evaluated, of whom 81 were diagnosed as having peripheral-type squamous cell carcinoma, and 255 as having adenocarcinoma.

Result: Among the 336 patients, the five-year survival rates for those who were VI-positive and VI-negative were 38.4% and 76.3%, respectively, the difference being significant (p<0.0001). Multivariate analysis identified VI as an independent prognostic factor (hazard ratio: 1.86). Although the difference in cancer-free survival between VI-positive and -negative patients was statistically significant for adenocarcinoma (p<0.0001), it was not significant for squamous cell carcinoma (p=0.086). For adenocarcinoma, the difference between the survival curves for VI-positive and -negative patients was significant for the subtypes with a predominant lepidic (p<0.0001), papillary (p=0.0026), and acinar (p=0.0060) component, whereas that for the predominantly solid subtype was not significant (p=0.58). Squamous cell carcinomas were then divided into two groups on the basis of the diameter of vessels that had been invaded by the cancer cells: large-vessel invasion (LVI; 1000 μm or more) and small-vessel invasion (SVI; less than 1000 μm). Although there was no difference in the survival curves between the LVI and SVI groups, the LVI group showed a significantly higher incidence of cavity formation and distant metastasis.

Conclusion: We conclude that VI is a useful prognostic indicator in lung carcinoma, although the clinical implications of VI differ between adenocarcinoma and squamous cell carcinoma.