Visceral pleural involvement in nonsmall cell lung cancer: Prognostic significance

Background. A tumor of any size that invades the visceral pleura is classified in the T2 category; however, the definition of the visceral pleural involvement has remained somewhat ambiguous. It is unclear whether the T2 category includes the p2 status alone or incorporates the extent of the p1 status. Methods. We retrospectively analyzed the survival of 474 patients with T1 and T2 nonsmall cell lung cancer to evaluate the influence of the degree of visceral pleural involvement (p0, p1, and p2) on the prognosis and to clarify the definition of the visceral pleural involvement. Results. The 5-year survival rates according to the degree of visceral pleural involvement were 68.0% in p0 (n = 345), 43.9% in P1 (n = 110), and 54.9% in p2 (n = 19; p0 versus p1, p = 0.0004; p0 versus p2, p = 0.013; and p1 versus p2, p = 0.61). The degree of visceral pleural involvement (p0 versus p1/p2) was a significant independent prognostic factor from tumor size and lymph node involvement, by multivariate analysis (relative risk = 1.47, P = 0.033). The prognosis of pN0 patients with p1 and tumor size 3 cm or less was significantly poorer than that of those with p0 and tumor size 3 cm or less (p = 0.0004), and the prognosis of patients with p1 and tumor size more than 3 cm was significantly poorer than that of those with p0 and tumor size more than 3 cm (p = 0.024). Conclusions. The degree of visceral pleural involvement (p0 versus p1/p2) is an important component of the lung cancer staging system. Tumors with p1 and p2 status should be regarded as representing visceral pleural involvement and T2 disease.