Objective. We assessed the outcome of surgical treatment for non-small cell lung cancer with interlobar pleural invasion to an adjacent lobe, and elucidated whether or not such lung cancer cases should be categorized as T2. Furthermore, the optimal operative method for treating the adjacent invaded lobe was discussed. Patients and Methods. Forty non-small cell lung cancer patients with invasion beyond the interlobar pleura and categorized as pT2 the ILp3pT2 group were studied. The outcomes of

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... e patients without interlobar pleural invasion and categorized as pT2 the ILp0-2pT2 group , and those categorized as pT3 the pT3 group were compared. Results. The 5-year survival rates for the ILp3pT2 group, the ILp0-2pT2 group and the pT3 group were 56.4 , 51.2 , and 33.4 , respectively. The survival of the ILp3pT2 group was significantly better than that of the pT3 group p 0.013 and similar to that of the ILp0-2pT2 group p 0.415 . The type of operative procedure selected for the treatment of the adjacent lobe invaded by cancer did not significantly influence survival. The locoregional recurrence rate did not substantially differ between the ILp3pT2 group, who underwent a partial resection to treat the adjacent lobe invaded by cancer, and the ILp0-2pT2 group. Conclusion. Our findings indicate that it is appropriate to categorize interlobar pleural invasion to the adjacent lobe as T2 and the optimal operative procedure is considered to be a partial resection of the adjacent invaded lobe. JJLC. 2005;45:1-4 KEY WORDS Lung cancer, Interlobar pleural invasion, Interlobar p3 1 2 2 802-0077 2-1-1