Outcome following surgery for primary lung cancer with interlobar pleural invasion

To determine whether interlobar pleural invasion into the adjacent lobe (interlobar P3) should be assessed as T3 according to the tumor-node metastasis classification.

Surgically treated patients with primary lung cancer (n = 322) were analyzed.

Tumors with interlobar P3 had a significantly lower incidence of mass screening detection, a higher occurrence rate of squamous cell carcinoma, and a larger tumor diameter than tumors without interlobar P3. The lymph node metastatic rate did not differ between the patients with and without interlobar P3. The 5-year survival rate of patients with interlobar P3 was 63% and the rates of other patients were 56% with T1 disease, 57% with T2, 31% with T3, and 19% with T4. The survival rate for patients with interlobar P3 was higher than for those with T3 without interlobar P3 (P < 0.05). The 5-year survival rate of the patients with interlobar P3 was lower in adenocarcinoma (39%) than in squamous cell carcinoma (69%, P < 0.01). The results were similar when the analysis was restricted to patients without lymph node metastasis. In adenocarcinoma, the survival rate for interlobar P3 was between the rates for T2 (53%) and T3 (13%) without interlobar P3, whereas in squamous cell carcinoma, the survival rate for interlobar P3 was between the rates for T1 (88%) and T2 (54%) without interlobar P3.

Tumors with interlobar P3 should be classified as T2 only in squamous cell carcinoma.