Should tumor with direct adjacent lobe invasion (Tdali) be assigned to T2 or T3 in non-small cell lung cancer: a meta-analysis

Background: The staging of tumor with direct adjacent lobe invasion (Tdali) or interlobar invasion pleural 3 (ILI PL3) in TNM system of non-small cell lung cancer (NSCLC) is still in controversy. We conducted a meta-analysis to compare the prognosis of Tdali with T2 or T3 disease. Methods: PubMed and Embase were searched for relevant studies. Ln hazard ratio (HR) and its standard error (SE) of each study were estimated in the comparison of overall survival (OS) between Tdali and T2 or T3 respectively. Forest plots were used to show the combined HRs. Results: The meta-analysis for comparison of OS of Tdali and T2 or T3 disease both showed a significant HR [Tdali versus T2, 1.39 (1.21, 1.61), P<0.000, Tdali versus T3, 0.73 (0.57, 0.93), P=0.01]. Comparisons of OS of Tdali specified to T2 (Tdali-T2) and that of all patients of T2 or T3 disease also both showed significant HRs [Tdali-T2 versus T2, 1.44 (1.23, 1.69), P<0.000, Tdali-T2 versus T3, 0.77 (0.64, 0.94), P=0.008]. When only analyzing the patients with N0 status, those with Tdali-T2N0 compared to the T2N0 group had a HR of 1.79 (1.37, 2.34) (P<0.000). For those with Tdali-T2N0 compared to the T3N0 group, the HR was 0.98 (0.71, 1.35) (P=0.91). Conclusions: Our meta-analysis showed that the prognosis of Tdali is poorer than T2 disease but similar to T3 disease after controlled for T and N status. We suggest that Tdali should be considered to be upgraded to T3. Our work challenges the current staging system regarding staging of Tdali, which might be important evidence of future revision of Tdali staging. As the malignancy of Tdali has been underrated till now, more attention needs to be drawn to proper treatment of Tdali patients.