Adjacent lobe invasion of T2 tumor in non-small cell lung cancer has T3 disease-like survival fissure invasion: T2 or T3?

Controversy still exists regarding the staging of non-small cell lung cancer (NSCLC) with adjacent lobe invasion (T-ALI) according to the TNM system in terms of T factor and the appropriate surgical resection method. We performed an analysis to compare the prognosis of T-ALI with T2 and T3 disease and to see the effect of our surgical method for these tumors. Two hundred consecutive patients between January 2012 and November 2020, with anatomical lobectomy for T2 or T3 tumor (Group-1) and non-anatomical lobectomy resection (lobectomy plus wedge resection [LWR]) (Group-2) for T-ALI (T2-ALI and T3-ALI) due to primary NSCLC, who did not have lymph node metastases were analyzed retrospectively. All surgeries were performed by two experienced surgeons who adopted the same surgical technique. Those who underwent additional segmentectomy and bilobectomy due to fissure invasion were excluded from the study. Overall survival rates of all patients were determined and factors affecting survival were evaluated by performing univariate and multivariate analyses. Of the patients with a mean age of 62.2 ± 7.8 years, 175 (87.5%) were male and 25 (12.5%) were female. There were 137 (68.5%) patients in Group 1 and 63 (31.5%) patients in Group 2. The mean tumor size in Group 1 (4.4 ± 1.4 cm) was significantly smaller than that in Group 2 (4.9 ± 1.4 cm) (p = 0.014). When T distribution within the groups was considered, the rate of pathological T3 in Group 1 (33.6%) was significantly lower than that in Group 2 (55.6%) (p = 0.005). While the 5-year overall survival rate was 70.1% in Group 1, it was 50.6% in Group 2 (p = 0.022). When tumors were grouped as T2, T2-ALI, T3, and T3-ALI according to T factor, the 5-year overall survival rates were 71.4% and 67.8% in T2 and T3 tumors, respectively, and 49.2% and 51.5% in T2-ALI and T3-ALI tumors, respectively. In the multivariate analysis of these four groups, the overall survival rates for T2-ALI and T3-ALI were significantly lower than those of T2 tumors (p = 0.046 and p = 0.025, respectively). In the analysis made between the T2 tumor group and the new T3 group (T2-ALI, T3, T3-ALI), which was formed by upgrading T2-ALI tumors to the T3 group, T2 tumors were found to have a significantly better survival rate (p = 0.019). The disease-free survival of pT2 patients and new T3 group patients was statistically significant, 63.7% and 45.7%, respectively (p = 0.050). Our results suggest that LWR for T-ALI can be performed with acceptable oncologic outcomes when compared to anatomical lobectomy. T2-ALI has a worse overall survival than T2 tumor and offers a similar prognosis to T3. Given this situation, it is more appropriate to classify T2-ALI as T3. Further studies based on larger series are needed to confirm these preliminary data.