Prediction for prognosis of resected pT1a-1bN0M0 adenocarcinoma based on tumor size and histological status: relationship of TNM and IASLC/ATS/ERS classifications.

OBJECTIVES

This study aimed to estimate the relationship between 7th TNM classification and IASLC/ATS/ERS classification with regard to tumor size and pathological status and to determine the utility of these classifications for predicting prognosis in resected node-negative adenocarcinoma with tumor size ≤2.0 cm and >2.0-3.0 cm.

MATERIALS AND METHODS

We reviewed 321 pN0M0 lung adenocarcinoma cases resected at Hiroshima University Hospital from January 1991 to December 2010. Histological differences between T1a and T1b based on the IASLC/ATS/ERS classification were estimated and followed by evaluation of overall survival (OS) and recurrence-free interval (RFI) based on differences in tumor size and histological features.

RESULTS

We found 188 cases of pT1a-1bN0M0 (135 T1a, 53 T1b). Pathological T1a tumors included significantly more adenocarcinoma in situ (AIS) cases and minimally invasive adenocarcinoma (MIA) cases than T1b tumors (60.7% vs 18.8%, respectively; p<0.0001), while more invasive adenocarcinoma cases were included in pT1b. By considering the two classifications simultaneously, the 5-year OS rates of T1a AIS/MIA, T1b AIS/MIA, T1a invasive adenocarcinoma, and T1b invasive adenocarcinoma were 97.5%, 87.5%, 95.8%, and 86.8%, respectively. The 5-year RFIs of T1a AIS/MIA, T1b AIS/MIA, T1a invasive adenocarcinoma, and T1b invasive adenocarcinoma were 100%, 100%, 91.3%, and 72.5%, respectively. T1a AIS/MIA and T1b AIS/MIA could be separated as good prognostic cases with a 100% RFI. Multivariate analysis indicated that only T1b invasive adenocarcinoma was an independent factor for predicting recurrence (p=0.001).

CONCLUSION

Compared to a single classification, combining TNM and IASLC/ATS/ERS classifications could provide more detail information concerning disease recurrence. AIS and MIA should be handled equally, regardless of tumor size, because their non-/less invasive status is more useful for predicting prognosis than their tumor size classification. In contrast, the T descriptors based on TNM classification are important for predicting prognosis in invasive adenocarcinoma.