Should minimally invasive lung adenocarcinoma be transferred from stage IA1 to stage 0 in future updates of the TNM staging system?

BACKGROUND

The 8th International Association Study of Lung Cancer (IASLC) TNM classification staging project for lung cancer has classified patients with adenocarcinoma in situ (AIS) into stage 0, while patients with a minimally invasive adenocarcinoma (MIA) were classified into stage IA1. However, MIA patients, similar to AIS patients, have an approximately a 100% 5-year survival. This study aimed to investigate if MIA could be transferred from stage IA to stage 0 in the next TNM staging system.

METHODS

We retrospectively reviewed 1,524 consecutive patients with a pathologically confirmed AIS, MIA and an invasive adenocarcinoma (IADC) in stage IA1. Disease-free survival (DFS) and overall survival (OS) were analyzed to evaluate survival difference between these three groups.

RESULTS

There were 412 AIS, 675 MIA and 437 IADC patients in stage IA1. No statistically significant differences for DFS and OS (P=0.109) were seen between the AIS and MIA groups. Patients of the IADC group had significantly worse DFS (P=0.003) but the OS rate (P=0.941) was insignificant when compared with the MIA patients. Similar survival results were seen when comparisons were made between the IADC and AIS/MIA groups. The IADC group had a worse DFS (P=0.001) rate but no OS (P=0.380) difference with the AIS/MIA groups.

CONCLUSIONS

Patients with AIS and MIA had similar post-surgical survival rates. We propose that MIA may potentially be transferred from IA1 to stage 0 in the future.