Comparing Part-Solid and Pure-Solid Tumors in the TNM Classification of Lung Cancer (Eighth Edition)

In the eighth edition of the TNM classification, the lung tumors that have the same solid components are categorized either as part-solid or pure-solid tumors. However, this is debatable since the tumors in the same T component categories were evaluated without considering this categorization, and was based on a more malignant behavior and a poorer prognosis of pure-solid tumors. The aim of this study was to investigate and compare the prognosis between part-solid and pure-solid tumors.

We retrospectively analyzed 530 patients who were diagnosed with clinical-T1a-cN0M0 non-small-cell lung cancer (NSCLC) and were treated surgically. The subjects were divided into part-solid and pure-solid tumor groups using thin-section computed tomography. The prognosis was compared between the groups.

Although relapse-free survival (RFS) was significantly shorter in the pure-solid tumor group (p = 0.016), no significant differences were observed in the overall survival (OS) between the two groups (p = 0.247). In 137 propensity score-matched pairs, including variables such as age, gender, Brinkman index, body mass index, forced expiratory volume in 1 second/forced vital capacity, Charlson comorbidity index, carcinoembryonic antigen levels, clinical-T status, surgical procedure, and extent of surgery, no significant differences were seen in the RFS and OS between the two groups (p = 0.709 and p = 0.517, respectively).

In the eighth edition of the TNM classification of clinical-T1a-cN0M0 NSCLC, the prognosis of part-solid and pure-solid tumors showed no significant differences. Solid component size of the tumor is considered important prognostic factor in early-stage NSCLC.