Should resection extent be decided by total lesion size or solid component size in ground glass opacity-containing lung adenocarcinomas?

BACKGROUND: Indication for sublobar resections in early-stage lung adenocarcinomas has been controversial. The purpose of this study was to find appropriate selection criteria for sublobar resections in ground glass opacity (GGO)-containing early-stage lung adenocarcinomas. METHODS: We retrospectively studied 985 consecutive patients with clinical stage IA, peripheral GGO-containing lung adenocarcinomas ≤3 cm in size. According to their radiological appearance, they were divided into a pure GGO group and a part-solid nodule (PSN) group. The PSN group was further divided into a GGO-predominant subgroup and a solid-predominant subgroup. Propensity-score matching (PSM) was conducted first in PSNs with similar total lesion size and then in those with similar solid component size to eliminate potential confounders. Histological characteristics and prognosis were compared between matched patients to investigate the prognostic value of total lesion size and solid component size. Then solid component size was chosen as the selection criterion to compare the prognosis of patients receiving lobectomy or sublobar resections. RESULTS: Comparing to PSNs, pure GGO lesions had significantly more favorable histological characteristics and prognosis, with 100% 5-year overall survival (OS), even though 33.3% of patients with pure GGO lesions >20 mm in total lesion size received sublobar resections. For 157 pairs of PSNs with similar total lesion size but different solid component size after the first PSM, the solid-predominant subgroup had significantly worse histological characteristics and prognosis than the GGO-predominant subgroup. After the second PSM, histological characteristics and prognosis were comparable between 73 pairs of PSNs with similar solid component size but different total lesion size. Multivariable analysis showed that solid component size, rather than total lesion size or consolidation-to-tumor ratio (CTR), was an independent prognostic factor. For PSNs containing solid component size ≤2 cm, relapse-free survival (RFS) was similar after sublobar resections or lobectomy (95.0% vs. 93.6%, P=0.592). The results remained similar for PSNs of total lesion size >2 cm but solid component size ≤2 cm (88.9% vs. 90.0%, P=0.893). CONCLUSIONS: Solid component size better predicts histological characteristics and prognosis than total lesion size in early-stage GGO-containing lung adenocarcinomas. Instead of total lesion size, solid component size ≤2 cm may be a more appropriate selection criterion for sublobar resections in such patients.