What is an Adequate Margin During Sublobar Resection of ≤3cm N0 Subsolid Lung Adenocarcinomas?

BACKGROUND Sublobar resection offers non-inferior survival vs. lobectomy for ≤2cm NSCLC and is commonly employed for subsolid tumors. While data exists for solid tumors, the minimum adequate margin of resection for subsolid adenocarcinomas remains unclear. METHODS Retrospective review of 1101 adenocarcinoma resections at our institution, 2006-2022. Inclusion criteria: tumors≤3cm with ≥10% radiographic ground glass, excised by sublobar resection. Exclusions: positive nodes, positive or unreported margin. The primary outcome was rate of local recurrence(LR) at multiple thresholds of margin distance. Relationship between margin distance and solid-component size was also explored. RESULTS 194 patients met inclusion criteria. Median(IQR) tumor diameter and margin distance were 12(9-17)mm and 10(5-17)mm, respectively. Median follow-up was 42.5 months. There was a progressive increase in LR with diminishing margin (0.1cm decrements) from 1.5cm to 0.5cm. The difference in the rate of LR between “over”(n=143) and “under”(n=51) was most significant at 0.5cm [8/51(15.7%) vs. 6/143(4.2%),p=0.01] but did not reach α adjusted for multiple comparisons. On Cox regression for LR-free survival (LRFS), margin ≤0.5cm(p=0.19) and %solid component (p=0.14) trended to significance. Combining these using margin-distance-to-solid-component-size ratio, a ratio≤1 did show a significantly higher rate of local recurrence [7(14.3%) vs. 2(2.0%),p=0.009]. Treatment of local recurrences provided at least intermediate-term survival in 87% of recurrences (median post-recurrence follow-up 44 months). CONCLUSIONS During sublobar resection of subsolid lung adenocarcinomas, margin-to-solid-component-size ratio>1.0 appears to be a more reliable factor than margin distance alone to minimize local recurrence. Local recurrence, however, may not impact survival in patients with subsolid adenocarcinomas if timely treatment is administered.