OA03.07 Three-Dimensional Immunofluorescence Analysis of Dynamic Vessel Co-Option of Spread Through Air Spaces (STAS) in Lung Cancer

Comprehensive analysis of spread through air spaces in lung adenocarcinoma and squamous cell carcinoma using the 8th edition AJCC/UICC staging system

BACKGROUND

This study aimed to comprehensively investigate the effect of spread through air spaces (STAS) on clinicopathologic features, molecular characteristics, immunohistochemical expression, and prognosis in lung adenocarcinomas (ADC) and squamous cell carcinomas (SQCC) based on the 8th edition AJCC/UICC staging system.

METHODS

In total, 303 ADC and 121 SQCC cases were assessed retrospectively. Immunohistochemical staining was performed for E-cadherin, vimentin, Ki67, survivin, Bcl-2, and Bim. Correlations between STAS and other parameters were analyzed statistically.

RESULTS

STAS was observed in 183 (60.4%) ADC and 39 (32.2%) SQCC cases. In ADC, the presence of STAS was associated with wild-type EGFR, ALK and ROS1 rearrangements, low E-cadherin expression, and high vimentin and Ki67 expression. In SQCC, STAS was associated with low E-cadherin expression and high vimentin and survivin expression. Based on univariate analysis, STAS was associated with significantly shorter disease-free survival (DFS) and overall survival (OS) in ADC. In SQCC, STAS tended to be associated with shorter OS. By multivariate analysis, STAS was an independent poor prognostic factor in ADC for DFS but not OS. Stratified analysis showed that STAS was correlated with shorter DFS for stage I, II, IA, IB, and IIA ADC based on univariate analysis and was an independent risk factor for DFS in stage I ADC cases based on multivariate analysis.

CONCLUSIONS

Our findings revealed that STAS is an independent negative prognostic factor for stage I ADC using the new 8th edition AJCC/UICC staging system. Stage I patients with STAS should be followed up more closely and might need different treatment strategies.

KRAS Mutations Predict Response and Outcome in Advanced Lung Adenocarcinoma Patients Receiving First-Line Bevacizumab and Platinum-Based Chemotherapy

Bevacizumab, combined with platinum-based chemotherapy, has been widely used in the treatment of advanced-stage lung adenocarcinoma (LADC). Although KRAS (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) mutation is the most common genetic alteration in human LADC and its role in promoting angiogenesis has been well established, its prognostic and predictive role in the above setting remains unclear. The association between KRAS exon 2 mutational status and clinicopathological variables including progression-free survival and overall survival (PFS and OS, respectively) was retrospectively analyzed in 501 Caucasian stage IIIB-IV LADC patients receiving first-line platinum-based chemotherapy (CHT) with or without bevacizumab (BEV). EGFR (epidermal growth factor receptor)-mutant cases were excluded. Of 247 BEV/CHT and 254 CHT patients, 95 (38.5%) and 75 (29.5%) had mutations in KRAS, respectively. KRAS mutation was associated with smoking (p = 0.008) and female gender (p = 0.002) in the BEV/CHT group. We found no difference in OS between patients with KRAS-mutant versus KRAS wild-type tumors in the CHT-alone group (p = 0.6771). Notably, patients with KRAS-mutant tumors demonstrated significantly shorter PFS (p = 0.0255) and OS (p = 0.0186) in response to BEV/CHT compared to KRAS wild-type patients. KRAS mutation was an independent predictor of shorter PFS (hazard ratio, 0.597; p = 0.011) and OS (hazard ratio, 0.645; p = 0.012) in the BEV/CHT group. G12D KRAS-mutant patients receiving BEV/CHT showed significantly shorter PFS (3.7 months versus 8.27 months in the G12/13x group; p = 0.0032) and OS (7.2 months versus 16.1 months in the G12/13x group; p = 0.0144). In this single-center, retrospective study, KRAS-mutant LADC patients receiving BEV/CHT treatment exhibited inferior PFS and OS compared to those with KRAS wild-type advanced LADC. G12D mutations may define a subset of KRAS-mutant LADC patients unsuitable for antiangiogenic therapy with BEV.