Pleural Contact in Clinical Early-Stage NSCLC: Recurrence Patterns and Survival

Abstract

<h3>Purpose/Objective(s)</h3> Visceral pleural invasion is a pathologic finding utilized for non-small cell lung cancer (NSCLC) staging that portends worse outcomes. There have been efforts to evaluate the utility of radiographic pleural contact as a surrogate for pleural invasion for the purposes of clinical staging. These efforts have produced conflicting results. We sought to contribute to this growing body of data and hypothesized that our cohort would validate previous findings that pleural contact carries prognostic value in early-stage NSCLC treated with stereotactic radiotherapy (SBRT). <h3>Materials/Methods</h3> Following IRB approval, we retrospectively reviewed patients treated with SBRT between 2007 and 2019 at a single institution and identified those treated for early-stage (T1-3N0M0) NSCLC. We stratified this group into tumor with or without evidence of pleural contact on pre-treatment imaging, defined as visible direct abutment of the visceral pleura on computed tomography. We then analyzed the impact of the presence or absence of pleural invasion on treatment outcomes including in-field control (IFC), lobar control (LC), locoregional control (ipsilateral lung + regional nodes) (LRC), distant control (DC), and overall survival (OS). Outcomes were analyzed using the Kaplan Meier method and the influence of pleural contact was assessed with the log-rank method. <h3>Results</h3> We identified 217 courses of SBRT performed for early-stage NSCLC. Pre-treatment imaging was unavailable for review for 29, leaving 188 evaluable courses. The cohort included 149 T1, 29 T2, and 10 T3 tumors, of which 101 had radiographic evidence of pleural contact. Tumors were treated to a median of 50 Gy (range: 48-60) in a median of 4 fractions (range: 3-8). Median follow up was 39.4 months (range: 2.1-137 months). We evaluated cancer outcomes between those with pleural contact and those without and found statistically significant differences in 3-year IFC (85.2% vs 94.6%, p=0.0018), LC (83.0% vs 93.2%, p=0.017), LRC (74.6% vs 89.2%, p=0.03), and DC (76.9% vs 93.5%, p=0.004). Most notably, we found that pleural contact was associated with a significant decrease in 3-year OS (56.1% vs 77.1%, p<0.001). Tumors with pleural contact were larger (median 21 versus 15 mm; p<0.0001) as compared to those without. However, in the subgroup of T1 tumors, pleural contact remained predictive of IFC (p=0.015), DC (p=0.02) and OS (p=0.0004). <h3>Conclusion</h3> Radiographic pleural contact in clinical early-stage NSCLC treated with SBRT is associated with significantly higher locoregional and distant recurrence rates and decreased overall survival. There is growing evidence to suggest pleural contact is of prognostic significance and future studies should focus on ongoing validation in larger patient cohorts. If confirmed, patients with radiographic pleural contact could be considered for treatment intensification strategies.