Patterns of Failure, Volume of Disease Progression, and Subsequent Ablative Management in Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) Treated with Definitive Chemoradiation and Consolidation Immune Checkpoint Inhibitors (ICI)

PURPOSE/OBJECTIVE(S)

For patients (pts) with LA-NSCLC treated with chemoradiation and consolidation ICI (CRT+ICI), the patterns of failure (POF) and volume of disease progression (PD) are not well characterized. The primary objective of this study was to classify POFs, the frequency of low volume relapse (LVR), and identify pts eligible for further ablative therapy.

MATERIALS/METHODS

We retrospectively identified pts with unresectable stage III NSCLC treated with CRT+ICI between October 2017 and December 2021 at a single institution. Site of first failure was classified as locoregional (LRF), distant (DF), or synchronous LRF + DF. Any LRF was subclassified as in field (IFF; PD within 90% isodose line), marginal (MF; within 50% isodose line) or out of field (OOF; outside of 50% isodose line). LVR was defined as < 3 discrete sites of PD in any number or location of organs. Pts with distant LVR were considered to have oligometastatic relapse. Ablative candidates were defined as pts with < 3 discrete sites of PD amenable to further RT or surgery. Cumulative incidence of PD was calculated with death as a competing risk. Progression free survival (PFS) and overall survival (OS) were calculated from the end of RT and assessed via Kaplan Meier. Multivariable Cox modeling was used to assess correlation of pt characteristics and time-to-event outcomes. Logistic regression was used to predict variables associated with LVR.

RESULTS

A total of 229 pts received CRT+ICI. Median follow up was 39 months and 119 pts experienced PD. Median PFS and OS were 18.4 and 34.5 months, respectively. Of pts with PD, 71 (60%) had DF, 28 (24%) had LRF+DF, and 20 (17%) had LRF. Of pts with any LRF, 28 (57%) had IFF, 10 (21%) had MF, and 10 (21%) had OOF. Estimated 1-year cumulative incidence of LRF, DF, and LRF+DF were 9.3% (95% CI 4.5-16), 39% (95% CI 31-48), and 19% (95% CI 12-27), respectively. A total of 63 (53%) pts had LVR. In pts with LVR, 19 (30%) had isolated thoracic relapse and 44 (69%) had oligometastatic relapse. Most oligometastatic disease was intracranial (22 metastases, 44%). Pts with LVR had a longer median OS vs pts with high volume relapse (37.4 vs 15.2 months, p<0.001). At time of PD, 56 (47%) pts were candidates for further ablative therapies. Subsequent anticancer therapies were local therapy alone (35%), local and systemic therapy (16%), systemic therapy alone (36%), or no therapy (13%). On multivariable analysis, LVR (HR 0.39; 95% CI 0.21-0.73, p = 0.003) and longer receipt of ICI (HR 0.96; 95% CI 0.95-0.98; p<0.001) were associated with improved survival while squamous histology (HR 2.26; 95% CI 1.18-4.32; p = 0.039) was associated with worse survival. Longer receipt of ICI was the only variable predictive for the development of LVR (OR 1.03; 95% CI 1.01-1.05; p = 0.004).

CONCLUSION

This is the largest real-world series reporting POF after CRT+ICI for stage III NSCLC. Approximately half of pts experience LVR and are candidates for further ablative therapy. Further data are needed to define optimal treatment strategies for pts with LVR after CRT+ICI.

Improving comprehensive genotyping in patients with newly diagnosed non-squamous NSCLC: Results from a prospective trial of a behavioral nudge intervention

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Background: Despite current guidelines, less than 50% of patients with metastatic (m) non-squamous (NSq) NSCLC undergo comprehensive molecular genotyping. At our institution, based on improved comprehensiveness of genotyping with use of concurrent tissue (T) and plasma (P) next generation sequencing (NGS), we designed an electronic medical record (EMR)-based “nudge intervention” to auto-generate an order for P NGS at the time of initial consultation, while T NGS was carried out reflexively based on institutional pathways. Methods: A prospective study was conducted at the Abramson Cancer Center and 2 community sites within the University of Pennsylvania Health System after IRB approval. A provider team-focused EMR-based “nudge intervention” was designed to order P NGS at the time of new patient consultation. Eligible patients for the nudge were identified using an EMR based checklist, that included 3 criteria i. newly diagnosed, ii. treatment naïve, iii. mNSq NSCLC. Results from the intervention period (4/2021-12/2021) were compared to baseline data from similar patients treated at our institution between 01/2019 and 03/2021. Categories of NCCN guideline recommended molecular genotyping were defined as: i) comprehensive: EGFR, ALK, BRAF, ROS1, MET, RET, NTRK testing, and ii) incomplete or no testing performed. The proportion of patients with comprehensive molecular genotyping prior to 1st-line therapy were compared in the pre- and post-intervention groups using the chi-square test. Results: 526 patients with mNSq NSCLC were included in this analysis: 381 in the pre-intervention cohort, 145 in the post-intervention cohort. After implementation of the EMR-based nudge, a higher proportion of patients underwent concurrent T+P testing resulting in improved comprehensive molecular genotyping. In addition, a greater proportion of patients had comprehensive genotyping available prior to 1st-line therapy in the post-intervention vs pre-intervention cohort (Table). Conclusions: Across 3 practice sites, a provider team-focused EMR-based nudge intervention was associated with a significantly higher proportion of patients with mNSq NSCLC undergoing comprehensive molecular genotyping, both overall and prior to 1st-line therapy. These findings demonstrate that behavioral, EMR-based nudges can promote guideline concordant diagnostic testing at both community and academic sites and should be studied further as a tool to improve rates of molecular testing in NSCLC.[Table: see text]

Checkpoint inhibitor consolidation after definitive chemoradiation for stage III non–small cell lung cancer: Real-world experience in a large academic health system

8523

Background: The PACIFIC trial demonstrated a 10% improvement in 5-year survival with the addition of consolidation durvalumab versus placebo after chemoradiation (CRT) in good performance status patients (pts) with stage III non-small cell lung cancer (NSCLC). However, not all patients who complete CRT go on to receive consolidation durvalumab. We sought to describe real-world use of consolidation durvalumab or other immune checkpoint inhibitors (ICI) in this setting within a single academic health system. Methods: We retrospectively identified pts with unresectable stage III NSCLC treated with definitive CRT between October 2017 and October 2020 within the University of Pennsylvania Health System, including two urban hospitals and two satellite centers. Pts either received consolidation ICI (ICI group) or did not (no ICI group). Baseline characteristics of the groups were compared with the Chi-squared, Fisher exact, or Wilcoxon rank-sum test as appropriate. Overall survival (OS), measured from the last day of CRT, was compared using the Kaplan-Meier method and log-rank test. Results: Of the 148 consecutively treated pts who completed CRT, 108 (73%) received consolidation ICI; 40 (27%) did not. Within the ICI group, 42% completed 1 year (yr) of treatment. Within the no ICI group, reasons for non-receipt included disease progression (n = 14, 35%), CRT toxicity (n = 7, 18%), comorbidity or decline unrelated to CRT (n = 7, 18%), provider choice (n = 6, 15%) due to EGFR mutation (n = 5) or atypical histology (n = 1), pt refusal (n = 3, 8%), and death without progression (n = 3, 8%). The ICI group had better performance status (ECOG 0/1/2, 46%/49%/5% ICI vs 25%/48%/28% no ICI, p < 0.001) lower Charlson Comorbidity Index (median, 5 [IQR 4-6] ICI vs 6 [IQR 5-8] no ICI, p = 0.02), and lower rates of active autoimmune disease or immunosuppression (5% ICI vs 15% no ICI, p = 0.03). There were no differences between groups in age (median, 68 yrs [IQR 63-73] ICI vs 71 yrs [IQR 65-73] no ICI, p = 0.25), sex (female, 60% ICI vs 50% no ICI, p = 0.27), race (Black, 19% ICI vs 20% no ICI, p = 0.82), stage (IIIA/B/C, 42%/48%/11% ICI vs 40%/50%/10% no ICI, p = 0.96), and PD-L1 expression ( < 1%/1-50%/ > 50%/unknown, 36%/25%/29%/10% ICI vs 40%/25%/28%/8% no ICI, p = 0.97). 1- and 2-yr OS were 83% and 61% in the ICI group versus 52% and 34% in the no ICI group, respectively (p < 0.001). Within the no ICI group, OS was worse among those with versus those without disease progression (PD) post-CRT (1-yr OS 24% vs 74%, p = 0.03). Conclusions: In this retrospective study within a large academic health system, we found that over one-quarter of pts who completed chemoradiation for stage III NSCLC did not receive consolidation ICI, most commonly due to disease progression, CRT toxicity, or comorbidity. Survival amongst these pts is particularly poor, especially for those who experience PD shortly after CRT.

Association of comprehensive molecular genotyping and overall survival in patients with advanced non-squamous non-small cell lung cancer

9022

Background: Current guidelines recommend comprehensive molecular genotyping for newly diagnosed patients (pts) with metastatic non-squamous (non-Sq) NSCLC. We have previously demonstrated that concurrent plasma (P) and tissue (T) based next-generation sequencing (NGS) improves detection of clinically actionable mutations in pts with advanced NSCLC. We analyzed the impact of concurrent T+P NGS on comprehensiveness of molecular genotyping and on overall survival (OS). Methods: A retrospective cohort study of pts with newly diagnosed stage IV non-Sq NSCLC who received therapy at our institution between 01/2019 and 12/2020 was performed. Categories of NCCN guideline testing were defined, i) comprehensive: EGFR, ALK, BRAF, ROS1, MET, RET, and NTRK testing, ii) incomplete: 2-6 genes tested, and iii) no testing performed. The proportion of pts with comprehensive molecular testing performed, prior to 1st-line therapy and by detection modality (T NGS vs. T+P NGS), were compared using Fisher’s exact test. Median OS was estimated using Kaplan-Meier methodology from diagnosis to death or censored at most recent follow-up. Results: 335 patients were included in this analysis, 98.5% (330/335) underwent molecular testing: either comprehensive: n = 291 (86.9%), incomplete testing: n = 39 (11.6%); or no testing n = 5 (1.5%). Testing with T NGS was completed in 32.7% (108/330); 67.2% (222/330) underwent concurrent T+P NGS. These groups were well balanced for baseline characteristics, with the exception of a higher number of never smokers in T+P vs. T NGS (30.2% vs. 14.8%, p < 0.0001). Proportion of pts with comprehensive molecular testing was higher among pts with T+P NGS: 99.5% (221/222) vs. T NGS: 64.8% (70/108), p < 0.0001. All pts with T+P NGS testing had results available prior to 1st line therapy; 100% (204/204) compared to 60.7% (51/84) for T NGS, p < 0.0001. With median follow up of 20.5 months (mos, range 0.3 - 33.1), median OS was 18.6 mos. Median OS for pts tested with T+P NGS vs T alone was numerically longer at 23.2 vs. 14.1 mos, but not statistically significant (p = 0.078). However, regardless of testing modality, patients with comprehensive molecular genotyping had superior OS compared to those with incomplete or no testing (22.1 mos vs. 11.6 mos, p = 0.017). The institution of oral targeted therapy had no bearing on this difference in OS (test for interaction, p = 0.6509). Conclusions: Performance of concurrent T+P NGS testing was associated with a higher likelihood of comprehensive molecular genotyping, as well as improved availability of results, including prior to first line therapy. Patients with comprehensive genotyping have improved OS compared to patients with incomplete or no testing. These results support implementation of a concurrent T+P NGS approach upon initial diagnosis of metastatic non-Sq NSCLC.

Analysis of MET exon 14skippingmutations in non–small cell lung cancer (NSCLC) by histology and specific mutation

9119

Background: MET exon 14 skipping mutations (METex14) join a growing list of viable therapeutic targets in advanced NSCLC. Several unique features distinguish METex14 from other established targets. METex14 has been characterized as a tumor-agnostic genomic alteration, though most frequently reported in lung adenocarcinoma. However, METex14 represents a family of mutations (mt), not a single alteration, and there is notable heterogeneity in histology. The degree and significance of heterogeneity within METex14 have not been well characterized. Methods: NSCLC tissue samples were analyzed with DNA-based next-generation sequencing (NGS; 592 genes, NextSeq) or whole-exome sequencing (NovaSeq), RNA-based whole transcriptome sequencing (WTS, NovaSeq), and immunohistochemistry (IHC) at Caris Life Sciences (Phoenix, AZ). PD-L1 expression utilized the 22C3 clone (Dako); TMB-high was defined as ≥ 10 mt/Mb. Wilcoxon or Fisher’s exact were used to determine statistical significance (p without and q with multi comparison correction). Immune cell fraction (QuanTiseq) and pathway analysis (ssGSEA) were informed by WTS analysis. Results: A total of 440 METex14 cases were identified: 49 (11.1%) with squamous histology, 381 (86.6%) with non-squamous histology, and 10 (0.2%) with adenosquamous histology. A total of 147 distinct METex14 mutations were detected. The most common METex14 mutations were D1028H (8.4%), D1028N (7.0%), c.3082+2T > C (5.7%), D1028Y (5.2%), and c.3082+1G > A (4.5%). Co-mutations in TP53 were common (43.9%) but varied by specific METex14 mutation; TP53 co-mutations were observed in 53.9% of c.3082+3A > T but only 21.1% of c.3082+1G > T. Among all METex14 cases, 8.6% were TMB-high, but this varied by specific mutation with a median TMB of 2 mt/Mb in MET c.3082+2T > A and a median of 7 mt/Mb in MET c.3082+1G > C (q < 0.05). PD-L1 expression ≥ 1% was present in 82.2% of METex14 samples but also varied by specific METex14 mutation with a median PD-L1 tumor proportion score (TPS) of 97.5% in MET c.3082+1G > C and a median TPS of 0% in MET c.3082+3A > G (q < 0.05). Co-mutations varied by histology: in squamous METex14, 90.4% had TP53 mt (p < 0.001), 17.9% had KMT2D mt (p < 0.05), and 10.7% had PIK3CA mt (p < 0.05), while in non-squamous METex14, 60.7% had TP53 mt, 2.7% had KMT2D mt, and 4.3% had PIK3CA mt. Survival was numerically shorter in squamous METex14 NSCLC compared to non-squamous (HR 1.22, p = 0.47, mOS 336 vs.1106 days). Conclusions: There is significant heterogeneity within METex14 NSCLC with differences in co-mutations, TMB, and PD-L1 expression noted among different METex14 mutations. While METex14 is detected in both squamous and non-squamous NSCLC, there are differences in enrichment of oncogenic pathways. The clinical impact of these differences warrants further investigation.

Clinical activity of pembrolizumab monotherapy in diffuse malignant peritoneal mesothelioma

8557

Background: Among patients with malignant mesothelioma, pembrolizumab has demonstrated activity in diffuse pleural mesothelioma (DPM), with limited data available for those with diffuse malignant peritoneal mesothelioma (DMPM). DMPM represents a clinically distinct entity from DPM and disease specific outcomes data is needed. We present real world data on the efficacy of pembrolizumab in DMPM. Methods: In this retrospective study, we identified patients with DMPM treated with pembrolizumab at two tertiary care cancer centers between 1/1/2009 and 1/1/2021. Clinicopathologic features were annotated. Median progression free survival (mPFS) and median overall survival (mOS) were calculated using Kaplan-Meier curves. Best overall response rate (BOR) was determined using RECIST 1.1 criteria. Association of partial response with disease characteristics was evaluated using Fisher’s exact test. Results: We identified 24 patients with DMPM who received pembrolizumab (median age 62 years, 63% never smokers, 58% female, 75% had epithelioid histology). All patients received systemic chemotherapy prior to pembrolizumab (median prior lines of therapy: 3). BOR was 17% (3 partial responses, 10 stable disease, 5 progressive disease, 6 lost to follow-up). With a median follow up time of 29.2 months, mPFS was 4.9 months and mOS 20.9 months from pembrolizumab initiation. Three patients experienced PFS of > 2 years. Among the 14 patients who underwent next generation sequencing of tumor tissue, there were 8 somatic BAP1 alterations. Among the 17 patients tested for PDL1, 6 had positive PDL1 expression (1-80%). There was no association between partial response and presence of a BAP1 somatic alteration (p = 0.453), PDL1 positivity (p = 0.7) or non-epithelioid histology (p = 0.55). Conclusions: Pembrolizumab is active in a PDL1 unselected cohort of patients with DMPM. The overall response rate of 17% and mPFS of 4.9 months in this 75% epithelioid histology cohort warrants further investigation to identify those most likely to respond to immunotherapy, especially among epithelioid histology.

Treatment patterns and outcomes in ALK or ROS1 altered NSCLC: An ATOMIC Registry Study

9077

Background: New tyrosine kinase inhibitors (TKIs) targeting ALK and ROS1 alterations in non-small cell lung cancer (NSCLC) have emerged over the last decade. Given the rarity of these genetic changes in NSCLC, data on long term outcomes with sequential therapies are limited. Methods: We conducted a multicenter retrospective cohort study of patients with metastatic NSCLC and ALK or ROS1 alterations across 12 Academic Thoracic Oncology Medical Investigators Consortium (ATOMIC) sites between 1/29/2007 and 3/31/2021. Data were abstracted from the electronic medical record. Median time to treatment discontinuation (TTD) of 1st TKI, overall survival (OS), and time to brain metastases were estimated using Kaplan-Meier methodology from start date of 1st TKI. Results: 566 patients with ALK (n = 464) or ROS1 (n = 102) were included. The majority (ALK: 426/464, 92%; ROS1: 88/102, 86%) received a TKI at some point during therapy (1st line TKI n = 262 ALK, 48 ROS1). Crizotinib was the most common 1st TKI (ALK: 57%; ROS1: 88%). Following crizotinib, alectinib (64%) and lorlatinib (41%) were the most common subsequent TKIs for ALK and ROS1, respectively. Alectinib (38%) and entrectinib (10.2%) were the 2nd most common initial TKIs used in ALK and ROS1, respectively. Additional treatment patterns presented in table. With a median follow up time of 31.1 (ALK, 95% CI, 27.6-35.0) and 32.6 (ROS1, 95% CI, 25.7-39.6) months, median OS from start of 1st TKI was 53.3 (ALK, 95% CI, 40.0-68.9) and 42.0 (ROS1, 95% CI, 31.8-NA) months. Out of the 321 patients with brain imaging prior to 1st line therapy, 40% (105/262, ALK) and 39% (23/59, ROS1) had CNS disease. Median time to development of brain metastases from start of 1st TKI in those without previous CNS disease (ALK: 278; ROS1: 58) was 30.0 (ALK, 95% CI, 25.3-39.1) and 27.0 (ROS1, 95% CI, 18.2-NA) months. Median TTD of 1st TKI was 11.2 (ALK) and 10.8 (ROS1) months. Conclusions: This is the largest retrospective cohort of NSCLC patients with ALK or ROS1 rearrangements treated in the real world setting. CNS metastases are common and subset analyses by agent and by year of diagnosis will be presented. Median time to CNS metastasis of > 2 years supports revision of the NCCN guidelines to include regular surveillance brain MRIs in this population. [Table: see text]

Incorporation of plasma-based next-generation sequencing to improve guideline-concordant molecular testing in patients with newly diagnosed metastatic nonsquamous non-small cell lung cancer

14

Background: Current NCCN guidelines recommend comprehensive molecular profiling for all newly diagnosed patients with metastatic non-squamous NSCLC to enable the delivery of personalized medicine. We have previously demonstrated that incorporation of plasma based next-generation gene sequencing (NGS) improves detection of clinically actionable mutations in patients with advanced NSCLC (Aggarwal et al, JAMA Oncology, 2018). To increase rates of comprehensive molecular testing at our institution, we adapted our clinical practice to include concurrent use of plasma (P) and tissue (T) based NGS upon initial diagnosis. P NGS testing was performed using a commercial 74 gene assay. We analyzed the impact of this practice change on guideline concordant molecular testing at our institution. Methods: A retrospective cohort study of patients with newly diagnosed metastatic non-squamous NSCLC following the implementation of this practice change in 12/2018 was performed. Tiers of NCCN guideline concordant testing were defined, Tier 1: complete EGFR, ALK, BRAF, ROS1, MET, RET, NTRK testing, Tier 2: included above, but with incomplete NTRK testing, Tier 3: > 2 genes tested, Tier 4: single gene testing, Tier 5: no testing. Proportion of patients with comprehensive molecular testing by modality (T NGS vs. T+P NGS) were compared using one-sided Fisher’s exact test. Results: Between 01/2019, and 12/2019, 170 patients with newly diagnosed metastatic non-Sq NSCLC were treated at our institution. Overall, 98.2% (167/170) patients underwent molecular testing, Tier 1: n = 100 (59%), Tier 2: n = 39 (23%), Tier 3/4: n = 28 (16.5%), Tier 5: n = 3 (2%). Amongst these patients, 43.1% (72/167) were tested with T NGS alone, 8% (15/167) with P NGS alone, and 47.9% (80/167) with T+P NGS. A higher proportion of patients underwent comprehensive molecular testing (Tiers 1+2) using T+P NGS: 95.7% (79/80) compared to T alone: 62.5% (45/72), p < 0.0005. Prior to the initiation of first line treatment, 72.4% (123/170) patients underwent molecular testing, Tier 1: n = 73 (59%), Tier 2: n = 27 (22%) and Tier 3/4: n = 23 (18%). Amongst these, 39% (48/123) were tested with T NGS alone, 7% (9/123) with P NGS alone and 53.6% (66/123) with T+P NGS. A higher proportion of patients underwent comprehensive molecular testing (Tiers 1+2) using T+P NGS, 100% (66/66) compared to 52% (25/48) with T NGS alone (p < 0.0005). Conclusions: Incorporation of concurrent T+P NGS testing in treatment naïve metastatic non-Sq NSCLC significantly increased the proportion of patients undergoing guideline concordant molecular testing, including prior to initiation of first-line therapy at our institution. Concurrent T+P NGS should be adopted into institutional pathways and routine clinical practice.

A single-center retrospective cohort study evaluating the role of neoadjuvant chemotherapy in malignant peritoneal mesothelioma

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Background: Malignant peritoneal mesothelioma (MPM) is a rare variant of malignant mesothelioma, representing < 30% of cases. Standard of care is cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) when feasible. The benefit of systemic chemotherapy (chemo) (Neoadjuvant- N, Adjuvant- A, or 1st-line metastatic –M) is not well established and some retrospective studies report worse outcomes with N chemo. However, our institution has favored use of N chemo prior to surgery for symptom relief and surgical optimization. We conducted a single-center retrospective cohort study of MPM patients treated at our institution to evaluate the effect of N vs. A chemo on outcomes. Methods: We identified non-papillary MPM patients via ICD9/10 codes seen at our institution between 1/1/2009 and 9/1/2019. Pts were followed until 1/1/2020. Patients without pathologic diagnosis were excluded. We explored the effect of receipt of CRS, type of systemic therapy, and histology on overall survival. Median overall survival (mOS) from diagnosis was estimated from Kaplan-Meier curves. A Cox proportional hazard model computed hazard ratios (HR) to assess the effect of the exposure on OS. Results: We identified 47 patients with non-papillary MPM: median age 62 years, 77% epithelioid histology, 74.5% white, 55.3% known asbestos exposure. CRS was performed in 24 (51%) and 18/24 (75%) received HIPEC. The majority received systemic therapy (34/47 (72%)). Among those that received chemo and surgery, N chemo was more common than A chemo (N:12 (all platinum/pemetrexed), A:7). Median OS was 52.7 months (mo) overall and 77.2 mo with surgery vs 20.2 mo without (log rank p = 0.006). Toxicity from N chemo did not prevent surgery with 8/12 successfully receiving surgery (1 surgery scheduled, 2 lost to follow up). Of the 10 pts with evaluable scans: 5 had radiographic reduction of disease (2 complete responses by RECIST 1.1), 4 stable disease and 1 with disease growth. N chemo reduced ascites in 3 out of 4 pts with baseline ascites. N chemo was not associated with worse mOS compared to A chemo (HR 0.64, 95% CI 0.1-3.0, p = 0.62). Non-epithelioid histology was not associated with a worse OS compared to epithelioid (HR 1.5, 95% CI 0.6-4.1, p = 0.4). Conclusions: N chemo was not associated with worse outcomes compared to A chemo and toxicity from N chemo did not preclude surgery. In addition, N chemo resulted in reduction of disease burden and ascites in pts with MPM.

Outcomes in patients with metastatic non-small cell lung cancer (mNSCLC) with brain metastases treated with pembrolizumab-based therapy

9599

Background: Patients (pts) with mNSCLC with active brain metastases (BM) are often excluded from clinical trials; data on efficacy and safety of immunotherapy in this population are limited. We compared outcomes of pts with mNSCLC with and without BM who received pembrolizumab-based therapy. Methods: We conducted a retrospective single-center study of pts with mNSCLC treated with pembrolizumab (P) with or without chemotherapy. Progression-free survival (PFS) and overall survival (OS) were determined by Kaplan-Meier methodology and compared using multivariable Cox regression and log rank testing. Results: We identified 587 consecutive pts with mNSCLC who began P-based therapy between 8/2013 and 12/2018: 306 (52%) female, median age 67 years (range 32-98), 437 (74%) adenocarcinoma, and 508 (87%) former/current smokers. 388 (66%) patients received P in first line therapy, and 334 (57%) received single-agent P. 131 pts (22%) had detectable BM at baseline (start of P-based therapy). Pts with BM were younger (median 65 y vs 68 y, p < 0.01) and more likely to have adenocarcinoma (86% vs. 71%, p < 0.01) and baseline steroid use (22% vs 1%, p < 0.01). Presence of BM did not differ by race, sex, line of therapy, treatment regimen, or PD-L1 status. Of the 131 patients with detectable BM on pre-treatment brain MRI, 55 (42%) had stable BM as a result of prior local therapy, while 76 (58%) had active (new or growing) BM on pre-treatment imaging. Most patients with active BM underwent radiation therapy (RT) in either the 30 days before (n = 46) or 30 days after (n = 17) P start; of the remaining 13 treated with P-based therapy alone, intracranial responses included 2 CR, 2 PR, 3 SD, and 4 PD. As of 1/1/2020, with 15-month median follow up, there was no difference in mPFS (9.2 vs 7.3 months, p = 0.41) or mOS (18.3 vs 18.0 mo, p = 0.67) between pts with and without BM in our P-treated cohort. On multivariable analysis, female sex, ECOG 0-1, adenocarcinoma histology, and P as first line therapy were associated with improved PFS and OS. Presence of BM, baseline steroid use, and timing of local RT (before vs. after P) were not associated with inferior survival. Conclusions: In our single-center experience of pts with mNSCLC treated with P, pts with and without BM had similar PFS and OS. We observed several intracranial responses to P-based therapy alone, but most pts with active BM underwent local RT. mNSCLC pts with BM should be considered for P-based therapy; BM may be treated with RT immediately before or even after P with similar survival outcomes.

Real-world outcomes after second-line treatment in non-small cell lung cancer (NSCLC) patients treated with immunotherapy

e21620

Background: In patients (pts) with advanced non-small cell lung cancer (NSCLC), national guidelines recommend against retrial of immunotherapy (IO) if there is disease progression on IO in the 1st-line (1L). However, optimal 2nd-line (2L) therapy after 1L IO remains unclear and there is significant practice variation. We compared outcomes of 2L approaches after 1L IO or chemoimmunotherapy (chemoIO). Methods: This retrospective cohort study utilized the Flatiron Health EHR-derived de-identified advanced NSCLC database. The study population included pts with disease progression on 1L IO or chemoIO and who subsequently received 2L therapy. Pts with targetable alterations were excluded. We defined the exposure by type of 2L therapy (IO, chemoIO, chemo). Multivariate covariates included age, sex, race, 1L progression-free survival (PFS) and PDL1 level. Median overall survival (mOS) and median real-world PFS (mPFS, based upon abstraction of clinician documentation) times were estimated from Kaplan-Meier curves. A multivariate Cox proportional hazard model computed hazard ratios (HRs) to assess the effectiveness of 2L treatment. Results: 532 NSCLC pts received 1L IO and a 2L therapy, of which 393 (74%) received 1L IO and 139 (26%) received 1L chemoIO. Among 1L IO patients, 2L therapies included chemo (315 (80%)), IO (39(10%), 18/39 (46%) switched IO), and chemoIO (39(10%)). Among 1L chemoIO patients, 2L therapies included: chemo (121 (87%)), IO (8(6%), 6/8 switched IO) and ChemoIO (10 (7%), 8/10 changed chemo used). All pts who received 2L ChemoIO continued the same IO agent. Demographics were well balanced between 2L groups except for higher PDL1 level in the IO-based groups and older age in the IO alone group. There was no statistically significant difference in mPFS or mOS between 2L IO and non-IO containing regimens (Table), nor were there differences among patients switching IO agents in the 2L (multivariate p interaction = 0.2 (PFS), 0.06 (OS)) (Table). Conclusions: Despite national guidelines against this practice, a small proportion of pts in routine care receive 2L IO-based therapies after disease progression on 1L IO or chemoIO. We found similar outcomes between IO and non-IO based 2L therapies after progression on 1L IO or chemoIO. [Table: see text]

Real-world outcomes of pembrolizumab in peritoneal mesothelioma

e21094

Background: Clinical trials evaluating pembrolizumab (P) in malignant mesothelioma (MM) have included small numbers of peritoneal MM (MPM) patients (pts), but the efficacy of P in the MPM subpopulation remains unclear. We evaluated the efficacy of P in a cohort of MPM pts treated at our institution. Methods: This retrospective cohort study identified MPM pts via ICD9/10 codes seen at our institution between 1/1/2009 and 9/1/2019. Pts were included if they received P as treatment for MPM. Median progression free survival (PFS) and median overall survival (mOS) were estimated from Kaplan-Meier curves. PFS was defined as the start of P until radiologic or clinical progression. Best overall response rate (BOR) and disease control rate (DCR) were determined retrospectively using RECIST 1.1 criteria. Results: We identified 13 non-papillary MPM pts who received P. All pts had received prior chemotherapy (12 platinum/pemetrexed, 1 pemetrexed). Median age at diagnosis was 65.6 years; 77% were white; 46% never smokers; 62% with known asbestos exposure; 70% epithelioid/15% biphasic/ 7.7% sarcomatoid/ 7.7% desmoplastic. BOR to P was 18% (Partial response (PR): 2, Progressive disease (PD): 2, Stable disease (SD): 7, Lost to follow up: 2). DCR was 81% and mPFS 5.7mo. From the start of P mOS was 20.9 mo. Only 3 pts had known PDL1 positivity (1%, 2%, 80%), 4 were negative, 6 untested. Median PFS was not statistically different between PDL1 positive and negative pts (mPFS 5.1mo vs. 5.7 mo, log rank p = 0.73, respectively). Three pts experienced a PFS of > 2 years (PDL1/BOR/% tumor change: Unknown/SD/19%, Negative/SD/-21%, 80%/PR/-70%). The patient with PDL1 80%, biphasic histology and a PR experienced skin toxicity requiring a treatment break. Outcomes for epithelioid histology vs non-epithelioid after P did not differ statistically (mPFS 5 mo vs 39 mo, log rank p = 0.14; mOS 17.5 mo vs NA, log rank p = 0.31). Conclusions: In a real world setting, P has clinically meaningful activity in a PDL1 unselected cohort of MPM pts and should be considered a treatment option for this subpopulation of MM. We did not detect a difference in outcomes based on PDL1 level or histology.

Association of STK11/LKB1 genomic alterations with lack of benefit from the addition of pembrolizumab to platinum doublet chemotherapy in non-squamous non-small cell lung cancer

102

Background: Addition of pembrolizumab (P) to platinum-doublet chemotherapy [carboplatin (or cisplatin) and pemetrexed (CP)] prolongs overall survival and is a standard of care (SOC) for the 1st line treatment of metastatic EGFR/ALK wild-type (wt) non-squamous non-small cell lung cancer (mnsNSCLC). Despite widespread adoption of the CPP regimen, molecular determinants of clinical benefit from the addition of P to CP remain poorly defined. We previously identified genomic alterations in STK11/LKB1 as a major driver of primary resistance to PD-1/PD-L1 blockade in mnsNSCLC. Here, we examine the impact of STK11/LKB1 alterations on clinical outcomes with CPP chemo-immunotherapy. Methods: 497 pts with mnsNSCLC and tumor genomic profiling encompassing STK11/LKB1 from 17 academic institutions in the US and Europe were included in this study. Clinical outcomes were collected for two distinct patient cohorts: a) 377 pts treated with first-line CPP (or > 1st line following FDA-approved TKIs) that were alive for 14 days thereafter and b) 120 STK11/LKB1-mt pts that received CP prior to regulatory approval of CPP. Results: Among 377 CPP-treated pts, STK11/LKB1 genomic alterations (N = 102) were associated with significantly shorter PFS (mPFS 4.8m vs 7.2m, HR 1.5, 95% CI 1.1 to 2.0; P = 0.0063) and shorter OS (mOS 10.6m vs 16.7m, HR 1.58, 95% CI 1.09 to 2.27; P = 0.0083) compared with STK11/LKB1-wt tumors (N = 275). ORR also differed significantly between the two groups (32.6% vs 44.7%, P = 0.049). Similar results were obtained when limiting the analysis to EGFR and ALK-wt tumors (N = 333). Importantly, in pts with STK11/LKB1-mt mnsNSCLC, addition of pembrolizumab to CP did not improve PFS (mPFS 4.8m vs 4.3m, HR 1.13, 95% CI 0.83 to 1.54, P = 0.75) or OS (mOS 10.6m vs 10.3m, HR 1.03, 95% CI 0.71 to 1.49, P = 0.79) compared to CP alone. Conclusions: In mnsNSCLC, STK11/LKB1 alterations define a subgroup of pts with inferior clinical outcomes with CPP and lack of benefit from the addition of pembrolizumab to CP chemotherapy. Novel therapeutic strategies are required to establish effective antitumor immunity in STK11/LKB1-mutant NSCLC.