Clinical outcomes of a quadruplet regimen (immunotherapy, chemotherapy, anti-angiogenic therapy) in non-small cell lung cancer with exon 20 insertion mutations: a case series.

Introduction
Epidermal growth factor receptor (EGFR) exon 20 insertion (ex20ins) mutations constitute a distinct and challenging subtype of non-small cell lung cancer (NSCLC), characterized by primary resistance to early-generation EGFR tyrosine kinase inhibitors (TKIs) (1). Although amivantamab combined with chemotherapy and sunvozertinib are now established standards, their high costs can limit accessibility (2,3). While immunotherapy combined with chemotherapy is a cornerstone of NSCLC treatment, its efficacy in EGFR ex20ins-mutated disease is limited (4). Consequently, there remains an unmet need for effective and accessible strategies. The IMpower150 (5) and ORIENT-31 (6) trials demonstrated that adding an anti-angiogenic agent to immunotherapy and chemotherapy can improve outcomes in EGFR-mutant NSCLC, providing a rationale for evaluating this quadruplet approach in the ex20ins subset. Therefore, we conducted this case series to describe the clinical outcomes and safety of this regimen in patients with EGFR ex20ins-mutated NSCLC. We present this article in accordance with the AME Case Series reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-242/rc).

Case presentation
This retrospective, multi-center case series consecutively enrolled eligible patients with advanced or recurrent EGFR ex20ins-mutated NSCLC from the First and Fifth Medical Centers of the Chinese PLA General Hospital between January 2015 and June 2023. Inclusion criteria were: (I) age ≥18 years; (II) histologically confirmed advanced or metastatic NSCLC; (III) tumor harboring an EGFR ex20ins mutation; and (IV) receipt of at least one cycle of the defined quadruplet regimen. Exclusion criteria included incomplete medical records or a concurrent active malignancy. Six patients were included. All procedures performed in this study were in accordance with the Declaration of Helsinki and its subsequent amendments. The study protocol was reviewed and approved by the Ethics Committee of the Fifth Medical Center of Chinese PLA General Hospital (approval No. KY-2025-1-12-1). Written informed consent was obtained from all patients for the publication of this case series and accompanying images. A copy of the written consent is available for review by the editorial office of this journal. This case series was registered in the Research Registry (ID: researchregistry11693).
The cohort consisted of four males and two females, with a mean age of 56.5 years. All patients had stage IV lung adenocarcinoma, and the majority (four out of six) had no history of smoking. The EGFR ex20ins mutation was confirmed by next-generation sequencing (NGS) or polymerase chain reaction (PCR). It should be noted that PCR assays are typically designed to identify common, predefined mutations; therefore, for patients tested solely by PCR, the precise ex20ins variant could not be specified. Detailed demographics and baseline characteristics are summarized in Table 1.
All patients received a quadruplet regimen consisting of immunotherapy (pembrolizumab 200 mg, camrelizumab 200 mg, atezolizumab 1,200 mg, or sintilimab 200 mg, administered intravenously every 3 weeks), platinum-based chemotherapy (pemetrexed/carboplatin or nab-paclitaxel/carboplatin, every 3 weeks), and bevacizumab (7.5 mg/kg every 3 weeks). Treatment continued until disease progression, unacceptable toxicity, or patient withdrawal. The quadruplet regimen was predefined and consistent for all patients. There were no protocol-mandated changes to the drug combinations or dosing schedules based on accumulating experience. However, as outlined in the treatment protocol, individual dose modifications, delays, or interruptions were permitted and implemented at the treating physician’s discretion to manage treatment-related adverse events (TRAEs), in accordance with standard clinical guidelines and each drug’s prescribing information. Given the small sample size and retrospective nature of this series, no major iterative learning that led to a formal evolution of the treatment strategy was identified.
Tumor response was assessed by contrast-enhanced computed tomography (CT) scans or every two treatment cycles according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. TRAEs were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.
As of the data cutoff on June 16, 2025, disease progression had occurred in five of the six patients. The quadruplet regimen was associated with antitumor activity in this cohort. Four out of six patients achieved a partial response (PR), one had stable disease (SD), and one had progressive disease (PD). The median progression-free survival (PFS) for the entire cohort was 14.7 months [95% confidence interval (CI): 2.1–27.3] (Figure 1). First-line patients (n=4) had a median PFS of 14.7 months (95% CI: 5.0–24.3). The two second-line patients had PFS of 2.0 and 49.4 months, respectively.
The regimen exhibited a manageable safety profile (Figure 2). Hematological toxicities (neutropenia and anemia) occurred in all six patients. Non-hematological TRAEs included hypertension (in five of the six patients), gastrointestinal reactions (in three of the six patients), and abnormal liver function (in two of the six patients). No grade three or higher TRAEs occurred, and no treatment discontinuations were due to toxicity.
By the last follow-up, two patients had died. The median overall survival (OS) was not reached (Figure 3), with a mean OS of 34.2 months (95% CI: 17.5–50.9).
Case 1 (patient 5): a 70-year-old female never-smoker was diagnosed with stage IV lung adenocarcinoma harboring an EGFR ex20ins mutation (p.D770_N771>NPH), along with co-mutations in FLT3, TP53, and PPP1R15A. She initially received first-line afatinib, achieving a PFS of 13.1 months. Upon radiographic progression, second-line therapy with a quadruplet regimen consisting of pemetrexed, carboplatin, bevacizumab, and sintilimab was initiated. Early tumor shrinkage was observed on the first follow-up CT scan after two cycles (Figure 4). This response was later confirmed as a durable PR, resulting in a PFS of 49.4 months from the start of quadruplet therapy. TRAEs were all grade one (neutropenia, anemia, hypertension) and were easily managed without treatment interruption.
Case 2 (patient 4): a 67-year-old male with a significant 30-year smoking history and a medical history of type 2 diabetes mellitus was diagnosed with stage IV lung adenocarcinoma harboring an EGFR ex20ins mutation (p.A767_V769delinsASVD). No concomitant mutations were detected in STK11 or KEAP1. He initially received first-line therapy with sunvozertinib, achieving a PFS of 10.2 months. Upon disease progression, he was initiated on a second-line quadruplet regimen consisting of nab-paclitaxel, carboplatin, bevacizumab, and atezolizumab. However, the patient exhibited primary resistance to this regimen. A follow-up CT scan after two cycles of treatment confirmed unequivocal disease progression (Figure 5), resulting in a PFS of only 2.0 months for the second-line therapy. His clinical condition deteriorated rapidly thereafter, and he died 2.6 months after progression.

Discussion
This retrospective case series presents real-world experience with a quadruplet regimen (immunotherapy, chemotherapy, and bevacizumab) in six patients with advanced EGFR ex20ins-mutated NSCLC. The primary observations were preliminary antitumor activity, evidenced by a median PFS of 14.7 months, and a manageable safety profile without high-grade toxicities or treatment discontinuations due to adverse events (4,7).
Patients with EGFR ex20ins-mutated NSCLC typically derive limited benefit from earlier-generation TKIs. While clinical trials such as PAPILLON (8) and WU-KONG6 (9) have established the efficacy of amivantamab plus chemotherapy and sunvozertinib, respectively—leading to their regulatory approval in the first- and later-line settings—their high cost restricts widespread accessibility in routine practice. As a result, treatment strategies for such patients often mirror those used for NSCLC without identifiable driver mutations.
Although immunotherapy combined with chemotherapy is a standard treatment for NSCLC, available evidence suggests that patients with EGFR ex20ins mutations derive limited clinical benefit from such dual therapy. For example, one Chinese real-world study reported a median PFS of only 6.53 months with first-line immunotherapy plus chemotherapy (7). In contrast, the IMpower150 (5) and ORIENT-31 (6) trials demonstrated that adding an anti-angiogenic agent to an immunotherapy-chemotherapy backbone can improve outcomes in EGFR-mutant NSCLC, particularly after progression on prior targeted therapy. This provides a rationale for evaluating a similar quadruplet strategy in the ex20ins subset. Supporting this concept, a German retrospective study that included nine patients with EGFR ex20ins mutations and other uncommon EGFR variants reported a median PFS of 13.6 months and a median OS of 30.7 months with a comparable quadruplet regimen (10). Motivated by these earlier observations, we conducted the present case series. In our cohort, the observed median PFS was 14.7 months and the mean OS was 34.2 months, which align with the outcomes reported in prior relevant studies. Collectively, these observations warrant further evaluation of the quadruplet regimen as a treatment approach for this patient population.
Bevacizumab is a recombinant humanized monoclonal antibody that targets vascular endothelial growth factor (VEGF). VEGF not only promotes abnormal proliferation of vascular endothelial cells, contributing to intratumoral hypoxia and acidosis, but also suppresses dendritic cell (DC) maturation, impedes T-cell infiltration, and facilitates the accumulation of immunosuppressive cells such as regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and M2-type tumor-associated macrophages (TAMs) (11). By inhibiting VEGF, bevacizumab promotes tumor vessel normalization, improves blood perfusion, alleviates the hypoxic tumor microenvironment, and enhances intratumoral infiltration of CD8+ T cells and natural killer (NK) cells (12,13). Therefore, the quadruplet regimen may modulate the immunosuppressive tumor microenvironment, which could help overcome the relative resistance to immunotherapy observed in this population (14).
The main strength of this report is its provision of real-world clinical data on this therapeutic strategy for a challenging-to-treat population, highlighting both the observed antitumor activity and manageable toxicity in a routine care setting. However, the interpretation of our findings must be circumscribed by several important limitations. First and foremost, the exceedingly small sample size of six patients precludes any definitive conclusions regarding efficacy and introduces the risk of bias. In particular, the reported median PFS and OS estimates can be disproportionately influenced by individual exceptional responders or non-responders, as observed in our cohort. Second, the retrospective, non-comparative design carries inherent risks of selection bias and unmeasured confounding. Third, heterogeneity in the specific agents used, while reflecting real-world flexibility, limits the precision of our assessment. Fourth, the absence of comprehensive biomarker data—such as PD-L1 expression, tumor mutational burden, and for some patients, the precise ex20ins variant subtype due to PCR-based testing—restricts our ability to explore correlations that might predict response or resistance.
The case of patient 4 critically underscores the heterogeneity of response and the limitations of our data. While clinical factors like heavy smoking history and comorbidities may be associated with poorer outcomes, the lack of a repeat biopsy at progression meant we could not assess potential resistance mechanisms such as histological transformation or the emergence of specific genomic alterations in such as STK11 or KEAP1. This case reinforces the imperative for thorough molecular profiling in both clinical practice and future research studies.
Despite these limitations, the findings from this study suggest that the quadruplet regimen merits further investigation in patients with EGFR ex20ins-mutated NSCLC. These observations support the rationale for further, larger-scale investigations to more comprehensively evaluate the efficacy and applicability of this therapeutic approach.

Conclusions
In conclusion, this case series provides preliminary real-world evidence suggesting that a quadruplet regimen combining chemotherapy, anti-angiogenic therapy, and immunotherapy may offer clinical benefit with a manageable safety profile in patients with EGFR ex20ins-mutated NSCLC. These observations add to the evidence that sensitivity to immunotherapy-based combinations in this population is heterogeneous and merits further study. While larger prospective studies are warranted to confirm these findings and to identify predictive biomarkers, this combination regimen could be considered a potential therapeutic option for patients ineligible for or progressing on targeted therapies. This approach may be considered within the treatment strategy for this challenging subtype of lung cancer.

Supplementary
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