The survival outcomes of the FLAURA trial support osimertinib as the new standard of care for untreated patients harboring activating mutations in the epidermal growth factor receptor (EGFR). Despite the initial response, disease progression invariably occurs. Although uncommon, BRAF V600E mutation arises as a unique mechanism of resistance, and thus far, no prospective studies are available to support concurrent EGFR/BRAF blockade. We report a case of impressive radiological and ctDNA response under dabrafenib, trametinib, and osimertinib in an advanced EGFR-mutant lung adenocarcinoma patient who developed BRAF V600E as one of the acquired resistance mechanisms to second-line osimertinib. Moreover, the patient experienced remarkable clinical improvement and good tolerance to combination therapy. The present case suggests the importance of prospective studies evaluating both efficacy and safety of the combination in later line settings and points towards the potential of ctDNA to monitor resistance mechanisms and treatment benefit in clinical practice.

The clinical significance of gene fusions detected by DNA-based next generation sequencing remains unclear as resistance mechanisms to EGFR tyrosine kinase inhibitors in EGFR mutant non-small cell lung cancer. By studying EGFR inhibitor-resistant patients treated with a combination of an EGFR inhibitor and a drug targeting the putative resistance-causing fusion oncogene, we identify patients who benefit and those who do not from this treatment approach. Through evaluation including RNA-seq of potential drug resistance-imparting fusion oncogenes in 504 patients with EGFR mutant lung cancer, we identify only a minority of them as functional, potentially capable of imparting EGFR inhibitor resistance. We further functionally validate fusion oncogenes in vitro using CRISPR-based editing of EGFR mutant cell lines and use these models to identify known and unknown drug resistance mechanisms to combination therapies. Collectively, our results partially reveal the complex nature of fusion oncogenes as potential drug resistance mechanisms and highlight approaches that can be undertaken to determine their functional significance.

Immune checkpoint inhibitors (ICI) cemiplimab and pembrolizumab have revolutionized the treatment of advanced cutaneous squamous cell carcinoma (cSCC). We aimed to evaluate the effectiveness and safety of ICI in a real-world cSCC population, including patients with conditions that would exclude clinical trial participation. In this single-center, retrospective cohort study, we included all non-trial patients with advanced cSCC treated with ICI between 2017 and 2022. We evaluated investigator-assessed best overall response (BOR) and immune-related adverse events (irAEs). We correlated survival outcomes with age, performance status, immune status and irAEs. Of the 36 patients identified, the best overall response (BOR) to ICI was a partial response (PR) in 41.7%, a complete response (CR) in 27.8%, and stable disease in (SD) 13.9%. The progression-free survival (PFS) rate for 1 year was 58.1%; the median PFS was 21.3 months (95% CI 6.4–NE). The 1-year overall survival (OS) was 76.7%, and the median OS was 38.6 months (95% CI 25.4–NE). Immune-compromised patients, ECOG performance 2–3, and age ≥ 75 years were not significantly associated with PFS or OS. IrAE grades 3–4 were seen in 13.9% of patients. In our Canadian experience with real-world patients, ICI was an effective and safe treatment for advanced cSCC patients. Patients achieved great benefits with ICI regardless of age, immune status or ECOG performance status. We acknowledge the small sample size and retrospective methodology as the main limitations of our study.

To report outcomes of four cases of chemo-refractory RET-rearranged non-small cell lung carcinomas (NSCLCs) treated with alectinib in a single center. we retrospectively assessed and reported the activity and tolerability of alectinib 600 mg twice daily in advanced and chemo-refractory RET-rearranged NSCLC patients treated in a Brazilian institution. Identification of RET rearrangements was performed using the FoundationOne® next-generation sequencing (NGS) platform. The four patients herein reported were white, female and non-smokers, ranging between 59-66 years of age. All patients had been previously treated with chemotherapy and were TKI naïve; three of them presented disease progression to nivolumab as well. Molecular tumor profiling showed a KIF5B-RET fusion in three patients and a CCDC6-RET in the fourth. One patient exhibited disease progression and clinical deterioration two months after treatment initiation. Disease control was documented in two patients with PFS ranging from 4 to 5 months (one partial metabolic response and one stable disease). In one of the cases, which developed oligoprogression on alectinib, radiation therapy plus post-progression alectinib were able to provide additional disease control for 9 more months. No grade 3/4 adverse events, dose reductions or discontinuation due to toxicity were documented. Although this is a small single center evaluation, alectinib was well tolerated and demonstrated clinical activity against advanced RET-rearranged NSCLCs, suggesting its potential role in this specific subset of malignancies. Clinical trials addressing its efficacy and the optimal dosing schedule in the present context are underway, and results are eagerly awaited.

Somatic mutations inactivating Tet methylcytosine dioxygenase 2 (TET2) are among the most common drivers of clonal hematopoiesis (CH). TET2 inactivation is associated with monocyte-derived inflammation and improved chimeric antigen receptor T-cell function, suggesting that it might also affect immunotherapy response. In this study, we found that hematopoietic Tet2 mutation in mouse models enhanced the immune checkpoint blockade (ICB) response, which required the combined presence of phagocytes, CD4+, and CD8+ T cells. The effect was lost with myeloid- or T-cell–restricted Tet2 inactivation or in mice with 20% Tet2-mutant hematopoiesis. Mechanistically, in Tet2-mutant tumor-infiltrating leukocytes, ICB preferentially restricted cell states linked to tumor progression while inducing antitumor states. Tet2-mutant monocytes activated costimulatory programs, whereas Tet2-mutant T cells showed enhanced T-cell memory signatures, alongside decreased exhaustion and regulatory phenotypes. Clinically, tumors from patients with colorectal cancer and melanoma with TET2-mutant CH showed enhanced immune infiltration, inflammation, and T-cell activation. In patients with melanoma treated with ICB, TET2-mutant CH was associated with six-fold greater odds of clinical benefit. Collectively, this work demonstrates that hematopoietic TET2 inactivation primes leukocytes for antitumor states associated with immunotherapy response and provides a potential biomarker for personalized therapy. Significance: TET2 mutations promote antitumor leukocyte states that can potentiate the efficacy of immunotherapy with checkpoint blockade. See related commentary by Yuan and Guryanova, p. 825

PURPOSE Li-Fraumeni syndrome (LFS) is rare in the worldwide population, but it is highly prevalent in the Brazilian population because of a founder mutation, TP53 p.R337H, accounting for 0.3% of south and southeastern population. Clinical criteria for LFS may not identify all individuals at risk of carrying the Brazilian founder mutation because of its lower penetrance and variable expressivity. This variant is rarely described in databases of somatic mutations. Somatic findings in tumor molecular profiling may give insight to identify individuals who might be carriers of LFS and allow the adoption of risk reduction strategies for cancer. MATERIALS AND METHODS We determined the frequency of the TP53 p.R337H variant in tumor genomic profiling from 755 consecutive Brazilian patients with pan-cancer. This is a retrospective cohort from January 2013 to March 2020 at a tertiary care center in Brazil. RESULTS The TP53 p.R337H variant was found in 2% (15 of 755) of the samples. The mutation allele frequency ranged from 30% to 91.7%. A total of seven patients were referred for genetic counseling and germline testing after tumor genomic profiling results were disclosed. All the patients who proceeded with germline testing (6 of 6) confirmed the diagnosis of LFS. Family history was available in 12 cases. Nine patients (9 of 12) did not meet LFS clinical criteria. CONCLUSION The identification of the TP53 p.R337H variant in tumor genomic profiling should be a predictive finding of LFS in the Brazilian population and should prompt testing for germline status confirmation. (C) 2021 by American Society of Clinical Oncology