Suspected Germline TP53 Variants and Clonal Hematopoiesis of Indeterminate Potential: Lessons Learned From a Molecular Tumor Board.

OBJECTIVE: Li-Fraumeni syndrome (LFS) is a pan-cancer predisposition syndrome caused by germline pathogenic variants in the gene TP53. The interpretation of TP53 variants in clinical scenarios outside the classic LFS criteria may be challenging. Here, we report a patient affected by 2 primary cancers at later ages, who harbored a likely pathogenic TP53 at low allele frequency detected in a blood sample. METHODS: The Molecular Tumor Board committee at our institution revisited the case of a patient who was enrolled in a research protocol for the investigation of genetic conditions associated with neuroendocrine tumors. Clinical, familial, and molecular data were reviewed. The patient received germline testing using a next generation sequencing multi-gene panel and was incidentally found to harbor a TP53 likely pathogenic variant, with 22% of variant allele fraction. Additional samples, including a second blood sample, oral swab, and saliva, were collected for DNA analysis. A new TP53 sequencing round was performed with the attempt to distinguish between a true constitutional germline variant and a somatically acquired variant due to aberrant clonal expansion of bone marrow precursors. RESULTS: Patient's personal and familial history of cancer did not meet classic nor Chompret LFS criteria. Environmental risk factors for cancer were identified, such as alcohol abuse and tobacco exposure. The TP53 variant initially found in the next-generation sequencing was confirmed by Sanger sequencing in the previous DNA sample extracted from blood for the first analysis and in a second blood sample collected 6 years later. The TP53 variant was not detected in the DNA extracted from the oral swab and saliva samples. CONCLUSION: Considering the low TP53 variant allele fraction in blood, absence of variant detection in oral swab and saliva samples, the lack of LFS clinical criteria, and history of exposure to environmental risk factors for cancer, the main hypothesis for this case was aberrant clonal expansion due to clonal hematopoiesis. Oncologists should interpret TP53 findings during germline testing with caution.

Interplay between Tumor Mutational Burden and Mutational Profile and Its Effect on Overall Survival: A Pilot Study of Metastatic Patients Treated with Immune Checkpoint Inhibitors.

Purpose: Solid tumors harboring tumor mutational burden (TMB) ≥10 mutations per megabase (mut/Mb) received agnostic approval for pembrolizumab. This work aims to analyze the somatic mutational profile's influence on the outcomes of patients with TMB-high tumors treated with immune checkpoint inhibitors (ICIs). Methods: This post-hoc analysis evaluated clinical and molecular features of patients with solid tumors treated with ICIs that could be either monoclonal antibody directed against programmed cell death protein-1 or monoclonal antibody directed against programmed cell death ligand 1 (anti-PD-1/anti-PD-L1), monoclonal antibody directed against cytotoxic T lymphocyte-associated antigen (anti-CTLA-4) or a combined treatment regimen including one anti-PD-1/anti-PD-L1 and one anti-CTLA-4 (ICIs combination). We performed OS analysis for TMB thresholds of ≥10, ≥20, and <10 mut/Mb. We assessed OS according to the mutational profile for a TMB ≥ 10 mut/Mb cutoff. For genes correlated with OS at the univariate assessment, we conducted a Cox multivariate analysis adjusted by median TMB, sex, age, microsatellite instability (MSI), and histology. Results: A total of 1661 patients were investigated; 488 with a TMB ≥10 mut/Mb (29.4%). The median OS was 42 months for TMB ≥10 or 20 mut/Mb, and 15 months for TMB <10 mut/Mb (p < 0.005). Among TMB ≥10 mut/Mb patients, mutations in E2F3 or STK11 correlated with worse OS, and mutations in NTRK3, PTPRD, RNF43, TENT5C, TET1, or ZFHX3 with better OS. These associations were confirmed with univariate and multivariate analyses (p < 0.05). Melanoma histology and TMB above the median endowed patients with better OS (p < 0.05), while MSI status, age, and gender did not have a statistically significant effect on OS. Conclusion: Combining TMB and mutation profiles in key cancer genes can better qualify patients for ICI treatment and predict their OS.

Trametinib and Hydroxychloroquine (HCQ) Combination Treatment in KRAS-Mutated Advanced Pancreatic Adenocarcinoma: Detailed Description of Two Cases.

PURPOSE: Over the last decades, cytotoxic chemotherapy has been the cornerstone of metastatic pancreatic adenocarcinoma treatment. In late-stage disease, a range of treatment regimens still offers minor benefits. Molecular profiling studies have shown that pancreatic adenocarcinoma (PDAC) is a mutation-driven tumor type, with KRAS mutations found in approximately 90% of cases, which could partially explain the resistance to chemotherapy. Preclinical data on selective targeting of a downstream point of the RAF-MEK-ERK pathway with a MEK inhibitor along with the concurrent use of an autophagy inhibitor such as hydroxychloroquine appears to be one alternative approach to overcome resistance and inhibit cell proliferation. METHODS: We herein aim to investigate the rationale of autophagy inhibitors use and describe the outcomes of patients who received this experimental treatment. RESULTS: Two patients have received this experimental regimen from January 2020 to the present date, achieving disease stabilization that is clinically meaningful, considering the chemoresistance scenario of the included patients. CONCLUSIONS: Our real-life data regarding KRAS-mutated PDAC patients who received treatment with the MEK inhibitor trametinib combined with hydroxychloroquine after experiencing disease progression are consistent with the preclinical data, pointing to the clinical benefits of this regimen.