Clinical utility of comprehensive liquid molecular profiling in patients with advanced endometrial cancer.

BACKGROUND: Molecular characterization has significantly improved the management of advanced endometrial cancer (EC). It distinguishes four molecular subclasses associated with prognosis and personalized therapeutic strategies. This study assesses the clinical utility of cell-free DNA (cfDNA) profiling in EC to identify targetable alterations. METHODS: Women with metastatic or recurrent EC were prospectively recruited within the framework of the STING trial (NCT04932525), during which cfDNA was analyzed. Genomic alterations were identified with the FoundationOne CDx assay. Each molecular report underwent review by a molecular tumor board. Alterations were categorized via the European Society of Medical Oncology Scale for Clinical Actionability of Molecular Targets (ESCAT). RESULTS: A total of 61 patients were enrolled. The median age was 66.9 years, with 43% presenting frontline metastatic disease. All histologic subgroups were represented. Notably, 89% of patients yielded informative cfDNA analysis. Six tumors were classified with deficient mismatch repair/microsatellite instability (11%) and 37 as TP53 gene mutant (67%), and 12 had nonspecific molecular profiles (22%). Molecular classification based on liquid biopsy showed 87.5% accuracy in correlating with tissue results. Moreover, 65% of cases exhibited ≥1 actionable alteration, including 25% ESCAT I alterations and 13% ESCAT II alterations. Consequently, 16% of patients received a molecularly matched therapy, and presented with a 56% response rate and median progression-free survival of 7.7 months. CONCLUSIONS: cfDNA sequencing in EC is a feasible approach that produces informative results in 89% of cases and accurately categorizes patients into the main molecular subclasses. It also reveals multiple actionable alterations, which offers the potential for personalized therapeutic strategies.

Impact of Clonal Hematopoiesis-Associated Mutations in Phase I Patients Treated for Solid Tumors: An Analysis of the STING Trial.

PURPOSE: With liquid biopsy's widespread adoption in oncology, an increased number of clonal hematopoiesis-associated mutations (CHm) have been identified in patients with solid tumors. However, its impact on patient outcomes remains unclear. This study aimed to analyze and describe CHm in a cohort of phase I patients. METHODS: Retrospective data collection from medical records and molecular profiles (Foundation One Liquid CDx Assay) was performed before first study drug administration at the Drug Development Department of Gustave Roussy (France) within the STING trial (ClinicalTrials.gov identifier: NCT04932525). CHm prevalence was assessed using any and ≥1% variant allele frequency (VAF) in epigenetic modifier genes (DNMT3A, TET2, and ASXL1). RESULTS: From January 2021 to December 2022, 255 patients were enrolled in a phase I clinical trial. A total of 55% were male, with a median age of 62 years (24-86). Principal tumor locations were GI (27%) and genitourinary (21%). Overall, 104 patients (41%) had at least one CHm in liquid biopsy, with 55 patients (22%) having a VAF of ≥ 1%. The most frequent mutation was DNMT3A 73% at any VAF (n = 76) and 22% at 1% VAF (n = 23). Median progression-free survival (PFS) and overall survival were 3.8 months (m) for the CHm group versus 3.2 m for nonclonal hematopoiesis (CH; P = .08) and 18.26 m CHm versus 15.8 m non-CH (P = .9), respectively. PFS increased in the CHm population treated with targeted therapy (hazard ratio, 0.6 [95% CI, 0.42 to 0.84]; P = .004). CONCLUSION: CHm was commonly found in patients with solid tumors treated in phase I trials, with a prevalence of 41% in our cohort. The most frequently mutated gene was DNMT3A. The presence of CHm had no impact on the population of patients treated in the phase I trials.

Development of Novel Models of Aggressive Variants of Castration-resistant Prostate Cancer.

BACKGROUND: Genomic studies have identified new subsets of aggressive prostate cancer (PCa) with poor prognosis (eg, neuroendocrine prostate cancer [NEPC], PCa with DNA damage response [DDR] alterations, or PCa resistant to androgen receptor pathway inhibitors [ARPIs]). Development of novel therapies relies on the availability of relevant preclinical models. OBJECTIVE: To develop new preclinical models (patient-derived xenograft [PDX], PDX-derived organoid [PDXO], and patient-derived organoid [PDO]) representative of the most aggressive variants of PCa and to develop a new drug evaluation strategy. DESIGN, SETTING, AND PARTICIPANTS: NEPC (n = 5), DDR (n = 7), and microsatellite instability (MSI)-high (n = 1) PDXs were established from 51 patients with metastatic PCa; PDXOs (n = 16) and PDOs (n = 6) were developed to perform drug screening. Histopathology and treatment response were characterized. Molecular profiling was performed by whole-exome sequencing (WES; n = 13), RNA sequencing (RNA-seq; n = 13), and single-cell RNA-seq (n = 14). WES and RNA-seq data from patient tumors were compared with the models. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Relationships with outcome were analyzed using the multivariable chi-square test and the tumor growth inhibition test. RESULTS AND LIMITATIONS: Our PDXs captured both common and rare molecular phenotypes and their molecular drivers, including alterations of BRCA2, CDK12, MSI-high status, and NEPC. RNA-seq profiling demonstrated broad representation of PCa subtypes. Single-cell RNA-seq indicates that PDXs reproduce cellular and molecular intratumor heterogeneity. WES of matched patient tumors showed preservation of most genetic driver alterations. PDXOs and PDOs preserve drug sensitivity of the matched tissue and can be used to determine drug sensitivity. CONCLUSIONS: Our models reproduce the phenotypic and genomic features of both common and aggressive PCa variants and capture their molecular heterogeneity. Successfully developed aggressive-variant PCa preclinical models provide an important tool for predicting tumor response to anticancer therapy and studying resistance mechanisms. PATIENT SUMMARY: In this report, we looked at the outcomes of preclinical models from patients with metastatic prostate cancer enrolled in the MATCH-R trial (NCT02517892).

Genomic landscape of liquid biopsy mutations in TP53 and DNA damage genes in cancer patients.

Next-generation sequencing (NGS) assays based on plasma cell-free DNA (cfDNA) are increasingly used for clinical trials inclusion. Their optimized limit of detection applied to a large number of genes leads to the identification of mutations not confirmed in tissue. It becomes essential to describe the characteristics and consequences of these liquid biopsy-only mutations. In the STING protocol (Gustave Roussy, NCT04932525), 542 patients with advanced solid cancer had cfDNA-based and tissue-based NGS analysis (performed by FoundationOne® Liquid CDx and FoundationOne CDx™, respectively). Mutations identified in the liquid biopsy but not in the paired tissue were considered as liquid biopsy-only mutations irrespective of their variant allelic frequency (VAF). Out of 542 patients, 281 (51.8%) harbored at least one liquid biopsy-only mutation. These patients were significantly older, and more heavily pretreated. Liquid biopsy-only mutations occurring in TP53, and in DDR genes (ATM, CHEK2, ATR, BRCA2, and BRCA1) accounted for 90.8% of all the mutations. The median VAF of these mutations was generally low (0.37% and 0.40% for TP53 and DDR genes respectively). The variant type repartition depended on the gene. Liquid biopsy-only mutations affected hotspot in TP53 codon 273, 125, 195, 176, 237 or 280 and ATM codon 2891 and 3008. In a subset of 37 patients, 75.0%, 53.5% and 83.3% of the liquid biopsy-only mutations occurring respectively in ATM, TP53, and CHEK2 were confirmed in the matching whole blood sample. Although liquid biopsy-only mutations makes the interpretation of liquid biopsy results more complex, they have distinct characteristics making them more easily identifiable.

Association of the Genomic Profile of Medullary Thyroid Carcinoma with Tumor Characteristics and Clinical Outcomes in an International Multicenter Study.

Purpose: The prognostic importance of RET and RAS mutations and their relationship to clinicopathologic parameters and outcomes in medullary thyroid carcinoma (MTC) need to be clarified. Experimental Design: A multicenter retrospective cohort study was performed utilizing data from 290 patients with MTC. The molecular profile was determined and associations were examined with clinicopathologic data and outcomes. Results: RET germ line mutations were detected in 40 patients (16.3%). Somatic RET and RAS mutations occurred in 135 (46.9%) and 57 (19.8%) patients, respectively. RETM918T was the most common somatic RET mutation (n = 75). RET somatic mutations were associated with male sex, larger tumor size, advanced American Joint Committee Cancer (AJCC) stage, vascular invasion, and high International Medullary Thyroid Carcinoma Grading System (IMTCGS) grade. When compared with other RET somatic mutations, RETM918T was associated with younger age, AJCC (eighth edition) IV, vascular invasion, extrathyroidal extension, and positive margins. RET somatic or germ line mutations were significantly associated with reduced distant metastasis-free survival on univariate analysis, but there were no significant independent associations on multivariable analysis, after adjusting for tumor grade and stage. There were no significant differences in outcomes between RET somatic and RET germ line mutations, or between RETM918T and other RET mutations. Other recurrent molecular alterations included TP53 (4.2%), ARID2 (2.9%), SETD2 (2.9%), KMT2A (2.9%), and KMT2C (2.9%). Among them, TP53 mutations were associated with decreased overall survival (OS) and disease-specific survival (DSS), independently of tumor grade and AJCC stage. Conclusions: RET somatic mutations were associated with high-grade, aggressive primary tumor characteristics, and decreased distant metastatic-free survival but this relationship was not significant after accounting for tumor grade and disease stage. RETM918T was associated with aggressive primary tumors but was not independently associated with clinical outcomes. TP53 mutation may represent an adverse molecular event associated with decreased OS and DSS in MTC, but its prognostic value needs to be confirmed in future studies.

Patterns of Treatment Failure After Selective Rearranged During Transfection (RET) Inhibitors in Patients With Metastatic Medullary Thyroid Carcinoma.

PURPOSE: Medullary thyroid cancer (MTC) harbors frequent mutations in RET oncogene. Selective RET inhibitors (RETi) have emerged as effective treatments. However, resistance almost invariably occurs. METHODS: MTC patients who were initiated on RETi between 2018 and 2022 were included. Baseline characteristics, RET mutational status, RETi response, available tumor tissue and molecular profiles sampled pre- and post-RETi were analyzed. RESULTS: Among 46 MTC patients on RETi during the study period, 26 patients had discontinued at data cut-off because of progression (n = 16), death (n = 4), and toxicity (n = 6). The most frequent RET mutations at baseline were p.M918T (n = 29), and p.C634X (n = 6). Pre- and post-RETi molecular profiles were available in 14 patients. There was no primary resistance on pre-RETi samples. Post-RETi profiles revealed a bypass mechanism of resistance in 75% of the cases including RAS genes mutations (50%), FGFR2 and ALK fusions and and MYC p.P44L. RET solvent from and hinge region mutations was the only resistance mechanisms in 25% of the cases. Tumor samples from initial thyroidectomy, pre- and post-RETi, from six patients, showed an increase of the mean Ki 67-index of 7%, 17% and 40% respectively (P = 0.037) and a more aggressive poorly differentiated histology in three patients. DISCUSSION: Bypass resistance may be the most frequent mechanism of progression under RETi. A more aggressive histology may arise following RETi and warrants further investigation.

Human virome profiling identified CMV as the major viral driver of a high accumulation of senescent CD8+ T cells in patients with advanced NSCLC.

Circulating senescent CD8+ T (T8sen) cells are characterized by a lack of proliferative capacities but retain cytotoxic activity and have been associated to resistance to immunotherapy in patients with advanced non-small cell lung cancer (aNSCLC). We aimed to better characterize T8sen and to determine which factors were associated with their accumulation in patients with aNSCLC. Circulating T8sen cells were characterized by a higher expression of SA-ßgal and the transcription factor T-bet, confirming their senescent status. Using whole virome profiling, cytomegalovirus (CMV) was the only virus associated with T8sen. CMV was necessary but not sufficient to explain high accumulation of T8sen (T8senhigh status). In CMV+ patients, the proportion of T8sen cells increased with cancer progression. Last, CMV-induced T8senhigh phenotype but not CMV seropositivity itself was associated with worse progression-free and overall survival in patients treated with anti-PD-(L)1 therapy but not with chemotherapy. Overall, CMV is the unique viral driver of T8sen-driven resistance to anti-PD-(L)1 antibodies in patients with aNSCLC.

Hepatic arterial oxaliplatin plus intravenous 5-fluorouracil and cetuximab for first-line treatment of colorectal liver metastases: A multicenter phase II trial.

BACKGROUND: The efficacy and tolerability of hepatic arterial infusion (HAI) oxaliplatin plus systemic 5-fluorouracil and cetuximab as frontline treatment in patients with colorectal liver metastases (CRLM) are unknown. METHODS: In this multicenter, single-arm phase II study, patients with CRLM not amenable to curative-intent resection or requiring complex/major liver resection, and no prior chemotherapy for metastatic disease, received HAI oxaliplatin and intravenous 5-fluorouracil, leucovorin and cetuximab, every two weeks until disease progression, limiting toxicity or at least 3 months after complete response or curative-intent resection/ablation. The primary endpoint was overall response rate (ORR). RESULTS: 35 patients, mostly with bilateral (89%), multiple CRLM (>4, 86%; >10, 46%) were enrolled in eight centers. The ORR was 88% (95% CI, 71%-96%) among evaluable patients (n = 32), and 95% (95% CI 70-100%) among the 22 wild-type RAS/BRAF evaluable patients. After a median follow-up of 8.8 years (95% CI, 8.7-not reached), median progression-free survival was 17.9 months (95% CI, 15-23) and median overall survival (OS) was 46.3 months (95% CI, 40.0-not reached). 23 of the 35 patients (66%), including 22 (79%) of the 25 patients with wild-type RAS tumor, underwent curative-intent surgical resection and/or ablation of CRLM. HAI catheter remained patent in 86% of patients, allowing for a median of eight oxaliplatin infusions (range, 1-19). Treatment toxicity was manageable, without toxic death. CONCLUSION: HAI oxaliplatin plus systemic 5-fluorouracil and cetuximab appears highly effective in the frontline treatment of patients with unresectable CRLM and should be investigated further.

Circulating tumor DNA landscape and prognostic impact of acquired resistance to targeted therapies in cancer patients: a national center for precision medicine (PRISM) study.

BACKGROUND: Despite the effectiveness of the various targeted therapies currently approved for solid tumors, acquired resistance remains a persistent problem that limits the ultimate effectiveness of these treatments. Polyclonal resistance to targeted therapy has been described in multiple solid tumors through high-throughput analysis of multiple tumor tissue samples from a single patient. However, biopsies at the time of acquired resistance to targeted agents may not always be feasible and may not capture the genetic heterogeneity that could exist within a patient. METHODS: We analyzed circulating tumor DNA (ctDNA) with a large next-generation sequencing panel to characterize the landscape of secondary resistance mechanisms in two independent prospective cohorts of patients (STING: n = 626; BIP: n = 437) with solid tumors who were treated with various types of targeted therapies: tyrosine kinase inhibitors, monoclonal antibodies and hormonal therapies. RESULTS: Emerging alterations involved in secondary resistance were observed in the plasma of up 34% of patients regardless of the type of targeted therapy. Alterations were polyclonal in up to 14% of patients. Emerging ctDNA alterations were associated with significantly shorter overall survival for patients with some tumor types. CONCLUSION: This comprehensive landscape of genomic aberrations indicates that genetic alterations involved in secondary resistance to targeted therapy occur frequently and suggests that the detection of such alterations before disease progression may guide personalized treatment and improve patient outcome.

Homologous recombination deficiency (HRD) testing on cell-free tumor DNA from peritoneal fluid.

BACKGROUND: Knowing the homologous recombination deficiency (HRD) status in advanced epithelial ovarian cancer (EOC) is vital for patient management. HRD is determined by BRCA1/BRCA2 pathogenic variants or genomic instability. However, tumor DNA analysis is inconclusive in 15-19% of cases. Peritoneal fluid, available in > 95% of advanced EOC cases, could serve as an alternative source of cell-free tumor DNA (cftDNA) for HRD testing. Limited data show the feasibility of cancer panel gene testing on ascites cfDNA but no study, to date, has investigated HRD testing. METHODS: We collected ascites/peritoneal washings from 53 EOC patients (19 from retrospective cohort and 34 from prospective cohort) and performed a Cancer Gene Panel (CGP) using NGS for TP53/HR genes and shallow Whole Genome Sequencing (sWGS) for genomic instability on cfDNA. RESULTS: cfDNA was detectable in 49 out of 53 patients (92.5%), including those with limited peritoneal fluid. Median cfDNA was 3700 ng/ml, with a turnaround time of 21 days. TP53 pathogenic variants were detected in 86% (42/49) of patients, all with HGSOC. BRCA1 and BRCA2 pathogenic variants were found in 14% (7/49) and 10% (5/49) of cases, respectively. Peritoneal cftDNA showed high sensitivity (97%), specificity (83%), and concordance (95%) with tumor-based TP53 variant detection. NGS CGP on cftDNA identified BRCA2 pathogenic variants in one case where tumor-based testing failed. sWGS on cftDNA provided informative results even when tumor-based genomic instability testing failed. CONCLUSION: Profiling cftDNA from peritoneal fluid is feasible, providing a significant amount of tumor DNA. This fast and reliable approach enables HRD testing, including BRCA1/2 mutations and genomic instability assessment. HRD testing on cfDNA from peritoneal fluid should be offered to all primary laparoscopy patients.

Clinical utility of plasma ctDNA sequencing in metastatic urothelial cancer.

BACKGROUND: Genomic stratification may help improve the management of patients with metastatic urothelial cancer (mUC), given the recent identification of targetable alterations. However, the collection of tissue samples remains challenging. Here, we assessed the clinical utility of plasma circulating tumour DNA (ctDNA) sequencing in these patients. METHODS: Patients with mUC were prospectively enroled in the STING trial (NCT04932525), in which ctDNA was profiled using the Foundation One Liquid CDx Assay (324 genes, blood tumour mutational burden [bTMB], microsatellite instability status). Each genomic report was reviewed by a multidisciplinary tumor board (MTB). RESULTS: Between January 2021 and June 2022, 140 mUC patients underwent molecular profiling. The median time to obtain the assay results was 20 days ((confidence interval) CI95%: [20,21]). The ctDNA analysis reproduced the somatic genomic landscape of previous tissue-based cohorts. Concordance for serial ctDNA samples was strong (r = 0.843 CI95%: [0.631-0.938], p < 0.001). At least one actionable target was detected in 63 patients (45%) with a total of 35 actionable alterations, including bTMB high (≥10 mutations/Mb) (N = 39, 21.1%), FGFR3 (N = 20, 10.8%), and Homologous recombination deficiency (HRD) alterations (N = 14, 7.6%). MTB recommended matched therapy in 63 patients (45.0%). Eight patients (5.7%) were treated, with an overall response rate of 50% (CI95%: 15.70-84.30) and a median progression-free survival (PFS) of 5.2 months (CI95%: 4.1 - NR). FGFR3 alterations were associated with a shorter PFS in patients treated with immunotherapy. CONCLUSION: Overall, we demonstrated that genomic profiling with ctDNAs in mUC is a reliable and feasible approach for the timely initiation of genotype-matched therapies.

Alkylating Agent-Induced High Tumor Mutational Burden in Medullary Thyroid Cancer and Response to Immune Checkpoint Inhibitors: Two Case Reports.

Background: Patients with metastatic medullary thyroid cancer (MTC) who progressed under tyrosine kinase inhibitors can benefit from an alkylating agent such as dacarbazine or temozolomide. Patient Findings: We describe two patients with metastatic MTC who developed a hypermutant phenotype after alkylating agent treatment. This phenotype was characterized by a high tumor mutational burden (TMB) and a mutational signature indicative of alkylating agent mutagenesis (single-base substitution 11). Both patients received immune checkpoint inhibitors, with partial morphological responses, clinical benefit, and progression-free survival of 6 and 9 months, respectively. Summary and Conclusions: Based on the described observations, we suggest that a hypermutant phenotype may be induced after alkylating agent treatment for MTC and the sequential use of immunotherapy should be further explored as a treatment option for MTC patients with increased TMB.

A biobank of pediatric patient-derived-xenograft models in cancer precision medicine trial MAPPYACTS for relapsed and refractory tumors.

Pediatric patients with recurrent and refractory cancers are in most need for new treatments. This study developed patient-derived-xenograft (PDX) models within the European MAPPYACTS cancer precision medicine trial (NCT02613962). To date, 131 PDX models were established following heterotopical and/or orthotopical implantation in immunocompromised mice: 76 sarcomas, 25 other solid tumors, 12 central nervous system tumors, 15 acute leukemias, and 3 lymphomas. PDX establishment rate was 43%. Histology, whole exome and RNA sequencing revealed a high concordance with the primary patient's tumor profile, human leukocyte-antigen characteristics and specific metabolic pathway signatures. A detailed patient molecular characterization, including specific mutations prioritized in the clinical molecular tumor boards are provided. Ninety models were shared with the IMI2 ITCC Pediatric Preclinical Proof-of-concept Platform (IMI2 ITCC-P4) for further exploitation. This PDX biobank of unique recurrent childhood cancers provides an essential support for basic and translational research and treatments development in advanced pediatric malignancies.

Trastuzumab deruxtecan in metastatic breast cancer with variable HER2 expression: the phase 2 DAISY trial.

The mechanisms of action of and resistance to trastuzumab deruxtecan (T-DXd), an anti-HER2-drug conjugate for breast cancer treatment, remain unclear. The phase 2 DAISY trial evaluated the efficacy of T-DXd in patients with HER2-overexpressing (n = 72, cohort 1), HER2-low (n = 74, cohort 2) and HER2 non-expressing (n = 40, cohort 3) metastatic breast cancer. In the full analysis set population (n = 177), the confirmed objective response rate (primary endpoint) was 70.6% (95% confidence interval (CI) 58.3-81) in cohort 1, 37.5% (95% CI 26.4-49.7) in cohort 2 and 29.7% (95% CI 15.9-47) in cohort 3. The primary endpoint was met in cohorts 1 and 2. Secondary endpoints included safety. No new safety signals were observed. During treatment, HER2-expressing tumors (n = 4) presented strong T-DXd staining. Conversely, HER2 immunohistochemistry 0 samples (n = 3) presented no or very few T-DXd staining (Pearson correlation coefficient r = 0.75, P = 0.053). Among patients with HER2 immunohistochemistry 0 metastatic breast cancer, 5 of 14 (35.7%, 95% CI 12.8-64.9) with ERBB2 expression below the median presented a confirmed objective response as compared to 3 of 10 (30%, 95% CI 6.7-65.2) with ERBB2 expression above the median. Although HER2 expression is a determinant of T-DXd efficacy, our study suggests that additional mechanisms may also be involved. (ClinicalTrials.gov identifier NCT04132960 .).

Combined Tumor-Based BRCA1/2 and TP53 Mutation Testing in Ovarian Cancer.

Somatic/germline BRCA1/2 mutations (m)/(likely) pathogenic variants (PV) (s/gBRCAm) remain the best predictive biomarker for PARP inhibitor efficacy. As >95% of high-grade serous ovarian cancers (HGSOC) have a somatic TP53m, combined tumor-based BRCA1/2 (tBRCA) and TP53 mutation testing (tBRCA/TP53m) may improve the quality of results in somatic BRCAm identification and interpretation of the 'second hit' event, i.e., loss of heterozygosity (LOH). A total of 237 patients with HGSOC underwent tBRCA/TP53m testing. The ratio of allelic fractions (AFs) for tBRCA/TP53m was calculated to estimate the proportion of cells carrying BRCAm and to infer LOH. Among the 142/237 gBRCA results, 16.2% demonstrated a pathogenic/deleterious variant (DEL) gBRCA1/2m. Among the 195 contributive tumor samples, 43 DEL of tBRCAm (22.1%) were identified (23 gBRCAm and 20 sBRCAm) with LOH identified in 37/41 conclusive samples. The median AF of TP53m was 0.52 (0.01-0.93), confirming huge variability in tumor cellularity. Initially, three samples were considered as wild type with <10% cellularity. However, additional testing detected a very low AF (<0.05) in both BRCA1/2m and TP53m, thus reidentifying them as sBRCA1/2m. Combined tBRCA/TP53m testing is rapid, sensitive, and identifies somatic and germline BRCA1/2m. AF TP53m is essential for interpreting sBRCA1/2m in low-cellularity samples and provides indirect evidence for LOH as the 'second hit' of BRCA1/2-related tumorigenesis.

Genomic Profiling of Metastatic Castration-Resistant Prostate Cancer Samples Resistant to Androgen Receptor Pathway Inhibitors.

PURPOSE: The androgen receptor axis inhibitors (ARPI; e.g., enzalutamide, abiraterone acetate) are administered in daily practice for men with metastatic castration-resistant prostate cancer (mCRPC). However, not all patients respond, and mechanisms of both primary and acquired resistance remain largely unknown. EXPERIMENTAL DESIGN: In the prospective trial MATCH-R (NCT02517892), 59 patients with mCRPC underwent whole-exome sequencing (WES) and/or RNA sequencing (RNA-seq) of samples collected before starting ARPI. Also, 18 patients with mCRPC underwent biopsy at time of resistance. The objectives were to identify genomic alterations associated with resistance to ARPIs as well as to describe clonal evolution. Associations of genomic and transcriptomic alterations with primary resistance were determined using Wilcoxon and Fisher exact tests. RESULTS: WES analysis indicated that no single-gene genomic alterations were strongly associated with primary resistance. RNA-seq analysis showed that androgen receptor (AR) gene alterations and expression levels were similar between responders and nonresponders. RNA-based pathway analysis found that patients with primary resistance had a higher Hedgehog pathway score, a lower AR pathway score and a lower NOTCH pathway score than patients with a response. Subclonal evolution and acquisition of new alterations in AR-related genes or neuroendocrine differentiation are associated with acquired resistance. ARPIs do not induce significant changes in the tumor transcriptome of most patients; however, programs associated with cell proliferation are enriched in resistant samples. CONCLUSIONS: Low AR activity, activation of stemness programs, and Hedgehog pathway were associated with primary ARPIs' resistance, whereas most acquired resistance was associated with subclonal evolution, AR-related events, and neuroendocrine differentiation. See related commentary by Slovin, p. 4323.

A Phase II Redifferentiation Trial with Dabrafenib-Trametinib and 131I in Metastatic Radioactive Iodine Refractory BRAF p.V600E-Mutated Differentiated Thyroid Cancer.

PURPOSE: To evaluate the efficacy and safety of dabrafenib-trametinib-131I for the treatment of radioactive iodine refractory metastatic differentiated thyroid cancer (DTC) with a BRAF p.V600E mutation. PATIENTS AND METHODS: A prospective phase II trial including patients with RECIST progression within 18 months and no lesion > 3 cm. Following a baseline recombinant human (rh)TSH-stimulated diagnostic whole-body scan (dc1-WBS), dabrafenib and trametinib were given for 42 days. A second rhTSH-stimulated dc WBS (dc2-WBS) was done at day 28 and 131I (5.5 GBq-150 mCi after rhTSH) was administered at day 35. Primary endpoint was the 6-month RECIST objective response rate. In case of partial response (PR) at 6 or 12 months, a second treatment course could be given. Among 24 enrolled patients, 21 were evaluable at 6 months. RESULTS: Abnormal 131I uptake was present on 5%, 65%, and 95% of the dc1-WBS, dc2-WBS, and post-therapy scans, respectively. At 6 months, PR was achieved in 38%, stable disease in 52%, and progressive disease (PD) in 10%. Ten patients received a second treatment course: one complete response and 6 PRs were observed at 6 months. The median progression-free survival (PFS) was not reached. The 12- and 24-month PFS were 82% and 68%, respectively. One death due to PD occurred at 24 months. Adverse events (AE) occurred in 96% of the patients, with 10 grade 3-4 AEs in 7 patients. CONCLUSIONS: Dabrafenib-trametinib is effective in BRAF p.V600E-mutated DTC patients for restoring 131I uptake with PR observed 6 months after 131I administration in 38% of the patients.

Liquid Biopsies for Circulating Tumor DNA Detection May Reveal Occult Hematologic Malignancies in Patients With Solid Tumors.

PURPOSE: High-risk clonal hematopoiesis (CH) is frequently incidentally found in patients with solid tumors undergoing plasma cell-free DNA sequencing. Here, we aimed to determine if the incidental detection of high-risk CH by liquid biopsy may reveal occult hematologic malignancies in patients with solid tumors. MATERIALS AND METHODS: Adult patients with advanced solid cancers enrolled in the Gustave Roussy Cancer Profiling study (ClinicalTrials.gov identifier: NCT04932525) underwent at least one liquid biopsy (FoundationOne Liquid CDx). Molecular reports were discussed within the Gustave Roussy Molecular Tumor Board (MTB). Potential CH alterations were observed, and patients referred to hematology consultation in the case of pathogenic mutations in JAK2, MPL, or MYD88, irrespective of the variant allele frequency (VAF), or in DNMT3A, TET2, ASXL1, IDH1, IDH2, SF3B1, or U2AF1 with VAF ≥ 10%, while also considering patient cancer-related prognosis. TP53 mutations were discussed case-by-case. RESULTS: Between March and October 2021, 1,416 patients were included. One hundred ten patients (7.7%) carried at least one high-risk CH mutation: DNMT3A (n = 32), JAK2 (n = 28), TET2 (n = 19), ASXL1 (n = 18), SF3B1 (n = 5), IDH1 (n = 4), IDH2 (n = 3), MPL (n = 3), and U2AF1 (n = 2). The MTB advised for hematologic consultation in 45 patients. Overall, 9 patients of 18 actually addressed had confirmed hematologic malignancies that were occult in six patients: two patients had myelodysplastic syndrome, two essential thrombocythemia, one a marginal lymphoma, and one a Waldenström macroglobulinemia. The other three patients were already followed up in hematology. CONCLUSION: The incidental findings of high-risk CH through liquid biopsy may trigger diagnostic hematologic tests and reveal an occult hematologic malignancy. Patients should have a multidisciplinary case-by-case evaluation.