Background:The direct comparison of CA19.9, circulating tumour cells (CTCs) and circulating tumour DNA (ctDNA) using endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) has never been performed for the diagnosis of solid pancreatic tumours (SPTs).Methods:We included 68 patients with a SPT referred for EUS-FNA. CTCs were analysed using size-based platform and ctDNA using digital PCR. The sensitivity, specificity, negative and positive predictive values were evaluated for each marker and their combination.Results:SPTs corresponded to 58 malignant tumours (52 pancreatic adenocarcinoma (PA) and 6 others) and 10 benign lesions. The sensitivity and specificity for PA diagnosis were 73% and 88% for EUS-FNA, 67% and 80% for CTC, 65% and 75% for ctDNA and 79% and 93% for CA19.9, respectively. The positivity of at least 2 markers was associated with a sensitivity and specificity of 78% and 91%, respectively. CtDNA was the only marker associated with overall survival (median 5.2 months for ctDNA+ vs 11.0 months for ctDNA−, P=0.01).Conclusions:CA19.9 alone and in combination with ctDNA and/or CTC analysis may represent an efficient method for diagnosing PA in patients with SPTs. Further studies including a larger cohort of patients with both malignant and benign lesions will be necessary to confirm these promising results.

Acquired estrogen receptor gene (ESR1) mutations have been recently reported as a marker of resistance to aromatase inhibitors in hormone receptor positive metastatic breast cancer. We retrospectively considered seven patients treated for metastatic breast cancer with available samples from the primary tumor before any treatment, cryopreserved metastasis removed during progression and concomitant plasmas. All these seven patients were in disease progression after previous exposure to aromatase inhibitors for at least 6 months, and were assessed for ESR1 mutations detection in tumor and circulating DNA. For these patients, Sanger sequencing identified four metastases with clear ESR1 mutation and one possible, whereas digital PCR identified six mutated metastases. Then, under blind conditions and using digital PCR, corresponding circulating ESR1 mutations were successfully detected in four of these six metastatic breast cancer patients. Moreover, in two patients with serial blood samples following treatments exposure, the monitoring of circulating ESR1 mutations clearly predicted disease evolution. In the context of high interest for ESR1 mutations, our results highlight that these acquired recurrent mutations may be tracked in circulating tumor DNA and may be of clinical relevance for metastatic breast cancer patient monitoring.Nearly 70% of breast cancers are hormone receptor positive (HR1) and potentially sensitive to hormonal therapy. Aromatase inhibitors (AI) or tamoxifen is the recommended first line hormonal therapy in postmenopausal HR1 metastatic breast cancer (MBC).1,2 Nevertheless, disease progression is usually observed within a few months after treatment initiation.3,4 Acquired resistance to hormonal therapy may be based on activating mutations in the estrogen receptor gene (ESR1). These mutations have been detected in HR1 MBC patients previously exposed to hormonal therapy, including treatment with an AI in all cases. The frequencies of ESR1 mutations was 25% (nine of 36), 38% (five of 13) and 54% (six of 11) among these cohorts. [5][6][7] Approximately 12 ESR1 point mutations have been described, with a hot spot confined to codons 537 and 538 in exon 8. 8 These mutations result in a ligand-independent estrogen receptor (ER) activity. In vitro and preclinical data suggest that ESR1 mutations lead to complete AI resistance and to partial resistance to ER agonists and antagonists.9,10 The detection of ESR1-activating mutations may be relevant for guiding clinicians between endocrine and nonendocrine therapy.11 Thus far, ESR1 genotyping must be performed on metastases: this method is hardly compatible with repetitive sampling analyses for disease monitoring. Circulating tumor DNA (ctDNA) analysis is considered a promising tool for providing relevant prognostic and/or predictive information instead of tumor sampling. 12,13

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