Real-Time Detection of ESR1 Mutation in Blood by Droplet Digital PCR in the PADA-1 Trial: Feasibility and Cross-Validation with NGS.

The clinical actionability of circulating tumor DNA requires sensitive detection methods with a short turnaround time. In the PADA-1 phase 3 trial (NCT03079011), metastatic breast cancer patients treated with an aromatase inhibitor and palbociclib were screened every 2 months for activating ESR1 mutations in blood (bESR1mut). We report the feasibility of the droplet digital polymerase chain reaction (ddPCR) and cross-validation with next-generation sequencing (NGS). bESR1mut testing was centralized in two platforms using the same ddPCR assay. Results were reported as copies/mL of plasma and mutant allele frequency (MAF). We analyzed 200 positive ddPCR samples with an NGS assay (0.5-1% sensitivity). Overall, 12,552 blood samples were collected from 1017 patients from 83 centers. Among the 12,525 available samples with ddPCR results, 11,533 (92%) were bESR1mut-negative. A total of 267 patients newly displayed bESR1mut (26% patients/2% samples) with a median copy number of 14/mL (range: 4-1225) and a median MAF of 0.83% (0.11-35), 648 samples (20% patients/5% samples) displayed persistent bESR1mut, and 77 (<1%) samples encountered a technical failure. The median turnaround time from blood drawing to result notification was 13 days (Q1:9; Q3:21 days). Among 200 ddPCR-positive samples tested, NGS detected bESR1mut in 168 (84%); 25 of the 32 cases missed by NGS had low MAF and/or low coverage. In these 200 samples, bESR1mut MAF by both techniques had an excellent intraclass correlation coefficient (ICC = 0.93; 95% CI [0.85; 0.97]). These results from a large-scale trial support the feasibility and accuracy of real-time bESR1mut tracking by ddPCR, opening new opportunities for therapeutic interventions.

Randomised, open-label, multicentric phase III trial to evaluate the safety and efficacy of palbociclib in combination with endocrine therapy, guided by ESR1 mutation monitoring in oestrogen receptor-positive, HER2-negative metastatic breast cancer patients: study design of PADA-1.

INTRODUCTION: The combination of a CDK4/6 inhibitor with an aromatase inhibitor (AI) has recently become the gold standard for AI-sensitive first line treatment of oestrogen receptor-positive (ER+) HER2-negative (HER2-) advanced breast cancer. However, most patients receiving this combination will ultimately progress and require further therapies.Several studies have demonstrated that the onset of a ESR1 gene mutation lead to AIs resistance in the advanced setting. ESR1 mutations can be detected in circulating tumour DNA (ctDNA) using a digital PCR assay. Our study aims to prove the clinical efficacy of periodic monitoring for emerging or rise of ESR1 mutations in ctDNA to trigger an early change from AI plus palbociclib to fulvestrant plus palbociclib treatment while assessing global safety. METHODS: PADA-1 is a randomised, open-label, multicentric, phase III trial conducted in patients receiving AI and palbociclib as first line therapy for metastatic ER +HER2- breast cancer. 1000 patients will be included and treated with palbociclib in combination with an AI. Patients will be screened for circulating blood ESR1 mutation detection at regular intervals. Patients for whom a rising circulating ESR1 mutation is detected without tumour progression (up to N=200) will be randomised (1:1) between (1) Arm A: no modification of therapy; and (2) Arm B: palbociclib in combination with fulvestrant, a selective ER down-regulator. At tumour progression, an optional crossover will be offered to patients randomised in arm A. The coprimary endpoints are (1) Grade ≥3 haematological toxicities and their associations with baseline characteristics and (2) progression-free survival in randomised patients. ETHICS AND DISSEMINATION: The study has been approved by the French medicines agency (ANSM) and by an ethics committee (ref 01/17_1 CPP Ouest-IV Nantes) in January 2017. The trial results will be published in academic conference presentations and international peer-reviewed journals. TRIAL REGISTRATION NUMBERS: EudraCT: 2016-004360-18; NCT03079011.

Simultaneous cell by cell study of both DNA fragmentation and chromosomal segregation in spermatozoa from chromosomal rearrangement carriers.

PURPOSE: Balanced chromosomal translocations are found in one out of 500 subjects in the general population. They usually do not carry any phenotypic consequences, except for possible infertility and for the production of unbalanced gametes leading to spontaneous abortions or chromosomal syndromes in the offspring. An association between chromosomal rearrangements and increased apoptosis markers has been demonstrated on a global scale in sperm samples of translocation and inversion carriers. In order to specify which kind of sperm cells is subject to an increased apoptosis process, this present study was aimed to analyse both chromosomal segregation and DNA fragmentation, sperm cell by sperm cell. METHODS: Six patients carrying a chromosomal rearrangement (three reciprocal translocations, two Robertsonian translocations, and one chromosomal pericentric inversion) were included in a retrospective manner. Both DNA fragmentation and chromosomal segregation in spermatozoa were evaluated simultaneously using a modified TUNEL assay associated with FISH. Two thousand spermatozoa were analysed for each patient. RESULTS: We showed a higher proportion of spermatozoa with fragmented DNA among the unbalanced sperm cells, compared to the balanced ones, in all six patients. CONCLUSIONS: These results suggest an increased fragility of unbalanced spermatozoa to exogenous fragmentation factors. The exact mechanisms of those processes remain to be elucidated.