Influence of cirrhosis on outcomes of patients with advanced intrahepatic cholangiocarcinoma receiving chemotherapy.

BACKGROUND: Cirrhosis is a risk factor for intrahepatic cholangiocarcinoma (iCC). However, its exact prevalence is uncertain and its impact on the management of advanced disease is not established. METHODS: Retrospective analysis of patients treated with systemic chemotherapy for advanced iCC in the 1st-line setting at 2 tertiary cancer referral centres. Cirrhosis was diagnosed based on at least one element prior to any treatment: pathological diagnosis, baseline platelets <150 × 109/L, portal hypertension and/or dysmorphic liver on imaging. RESULTS: In the cohort of patients (n = 287), 82 (28.6%) had cirrhosis (45 based on pathological diagnosis). Patients with cirrhosis experienced more grade 3/4 haematologic toxicity (44% vs 22%, respectively, P = 0.001), and more grade 3/4 non-haematologic toxicity (34% vs 14%, respectively, P = 0.001) than those without. The overall survival (OS) was significantly shorter in patients with cirrhosis: median 9.1 vs 13.1 months for those without (HR = 1.56 [95% CI: 1.19-2.05]); P = 0.002), confirmed on multivariable analysis (HR = 1.48 [95% CI: 1.04-2.60]; P = 0.028). CONCLUSION: Cirrhosis was relatively common in patients with advanced iCC and was associated with increased chemotherapy-induced toxicity and shorter OS. Formal assessment and consideration of cirrhosis in therapeutic management is recommended.

Resection Postradioembolization in Patients With Single Large Hepatocellular Carcinoma.

OBJECTIVE: The aim of this study was to evaluate the efficacy of yttrium-90 transarterial radioembolization (TARE) to convert to resection initially unresectable, single, large (≥5 cm) hepatocellular carcinoma (HCC). BACKGROUND: TARE can downsize cholangiocarcinoma to resection but its role in HCC resectability remains debatable. METHODS: All consecutive patients with a single large HCC treated between 2015 and 2020 in a single tertiary center were reviewed. When indicated, patients were either readily resected (upfront surgery) or underwent TARE. TARE patients were converted to resection (TARE surgery) or not (TARE-only). To further assess the effect of TARE on the long-term and short-term outcomes, a propensity score matching analysis was performed. RESULTS: Among 216 patients, 144 (66.7%) underwent upfront surgery. Among 72 TARE patients, 20 (27.7%) were converted to resection. TARE-surgery patients received a higher mean yttrium-90 dose that the 52 remaining TARE-only patients (211.89±107.98 vs 128.7±36.52 Gy, P <0.001). Postoperative outcomes between upfront-surgery and TARE-surgery patients were similar. In the unmatched population, overall survival at 1, 3, and 5 years was similar between upfront-surgery and TARE-surgery patients (83.0%, 60.0%, 47% vs 94.0%, 86.0%, 55.0%, P =0.43) and compared favorably with TARE-only patients (61.0%, 16.0% and 9.0%, P <0.0001). After propensity score matching, TARE-surgery patients had significantly better overall survival than upfront-surgery patients ( P =0.021), while disease-free survival was similar ( P =0.29). CONCLUSION: TARE may be a useful downstaging treatment for unresectable localized single large HCC providing comparable short-term and long-term outcomes with readily resectable tumors.

"Chronic fatigue, quality of life and long-term side-effects of chemotherapy in patients treated for non-epithelial ovarian cancer: national case-control protocol study of the GINECO-Vivrovaire rare tumors INCa French network for rare malignant ovarian tumors".

BACKGROUND: Germ cell tumors and sex cord stromal tumors are rare cancers of the ovary. They mainly affect young women and are associated with a high survival rate. The standard treatment mainly involves conservative surgery combined with chemotherapy [bleomycin, etoposide and cisplatin (BEP)] depending on the stage and the prognostic factors, as for testicular cancers. As reported in testicular cancer survivors, chemotherapy may induce sequelae impacting quality of life, which has not yet been evaluated in survivors of germ cell tumors and sex cord stromal tumors. The GINECO-VIVROVAIRE-Rare tumor study is a two-step investigation aiming to assess i) chronic fatigue and quality of life and ii) long-term side-effects of chemotherapy with a focus on cardiovascular and pulmonary disorders. METHODS: Using self-reported questionnaires, chronic fatigue and quality of life are compared between 134 ovarian cancer survivors (cancer-free ≥2 years after treatment) treated with surgery and chemotherapy and 2 control groups (67 ovarian cancer survivors treated with surgery alone and 67 age-matched healthy women). Medical data are collected from patient records. In the second step evaluating the long-term side-effects of chemotherapy, a subgroup of 90 patients treated with chemotherapy and 45 controls undergo the following work-up: cardiovascular evaluation (clinical examination, non-invasive cardiovascular tests to explore heart disease, blood tests), pulmonary function testing, audiogram, metabolic and hormonal blood tests. Costs of sequelae will be also assessed. Patients are selected from the registry of the INCa French Network for Rare Malignant Ovarian Tumors, and healthy women by the 'Seintinelles' connected network (collaborative research platform). DISCUSSION: This study will provide important data on the potential long-term physical side-effects of chemotherapy in survivors of Germ Cell Tumors (GCT) and Sex Cord Stromal Tumors (SCST), especially cardiovascular and pulmonary disorders, and neurotoxicity. The identification of long-term side-effects can contribute to adjusting the treatment of ovarian GCT or SCST patients and to managing follow-up with adapted recommendations regarding practices and chemotherapy regimens, in order to reduce toxicity while maintaining efficacy. Based on the results, intervention strategies could be proposed to improve the management of these patients during their treatment and in the long term. TRIAL REGISTRATION: This trial was registered at clinicaltrials.gov : 03418844 , on 1 February 2018. This trial was registered on 25 October 2017 under the unique European identification number (ID-RCB): 2017-A03028-45. Recruitment Status: Recruiting. PROTOCOL VERSION: Version n° 4.2 dated from Feb 19, 2021. TRIAL SPONSOR: Centre François Baclesse, 3 avenue du Général Harris, F-14076 Caen cedex 05, France.

Downstaging with Radioembolization or Chemotherapy for Initially Unresectable Intrahepatic Cholangiocarcinoma.

OBJECTIVE: The aim of this retrospective study was to compare the outcomes of patients resected for intrahepatic cholangiocarcinoma (ICC) with upfront surgery or after downstaging treatment. METHODS: All consecutive patients with ICC between January 1997 and November 2017 were included in a single-center database and retrospectively reviewed. Patients were divided into two groups: upfront resection or resection after downstaging using either chemotherapy alone or selective internal radiation therapy (SIRT) combined with chemotherapy. Survival rates of patients who underwent upfront surgery for ICC were compared with those of patients who underwent surgery after downstaging therapy. RESULTS: A total of 169 patients resected for ICC were included: 137 underwent upfront surgery and 32 received downstaging treatment because their tumor was initially unresectable (13 received chemotherapy, 19 received SIRT). Median OS was not different between the two groups: 32.3 months [95% confidence interval (CI) 23.9-40.7] with primary surgery versus 45.9 months (95% CI 32.3-59.4) with downstaging treatment (p = 0.54, log-rank test). In a multivariable Cox regression model, downstaging treatment was not associated with a better or worse prognosis; however, delivery of SIRT as a downstaging treatment was associated with a significant benefit in multivariable analysis (hazard ratio 0.34, 95% CI 0.14-0.84; p = 0.019). CONCLUSIONS: Overall survival of patients resected after downstaging treatment was not different compared with the OS of patients resected upfront. Patients should therefore again be discussed with the surgeon following medical treatment. SIRT may be an efficient neoadjuvant therapy in patients with resectable ICC, in order to improve surgical results.

Implementation of a molecular tumor board at a regional level to improve access to targeted therapy.

BACKGROUND: With the development of precision oncology, Molecular Tumor Boards (MTB) are developing in many institutions. However, the implementation of MTB in routine clinical practice has still not been thoroughly studied. MATERIAL AND METHODS: Since the first drugs approved for targeted therapies, patient tumor samples were centralized to genomic testing platforms. In our institution, all tumor samples have been analyzed since 2014 by Next Generation Sequencing (NGS). In 2015, we established a regional MTB to discuss patient cases with 1 or more alterations identified by NGS, in genes different from those related to drug approval. We conducted a retrospective comparative analysis to study whether our MTB increased the prescriptions of Molecular Targeted Therapies (MTT) and the inclusions of patients in clinical trials with MTT, in comparison with patients with available NGS data but no MTB discussion. RESULTS: In 2014, 86 patients had UGA, but the results were not available to clinicians and not discussed in MTB. During the years 2015 and 2016, 113 patients with an UGA (unreferenced genomic alteration) were discussed in MTB. No patients with an UGA were included in 2014 in a clinical trial, versus 2 (2%) in 2015-2016. 13 patients with an UGA (12%) were treated in 2015-2016 with a MTT whereas in 2014, no patient (p = 0.001). CONCLUSIONS: In this retrospective analysis, we showed that the association of large-scale genomic testing and MTB was feasible, and could increase the prescription of MTT. However, in routine clinical practice, the majority of patients with UGA still do not have access to MTT.

Characteristics of BRAFV600E Mutant, Deficient Mismatch Repair/Proficient Mismatch Repair, Metastatic Colorectal Cancer: A Multicenter Series of 287 Patients.

BACKGROUND: BRAFV600E mutations occurring in about 10% of metastatic colorectal cancers (mCRCs) are usually associated with a poor outcome. However, their prognostic factors are unknown. MATERIALS AND METHODS: We built a multicenter clinico-biological database gathering data from patients with BRAFV600E -mutant mCRC treated in one of the 16 French centers from 2006 to 2017. The primary endpoint was to identify prognostic factors using a Cox model. RESULTS: We included 287 patients (median age, 67 years [28-95]; female, 57%). Their median overall survival was 20.8 months (95% confidence interval [CI], 17.97-27.04), and median progression-free survival in the first-line setting was 4.34 months (95% CI, 3.81-5.03). Chemotherapy regimen and biological agents (antiangiogenic or anti-epidermal growth factor receptor) were not associated with overall and progression-free survival. Stage IV disease (synchronous metastases) and absence of curative-intent surgery were statistically associated with poor overall survival. Among the 194 patients with mismatch repair (MMR) status available, overall survival was significantly longer in patients with deficient MMR tumors compared with those with proficient MMR tumors (adjusted hazard ratio = 0.56; p = .009). CONCLUSION: Despite that BRAFV600E -mutant mCRCs are associated with poor overall and progression-free-survival, patients with deficient MMR tumors and/or resectable disease experienced a longer survival. These results highlight the importance of MMR testing and resectability discussion in patients with BRAFV600E mCRC in day-to-day practice. IMPLICATIONS FOR PRACTICE: Mismatch repair (MMR) testing and resectability discussion in patients with BRAFV600E metastatic colorectal cancer (mCRC) should be performed in day-to-day practice to steer treatment decision making in patients with BRAFV600E -mutant mCRC.

Yttrium-90 glass microspheres radioembolization (RE) for biliary tract cancer: a large single-center experience.

PURPOSE: Radioembolization (RE) is a promising treatment option for biliary tract cancers (BTC). We report here the largest series to date using this treatment modality. METHODS: We retrospectively studied data from 64 patients treated outside prospective clinical trial at our institution. We studied baseline characteristics as potential prognostic factors. We studied dose delivered to the tumor as predictive factors of outcomes in patients not receiving concomitant chemotherapy. RESULTS: The Progression-Free Survival and Overall Survival (OS) were 7.6 months [95% Confidence Interval (CI): 4.6-10.6] and 16.4 months [95% CI: 7.8-25.0] in the whole cohort. The factors independently associated with OS in multivariable analysis were the primary localization of ICC (HR = 0.27, 95% CI: 0.11-0.68, p = 0.005) and a PS > 0 (HR = 2.21, 95% CI: 1.11-4.38, p = 0.024). During follow-up, 12 patients (19%) underwent surgery following downstaging, with a median OS of 51.9 months. In patients not treated with concomitant chemotherapy (n = 31), OS was significantly higher in patients with a dose delivered to the tumor 260Gy or higher than in patients with a dose delivered to the tumor lower than 260Gy (median 28.2 vs 11.4 months, log-rank p = 0.019). CONCLUSION: Our results confirm that RE is a promising treatment modality in BTC. A high proportion of patients could be downstaged to surgery, with promising long-term survival. Dose delivered to the tumor correlated with clinical outcomes when chemotherapy was not used concomitantly.

Plasma-based analysis of ERBB2 mutational status by multiplex digital PCR in a large series of patients with metastatic breast cancer.

Erb-b2 receptor tyrosine kinase 2 (ERBB2)-activating mutations are therapeutically actionable alterations found in various cancers, including metastatic breast cancer (MBC). We developed multiplex digital PCR assays to detect and quantify ERBB2 mutations in circulating tumor DNA from liquid biopsies. We studied the plasma from 272 patients with hormone-receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) MBC to detect 17 ERBB2 mutations using a screening assay. The assay was developed on the three-color Crystal dPCR™ naica® platform with a two-step strategy for precise mutation identification. We found that nine patients (3.3%) harbored at least one ERBB2 mutation. The mutation rate was higher in patients with lobular histology (5.9%) compared to invasive breast carcinoma of no special type (2.6%). A total of 12 mutations were found with the following frequencies: L755S (25.00%), V777L (25.00%), S310Y (16.67%), L869R (16.67%), S310F (8.33%), and D769H (8.33%). Matched tumor samples from six patients identified the same mutations with an 83% concordance rate. In summary, our highly sensitive multiplex digital PCR assays are well suited for plasma-based monitoring of ERBB2 mutational status in patients with MBC.

Locoregional Treatment in Intrahepatic Cholangiocarcinoma: Which Treatment for Which Patient?

For unresectable intrahepatic cholangiocarcinoma (iCC), different locoregional treatments (LRT) could be proposed to patients, including radiofrequency ablation (RFA) and microwave ablation (MWA), external beam radiotherapy (EBRT) or transarterial treatments, depending on patient and tumor characteristics and local expertise. These different techniques of LRT have not been compared in a randomized clinical trial; most of the relevant studies are retrospective and not comparative. The aim of this narrative review is to help clinicians in their everyday practice discuss the pros and cons of each LRT, depending on the individual characteristics of their patients.

Real-World Data on Olaparib in Relapsed BRCA-mutated Ovarian Cancer: A Multicenter GINECO RETROLA Cohort Study.

BACKGROUND/AIM: Olaparib was approved in 2014 by the European Medicines Agency (EMA) as maintenance treatment for patients with breast cancer gene (BRCA)-mutated platinum-sensitive relapsed high-grade epithelial ovarian cancer (EOC) following the results of the Study 19. We present the results of a national real-world study on the effectiveness of olaparib in relapsed BRCA-mutated EOC patients. PATIENTS AND METHODS: Patients with EOC, peritoneal, and/or fallopian-tube cancer treated with olaparib in a French Center between May 2014 and March 2017 were included. The primary end-point of the study was progression-free survival. RESULTS: Of the 128 patients analyzed, 89 were treated according to the EMA label. The median progression-free survival was 17.0 months. The most common treatment-related toxicity was fatigue. Treatment-related myelodysplastic syndrome (n=5) and a second cancer (n=1) were diagnosed. CONCLUSION: In this real-life setting, olaparib confirmed its efficacy and safety profile, as previously shown in clinical trials.

Development of sensitive and robust multiplex digital PCR assays for the detection of ESR1 mutations in the plasma of metastatic breast cancer patients.

BACKGROUND: Early detection of ESR1 mutations is a key element for better personalization of the management of patients with HR+/HER2- Metastatic Breast Cancer (MBC). Analysis of circulating tumor DNA from liquid biopsies is a particularly well-suited strategy for longitudinal monitoring of such patients. MATERIALS AND METHODS: Using the naica® three-color digital PCR platform, we developed a screening assay allowing the detection of 11 ESR1 mutations and designed a sequential strategy for precise mutation identification. We then applied this strategy in the analysis of plasma circulating cell-free DNA from 109 HR+/HER2- MBC patients and performed a double-blind comparison study on a subset of patients with the multiplex assay used at the Institut Curie (IC) for the PADA-1 study. RESULTS: Thirty-one patients (28.4%) harboured at least one ESR1 mutation, with the following frequencies: D538G (41.03%), Y537S (25.64%), E380Q (10.26%), Y537N (10.26%), "(536-540)" (7.69%), Y537C (2.56%), and L536R (2.56%). The presence of ESR1 mutation(s) was significantly associated with liver metastases (p = 0.0091). A very good agreement (91%) was observed with the IC assay. CONCLUSION: Our assays have proven to be robust and highly sensitive and are very well-suited for monitoring ESR1 mutations in the plasma of MBC patients.

Atezolizumab and paclitaxel as first line therapy in advanced triple-negative breast cancer patients included in the French early access program.

Following the results of the IMpassion130 trial, an early access program (EAP) was opened in France, allowing patients with PD-L1-positive advanced triple negative breast cancer (aTNBC) to receive a combination of paclitaxel and atezolizumab as first line therapy. This EAP was later discontinued when the IMpassion131 trial read out with negative results. We performed a retrospective multicentric analysis in patients who were prospectively enrolled in the French EAP. Efficacy and toxicity data were obtained on 64 patients treated from August 2019 to August 2020 in 10 French cancer centers. Median progression-free survival (PFS) and overall survival (OS) were 4.1 months (95% CI [3.0-5.8]) and 17.9 months (95% CI [12.4-NR]), respectively. The 6-months PFS rate was 28% (95% CI [16-40%]) (N = 18/64), while N = 33/64 patients (52%, 95% CI [38-63%]) experienced a tumor response. Exploratory subgroup analyses retrieved that corticosteroid use at inclusion in the EAP, before treatment initiation, was the only independent unfavorable prognostic factor for PFS (HR 2.7, 95% CI [1.3-5.6]). No new safety signal was observed. This real-life study, unique by its setting (EAP granted by anticipation and later withdrawn), suggests atezolizumab and paclitaxel has a limited efficacy in PD-L1-positive aTNBC, especially in patients receiving corticosteroids as comedication before treatment start.

Selective internal radiation therapy in older patients with hepatocellular carcinoma: a retrospective analysis.

BACKGROUND: Selective internal radiation therapy (SIRT) is applied to hepatocellular carcinoma (HCC), a disease with increased incidence in the elderly. However, SIRT has rarely been specifically studied in elderly population. The aim of this study was to investigate efficacy and safety of SIRT in elderly HCC patients. METHODS: We studied retrospectively data from patients treated with SIRT for HCC. Clinical and laboratory data were retrieved. We used 70-years old as threshold between younger and elderly populations, to compare outcomes. RESULTS: A total of 222 patients treated with SIRT for HCC were studied, of which 134 patients were younger and 88 older. Median overall survival (OS) was not significantly different between younger and elderly group: 15.6 months (95% CI, 11.7-19.5) and 14.8 months (95% CI, 9.4-20.3) (P = 0.86). Age was not associated with OS in multivariable analysis, with a Hazard ratio of 1.09 (95% CI, 0.82-1.45, P = 0.55). Results of progression-free survival and responses were also similar in both groups. Toxicities were similar between the two groups, including the occurrence of radioembolization-induced liver disease (11.5 vs. 11.4%, P = 0.97). CONCLUSION: SIRT appears to be a well-tolerated treatment with the same efficacy in elderly compared to younger patients in HCC. Our study is the first to study its impact with glass microspheres. This warrants confirmation in large prospective studies.

Patients' Experience of Systemic Treatment of Hepatocellular Carcinoma: A Review of the Impact on Quality of Life.

Quality of life (QoL) in oncology is an outcome becoming more and more important and relevant to explore. Some studies have demonstrated its prognostic impact in different cancers, such as colorectal, breast, and prostate cancers, but also in hepatocellular carcinoma (HCC). Different tools have been developed for assessing quality of life, some general, such as EORTC QLQ-C30, but also specific tools depending on cancer origin which seem to be more pertinent for patients. Systemic treatments and specific symptoms due to cancer evolution could decrease quality of life. For approval of new systemic treatments, authorities ask for benefit in terms of efficacy but also benefit in quality of life, which is crucial for patients. This review reports data about QoL in HCC, including specific tools used, impact of systemic treatments and prognosis for QoL for HCC patients. Management of adverse events is essential to enhance compliance with treatment and quality of life. Assessing quality of life in clinical trials appears quite systematic, but its application in clinical routine requires development.

Druggable molecular alterations in bile duct cancer: potential and current therapeutic applications in clinical trials.

Introduction: Cholangiocarcinomas (CCA) are rare tumors that are associated with a variety of molecular alterations. Many of these alterations are now actionable using drugs currently in development, and CCA may be a perfect example of application of a precision oncology approach. However, development of drugs in CCA faces the challenge of targeting rare alterations in a rare disease.Areas covered: In this review, we present the current data on targeted therapies in development for CCA, focusing on IDH1, FGFR2, BRAF, and HER2 alterations. We also discuss rationale for targeting other alterations, currently without specific development in CCA. We searched PubMed and google scholar in February 2021 for relevant articles and presentation in recent congress regarding the literature on molecular alterations, drugs in cholangiocarcinomas and biliary tract cancers.Expert opinion: Despite a strong rationale and promising early results, applying a precision oncology approach in CCA for everyday patients is still exposed to significant challenges: obtaining the molecular portrait of these tumors due to difficulties with biopsy access, complexities of drug development in subgroups of these relatively rare tumors, and sub-optimal access to drugs outside clinical trials.

Impact of EPclin on adjuvant therapeutic decision making and comparison of EPclin to the PREDICT tool.

PURPOSE: Genomic signatures, such as EndoPredict®, may help clinicians to decide which adjuvant treatment is the most appropriate. METHODS: We propose the EndoPredict® assay for unclear cases of adjuvant treatment in patients treated in our comprehensive cancer center. We prospectively and retrospectively report the decision of adjuvant treatment before and after the EndoPredict® assay, respectively, compared to the PREDICT's tool scores. RESULTS: From November 2016 to March 2019, 159 breast cancer tumors were analyzed and presented before and after the EndoPredict® assay. Before the EndoPredict® results, clinicians recommended chemotherapy for 57 patients (57/159, 36%). A total of 108 patients (108/159, 68%) were classified as EPclin high-risk score. There was only a slight agreement between clinicians' decisions and EPclin risk score. The EPclin score led to 37% changes in treatment (59/159); chemotherapy was favored in 80% of cases (47/59). The PREDICT tool recommended chemotherapy for 16 high-risk patients (16/159, 10%). CONCLUSION: Although genomic tests were developed in order to de-escalate adjuvant treatment, in our comprehensive cancer center the use of the EndoPredict® assay led to an increase in prescribed chemotherapy.

ALBI Score Is a Strong Predictor of Toxicity Following SIRT for Hepatocellular Carcinoma.

BACKGROUND: Selective internal radiation therapy (SIRT) is an innovative treatment of hepatocellular carcinoma (HCC). The albumin-bilirubin (ALBI) score was designed to better evaluate liver functions in HCC. METHODS: We studied, retrospectively, data from patients treated with SIRT for HCC. The primary endpoint was the occurrence of radioembolization-induced liver disease (REILD). The secondary endpoint was overall survival (OS). RESULTS: 222 patients were studied. The ALBI grade 1 patients had significantly less REILD (3.4%) after the first SIRT than ALBI grade 2 or 3 patients (16.8%, p = 0.002). Of the 207 patients with data, 77 (37.2%) had a worsening of ALBI grade after one SIRT. The baseline ALBI grade was significantly associated with OS (p = 0.001), also in the multivariable analysis. The ALBI grade after the first SIRT was significantly associated with OS (p ≤ 0.001), with median OS of 26.4 months (CI 95% 18.2-34.7) for ALBI grade 1 patients (n = 48) versus 17.3 months (CI 95% 12.9-21.8) for ALBI grade 2 patients (n = 123) and 8.1 months (CI 95% 4.1-12.1) for ALBI grade 3 patients (n = 36). CONCLUSIONS: The baseline ALBI grade is a strong predictor of REILD. The baseline ALBI score and variations of ALBI are prognostic after SIRT.

Development of multiplex digital PCR assays for the detection of PIK3CA mutations in the plasma of metastatic breast cancer patients.

With the approval of new therapies targeting the PI3K pathway, the detection of PIK3CA mutations has become a key factor in treatment management for HR+/HER2- metastatic breast cancer (MBC). We developed multiplex digital PCR (dPCR) assays to detect and quantify PIK3CA mutations. A first screening assay allows the detection of 21 mutations, with a drop-off system targeting the 542-546 hotspot mutations combined with the simultaneous detection of N345K, C420R, H1047L and H1047R mutations. In the case of a positive result, a sequential strategy based on other assays that we have developped allows for precise mutation identification. Clinical validity was determined by analyzing plasma circulating free DNA (cfDNA) from 213 HR+/HER2- MBC samples, as well as DNA extracted from 97 available matched tumors from 89 patients. Our assays have shown reliable specificity, accuracy and reproducibility, with limits of blank of three and four droplets for the screening assay. Sixty-eight patients (32%) had at least one PIK3CA mutation detectable in their plasma, and we obtained 83.1% agreement between the cfDNA analysis and the corresponding tumors. The high sensitivity and robustness of these new dPCR assays make them well-suited for rapid and cost-effective detection of PIK3CA mutations in the plasma of MBC patients.