scholarly journals PTEN is a predictive biomarker of trastuzumab resistance and prognostic factor in HER2-overexpressing gastroesophageal adenocarcinoma

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daiju Yokoyama ◽  
Shigeo Hisamori ◽  
Yasunori Deguchi ◽  
Tatsuto Nishigori ◽  
Hiroshi Okabe ◽  
...  
Keyword(s):  
Prognostic Factor ◽  
Mtor Inhibitor ◽  
Gastroesophageal Junction ◽  
Growth Factor Receptor ◽  
Progression Free Survival ◽  
Predictive Biomarker ◽  
Pten Expression ◽  
Trastuzumab Resistance ◽  
Pten Loss

AbstractPoor trastuzumab (Tmab) response of patients with human epidermal growth factor receptor 2-overexpressing gastric or gastroesophageal junction adenocarcinoma (HER2-GEA) is associated with the inhibition of phosphatase and tensin homolog (PTEN) expression. In this multicenter, retrospective observational study, pathological samples of patients with HER2-GEA receiving Tmab-combined chemotherapy were immunohistochemically analyzed for PTEN expression. The primary endpoints were disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). We assessed the effect of conventional chemotherapy and Tmab alone or combined with PI3K pathway inhibitors in vitro in HER2-GEA cells with or without PTEN expression. Twenty-nine and 116 patients were in the PTEN-loss and PTEN-positive groups, respectively. In patients with the target region, DCR was significantly lower in PTEN-loss patients than in PTEN-positive patients (67% and 87%, respectively, p = 0.049). The multivariate analysis demonstrated that PTEN loss was significantly associated with shorter PFS (HR = 1.63, p = 0.035) and OS (HR = 1.83, p = 0.022). PTEN knockdown did not affect the cytostatic effect of 5-FU and cisplatin, whereas Tmab combined with the PI3K/mTOR inhibitor NPV-BEZ235 suppressed PTEN-knockdown cell proliferation. In patients with HER2-GEA, PTEN loss is a predictive biomarker of Tmab resistance and prognostic factor. Molecular-targeted therapy with a PI3K/mTOR inhibitor would be effective for HER2-GEA with PTEN loss.

scholarly journals PTEN is a Predictive Biomarker of Trastuzumab Resistance and Prognostic Factor in HER2-overexpressing Gastroesophageal Adenocarcinoma

2021 ◽  
Author(s):  
Daiju Yokoyama ◽  
Shigeo Hisamori ◽  
Yasunori Deguchi ◽  
Tatsuto Nishigori ◽  
Hiroshi Okabe ◽  
...  
Keyword(s):  
Prognostic Factor ◽  
Mtor Inhibitor ◽  
Gastroesophageal Junction ◽  
Progression Free Survival ◽  
Predictive Biomarker ◽  
Pten Expression ◽  
Trastuzumab Resistance ◽  
Effective Treatment Option ◽  
Pten Loss

Abstract IntroductionPoor Trastuzumab (Tmab) response in human epidermal growth factor receptor 2-overexpressing gastric or gastroesophageal junction adenocarcinoma (HER2-GEA) is reported to be associated with loss of phosphatase and tensin homolog (PTEN) expression.MethodsIn a multicenter, retrospective observational study, pathological samples of HER2-GEA patients receiving Tmab-combined chemotherapy were immunohistochemically analyzed for PTEN expression. Primary endpoints were disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). The effect of PI3K pathway inhibitors on HER2-GEA cell lines were evaluated in in-vitro.ResultsAmong 145 HER2-GEA patients, 29 formed the PTEN-loss group and 116 the PTEN-positive group. In patients with target region, DCR was significantly lower in PTEN-loss than in PTEN-positive patients (67% and 87%, respectively, p=0.049). Multivariate analysis demonstrated that PTEN loss was significantly associated with shorter PFS (HR=1.63, p=0.035) and OS (HR=1.83, p=0.022). PTEN knockdown did not affect the cytostatic effect of 5-FU and cisplatin, while Tmab combined with PI3K/mTOR inhibitor NPV-BEZ235 suppressed the proliferation of PTEN knockdown cells which were resistant to Tmab alone.ConclusionIn HER2-GEA patients, PTEN loss is a predictive biomarker of Tmab resistance and prognostic factor. Molecular-targeted therapy with PI3K/mTOR inhibitor would be an effective treatment option for HER2-GEA with PTEN loss.

PTEN Expression and KRAS Mutations on Primary Tumors and Metastases in the Prediction of Benefit From Cetuximab Plus Irinotecan for Patients With Metastatic Colorectal Cancer

2009 ◽  
Vol 27 (16) ◽  
pp. 2622-2629 ◽  
Author(s):  
Fotios Loupakis ◽  
Luca Pollina ◽  
Irene Stasi ◽  
Annamaria Ruzzo ◽  
Mario Scartozzi ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Metastatic Colorectal Cancer ◽  
Growth Factor Receptor ◽  
Progression Free Survival ◽  
Pten Expression ◽  
Kras Mutations ◽  
Primary Tumors ◽  
Pten Loss ◽  
Egfr Inhibition ◽  
Paired Samples

PurposePTEN, AKT, and KRAS are epidermal growth factor receptor (EGFR) downstream regulators. KRAS mutations confer resistance to cetuximab. This retrospective study investigated the role of PTEN loss, AKT phosphorylation, and KRAS mutations on the activity of cetuximab plus irinotecan in patients with metastatic colorectal cancer (mCRC).Patients and MethodsA cohort of patients with irinotecan-refractory mCRC who were treated with cetuximab plus irinotecan was tested for PTEN immunoreactivity (ie, immunohistochemistry; IHC), pAKT IHC, and KRAS mutations. Analyses were performed both on primary tumors and on related metastases, and the association among IHC, mutational results, and treatment outcomes was investigated.ResultsOne-hundred two patients were eligible. Ninety-six primary tumors, 59 metastases, and 53 paired samples were available. Forty-nine primary tumors (58% of assessable samples) had a preserved PTEN expression (PTEN-positive), whereas 35 (40% of assessable samples) were pAKT-positive. Levels of concordance between primary tumors and metastases were 60%, 68%, and 95% for PTEN, pAKT, and KRAS, respectively. PTEN status on primary tumors and pAKT status both on primary tumors and on metastases did not predict response or progression-free survival (PFS). On metastases, 12 (36%) of 33 patients with PTEN-positive tumors were responders compared with one (5%) of 22 who had PTEN-negative tumors (P = .007). The median PFS of patients with PTEN-positive metastases was 4.7 months compared with 3.3 months for those with PTEN-negative metastases (hazard ratio [HR], 0.49; P = .005). Patients with PTEN-positive metastases and KRAS wild type had longer PFS compared with other patients (5.5 months v 3.8 months; HR, 0.42; P = .001).ConclusionPTEN loss in metastases may be predictive of resistance to cetuximab plus irinotecan. The combination of PTEN IHC and KRAS mutational analyses could help to identify a subgroup of patients with mCRC who have higher chances of benefiting from EGFR inhibition.

scholarly journals Emerging Targeted Therapies for HER2 Positive Gastric Cancer That Can Overcome Trastuzumab Resistance

Cancers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 400 ◽  
Author(s):  
Seiichiro Mitani ◽  
Hisato Kawakami
Keyword(s):  
Gastroesophageal Junction ◽  
Treatment Strategies ◽  
Growth Factor Receptor ◽  
Trastuzumab Resistance ◽  
Her2 Positive ◽  
Drug Conjugates ◽  
Gastroesophageal Junction Cancer ◽  
Development Of Resistance ◽  
Epidermal Growth ◽  
Antibody Drug

Trastuzumab, a monoclonal antibody to human epidermal growth factor receptor 2 (HER2), has improved survival in patients with HER2-positive advanced gastric or gastroesophageal junction cancer (AGC). The inevitable development of resistance to trastuzumab remains a problem, however, with several treatment strategies that have proven effective in breast cancer having failed to show clinical benefit in AGC. In this review, we summarize the mechanisms underlying resistance to HER2-targeted therapy and outline past and current challenges in the treatment of HER2-positive AGC refractory to trastuzumab. We further describe novel agents such as HER2 antibody–drug conjugates that are under development and have shown promising antitumor activity in early studies.

scholarly journals Loss of Phosphatase and Tensin Homolog or Phosphoinositol-3 Kinase Activation and Response to Trastuzumab or Lapatinib in Human Epidermal Growth Factor Receptor 2–Overexpressing Locally Advanced Breast Cancers

2011 ◽  
Vol 29 (2) ◽  
pp. 166-173 ◽  
Author(s):  
Bhuvanesh Dave ◽  
Ilenia Migliaccio ◽  
M. Carolina Gutierrez ◽  
Meng-Fen Wu ◽  
Gary C. Chamness ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Single Agent ◽  
Growth Factor Receptor ◽  
Breast Cancers ◽  
Trastuzumab Resistance ◽  
Epidermal Growth

Purpose Phosphatase and tensin homolog (PTEN) loss or activating mutations of phosphoinositol-3 (PI3) kinase (PIK3CA) may be associated with trastuzumab resistance. Trastuzumab, the humanized human epidermal growth factor receptor 2 (HER2) monoclonal antibody, and lapatinib, an epidermal growth factor receptor/HER2 tyrosine kinase inhibitor, are both established treatments for HER2-overexpressing breast cancers. Understanding of the cellular response to HER2-targeted therapies is needed to tailor treatments and to identify patients less likely to benefit. Methods We evaluated the effect of trastuzumab or lapatinib in three HER2-overexpressing cell lines. We confirmed the in vitro observations in two neoadjuvant clinical trials in patients with HER2 overexpression; 35 patients received trastuzumab as a single agent for the first 3 weeks, then docetaxel every 3 weeks for 12 weeks (trastuzumab regimen), whereas 49 patients received lapatinib as a single agent for 6 weeks, followed by trastuzumab/docetaxel for 12 weeks before primary surgery (lapatinib regimen). Apoptosis, Ki67, p-MAPK, p-AKT, and PTEN were assessed by immunohistochemistry. Genomic DNA was sequenced for PIK3CA mutations. Results Under low PTEN conditions, in vitro data indicate that lapatinib alone and in combination with trastuzumab was effective in decreasing p-MAPK and p-AKT levels, whereas trastuzumab was ineffective. In the clinical trials, we confirmed that low PTEN or activating mutation in PIK3CA conferred resistance to the trastuzumab regimen (P = .015), whereas low PTEN tumors were associated with a high pathologic complete response rate (P = .007). Conclusion Activation of PI3 kinase pathway is associated with trastuzumab resistance, whereas low PTEN predicted for response to lapatinib. These observations support clinical trials with the combination of both agents.

KRASandBRAFMutations in Advanced Colorectal Cancer Are Associated With Poor Prognosis but Do Not Preclude Benefit From Oxaliplatin or Irinotecan: Results From the MRC FOCUS Trial

2009 ◽  
Vol 27 (35) ◽  
pp. 5931-5937 ◽  
Author(s):  
Susan D. Richman ◽  
Matthew T. Seymour ◽  
Philip Chambers ◽  
Faye Elliott ◽  
Catherine L. Daly ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Prognostic Factor ◽  
Braf Mutation ◽  
Poor Prognosis ◽  
Advanced Colorectal Cancer ◽  
Progression Free Survival ◽  
Predictive Biomarker ◽  
Poor Prognostic Factor ◽  
Minimal Impact ◽  
The Impact

PurposeActivating mutation of the KRAS oncogene is an established predictive biomarker for resistance to anti–epidermal growth factor receptor (anti-EGFR) therapies in advanced colorectal cancer (aCRC). We wanted to determine whether KRAS and/or BRAF mutation is also a predictive biomarker for other aCRC therapies.Patients and MethodsThe Medical Research Council Fluorouracil, Oxaliplatin and Irinotecan: Use and Sequencing (MRC FOCUS) trial compared treatment sequences including first-line fluorouracil (FU), FU/irinotecan or FU/oxaliplatin in aCRC. Tumor blocks were obtained from 711 consenting patients. DNA was extracted and KRAS codons 12, 13, and 61 and BRAF codon 600 were assessed by pyrosequencing. Mutation (mut) status was assessed first as a prognostic factor and then as a predictive biomarker for the benefit of adding irinotecan or oxaliplatin to FU. The association of BRAF-mut with loss of MLH1 was assessed by immunohistochemistry.ResultsThree hundred eight (43.3%) of 711 patients had KRAS-mut and 56 (7.9%) of 711 had BRAF-mut. Mutation of KRAS, BRAF, or both was present in 360 (50.6%) of 711 patients. Mutation in either KRAS or BRAF was a poor prognostic factor for overall survival (OS; hazard ratio [HR], 1.40; 95% CI, 1.20 to 1.65; P < .0001) but had minimal impact on progression-free survival (PFS; HR, 1.16; 95% CI, 1.00 to 1.36; P = .05). Mutation status did not affect the impact of irinotecan or oxaliplatin on PFS or OS. BRAF-mut was weakly associated with loss of MLH1 staining (P = .012).ConclusionKRAS/BRAF mutation is associated with poor prognosis but is not a predictive biomarker for irinotecan or oxaliplatin. There is no evidence that patients with KRAS/BRAF mutated tumors are less likely to benefit from these standard chemotherapy agents.

scholarly journals No Correlation between KRAS Status and Advanced Pancreatic Adenocarcinoma Survival

2017 ◽  
Vol 6 (2) ◽  
pp. 45 ◽  
Author(s):  
Misato Ogata ◽  
Hironaga Satake ◽  
Takatsugu Ogata ◽  
Yukihiro Imai ◽  
Yukimasa Hatachi ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Growth Factor Receptor ◽  
Gene Mutations ◽  
Progression Free Survival ◽  
Patient Characteristics ◽  
Predictive Biomarker ◽  
First Line ◽  
Kras Mutations ◽  
Kras Status ◽  
The Impact

Erlotinib plus gemcitabine is one of the standard chemotherapies for unresectable pancreatic cancer. Pancreatic cancer has the highest frequency of KRAS gene mutations among human cancers, and some studies suggest that KRAS status might be a predictive biomarker for anti-epidermal growth factor receptor treatment. However, the reliability of this biomarker has not been confirmed. Here, we evaluated the impact of KRAS mutations in pancreatic cancer patients treated with first line gemcitabine-based chemotherapy. 23 patients treated with gemcitabine-based chemotherapy whose KRAS status could be examined from primary or metastatic lesions were enrolled. KRAS mutations were analyzed by sequencing codons 12 and 13. We retrospectively evaluated the correlation between KRAS status, and prognosis and treatment efficacy. Patient characteristics were as follows: median age 68 years, male/female=6/17, PS 0/1=9/14, TNM stage III/IV=1/22, and gemcitabine alone/erlotinib plus gemcitabine=13/10. Among the 23 patients, KRAS codon 12 was mutated in 15, one of whom also had mutation on codon 13. Median progression-free survival (PFS) and overall survival (OS) of all patients were 4.3 months (95% confidence interval (CI): 3.1 to 5.4) and 8.1 months (95% CI: 5.9 to 10.0; events in 96%), respectively. KRAS status showed no association with PFS (p=0.310), OS (p=0.934), or the efficacy of treatment with (p=0.833) or without erlotinib (p=0.478). Thus, in this study, there was no correlation between KRAS status and the efficacy of first line chemotherapy with gemcitabine with or without erlotinib. Identification of a rationale for personalized medicine in pancreatic cancer will require further exploratory prospective studies.

scholarly journals BRAF status modulates Interelukin-8 expression through a CHOP-dependent mechanism in colorectal cancer

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Fabiana Conciatori ◽  
Chiara Bazzichetto ◽  
Carla Azzurra Amoreo ◽  
Isabella Sperduti ◽  
Sara Donzelli ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Gene Promoter ◽  
Predictive Biomarker ◽  
Open Chromatin ◽  
Therapeutic Success ◽  
Rna Pol Ii ◽  
Pten Loss ◽  
Braf Inhibition ◽  
Dependent Mechanism

Abstract Inflammation might substantially contribute to the limited therapeutic success of current systemic therapies in colorectal cancer (CRC). Amongst cytokines involved in CRC biology, the proinflammatory chemokine IL-8 has recently emerged as a potential prognostic/predictive biomarker. Here, we show that BRAF mutations and PTEN-loss are associated with high IL-8 levels in CRC models in vitro and that BRAF/MEK/ERK, but not PI3K/mTOR, targeting controls its production in different genetic contexts. In particular, we identified a BRAF/ERK2/CHOP axis affecting IL-8 transcription, through regulation of CHOP subcellular localization, and response to targeted inhibitors. Moreover, RNA Pol II and an open chromatin status in the CHOP-binding region of the IL-8 gene promoter cooperate towards increased IL-8 expression, after a selective BRAF inhibition. Overall, our data show that IL-8 production is finely and differentially regulated depending on the tumor genetic context and might be targeted for therapeutic purposes in molecularly defined subgroups of CRC patients.

Effect of the leukocyte chemoattractant chemerin on PTEN via CMKLR1 in human prostate cancer.

2018 ◽  
Vol 36 (6_suppl) ◽  
pp. 282-282
Author(s):  
Russell Kent Pachynski ◽  
Robert Crowder ◽  
William Shin ◽  
Keith Rennier
Keyword(s):  
Tumor Cell ◽  
Immune Cell ◽  
Pten Expression ◽  
Intrinsic Activity ◽  
Dependent Manner ◽  
In Vitro Proliferation ◽  
Immune Effector ◽  
Pten Loss ◽  
Protein Levels

282 Background: Recent data in preclinical models has shown that phosphatase and tensin homolog (PTEN) loss correlated with decreased tumor immune cell infiltration as well as decreased response to T cell-based immunotherapy. Chemerin ( RARRES2) is a recently identified endogenous leukocyte chemoattractant shown to recruit innate immune cells through its G-protein coupled receptor CMKLR1. RARRES2 is commonly downregulated in prostate and other cancers (eg sarcoma) compared to their normal tissue counterparts. Our previous preclinical studies showed that forced overexpression of chemerin in tumors was capable of recruiting immune effector cells into the tumor microenvironment and suppressing tumor growth. Methods: Here, we investigate the effects of chemerin on tumor cell intrinsic processes by exposing prostate and sarcoma tumor lines to exogenous recombinant chemerin in vitro. Evaluation of PTEN was performed at both the mRNA and protein levels, using both quantitative PCR as well as Western blotting. PTEN immunoprecipitation by and Malachite Green assays were used to determine PTEN activity. In vitro invasion assays were performed to investigate the functional impact of chemerin exposure on tumor intrinsic activity. Knockdown of CMKLR1 using siRNA was performed to determine its role in tumor response. Results: Using both prostate and sarcoma tumor lines, we found exogenous chemerin was able to significantly upregulate PTEN expression at both the mRNA and protein levels in a dose-dependent manner. PTEN phosphatase activity was also significantly increased by chemerin. Exposure to chemerin did not result in increased apoptosis or altered in vitro proliferation. Importantly, chemerin treatment significantly decreased in vitro tumor invasion. Knockdown of CMKLR1 resulted in loss of chemerin-induced PTEN and PTEN activity and restored tumor migration, suggesting a link between this GPCR and PTEN. Conclusions: For the first time to our knowledge, we have shown a link between chemerin and PTEN expression and activity in both prostate and sarcoma tumor lines. This work has potential clinical implications on both tumor cell intrinsic and extrinsic responses to chemerin-based immunotherapeutic strategies.

Prospective analysis of microRNA 31-3p (miR31-3p) as a predictive biomarker of response to anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies (mABs) in patients with metastatic colorectal cancer (mCRC).

2019 ◽  
Vol 37 (4_suppl) ◽  
pp. 548-548
Author(s):  
Gayathri Anandappa ◽  
Andrea Lampis ◽  
David Cunningham ◽  
Kyriakos Kouvelakis ◽  
Khurum Khan ◽  
...  
Keyword(s):  
Single Agent ◽  
Growth Factor Receptor ◽  
Previous Treatment ◽  
Progression Free Survival ◽  
Predictive Biomarker ◽  
Liquid Biopsies ◽  
Logistic Regression Models ◽  
Best Response ◽  
Ras Status ◽  
Pre Treatment

548 Background: RAS status in tissue and/or liquid biopsies and tumour location (sidedness) are predictive markers of patients’ response to anti-EGFR mABs. MiR-31-3p expression has been correlated with clinical benefit from anti-EGFR mABs with chemotherapy. We aimed to validate the predictive power of miR-31-3p in a prospective cohort of chemo-refractory mCRC patients treated with single agent anti-EGFR mABs in the PROSPECT-C trial (NCT02994888). Methods: MiR-31-3p was tested by in-situ hybridization in 91 pre-treatment (PT) core biopsies from 45 mCRC patients. Sequential tissue biopsies obtained PT, at time of best response and at disease progression were tested to monitor changes in miR-31-3p expression over treatment. In 34 patients miR-31-3p, gender, sidedness, previous lines of treatment and RAS status in PT cell free (cf) DNA were evaluated in multivariate Cox and logistic regression models. Results: Patients with low miR-31-3p expression in PT biopsies showed better overall response rate (ORR: 58.3% vs 22.2%), median progression free survival (mPFS: 4.21 vs 2.27 months) and overall survival (mOS: 4.21 vs 2.27 mo) compared to those with high miR-31-3p expression (Hazard Ratio for PFS high vs low: 1.96; 95% CI: 0.98-3.88; p: 0.06 and HR for OS high vs low: 2.14; 95% CI: 1.04- 4.40; p: 0.04) adjusting for age, gender and sidedness. There was significant association between ORR and miR-31-3p expression (χ2 test p: 0.029). MiR-31-3p expression was an independent predictor of response, adjusting for gender, previous treatment lines and RAS (odds ratio: 0.14; 95% CI: 0.02-1.00, p: 0.048). A trend towards improved mPFS (5.10 vs 2.27 mo) and mOS (15.23 vs 4.67 mo) was noted in miR31-3p low vs high group in cfDNA RAS wild-type patients. No significant change in miR-31-3p expression were observed in archival tissue and sequential tissue biopsies. Conclusions: Our study validates the role of miR-31-3p as potential predictive biomarker of selection for anti-EGFR mABs. Further studies are needed to test if miR-31-3p combined with cfDNA RAS test can identify best responders in specific clinical niches.

Role of HER3 expression and PTEN loss in patients with HER2-overexpressing metastatic breast cancer (MBC) patients who received taxane plus trastuzumab treatment.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 637-637
Author(s):  
Yeon Hee Park ◽  
Hyun Ae Jung ◽  
Won Jin Chang ◽  
Moon Ki Choi ◽  
Jung Yong Hong ◽  
...  
Keyword(s):  
Metastatic Breast ◽  
Progression Free Survival ◽  
Pi3k Pathway ◽  
Pten Expression ◽  
Her2 Positive ◽  
Pten Loss ◽  
Trastuzumab Treatment ◽  
First Line Therapy ◽  
Predictive And Prognostic Biomarker

637 Background: The HER3 receptor is a key member of ErbB family and preferentially signals through the PI3K pathway. Formation of dimers between HER3 and HER2 seems to be crucial for HER2-driven signals in HER2 overexpressing tumors. Given the fact that HER2-HER3 is considered the most active signalling dimer of the ErbB system, HER3 activity may contribute to the resistance of trastuzumab. PTEN plays a well-established role in the negative regulation of the PI3K pathway. Our aim of this study was to investigate the role of HER3 and PTEN expression in patients with HER2 overexpressed MBC. Methods: One-hundred twenty-five MBC patients who were treated with taxane plus trastuzumab chemotherapy as the first line therapy were included in this analysis. Immunohistochemical stainings (IHC) with HER3 and PTEN antibody were conducted retrospectively. Results: Median age was 48 years. HER3 IHC was graded from 0 to 3. PTEN IHC was scored as multiplication of intensity and proportion from 0 to 300. The patients who had negative HER3 stain showed better progression free survival (PFS) to taxane plus trastuzumab chemotherapy than those positive HER3 stain (p=0.001, median PFS 21 vs. 11 mo.). The patients who had PTEN score of more than 20 showed longer PFS than those PTEN score of 20 or less than 20 (p=0.006, median PFS 13 vs. 9 mo.). The patients who had PTEN score of more than 20 showed longer overall survival (OS) than those PTEN score of 20 or less than 20 (p=0.005, median OS 48 vs. 25 mo.). HER3 negativity and PTEN loss were identified as independent risk factors for PFS [Hazard Ratio (HR) 0.4 (95% CI 0.3-0.8 for HER3 negativity; HR 2.1 (95% CI 1.2-3.7) for PTEN loss]. However, PTEN loss (HR 3.1 [95% CI 1.6-6.3]) was identified as an independent risk factor for OS. Conclusions: HER3 and PTEN expression may be predictive markers for trastuzumab treatment in HER2-positive MBCs. PTEN expression may have a potential predictive and prognostic biomarker for trastuzumab treatment.

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