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Dive into the research topics where Maartje Los is active.

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Featured researches published by Maartje Los.


Cancer | 2014

Clinical Activity and Tolerability of Enzalutamide ( MDV3100) in Patients With Metastatic, Castration- Resistant Prostate Cancer Who Progress After Docetaxel and Abiraterone Treatment

Sushil K. Badrising; Vincent van der Noort; Inge M. van Oort; H. Pieter van den Berg; Maartje Los; Paul Hamberg; Jules L.L.M. Coenen; Alfons J.M. van den Eertwegh; Igle J. de Jong; Emile D. Kerver; Harm van Tinteren; Andries M. Bergman

Enzalutamide (Enz) and abiraterone acetate (AA) are hormone treatments that have a proven survival advantage in patients with metastatic, castration‐resistant prostate cancer who previously received docetaxel (Doc). Recently, limited activity of AA after Enz and of Enz after AA was demonstrated in small cohort studies. Here, the authors present the activity and tolerability of Enz in patients who previously received AA and Doc in the largest cohort to date.


Seminars in Oncology | 2001

The potential role of antivascular therapy in the adjuvant and neoadjuvant treatment of cancer.

Maartje Los; Emile E. Voest

Antivascular therapy may be considered as one of the most promising approaches in the treatment of cancer. Antivascular treatment may be divided in antiangiogenesis and vascular targeting. Antiangiogenic therapy prevents neovascularization by inhibiting proliferation, migration, and/or differentiation of endothelial cells. Vascular targeting is directed at the existing tumor vasculature. Several inhibitors of angiogenesis are currently being tested in clinical cancer trials. The challenge for the next decade is to incorporate antivascular approaches into conventional treatment strategies. This review will summarize the conceptual basis of antivascular therapy and discuss the potential role of these agents in the adjuvant, neoadjuvant, and perioperative treatment of cancer.


FEBS Letters | 2004

Fibronectin is a hypoxia-independent target of the tumor suppressor VHL

Hans A.R. Bluyssen; Martijn P. Lolkema; Moniek van Beest; Michelle Boone; Cristel Snijckers; Maartje Los; Martijn F. B. G. Gebbink; Branko Braam; Frank C. P. Holstege; Rachel H. Giles; Emile E. Voest

The von Hippel–Lindau (VHL) tumor suppressor gene regulates the extracellular matrix by controlling fibronectin deposition. To identify novel VHL target genes, we subjected mRNA from VHL‐deficient RCC cells (786‐0‐pRC) and a transfectant re‐expressing wildtype VHL (786‐0‐VHL) to differential expression profiling. Among the differentially expressed genes, we detected that fibronectin is upregulated in the presence of VHL, while it is not affected by hypoxia. Thus regulation of fibronectin deposition by VHL occurs at the transcriptional level, irrespective of oxygen levels.


JAMA Oncology | 2016

Angiotensin II-Receptor Inhibition With Candesartan to Prevent Trastuzumab-Related Cardiotoxic Effects in Patients With Early Breast Cancer : A Randomized Clinical Trial

Annelies H. Boekhout; Jourik A. Gietema; Bojana Milojkovic Kerklaan; Erik van Werkhoven; Renske Altena; Aafke Honkoop; Maartje Los; Willem M. Smit; Peter Nieboer; Carolien H. Smorenburg; Caroline M. Mandigers; Agnes J. van der Wouw; Lonneke Kessels; Annette W. G. van der Velden; P.B. Ottevanger; Tineke J. Smilde; Jaap de Boer; Dirk J. van Veldhuisen; Ido P. Kema; Elisabeth G.E. de Vries; Jan H. M. Schellens

IMPORTANCE This is the first randomized placebo-controlled evaluation of a medical intervention for the prevention of trastuzumab-related cardiotoxic effects. OBJECTIVE To determine as the primary end point whether angiotensin II antagonist treatment with candesartan can prevent or ameliorate trastuzumab-related cardiotoxic effects, defined as a decline in left ventricular ejection fraction (LVEF) of more than 15% or a decrease below the absolute value 45%. DESIGN This randomized, placebo-controlled clinical study was conducted between October 2007 and October 2011 in 19 hospitals in the Netherlands, enrolling 210 women with early breast cancer testing positive for human epidermal growth factor receptor 2 (HER2) who were being considered for adjuvant systemic treatment with anthracycline-containing chemotherapy followed by trastuzumab. INTERVENTIONS A total of 78 weeks of candesartan (32 mg/d) or placebo treatment; study treatment started at the same day as the first trastuzumab administration and continued until 26 weeks after completion of trastuzumab treatment. MAIN OUTCOMES AND MEASURES The primary outcome was LVEF. Secondary end points included whether the N-terminal of the prohormone brain natriuretic peptide (NT-proBNP) and high-sensitivity troponin T (hs-TnT) can be used as surrogate markers and whether genetic variability in germline ERBB2 (formerly HER2 or HER2/neu) correlates with trastuzumab-related cardiotoxic effects. RESULTS A total of 206 participants were evaluable (mean age, 49 years; age range, 25-69 years) 103 in the candesartan group (mean age, 50 years; age range, 25-69 years) and 103 in the placebo group (mean age, 50 years; age range, 30-67 years). Of these, 36 manifested at least 1 of the 2 primary cardiac end points. There were 3.8% more cardiac events in the candesartan group than in the placebo group (95% CI, -7% to 15%; P = .58): 20 events (19%) and 16 events (16%), respectively. The 2-year cumulative incidence of cardiac events was 0.28 (95% CI, 0.13-0.40) in the candesartan group and 0.16 (95% CI, 0.08-0.22) in the placebo group (P = .56). Candesartan did not affect changes in NT-proBNP and hs-TnT values, and these biomarkers were not associated with significant changes in LVEF. The Ala1170Pro homozygous ERBB2 genotype was associated with a lower likelihood of the occurrence of a cardiac event compared with Pro/Pro + Ala/Pro genotypes in multivariate analysis (odds ratio, 0.09; 95% CI, 0.02-0.45; P = .003). CONCLUSIONS AND RELEVANCE The findings do not support the hypothesis that concomitant use of candesartan protects against a decrease in left ventricular ejection fraction during or shortly after trastuzumab treatment in early breast cancer. The ERBB2 germline Ala1170Pro single nucleotide polymorphism may be used to identify patients who are at increased risk of trastuzumab-related cardiotoxic effects. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00459771.


Annals of Oncology | 2011

Response to influenza virus vaccination during chemotherapy in patients with breast cancer

A. Meerveld-Eggink; O. de Weerdt; A.M.T. van der Velden; Maartje Los; A. W G van der Velden; Jacqueline Stouthard; Marten Nijziel; M. Westerman; Aart Beeker; R. van Beek; Ger T. Rijkers; Douwe H. Biesma

BACKGROUND Patients receiving chemotherapy are at increased risk for influenza virus infection. Little is known about the preferred moment of vaccination during chemotherapy. PATIENTS AND METHODS Breast cancer patients received influenza vaccination during FEC (5-fluorouracil, epirubicin and cyclophosphamide)-containing chemotherapy regimens. Patients were randomised for early (day 4) or late (day 16) vaccination during the chemotherapy cycle. Influenza virus-specific antibody titres were determined before and 3 weeks after vaccination by haemagglutination inhibition. RESULTS We included 38 breast cancer patients (20 in the early and 18 in the late group) and 21 healthy controls. The overall patient group had significant lower responses to the vaccine compared with healthy controls. Patients vaccinated at day 4 tended to have higher antibody titres as compared with patients vaccinated at day 16, although the difference in post-vaccination titres is not statistically significant. Geometric mean titres post-vaccination for day 4 versus day 16 were 63.7 versus 29.5 (H3N2), 28.2 versus 19.6 (H1N1) and 29.8 versus 16.0 (B/Brisbane), respectively. CONCLUSIONS Patients on chemotherapy have significantly lower responses to influenza virus vaccination compared with healthy controls. Vaccination early during the chemotherapy cycle induces better responses than does vaccination at day 16 of the cycle. Follow-up studies are needed to confirm this effect.


Annals of Oncology | 2014

A randomized phase III study comparing pegylated liposomal doxorubicin with capecitabine as first-line chemotherapy in elderly patients with metastatic breast cancer: results of the OMEGA study of the Dutch Breast Cancer Research Group BOOG

C.H. Smorenburg; S. de Groot; A.E. van Leeuwen-Stok; Marije E. Hamaker; A.N.M. Wymenga; H de Graaf; F. E. de Jongh; J.J. Braun; Maartje Los; E. Maartense; H. van Tinteren; J. W. R. Nortier; C. Seynaeve

BACKGROUND Prospective data on chemotherapy for elderly patients with metastatic breast cancer (MBC) remain scarce. We compared the efficacy and safety of first-line chemotherapy with pegylated liposomal doxorubicin (PLD) versus capecitabine in MBC patients aged ≥65 years in a multicentre, phase III trial. PATIENTS AND METHODS Patients were randomized to six cycles of PLD (45 mg/m2 every 4 weeks) or eight cycles of capecitabine (1000 mg/m2 twice daily, day 1-14 every 3 weeks). RESULTS The study enrolled 78 of the planned 154 patients and was closed prematurely due to slow accrual and supply problems of PLD. Many included patients were aged ≥75 years (54%) and vulnerable (≥1 geriatric condition: 71%). The median dose intensity was 85% for PLD and 84% for capecitabine, respectively. In both arms, the majority of patients completed at least 12 weeks of treatment (PLD 73%; capecitabine 74%). After a median follow-up of 39 months, 77 patients had progressed and 62 patients had died of MBC. Median progression-free survival was 5.6 versus 7.7 months (P = 0.11) for PLD and capecitabine, respectively. Median overall survival was 13.8 months for PLD and 16.8 months for capecitabine (P = 0.59). Both treatments were feasible, grade 3 toxicities consisting of fatigue (both arms: 13%), hand-foot syndrome (PLD: 10%; capecitabine: 16%), stomatitis (PLD: 10%; capecitabine: 3%), exanthema (PLD: 5%) and diarrhoea (PLD: 3%; capecitabine: 5%). Only 1 of 10 patients aged ≥80 years completed chemotherapy, while 3 and 6 patients discontinued treatment due to toxicity or progressive disease, respectively. CONCLUSION Both PLD and capecitabine demonstrated comparable efficacy and acceptable tolerance as first-line single-agent chemotherapy in elderly patients with MBC, even in vulnerable patients or patients aged ≥75 years. However, patients aged ≥80 years were unlikely to complete chemotherapy successfully. CLINICAL TRIAL NUMBERS EudraCT 2006-002046-10; ISRCTN 11114726; CKTO 2006-09; BOOG 2006-02.BACKGROUND Prospective data on chemotherapy for elderly patients with metastatic breast cancer (MBC) remain scarce. We compared the efficacy and safety of first-line chemotherapy with pegylated liposomal doxorubicin (PLD) versus capecitabine in MBC patients aged ≥65 years in a multicentre, phase III trial. PATIENTS AND METHODS Patients were randomized to six cycles of PLD (45 mg/m(2) every 4 weeks) or eight cycles of capecitabine (1000 mg/m(2) twice daily, day 1-14 every 3 weeks). RESULTS The study enrolled 78 of the planned 154 patients and was closed prematurely due to slow accrual and supply problems of PLD. Many included patients were aged ≥75 years (54%) and vulnerable (≥1 geriatric condition: 71%). The median dose intensity was 85% for PLD and 84% for capecitabine, respectively. In both arms, the majority of patients completed at least 12 weeks of treatment (PLD 73%; capecitabine 74%). After a median follow-up of 39 months, 77 patients had progressed and 62 patients had died of MBC. Median progression-free survival was 5.6 versus 7.7 months (P = 0.11) for PLD and capecitabine, respectively. Median overall survival was 13.8 months for PLD and 16.8 months for capecitabine (P = 0.59). Both treatments were feasible, grade 3 toxicities consisting of fatigue (both arms: 13%), hand-foot syndrome (PLD: 10%; capecitabine: 16%), stomatitis (PLD: 10%; capecitabine: 3%), exanthema (PLD: 5%) and diarrhoea (PLD: 3%; capecitabine: 5%). Only 1 of 10 patients aged ≥80 years completed chemotherapy, while 3 and 6 patients discontinued treatment due to toxicity or progressive disease, respectively. CONCLUSION Both PLD and capecitabine demonstrated comparable efficacy and acceptable tolerance as first-line single-agent chemotherapy in elderly patients with MBC, even in vulnerable patients or patients aged ≥75 years. However, patients aged ≥80 years were unlikely to complete chemotherapy successfully. CLINICAL TRIAL NUMBERS EudraCT 2006-002046-10; ISRCTN 11114726; CKTO 2006-09; BOOG 2006-02.


International Journal of Cancer | 2015

CAST: A retrospective analysis of cabazitaxel and abiraterone acetate sequential treatment in patients with metastatic castrate-resistant prostate cancer previously treated with docetaxel

Michel D. Wissing; Jules L.L.M. Coenen; Pieter H. van den Berg; Hans M. Westgeest; Alfons J.M. van den Eertwegh; Inge M. van Oort; Monique M.E.M. Bos; Andre M. Bergman; Paul Hamberg; Albert J. ten Tije; Maartje Los; Martijn P. Lolkema; Ronald de Wit; Hans Gelderblom

Cabazitaxel and abiraterone have both received approval for treating metastatic castrate‐resistant prostate cancer (mCRPC) patients after first‐line docetaxel therapy. In the cabazitaxel and abiraterone sequential treatment (CAST) study, the clinical outcome of docetaxel‐treated mCRPC patients treated sequentially with both cabazitaxel and abiraterone was studied. Data were collected retrospectively from mCRPC patients at 12 hospitals across the Netherlands who initiated cabazitaxel and/or abiraterone before December 2012. Primary outcome measure was overall survival (OS); secondary measures were progression‐free survival (PFS), biochemical PFS, and best clinical and PSA response. Hospital admission data during treatment were collected, as well as toxicities resulting in treatment discontinuation or patient death. Sixty‐three and 69 patients received Cab→Abi (cabazitaxel prior to abiraterone) and Abi→Cab before July 10th, 2013, respectively. Median OS was 19.1 months and 17.0 months in Cab→Abi and Abi→Cab treated patients, respectively (p = 0.369). Median PFS and biochemical PFS were significantly longer in Cab→Abi treated patients: 8.1 versus 6.5 (p = 0.050) and 9.5 versus 7.7 months (p = 0.024), respectively. Although partial responses to cabazitaxel occurred in both groups, Abi→Cab treated patients had a significantly decreased antitumor response from cabazitaxel than Cab→Abi treated patients (median PFS 5.0 versus 2.6 months, p < 0.001). Minor differences in toxicities were observed based on therapy sequence; generally, toxicity from cabazitaxel could be severe, while abiraterone toxicity was milder. This retrospective analysis indicates that primary progression on cabazitaxel or abiraterone did not preclude a response to the other agent in mCRPC patients. However, tumor response of both agents, particularly cabazitaxel, was lower when administered as higher‐line therapy in the selected study population.


European Journal of Cancer | 2013

Analysis of docetaxel therapy in elderly (⩾70 years) castration resistant prostate cancer patients enrolled in the Netherlands Prostate Study

Frank L. Gerritse; Hielke J. Meulenbeld; Jeanine M.L. Roodhart; A. Van der Velden; R.J.B. Blaisse; Tineke J. Smilde; Z. Erjavec; R. de Wit; Maartje Los

BACKGROUND Prostate cancer truly is an age-associated disease. Due to the increased life expectancy and more sensitive diagnostic techniques in the Western world, prostate cancer is diagnosed more frequently and with rapidly increasing incidence and prevalence rates. However, age above 65 or 70 years has been an exclusion criterion in clinical trials for decades and the knowledge about chemotherapy tolerance in elderly is limited. METHODS We performed a retrospective analysis of data acquired from the recently published Netherlands Prostate Study (NePro) to evaluate the influence of advanced age on docetaxel therapy in elderly men (>70 years) with castration resistant prostate cancer (CRPC) and bone metastases. Statistical analyses were performed stratified for age into four categories: <70 (n=315), 70-74 (n=150), 75-79 (n=85), and ≥80 years old (n=18). RESULTS We analysed 568 patients (median age 68.1 years, range 46-89 years, 44.5% aged ≥70 years). There was no relation between dosage and age (p=0.60). We found no significant differences between the number of dose reductions, time to progression (TTP), overall survival, chemotherapy tolerance and toxicity up to the age of 80 years. However, when compared to younger men, men aged 80 years or above more frequently experienced grade 3/4 toxicity and were five times less likely to complete the first three treatment cycles at the intended dose (Odds ratio (OR) 5.34, p=0.0052) and showed decreased overall survival (15.3 months versus 24.5 months in <80 years group, p=0.020). CONCLUSION In CRPC patients up to the age of 80 years, docetaxel chemotherapy is well tolerated, with toxicity levels and TTP comparable to those of younger patients. For chemotherapeutic treatment of patients above the age of 80 years an individual assessment should be made.


Medicine and Science in Sports and Exercise | 2016

Effects of an Exercise Program in Colon Cancer Patients undergoing Chemotherapy.

Jonna K. van Vulpen; Miranda J. Velthuis; Charlotte N. Steins Bisschop; Noémie Travier; Bram van den Buijs; Frank J.G. Backx; Maartje Los; Frans Erdkamp; Haiko J. Bloemendal; Miriam Koopman; Marnix A J de Roos; Marlies Verhaar; Daan ten Bokkel-Huinink; Elsken van der Wall; Petra H.M. Peeters; Anne M. May

PURPOSE Fatigue is a common problem among colon cancer patients and typically increases during chemotherapy. Exercise during chemotherapy might have beneficial effects on fatigue. To investigate the short- and long-term effects of an exercise program in colon cancer patients during adjuvant treatment, the Physical Activity During Cancer Treatment study was conducted. METHODS In this multicenter randomized controlled trial, 33 colon cancer patients undergoing chemotherapy (21 men and 12 women) were randomly assigned to either a group receiving an 18-wk supervised exercise program (n = 17) or to usual care (n = 16). The primary outcome was fatigue as measured by the Multidimensional Fatigue Inventory and the Fatigue Quality List. Secondary outcomes were quality of life, physical fitness, anxiety, depression, body weight, and chemotherapy completion rate. Outcome assessment took place at baseline, postintervention (18 wk) and at 36 wk. RESULTS Intention-to-treat mixed linear model analyses showed that patients in the intervention group experienced significantly less physical fatigue at 18 wk and general fatigue at 36 wk (mean between group differences, -3.2; 95% confidence interval [CI], -6.2 to -0.2; effect size [ES], -0.9 and -2.7; 95% CI, -5.2 to -0.1; ES, -0.8, respectively), and reported higher physical functioning (12.3; 95% CI, 3.3-21.4; ES, 1.0) compared with patients in the usual care group. CONCLUSION The Physical Activity During Cancer Treatment trial shows that an 18-wk supervised exercise program in colon cancer patients during chemotherapy is safe and feasible. The intervention significantly reduced physical fatigue at 18 wk and general fatigue at 36 wk. Considering the number of patients included in the present study, replication in a larger study population is required.


Vaccine | 2013

Serum antibody response to influenza virus vaccination during chemotherapy treatment in adult patients with solid tumours.

M. Wumkes; A.M.T. van der Velden; Maartje Los; Mathias Leys; Aart Beeker; Marten Nijziel; A. W G van der Velden; M. Westerman; A. Meerveld-Eggink; Ger T. Rijkers; Douwe H. Biesma

BACKGROUND Higher rates of hospitalization and mortality are described in oncology patients with influenza virus infection compared to the general population. Yearly influenza vaccination is recommended for patients treated with chemotherapy. The optimal moment to administer the vaccine during a treatment cycle has not been studied extensively. PATIENTS AND METHODS During the influenza season 2011-2012 we conducted a multicenter randomized controlled trial (OFLUVAC, NTR2858, no sponsoring) in the Netherlands. Patients receiving adjuvant chemotherapy for breast or colorectal cancer were randomized between early (day 5 after chemotherapy) and late (day 16 after chemotherapy) vaccination with the influenza virus vaccine (Influvac(®) 2011/2012-Vaxigrip(®) 2011/2012). Influenza virus-specific antibody titres were determined before, 3 and 12 weeks after vaccination by haemagglutination inhibition. RESULTS Thirty-eight breast cancer patients (early=21; late=17) and 18 colorectal cancer patients (early=8; late=10) were analyzed. In breast cancer patients overall serologic responses were adequate. A statistically significant higher response in patients who received early compared to late vaccination in the chemotherapy cycle was observed. Geometric mean titres post vaccination on day 5 versus day 16 were 69.3 versus 27.4 (H3N2), 76.4 versus 17.5 (H1N1) and 34.4 versus 26.0 (B/Brisbane), respectively. In colorectal cancer patients overall serologic responses were adequate, no significant difference was found between early and late vaccination. Geometric mean titres post vaccination on day 5 versus day 16 were 170.1 versus 192.4 (H3N2), 233.0 versus 280.8 (H1N1) and 62.6 versus 75.9 (B/Brisbane), respectively. CONCLUSION Overall antibody response to the influenza virus vaccine in patients treated with chemotherapy for breast or colorectal cancer patients is adequate. Breast cancer patients seem to mount the best antibody response when vaccinated early after a chemotherapy cycle (≤day 5). No difference was found between early and late vaccination in colorectal cancer patients.

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Paul Hamberg

Erasmus University Medical Center

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Agnes Jager

Erasmus University Rotterdam

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Hans Gelderblom

Leiden University Medical Center

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