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Biomedical subjects

P J Bakker

Publications and source records attributed to P J Bakker.

At least 19 recordsLinked to original sources
PubMed2001

High concentration of Daunorubicin and Daunorubicinol in human malignant astrocytomas after systemic administration of liposomal Daunorubicin.

The value of chemotherapy in patients with malignant astrocytoma remains controversial. In our laboratories in vitro experiments with organotypic spheroid cultures showed superior effectiveness of anthracyclines. Systemic administration did not provide in therapeutic concentrations so far. Because recent studies on Daunorubicin in liposomes in the treatment of Kaposi sarcoma have shown effectiveness with diminished systemic toxicity, we administered intravenously a single dose of Daunorubicin in liposomes in eight patients at different intervals prior to surgery (12-50 h). In samples taken from tumor, tumor-edge and where possible from adjacent brain, the levels of Daunorubicin and its active metabolite Daunorubicinol were assessed with high performance liquid chromatography. Here we report that high concentrations of Daunorubicin and Daunorubicinol were found in malignant gliomas after systemic administration of liposomal Daunorubicin.

Adult↗
PubMed2000

Long term survivors of childhood brain cancer have an increased risk for cardiovascular disease.

BACKGROUND: Cranial irradiation for children with brain tumors frequently leads to neuroendocrine deficiencies. In this controlled study, the authors investigated risk factors for cardiovascular disease (CVD) for long term survivors of childhood brain cancer. They also tested whether the presence of these risk factors was related to endocrine status. METHODS: In 26 survivors of childhood brain cancer (mean age, 25.8 years; mean posttreatment interval, 16 years) and 29 healthy controls (mean age, 27.7 years), the blood pressure, smoking habits, body mass index (BMI), and waist/hip (W/H) ratio were determined. Lipids and lipoproteins were measured and endocrine function was assessed. Carotid intima-media thickness (IMT) measurements were performed by high resolution ultrasonography. RESULTS: In the survivors of childhood brain cancer, systolic blood pressure and W/H ratio were elevated compared with controls. The cholesterol/high density lipoprotein ratio (4.7 +/- 1.7 vs. 3.4 +/- 0.8 mmol/L, P = 0.0005), low density lipoprotein cholesterol level (3.3 +/- 0.9 vs. 2.8 +/- 0.6 mmol/L, P = 0.027), and apolipoprotein B level (P = 0.001) were higher in survivors of childhood brain cancer, whereas HDL cholesterol was lower (P = 0.005). The IMT was increased in the survivor group, but only in the carotid bulb (0.63 mm +/- 1.6 vs. 0.53 mm +/- 1.1, P = 0.02), not in the internal or common carotid artery. In the absolute growth hormone deficient (GHD) population (n = 9), LDL cholesterol and apolipoprotein B levels were elevated and the W/H ratio was particularly increased compared with the other survivors of childhood brain cancer. CONCLUSIONS: For long term survivors of brain cancer, the risk for CVD is strongly increased due to dyslipidemia, central obesity, and elevated systolic blood pressure, particularly for those with GHD. The first effects of this increased risk for CVD were observed in the carotic bulb, as assessed by IMT measurements. Efforts should be directed at CVD prevention by risk factor control.

Adolescent↗
PubMed2000

[Malignant intracranial germ cell tumor treated with chemotherapy and radiotherapy without histopathological confirmation].

In two men aged 19 and 24 years, a rare malignant intracranial germ cell tumour was diagnosed in the pineal gland region and in the second patient in a suprasellar position as well. Although histological confirmation is required in general to diagnose a malignancy, obtaining it can be difficult and potentially dangerous in case of intracranial neoplasms. The clinical picture of a young patient with an intracerebral tumour localised in the midline of the brain and increased levels of the tumour markers alpha-foetoprotein and/or human chorion gonadotrophin (beta-HCG) in blood and/or CSF makes any other diagnosis highly unlikely. There is no place for radical surgery in the first-line treatment of malignant intracerebral germ cell tumours because of the sensitivity to radio- and chemotherapy. Also, the sensitivity to chemotherapy makes it possible to reduce radiation volume and dose in an effort to avoid the serious complications of craniospinal irradiation. Both patients responded well to chemotherapy based on cisplatin followed by radiotherapy.

Adult↗
PubMed2000

The effect of p53-function on the sensitivity to paclitaxel with or without hyperthermia in human colorectal carcinoma cells.

The importance of p53-function for the sensitivity to paclitaxel with and without hyperthermia (HT) was studied in an isogenic cell line system. The inactivation of p53 decreased sensitivity to paclitaxel (1.1-2.5-fold), which correlated with a lower induction of apoptosis. The magnitude of the G2/M arrest after treatment with paclitaxel was similar in all cell lines. The cytotoxicity of paclitaxel was not enhanced by HT in either wild-type p53 or p53-inactivated cells. In conclusion, cellular sensitivity to paclitaxel depends on p53-function by its ability to induce apoptosis. Irrespective of the p53-function HT was not able to enhance the sensitivity to paclitaxel.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Inactivation of p53 and of pRb protects human colorectal carcinoma cells against hyperthermia-induced cytotoxicity and apoptosis.

Cell-cycle checkpoints are thought to govern the cellular response to external stimuli. The involvement of the p53 tumour-suppressor protein and the retinoblastoma protein (pRb) in the cell-cycle checkpoint in G1 phase is well established. However, little is known about the importance of these G1 checkpoint regulators in hyperthermia-induced cytotoxicity. Such information is relevant because of the clinical application of hyperthermia in combination with chemotherapy or with radiotherapy. The effects of p53 or pRb inactivation were studied in a well-established isogenic system using the human colorectal carcinoma cell line (RKO). The cells were treated with clinically relevant heat doses (60 min at 40-43 degrees C). Cell survival, cell-cycle redistribution and induction of apoptosis were investigated. Survival of the p53-inactivated transfectants was higher than that of the wild-type p53 cells. The pRb-inactivated transfectants showed an intermediate sensitivity to hyperthermia. All transfectants showed G2 arrest after hyperthermia and the appearance of a sub-G1 population. The induction of apoptosis was inhibited in p53-inactivated and pRb-inactivated transfectants. These results suggest that p53 and/or pRb status may be an important determinant of the clinical response to hyperthermia.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

A multi-center prospective phase II study of high-dose chemotherapy in germ-cell cancer patients relapsing from complete remission.

PURPOSE: To prospectively determine the efficacy of repeated high-dose alkylating chemotherapy to salvage patients with germ-cell tumors who relapsed after adequate first-line chemotherapy. PATIENTS AND METHODS: Patients with germ-cell cancers relapsing from a first, second or third complete remission induced by chemotherapy were offered to participate in a Dutch national prospective trial with broad entry criteria. The salvage treatment began with a conventional dose of ifosfamide (4 g/m2 on day 1) and etoposide (100 mg/m2 on days 1, 2 and 3) followed by daily s.c. administration of G-CSF (10 micrograms/kg) until peripheral blood progenitor cells had been harvested. Immediately after bone marrow recovery, an intermediate dose chemotherapy course of carboplatin (target AUC: 10 mg.ml-1 min on day 1) and etoposide (500 mg/m2 on days 1, 3 and 5) was given with G-CSF daily s.c. After bone marrow recovery, two subsequent courses of high-dose 'CTC' chemotherapy were given, each containing cyclophosphamide (6 g/m2), thiotepa (480 mg/m2) and carboplatin (target AUC: 20 mg.ml-1 min). The high-dose chemotherapy was administered as 30-60-minute infusions, divided over 4 days and the stem-cell transplants were given 48-72 hours after the last chemotherapy infusion. Whenever possible, residual masses were resected at the end of treatment. RESULTS: Thirty-five patients were treated between January 1994 and October 1997. The toxicity of the treatment was manageable. Second CTC courses were administered in 25 patients and were associated with hemorrhagic cystitis and veno-occlusive disease in 3 and 4 patients, respectively. One patient who had recently undergone a partial hepatectomy, died of veno-occlusive disease. At the time of analysis, the median follow-up of the surviving patients was 37 months (range 12-56 months). The median progression-free survival for all patients was 44 months, and the median overall survival has not been reached. According to the internationally accepted criteria for predicting the outcome of salvage chemotherapy in germ-cell cancer (Beyer et al. J Clin Oncol 1996; 14: 2638-45), 30 patients had 'good risk' criteria. Of these, 29 received high-dose chemotherapy. Of this group, the salvage rate at two years was 65% (95% confidence interval: 49.5%-85.1%). CONCLUSIONS: Over half of the germ-cell cancer patients relapsing from a chemotherapy-induced complete remission can be salvaged by a treatment strategy that incorporates high-dose chemotherapy, even when treatment is given in a multi-center setting. These data confirm the international prognostic model proposed by Beyer et al. in a prospectively studied, independent patient group and provide further evidence that high-dose therapy has a role in the salvage setting of patients with germ-cell cancer.

Adult↗
PubMed1999

Surgery, radiotherapy, and chemotherapy for esophageal cancer.

Operative resection, the standard of care in the radical management of locoregional esophageal cancer, is a major surgical procedure, with a clear learning curve. It should be performed by experienced surgeons with a sufficient annual volume of procedures to maintain competence. Within specialized units esophagectomy can be safely offered to appropriately selected patients of all age groups. So far, the choice of operative approach (transhiatal, limited transthoracic, extended transthoracic) still cannot be based on randomized data with sufficient discriminating power. To date, the role of preoperative neoadjuvant therapy has not been clearly defined. A meta-analysis of five randomized trials did not confirm a substantial benefit for preoperative radiotherapy. A large randomized trial failed to show any benefit for preoperative chemotherapy. Improving systemic therapy, probably in combination with radiotherapy, remains a high priority for the coming years. The recent identification of new, highly active, chemotherapeutic agents shows promising, albeit preliminary, results.

Journal Article↗
PubMed1998

[Late sequelae of oncologic treatment in children].

The risk of late effects of cancer treatment in children is higher than that after treatment during adulthood. The late effects of chemotherapy are proportional to the dosage and those of irradiation to the size of the radiation field, fractionation and dose. Irradiation may lead to impaired growth of bone and soft tissues, cranial irradiation to pituitary deficiencies, alopecia and impaired cognitive function, irradiation of the neck to altered thyroid function, thoracic irradiation to diminished pulmonary function and cardiovascular morbidity, radiation therapy of the abdomen to infertility in females, impaired renal function and chronic enteritis. Chemotherapy-induced damage is more organ-specific. Well-known cardiotoxic agents are the anthracycline derivatives. Restricted pulmonary function is seen after treatment with bleomycin and nitrourea derivatives. Several antineoplastic agents are gonadotoxic in men. Nephrotoxic agents are cisplatin and ifosfamide. The cumulative relative risk of developing a second primary neoplasm is 3,8-6,9 after a follow-up period of 25 years. Alkylating agents and the topoisomerase inhibitors are known to increase the risk of haematologic malignancy, while radiation therapy is associated with bone, soft tissue, thyroid, breast, brain and gastrointestinal malignancies.

Adolescent↗
PubMed1998

Spatial distributions of early and late replicating chromatin in interphase chromosome territories.

The surface area of chromosome territories has been suggested as a preferred site for genes, specific RNAs, and accumulations of splicing factors. Here, we investigated the localization of sites of replication within individual chromosome territories. In vivo replication labeling with thymidine analogues IdUrd and CldUrd was combined with chromosome painting by fluorescent in situ hybridization on three-dimensionally preserved human fibroblast nuclei. Spatial distributions of replication labels over the chromosome territory, as well as the territory volume and shape, were determined by 3D image analysis. During late S-phase a previously observed shape difference between the active and inactive X-chromosome in female cells was maintained, while the volumes of the two territories did not differ significantly. Domains containing early or mid to late replicating chromatin were distributed throughout territories of chromome 8 and the active X. In the inactive X-chromosome early replicating chromatin was observed preferentially near the territory surface. Most important, we established that the process of replication takes place in foci throughout the entire chromosome territory volume, in early as well as in late S-phase. This demonstrates that activity of macromolecular enzyme complexes takes place throughout chromosome territories and is not confined to the territory surface as suggested previously.

Cells, Cultured↗
PubMed1998

Long-term neuro-endocrine sequelae after treatment for childhood medulloblastoma.

The occurrence of neuro-endocrine deficiencies following craniospinal irradiation for medulloblastoma is well known, but data concerning the spectrum and prevalence of endocrine abnormalities in adulthood are scarce. We studied endocrine function in 20 (median age 25 years) adult subjects, 8-25 years (median 16 years) after therapy. The radiation dose to the whole cranium and spinal axis was 35 +/- 2.6 Gray (mean +/- standard deviation) with a boost to the posterior fossa of 18 +/- 3.7 Gray. 13 subjects had received additional chemotherapy. In 15 of 20 (75%) subjects, endocrine abnormalities were observed. In 14 (70%), growth hormone (GH) secretion was impaired; 7 (35%) subjects had an absolute GH deficiency, while 7 (35%) showed subnormal responses to insulin-induced hypoglycaemia. In contrast, only 20% (4) of these subjects showed impairment of the hypothalamus-pituitary-thyroid (HPT) axis, while 15% (3) showed central impairment of hypothalamus-pituitary-gonadal (HPG) function. Central impairment of the HPG axis was associated with impaired GH secretion in all cases. Central adrenal insufficiency was not observed. Basal levels of prolactin were normal in all subjects. Young age at treatment was a determinant of GH deficiency in adulthood (P = 0.014). Neither post-treatment interval, nor the use of chemotherapy were determinants of central endocrine impairment in adulthood. In long-term survivors of medulloblastoma, GH deficiency has a high prevalence. In contrast, impairment of the HPG and HPT axis is less common, while central adrenal insufficiency was not observed.

Adolescent↗
PubMed1998

Continuous infusion of chemotherapy: focus on 5-fluorouracil and fluorodeoxyuridine.

Continuous infusion of chemotherapy is one of the developments to try to improve the treatment of metastatic cancer. There is a sound theoretical rationale to deliver cytotoxic drugs as a continuous infusion. Furthermore, the development of reliable venous access devices and portable infusion pumps enables patients to be treated in an ambulatory setting. This review focuses on the continuous infusion of the most frequently used drugs: 5-fluorouracil (5-FU) and fluorodeoxyuridine (FUDR). An overview is given of both preclinical studies and studies in humans. Continuous infusion of 5-FU and FUDR has proven to be feasible in all studies. However, the results (response rate and especially survival) are rather disappointing. So far, continuous infusion of cytostatic drugs can still be considered as an experimental procedure. Whether protracted, intermittent of circadian modulated continuous infusion is the optimal treatment schedule has still to be proven in future studies. Furthermore, studies are needed to demonstrate whether dose intensity for most tumours is important for treatment outcome. Also, studies are needed to investigate quality of life and economic issues.

Animals↗
PubMed1998

Improving the resolution of cryopreserved X- and Y-sperm during DNA flow cytometric analysis with the addition of Percoll to quench the fluorescence of dead sperm.

The most effective method to control the sex of offspring is by separating X- from Y-bearing sperm on the basis of their DNA content. Sperm can be stained with Hoechst 33342 and efficiently sexed using a flow cytometer/cell sorter. However, applying this established assay to cryopreserved bovine sperm presents specific problems, such as broad fluorescence distributions without a distinct X- and Y-peak. Our results indicate that these problems are mainly caused by the large amount of dead sperm normally present in a thawed sperm population. We showed that Percoll quenches the fluorescence of chromatin stained with Hoechst 33342 and that this quenching can be applied to reduce the fluorescence of dead sperm. We used this finding to exclude the dead sperm from the sorting window and thus obtained narrower fluorescence distributions and sorted X- and Y-bearing sperm populations containing up to 85 to 92% viable sperm. The viability of the sorted sperm was monitored by propidium iodide exclusion.

Animals↗
PubMed1997

[Joint decisions, how? Physician-patient communication about palliative chemotherapy].

The discomfort and benefits of a medical treatment may be appreciated differently by different patients. This is one of the reasons why patients should be informed thoroughly and included in the decision-making about treatment. The obligation to inform was laid down in 1995 in the Decree on the Medical Contract. In a case of metastasized cancer of the prostate it was decided more or less by mutual agreement between doctor and patient to administer palliative chemotherapy. It appeared subsequently that the physician had short-term palliation in mind, and the patient prolongation of survival. Although both are of the opinion that the patient was included actively in the decision-making, this was in reality not at all the case. The question arises whether the Decree on the Medical Contract does not demand too much from certain patients regarding their capacity to make a decision about the treatment of a terminal disease.

Aged↗
PubMed1997

Hyperthermia and incorporation of halogenated pyrimidines: radiosensitization in cultured rodent and human tumor cells.

PURPOSE: To investigate the possible benefit of hyperthermia (HT) in combination with radiosensitization by halogenated pyrimidines (HPs) in rodent as well as in human tumor cells. METHODS AND MATERIALS: Exponentially growing rodent cells, radiosensitive R-1 and MOS cells and radioresistant RUC-II and V79 cells, and human SW1573 cells, were exposed to 0, 1, 2, and 4 microM of chloro- (CldUrd), bromo- (BrdUrd), or iodo-deoxyuridine (IdUrd) in the culture medium. Survival after irradiation with gamma-rays from a 137Cs source and/or hyperthermic treatment (HT, 60 min at 42 degrees C) was determined by clonogenic assay. Linear-quadratic analyses of the radiation survival curves were performed to assess sensitization in the dose range 1 to 3 Gy relevant to radiotherapy. RESULTS: The incorporation of HPs sensitized all cell lines to HT and resulted in radiosensitization dependent on the percentage of thymidine replacement. At equal levels of thymidine replacement, IdUrd was the most potent radiosensitizer. HT further increased radiation-induced lethality of cells that had incorporated HPs. Linear-quadratic analyses showed that HT further increased the linear parameter of the LQ formula while the quadratic parameter was not significantly changed. CONCLUSION: The combination of HT and HPs act additively in increasing the radiosensitivity of rodent tumor cell lines with varying radiosensitivities as well as of a human tumor cell line. In particular, the ratio of the linear parameter to the quadratic parameter, relevant for fractionation effects in radiotherapy, was increased.

Animals↗
PubMed1997

Phase II trial of weekly locoregional hyperthermia and cisplatin in patients with a previously irradiated recurrent carcinoma of the uterine cervix.

BACKGROUND: The biologic rationale for combining cisplatin with locoregional hyperthermia (HT) relates to the potentiating effect of HT on cisplatin cytotoxicity. METHODS: Patients with recurrent cervical carcinoma, who had a pelvic recurrence after radiotherapy, were treated with weekly cycles of locoregional HT (using the 70-megahertz, 4 antenna-phased array system for 1 hour and cisplatin, 50 mg/m2 intravenously [i.v.], for a maximum of 12 cycles.) RESULTS: Twenty-three patients were entered in this study. A total of 169 cycles were given. Responses were observed in 12 of 23 patients, a response rate of 52% (95% confidence interval, 31-73%). Salvage surgery became possible in 3 of 12 responding patients, whose tumors were previously considered unresectable. The median duration of response was 9.5+ months, the median overall survival was 8+ months, and the 1-year survival was 42%. No correlation was found between treatment outcome and clinical parameters such as age, weight, performance status, and histology. Thermal parameters such as T20, T50, and T90 were higher in responding patients, but were not significantly different from nonresponding patients. Overall toxicity was moderate. Subcutaneous fatty necrosis due to HT occurred in 10% of the cycles, whereas 2 patients developed skin burns. Squamous cell carcinoma antigen proved to be a valuable tool for the evaluation of response and detection of progression. CONCLUSIONS: Weekly locoregional HT and cisplatin, 50 mg/ m2 i.v., for a maximum of 12 cycles was effective treatment in patients with a previously irradiated recurrent carcinoma of the uterine cervix.

Antigens, Neoplasm↗
PubMed1997

Hyperthermia enhances the cytotoxicity and platinum-DNA adduct formation of lobaplatin and oxaliplatin in cultured SW 1573 cells.

The cytotoxicity of cisplatin and cisplatin-DNA adduct formation in vitro and in vivo is clearly enhanced by hyperthermia. We investigated whether cytotoxicity and platinum-DNA adduct formation of two promising new third-generation platinum derivatives, lobaplatin [1,2-diamminomethylcyclobutane platinum(II) lactate] and oxaliplatin [oxalato-1,2-diaminocyclohexane platinum(II)], are also enhanced by hyperthermia. Cisplatin was used for comparison. SW 1573 cells were incubated with cisplatin, lobaplatin or oxaliplatin at different concentrations for 1 h at 37 degrees, 41 degrees and 43 degrees C. The reproductive capacity of cells was determined by cloning experiments. Immunocytochemical detection of platinum-DNA adducts was performed with the rabbit antiserum NKI-A59. At 37 degrees C, cisplatin was the most cytotoxic, followed by oxaliplatin and lobaplatin. Hyperthermia clearly enhanced the cytotoxicity of cisplatin, lobaplatin and oxaliplatin. There was no further increase in cytotoxicity at 43 degrees C compared to 41 degrees C for cisplatin and oxaliplatin. A further increase in cytotoxicity at 43 degrees C was observed for lobaplatin. At 43 degrees C thermal enhancement was higher for lobaplatin than for oxaliplatin, with the reverse pattern at 41 degrees C. For both drugs, thermal enhancement of cytotoxicity was lower than observed for cisplatin. Immunocytochemical detection of platinum-DNA adducts was feasible for all the drugs. Adduct formation was enhanced at 43 degrees C for cisplatin, lobaplatin and oxaliplatin with a relative increase of 410%, 170% and 180%. These results seem to confirm that an increase in platinum-DNA adduct formation is involved in the in vitro thermal enhancement of cytotoxicity. The observed thermal enhancement of cytotoxicity of lobaplatin and oxaliplatin in vitro warrants further in vivo investigations.

Antineoplastic Agents↗