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Johannes H M Merks

Publications and source records attributed to Johannes H M Merks.

6 recordsLinked to original sources
PubMed2006

Normal values for morphological abnormalities in school children.

Clinical morphology has proven to be a strong tool in the delineation of many syndromes and a helpful instrument in molecular studies. Numerous studies have been performed investigating the prevalence of minor anomalies in various disorders; all concluding that minor anomalies can well be utilized as indicators of altered embryonic differentiation. However, for adequate evaluation, normal values for phenotypic abnormalities are essential. So far, only few studies on the frequency of phenotypic abnormalities in the normal population have been done having one thing in common: all were performed in newborn infants. We studied morphological characteristics in a group of 1,007 school children, representative for the Dutch population, through a body surface examination using detailed definitions for all morphological findings. The region of study and distribution of children over various school types was chosen in such a way that it represented the general Dutch population. The median age of the studied children was 11 years (range 8-14 years), sex ratio (M:F) was 0.93. Nine hundred twenty-three children were of Caucasian descent, 84 others of mixed ethnic backgrounds. The reliability of the examinations was tested by independent scoring of 111 children by two observers, showing a kappa score of 0.85. Normal values for the morphological findings are presented together with their age-adjusted classification. These normal values provide a valuable source for validation of classifications of phenotypic abnormalities, especially those that are depending on frequency, that is, minor anomalies and common variants. Furthermore, they will allow a proper evaluation of patterns of phenotypic abnormalities found in patient groups with specific disorders.

Adolescent↗
PubMed2005

Prevalence of rib anomalies in normal Caucasian children and childhood cancer patients.

PURPOSE: To evaluate the prevalence of abnormalities of rib development in normal Caucasian children and patients with childhood cancer. MATERIALS AND METHODS: Chest radiographs of 881 Caucasian pediatric controls and 906 childhood cancer patients were reviewed, and independently scored by four blinded observers, using strict definitions. Prevalences of 6 major rib anomaly categories in controls were compared to their prevalence in the total group of childhood cancer patients, and the 12 individual larger tumor groups using Chi-square tests. RESULTS: Values in the control population were generated for the occurrence of six major rib anomaly categories; cervical rib anomalies were present in 6.1% of controls, aplasia of 12th ribs in 6.6%, lumbar ribs in 0.9%, bifurcations in 0.7%, synostosis-bridging in 0.3%, and segmentations were not found. The overall prevalence of total rib anomalies in cases and controls was equal (14.9% and 14.2%, respectively). Cervical rib anomalies were found significantly more often in cases (8.6%) compared to controls (p-value=0.047), three groups accounting for this higher prevalence: 12.1% of acute lymphoblastic leukemia patients (p=0.011), 18.2% of astrocytoma patients (p=0.023), and 14.7% of germ cell tumor patients (p=0.046) had a cervical rib anomaly. CONCLUSION: Prevalence figures for the presence and type of rib anomalies in a large group of normal Caucasian children were generated. In childhood cancer patients a significantly higher prevalence of cervical rib anomalies was demonstrated in patients with acute lymphoblastic leukemia, astrocytoma, and germ cell tumors.

Adolescent↗
PubMed2005

AMORE protocol in pediatric head and neck rhabdomyosarcoma: descriptive analysis of failure patterns.

BACKGROUND: The AMORE protocol is a local treatment for patients with nonorbital pediatric head and neck rhabdomyosarcoma (HNRMS). The objectives of this study were: (1) to assess the adequacy of the concept, and (2) to identify factors associated with relapse. METHODS: We performed a retrospective multidisciplinary review of 22 children primarily treated according to the AMORE protocol, excluding two children with inadequate imaging data. RESULTS: Seven patients had a local relapse, six within and one outside the residual tumor area. Five of the six patients with relapse in the residual area had gross total or debulking (incomplete) surgery, suboptimal position of the mold for brachytherapy, or both. In the 15 nonrecurrent cases, four patients had either incomplete surgery or suboptimal mold position. Both surgical and brachytherapeutic factors seem to be associated with relapse. CONCLUSIONS: AMORE is an adequate concept. More rigid preoperative imaging and intraoperative verification of the brachytherapy mold position might lead to a reduction in the number of local failures.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Vinorelbine and low-dose cyclophosphamide in the treatment of pediatric sarcomas: pilot study for the upcoming European Rhabdomyosarcoma Protocol.

BACKGROUND: Following their previous report on the activity of vinorelbine in the treatment of rhabdomyosarcoma, the authors report the results of a pilot study aimed at defining the optimal dose of vinorelbine when this agent is used in conjunction with continuous, orally administered low-dose cyclophosphamide to treat patients with refractory or recurrent sarcoma. It is hoped that the combination of vinorelbine and low-dose cyclophosphamide can be used as a maintenance regimen in an upcoming European trial involving high-risk patients with rhabdomyosarcoma. METHODS: In the current pilot study, the cyclophosphamide dose was fixed at 25 mg/m2 per day for 28 days. Vinorelbine was administered intravenously on Days 1, 8, and 15, with trial doses escalated from an initial level of 15 mg/m2 in steps of 5 mg/m2; intrapatient dose escalation was not allowed. RESULTS: Between April 2002 and November 2003, 18 patients ages 2-23 years were treated with the study regimen after having received 1-4 (median, 2) other regimens previously. Ninety cycles were administered in total (median, 5 cycles per patient; range, 1-10 cycles per patient). Two cases of dose-limiting toxicity (Grade 4 neutropenia in both cases) were observed among the 5 patients who received vinorelbine at a dose of 30 mg/m2. Of the 41 cycles in which vinorelbine was administered at a dose of 25 mg/m2, Grade > or = 3 neutropenia was observed in 15 (37%); no other major toxicity was documented in association with these cycles. One complete remission and 6 partial remissions were noted among the 17 patients who had measurable disease. Three of the eight assessable patients with rhabdomyosarcoma (which was embryonal in two cases and alveolar in one) had responses to treatment. CONCLUSIONS: Combination therapy involving vinorelbine and low-dose cyclophosphamide was found to be feasible and to possess activity against recurrent sarcomas. The maintenance therapy doses recommended for use in the upcoming European trial are cyclophosphamide 25 mg/m2 per day for 28 days and vinorelbine 25 mg/m2 on Days 1, 8, and 15.

Adolescent↗
PubMed2003

Phenotypic abnormalities: terminology and classification.

Clinical morphology has proved essential for the successful delineation of hundreds of syndromes and as a powerful instrument for detecting (candidate) genes (Gorlin et al. [2001]; Syndromes of the Head and Neck; Oxford: Oxford University Press. 1 p]. The major approach to reach this has been careful clinical evaluations of patients, focused on congenital anomalies. A similar careful physical examination performed in patients, who have been treated for childhood cancer, may allow detection of concurrent patterns of anomalies and provide clues for causative genes. In the past, several studies were performed describing the prevalence of anomalies in patients with cancer. However, in most studies, it was not possible to indicate the biologic relevance of the recorded anomalies, or to judge their relative importance. Are the detected anomalies common variants, and should they thus be regarded as normal, or are they minor anomalies or true abnormalities, indicating a possible developmental cause? Classification of items in the categories of common variants (disturbances of phenogenesis with a prevalence >4%), minor anomalies (disturbances of phenogenesis with a prevalence </=4%), and malformations (disturbances of embryogenesis) should allow weighing the importance of the scored items in the population under study, and should facilitate assessment of developmental disturbances (if any) in a study group. The lack of published consensus in the literature led us to produce a classification list with a twofold goal. First, we wanted to enhance uniformity in the scoring and classification of apparently abnormal physical findings by a nomenclature for errors of morphogenesis detectable on surface examination, and secondly a uniform classification system. This should allow investigators to evaluate systematically the presence of patterns in phenotypic anomalies, in the general population, and in patients with various disorders, suspected to be a developmental anomaly. Also, normal values may be obtained this way. Second, the list will allow a determination of the importance of the collected symptoms in a study population. We tested the feasibility of the application of the classification list in a study population: the list was piloted in a group of patients who have had cancer as a child, to detect patterns of anomalies related to specific types of tumors.

Adult↗