Biomedical subjects

Henk B Kal

Publications and source records attributed to Henk B Kal.

21 records · Page 2Linked to original sources

PubMed2002

DNA ploidy of primary and recurrent irradiated laryngeal tumors.

PURPOSE: Radiosensitivity of diploid laryngeal cancers, as compared with that of aneuploid ones, appears to be increased. However, no conclusive data exist. If a causal relationship exists, then recurrent laryngeal cancer after irradiation should predominantly be characterized by aneuploidy. PATIENTS AND METHODS: To test this hypothesis we compared ploidy of 24 primarily irradiated laryngeal cancers and their subsequent recurrences. T and N stages were assessed in accordance with the TNM classification system of the UICC. With flow cytometry DNA ploidy was assessed. RESULTS: 1. Ploidy of 16 locally recurrent tumors did not differ from those of primary tumors, i.e. ten and six recurrences of diploid and aneuploid primary tumors, respectively, remained unchanged, 2. recurrences of four aneuploid primary tumors showed diploidy, 3. recurrences of four diploid primary tumors showed aneuploidy. CONCLUSIONS: The results of our study do not support the hypothesis that recurrent laryngeal cancer after irradiation of the primary tumor is characterized by aneuploidy.

Aneuploidy↗

PubMedDate not supplied

Changes in blood-brain barrier permeability induced by radiotherapy: implications for timing of chemotherapy? (Review).

The brain requires a stable internal environment, which is established by the integrity of the blood-brain barrier (BBB). The efficacy of chemotherapeutics in the treatment of brain malignancies is often hampered by the presence of the BBB. BBB disruption can be performed either by osmotic disruption, bradykinin or irradiation. Radiotherapy with doses of 20 to 30 Gy with fraction size of 2 Gy may be used to increase the permeability of the BBB. These radiation doses by themselves will not give rise to serious side effects or long-term complications. Disruption of the BBB by radiotherapy might have implications in the treatment of primary brain tumors, cerebral metastases, and prophylactic cranial irradiation in small cell lung cancer since irradiation will cause cell kill and may enhance the effect of chemotherapy. We present a review on the effects of irradiation on the BBB and subsequently discuss the potential value for therapeutic applications.

Antineoplastic Agents↗

PubMedDate not supplied

Gemcitabine as a radiosensitizer in undifferentiated tumors.

BACKGROUND: Gemcitabine (dFdC) may cause radiosensitization by specific interference with homologous recombination-mediated DNA double-strand break repair. The radiosensitizing effect of dFdC might be less in normal healthy tissue and more restricted to undifferentiated tumor cells, making it a tumor-selective radiosensitizer. Whether dFdC acts as a radiosensitizer in undifferentiated and well-differentiated rat tumors and on rat foot skin was tested. MATERIALS AND METHODS: Undifferentiated L44 lung tumors in BN rats, MLL prostate tumors in Copenhagen rats, and well-differentiated L42 lung tumors in WAG/Rij rats were used. The tumors were treated with a single X-ray dose, combined or not with dFdC (30 mg/kg) administered 24 h earlier. Tumor volume growth delay was the end-point used. In addition, rat foot skin was treated with a single dose of 22.5 Gy, with or without dFdC. The degree of skin damage was determined according to a scoring system. RESULTS: For tumor growth delay, the dose-enhancement ratios were 1.37 and 1.23-1.36 for the L44 and MLL tumors, respectively. No radiosensitization was observed for the well-differentiated L42 tumor and foot skin. CONCLUSION: Radiosensitization by dFdC was observed in the undifferentiated tumors, but not in the well-differentiated tumor and skin. Our data support further trials to evaluate the usefulness of dFdC as a radiosensitizer in undifferentiated tumors.

Animals↗