Chromosomal radiosensitivity in South African breast cancer patients before and after radiotherapy

Introduction: Radiosensitivity (RS) of South African women with breast cancer was investigated as it has been studied in European women, but to date this has not been studied in South African women. The micronucleus assay was used to determine the amount of DNA damage on lymphocytes of breast cancer patients. Materials and Methods: The first component to this study involved the collection of blood samples from breast cancer patients and healthy individuals. For the second component, blood samples from breast cancer patients were collected before and after the completion of radiotherapy (RT). A centromeric micronucleus assay using the Fluorescent in situ Hybridisation (FISH) pancentromeric probe was used to investigate the origin of the micronuclei (MN) and to distinguish between radiation-induced [centromere negative (CM-)] and spontaneous [centromere positive (CM+)] MN. Results: Micronucleus frequencies were slightly higher in breast cancer patients than those observed in lymphocytes of healthy donors. This was noted for the different radiation doses and indicated a trend towards an enhanced chromosomal radiosensitivity in this cancer population. Results were compared before and after radiotherapy. The micronucleus scores for the 0 Gy (sham irradiated samples) were significantly higher (p < 0.05) post radiotherapy. This is an expected result as ionising radiation causes more damage. However, blood samples from post-therapy patients, were shown to have fewer MN after subsequent in vitro 2 Gy and 4 Gy irradiation respectively. When assessing the centromeric micronucleus assay results, a significantly (p < 0.05) higher number of CM- MN was observed than CM+ MN after RT, thereby indicating that ionising radiation causes more breaks in the chromosomes (clastogenic damage). Discussion and Conclusion: This study demonstrates that a group of South African breast cancer patients have slightly higher micronucleus frequencies compared to a population of healthy women, indicating a trend towards a higher sensitivity to radiation

Chromosomal radiosensitivity of human immunodeficiency virus positive/negative cervical cancer patients in South Africa

Cervical cancer is the second most common cancer amongst South African women and is the leading cause of cancer-associated mortality in this region. Several international studies on radiation-induced DNA damage in lymphocytes of cervical cancer patients have remained inconclusive. Despite the high incidence of cervical cancer in South Africa, and the extensive use of radiotherapy to treat it, the chromosomal radiosensitivity of South African cervical cancer patients has not been studied to date. Since a high number of these patients are human immunodeficiency virus (HIV)-positive, the effect of HIV infection on chromosomal radiosensitivity was also investigated. Blood samples from 35 cervical cancer patients (20 HIV-negative and 15 HIV-positive) and 20 healthy controls were exposed to X-rays at doses of 6 MV of 2 and 4 Gy in vitro. Chromosomal radiosensitivity was assessed using the micronucleus (MN) assay. MN scores were obtained using the Metafer 4 platform, an automated microscopic system. Three scoring methods of the MNScore module of Metafer were applied and compared. Cervical cancer patients had higher MN values than healthy controls, with HIV-positive patients having the highest MN values. Differences between groups were significant when using a scoring method that corrects for false positive and false negative MN. The present study suggested increased chromosomal radiosensitivity in HIV-positive South African cervical cancer patients