Effect of Race and Ethnicity on Risk of Radiotherapy Toxicity and Implications for Radiogenomics.

AIMS: Patient factors affect the risk of radiotherapy toxicity, but many are poorly defined. Studies have shown that race affects cancer incidence, survival, drug response, molecular pathways and epigenetics. Effects on radiosensitivity and radiotherapy toxicity are not well studied. The aim of the present study was to identify the effects of race and ethnicity on the risk of radiotherapy toxicity. MATERIALS AND METHODS: A systematic review was carried out of PubMed, Ovid Medline and Ovid Embase with no year limit. PRISMA 2020 guidelines were followed. Two independent assessors reviewed papers. RESULTS: Of 607 papers screened, 46 fulfilled the inclusion criteria. Papers were published between 1996 and 2021 and involved 30-28,354 individuals (median 433). Most involved patients with prostate (33%), breast (26%) and lung (9%) cancer. Both early and late toxicities were studied. Some studies reported a higher risk of toxicity in White men with prostate cancer compared with other races and ethnicities. For breast cancer patients, some reported an increased risk of toxicity in White women compared with other race and ethnic groups. In general, it was difficult to draw conclusions due to insufficient reporting and analysis of race and ethnicity in published literature. CONCLUSIONS: Reporting of race and ethnicity in radiotherapy studies must be harmonised and improved and frameworks are needed to improve the quality of reporting. Further research is needed to understand how ancestral heritage might affect radiosensitivity and risk of radiotherapy toxicity.

Epigenetic inactivation of the RASSF10 candidate tumor suppressor gene is a frequent and an early event in gliomagenesis.

We have recently described the N-terminal RAS association domain family of genes, RASSF7-10. Previously, we cloned the N-terminal RASSF10 gene and demonstrated frequent methylation of the associated 5'-CpG island in acute lymphoblastic leukemia. To characterize RASSF10 gene expression, we demonstrate that in developing Xenopus embryos, RASSF10 shows a very striking pattern in the rhombencephalon (hind brain). It is also expressed in other parts of the brain and other organs. Due to the well-defined expression pattern in the brain of Xenopus embryos, we analyzed the methylation status of the RASSF10-associated 5'-CpG island in astrocytic gliomas. RASSF10 was frequently methylated in WHO grade II-III astrocytomas and WHO grade IV primary glioblastomas (67.5%), but was unmethylated in grade I astrocytomas and in DNA from age matched control brain samples. RASSF10 gene expression both at the mRNA and protein levels could be switched back on in methylated glioma cell lines after treatment with 5-aza-2'-deoxycytidine. In secondary glioblastomas (sGBM), RASSF10 methylation was an independent prognostic factor associated with worst progression-free survival and overall survival and occurred at an early stage in their development. In cell culture experiments, overexpression of RASSF10 mediated a reduction in the colony forming ability of two RASSF10-methylated glioma cell lines. Conversely, RNAi-mediated knockdown of RASSF10-stimulated anchorage-independent growth of U87 glioma cells, increased their viability and caused an increase in the cells' proliferative ability. We generated and characterized a RASSF10-specific antibody and demonstrated for the first time that RASSF10 subcellular localization is cell-cycle dependent with RASSF10 colocalizing to centrosomes and associated microtubules during mitosis. This is the first report demonstrating that RASSF10 can act as a tumor suppressor gene and is frequently methylated in gliomas and can potentially be developed into a prognostic marker for sGBM.