Identification of Interaction Tests of Predictive Biomarkers in Cancer Clinical Trials

Predictive biomarkers are covariates that interact with treatment in relation to the outcome and thus; predictive biomarkers are characterized by interactions between the treatment and covariates. Many questions remain unanswered in this topic: What is the best design for detecting and validating a predictive biomarker? What can be the sample size required? What could be the statistical methods used to identify those interactions? The major problem of interaction tests is that they lack power; so that a very large trial would be required for the test to reach significance. The identification of a predictive factor becomes difficult if interactions of higher orders have to be investigated. We discussed the use of Martingale residuals combined with the classification and regression trees (CART) to identify which could be the optimal cut point in a continuous marker through data simulation. Our findings using these methods were very close to the expected results given the parameters of the simulation. Our conclusion is that the CART applied to Martingale residuals can be the good alternative of identifying predictive biomarkers. In practice we may need a cut point for a predictive biomarker so that we can know who among patients can benefit from the treatment and those who may be harmed by the treatment; especially when drugs are highly toxic

Experiences of sexual relationships of young black women in an atmosphere of coercion

Negotiations surrounding sexual activity are characterised by multiple power disparities that include race; social status and age; with gender being the most dominant differential in heterosexual interactions. Research has shown that women are physiologically more at risk of contracting HIV than men; as indicated by the higher infection rates of the former. Many African societies operate via a hegemonic masculinity; with patriarchal governance and female subordination being the norm; placing women at even greater risk of HIV infection. In this qualitative phenomenological study; four black school-going adolescent women living in Grahamstown were interviewed using a semi-structured interview to gather data. An interpretative phenomenological analysis was conducted on the data to provide subjective insights of the experiences of the participants with regard to their interactions with men. From the findings; it became apparent that the participants felt pressured; coerced or manipulated by male counterparts. This pressure and coercion was not just felt in their interactions with older men; but also in their romantic partnerships. Three of the participants experienced pressure to engage in sexual intercourse with their boyfriends when they were unwilling or unready; and they reported being faced with additional pressure to engage in unprotected sex. Furthermore; it became apparent that each participant had an underlying fear of being raped and considered this as a genuine threat to her safety and sexual health. The atmosphere within which these participants negotiate their sexual agency is thus heavily informed by male control; coercion and the threat of violence or rape