Changes over time in socio-economic inequalities in cancer survival. Can “Victora’s law” help us?

Lyratzopoulos G, Barbiere JM, Rachet B, Baum M, Thompson MR, & Coleman MP (2011). Changes over time in socioeconomic inequalities in breast and rectal cancer survival in England and Wales during a 32-year period (1973-2004): the potential role of health care. Annals of oncology : official journal of the European Society for Medical Oncology / ESMO, 22 (7), 1661-6 PMID: 21199888 Access this article.

A few years ago a group of Brazilian epidemiologists led by Cesar Victora proposed a conceptual framework to explain the changing nature of inequalities in health care. At its root this framework has Hart’s famous inverse care law.

Let’s think of the advent of any new health care intervention. A drug or a new type of interventional procedure (or even a new preventive intervention like a new vaccine or a new screening programme) would all fit the example nicely. Once the intervention is introduced into the health care system, richer and better educated (and, usually, also more healthy) patients typically can access the new intervention more often than poorer and less well educated patients. During this initial period, socio-economic inequalities in its use increase rapidly. In a subsequent phase, nearly all patients in higher socio-economic strata can obtain access to the intervention and no further improvement is possible (because of saturation or ‘ceiling’ effects). At the same time, broader dissemination becomes more widespread (perhaps helped by government policies or incentivisation schemes) and access to the intervention by less privileged patient groups also increases. Until a point in time that inequality in respect of this specific (and now rather old) treatment disappears completely.

Empirical evidence supporting the relevance of this concept also exists, including work on cervical cancer screening led by the late Deborah Baker, and also studies of the Quality and Outcomes Framework.

Things get more complex when one considers that health care interventions are very rarely introduced in isolation – waves of innovations occur in close sequence if not simultaneously. And even more so when one considers outcomes (such as survival) as opposed to process measures (such as use proportion of patients treated).

But for what it is worth, that’s the type of problem that colleagues tried to address in this paper. Our inquiry was stimulated by the observation that in the UK socio-economic inequalities in survival in respect of breast cancer have been diminishing in recent decades, whilst at the same time the opposite was true for rectal cancer. We argue in the paper that the time-lagged dissemination of new treatments of different efficacy may be responsible for part of these seemingly opposing phenomena. We should not forget the very substantial improvements in survival from either cancer that have occurred since the 1970’s. Extremely welcome changes over time, for rich and poor alike.

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