I was recently at a wonderful conference in Toronto, where 1900 folk interested in childhood cancer came together to learn, argue, network, present and be merry – #SIOP2014.

There was a particularly interesting debate between two very clever oncologists about whether or not we should use antifungal prophylaxis in children with AML and post-stem-cell-transplant. (Both are at high risk ~10% of developing fungal disease.) Now there are, as you probably know, two main classes of antifungals – the anti-yeast agents, and those with broader, anti-mould activity. Invasive yeast infections can be deadly; about 25% mortality. But invasive mould infections are said to be worse – around 50% mortality.

The debate centred around what class we should be prescribing. One group advised anti-mould, and one anti-yeast. They both had the same evidence to work from. Why the difference?

One group looked to see what the evidence said, in terms of reducing mortality and invasive mould infections; they chose the anti-moulds. One group just looked at mortality outcomes; they chose the anti-yeast alone.

The question they asked was different. The answers were congruent with the evidence and their questions. Which one is right?

There’s an assumption being made that if you develop an invasive mould infection, you’ll have an increased risk of death or serious morbidity, so it’s worth classing into the outcome to be avoided. The alternative view is that as mortality is being measured, if it’s not different then it doesn’t matter (assuming, perhaps, that if you develop and infection it can be effectively treated). It may be that the acceptable balance of risk and harm varies per person, or per centre, or per country. It may be that consistency within a unit is more valued than individual choice and variation.

Without more data there is no clear way of telling which is ‘right’. But there is a fruitful area for debate.

– Bob Phillips

@drbobphillips