Intended for healthcare professionals

Minerva

# Taking the uncertainty out of NNT . . . and other stories

BMJ 2017; 357 (Published 15 June 2017) Cite this as: BMJ 2017;357:j2820

## Numbers needed to treat

The concept of numbers needed to treat is nearly 30 years old, but behind their seemingly simple digits, NNTs often hide complexity and uncertainty about treatment effects. An analysis of 51 meta-analyses and study reports in leading general medical journals (BMC Med doi:10.1186/s12916-017-0875-8) concludes that authors frequently fall short of basic methodological recommendations in reporting NNTs. As a result, clinicians already struggling to explain benefits (and harms) to patients might be working with figures that are unreliable, as well as poorly matched to the individuals they are talking to.

## Less is more for responsive chronic myeloid leukaemia

Like so many cancer treatments, tyrosine kinase inhibitors for chronic myeloid leukaemia are both toxic and extremely expensive. Imatinib, dasatinib, and nilotinib typically cost between £20 000 and £30 000 (€22 800–€35 000; $25 500–$38 300) per year, but in a trial of patients with the condition who had been taking a TK inhibitor for three years or more with a stable molecular response, it proved possible to halve the dose and maintain the response (Lancet Haematol doi:10.1016/S2352-3026(17)30066-2). Previous trials have shown that it is possible to discontinue them entirely if there is a deep molecular response.

## Lithium and severe unipolar depression

Depression serious enough to cause hospital admission affected 123 712 people in Finland over a period of nearly eight years. In a nationwide cohort study, those who were given lithium for unipolar depression had half the rate of readmission compared with those given standard antidepressants or antipsychotics (Lancet Psychiatry doi: /10.1016/S2215-0366(17)30134-7).

## Biphasic blood pressure response

When the massive ALLHAT trial was reported in 2002, one striking finding was that the thiazide-like diuretic chlortalidone was more effective than other blood pressure lowering agents in preventing cardiovascular events. Oddly, this has been mostly ignored since. It re-emerges in a new analysis of the trial data (Hypertension doi:10.1161/HYPERTENSIONAHA.117.09221), which also for the first time detects a surprising difference in responses to the drug combination used in ALLHAT. Most of the nearly 40 000 participants showed an immediate drop in systolic blood pressure, but about 15% took more than 30 days to respond. Over the following 6-24 months, these delayed responders showed a higher incidence of stroke and heart failure.

“A rare and laudable clinical trial” is how JAMA Oncology describes a long term prospective trial evaluating the efficacy of stereotactic conformal radiotherapy compared with conventional radiotherapy in 200 young patients with benign or low-grade brain tumours (JAMA Oncol doi: 10.1001/jamaoncol.2017.0997). Over five years, it is clear that stereotactic conformal radiotherapy achieves better neurocognitive and neuroendocrine functional outcomes without compromising survival. Trials like this that address important clinical questions simply and over the right period of time are indeed laudable, and sadly rare.

## Keep your money, I'm a woman

In the USA, the CMS Open Payment Database reveals industry payments to doctors, and an article in (JAMA Otolaryngol Head Neck Surg doi:10.1001/jamaoto.2017.0276) looked specifically at 1514 academic otolaryngologists. Of these, 79.4% were men, and they received 88.5% of the \$4.3m (£3.3m; €3.8m) that industry lavished on these specialists. Overall, a greater proportion of men received industry contributions than women (68.0% v 56.1%). Minerva likes to think that this is due to the superior integrity of women, and not just because they don't happen to belong to the right old boy networks.

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