A leading epidemiologist has attacked Swedish research that looked at inequalities in patients' access to cancer drugs across Europe and the world.
In a commentary published in the September issue of the cancer journal, Annals of Oncology, Professor Michel Coleman says the Karolinska report is so badly flawed that no safe conclusions can be drawn from it about cancer survival, and he highlights the role played by a major drug company in funding the research.
In May 2007 Annals of Oncology published “A global comparison regarding patient access to cancer drugs” by Dr Nils Wilking, a clinical oncologist at the Karolinska Institute in Stockholm and Dr Bengt Jönsson, director of the Centre for Health Economics at the Stockholm School of Economics.
Their report concluded there was a link between national cancer survival rates and access to cancer drugs, with some countries being better at making new drugs available quickly and, according to the authors of the report, having better cancer survival than other countries as a result.
However, in his commentary, entitled “Not credible: a subversion of science by the pharmaceutical industry”, Prof Coleman, who is professor of epidemiology and vital statistics at the London School of Hygiene and Tropical Medicine, writes that the report “uses flawed methods to reach flawed conclusions about the link between cancer drug ‘vintage' and cancer survival in European countries”.
He says that the survival estimates in the Karolinska report are not survival estimates at all. “The ‘survival rates' in the report are not even calculated from the cancer patients' actual duration of survival, which has been standard practice for over 50 years,” he writes. Furthermore, he says the estimates are wrong, and he gives an example for France, where the Karolinska report estimates five-year survival from all cancers combined as 71% for women and 53% for men, whereas cancer survival specialists at the French Cancer Registry Network estimate crude five-year survival rates as 55% and 36%, respectively, some 16-17% lower than the Karolinska team.
He also points out that the cancer drug data come from patients treated around 2003, whereas the cancer survival rates with which they are compared are for completely different patients who were diagnosed during 1990-94. “The authors side-step this issue by claiming that national cancer drug uptake in 2003 is still likely to be representative of uptake in or around 1993,” writes Prof Coleman. “Such a speculative assumption cannot reliably underpin the conclusion that low usage or expenditure on cancer drugs today is the cause of low survival for patients diagnosed ten years ago. It is all the more surprising because the report focuses on anti-cancer drugs licensed after 1995, such as rituximab (Mabthera, 1997), trastuzumab (Herceptin, 1998) and imatinib (Glivec, 2001), which were not even available to treat patients diagnosed during 1990-1994.”
Other criticisms include:
- The drug data come from patient histories supplied to a commercial database – no information is given about whether or not those data provide an accurate picture of drug use in each country, or on the precise years to which they relate (about 2003).
- The authors said that they used national, grouped data because individual cancer patient data were not available to study the impact of drugs on survival. Prof Coleman points to a number of such studies, and adds: “The data they used to assess drugs usage are, in fact, individual cancer patient data, so they could have analysed the survival of those patients, but chose not to.”
- The report does not consider other, probably more important influences on survival, such as early diagnosis or surgery and radiotherapy. “This is despite the fact that detailed information on those treatments is available for each patient in the same commercial database that they used for information about drug usage,” he said.
Responding to an editorial in the Lancet that said it would be “premature and petulant” to dismiss the Karolinska report, Prof Coleman writes: “It is neither premature nor petulant to criticise a 75-page report that invents an incorrect method of estimating cancer survival in a single short sentence, gets the wrong answer, models the incorrect results with drug data for a period some ten years after the patients were diagnosed, and then concludes that low national survival rates are due to poor access to cancer drugs and slow national drug licensing.”
He directs particular criticism at the way the research was funded. Roche Pharmaceuticals funded the research via an unrestricted grant, which is usually taken to mean that the company does not have any power to influence the research or its conclusions.