While indolent Americans are sleeping off their turkey comas, hard- working Canadians, who would never indulge in such gormandising excess, continue to think big thoughts on psychology. Here´s one.
It is widely believed, despite the absence of convincing evidence, that cancer can be influenced by psychological factors, such as thinking positive thoughts, having a healthful lifestyle, attending support groups, or receiving therapy. This drives me nuts. It´s hard enough for psychology to show any direct benefit from psychological intervention. How much less likely that psychology can influence the course of a dread disease with a clear biological basis. And this claim carries the pernicious implication that if you´ve got cancer, it must be because you´re doing something wrong. Yet. A just-published study (Andersen et al, 2008) reports on the progress of disease in women surgically treated for breast cancer and continuing with medical treatment. They report that women additionally exposed to 12 months of intensive group therapy, which included "strategies to reduce stress, improve mood, alter health behaviours, and maintain adherence to cancer treatment", produced significant long-term benefits against their disease. In particular, these women had "a reduced risk of breast cancer recurrence...and [a reduced risk of] death from breast cancer". I´ve saved the best for last. In contrast to our usual complaints about correlational studies, this was a _randomized_ study, in which the control group received assessment only. True, there was no placebo, but I´m nevertheless gobsmacked that _anything _ like that, whatever it was, could produce such a striking outcome. Even more remarkable, they also reported "a reduced risk of death from all causes", which Gigerenzer (2008, see comments below) considers the ultimate bottom line, one which is rarely achieved. And the results were analyzed on an "intention to treat" basis, which means that dropouts were counted as failures. Do we therefore accept these exceptionally-encouraging conclusions? This is where I bring in Gigerenzer (and you, gentle readers). There´s been a lot of admiration expressed on this list lately for Gigerenzer et al (2008), and justifiably. Their paper is clear and insightful and I´ve learned a lot from it. I´ve been trying to use Gigerenzer´s ideas in evaluating this paper, but I´m not sure I´ve got it right. Gigerenzer recommends transparent framing of information, and recommends that data be expressed as natural frequencies. The Andersen paper uses "Cox proportional hazards analysis" (which is not transparent to me) in an analysis of survival times. Gigerenzer criticizes the use of survival time data and says it is uncorrelated with mortality, which he recommends should be used instead. Yet his argument is based on the use of survival times when methods of diagnosis differ (e.g. his Rudy Giuliani/prostate cancer example). This is not the case here, as the groups are randomized after receiving diagnosis by the same method, so any improvement in the therapy group in survival time should be meaningful, and not subject to this criticism . But I´m concerned that while the analysis is for survival time and the critical finding is displayed as a set of three graphs (Figure 3) of recurrence-free survival time, breast cancer specific survival time, and overall survival time, the language is frequently that of mortality (e.g. the abstract claims "reduced...death from breast cancer [and]...from all causes". I don´t see how they get from one to the other, and I wonder whether this is just sloppy language for survival time data. Then there´s this. Their Figure 2 provides all the data necessary at the study end (median of 11 years follow-up) to do a natural frequency analysis as recommended by Gigerenzer (but they don't). For the control group (assessment only) 25 of 113 died of breast cancer; for the therapy group, it was 19 of 114. For all causes of death, for the control, 30 of 113 died, while for the therapy group it was 24 of 114. Deaths in each case are reduced by about 6% after therapy compared with control, which seems meaningful (Hazard ratios around 0.8). But neither control vs therapy comparison is even close to significance by a chi-square test (e.g. Fisher´s exact), which means either there´s nothing there, or not enough subjects were studied to show it. So, what´s going on? Can Cox proportional hazards analysis demonstrate something not evident by simple statistics? Are they justified in using their mortality language when analyzing by survival times? Or are they playing with statistics, and avoiding using an analysis which turns out negative? My own feeling is that they should have explicitly carried out the analysis I did, noted their failure to show an effect on mortality, and discussed the implications for their Cox analysis. The press release I have, BTW, prominently refers to the mortality claim, "The study also found that patients receiving the intervention had less than half the risk (44 percent) of death from breast cancer compared to those who did not receive the intervention, and had a reduced risk of death from all causes, not just cancer" (Science Daily, 2008/11/08). Not according to my analysis of their data, though. I would really like to hear from our statistics experts on this. The abstract is here: http://tinyurl.com/5z8fn2, although it would be better to read the paper. If you don´t have access to it, I can supply a copy, or you can get it direct from the author, who answered my request promptly. She´s a psychologist at Ohio State University. Her address is [EMAIL PROTECTED] (As usual, I´m thinking about going the letter-to-the-editor route. But I´m not sure I´ve got it right). Stephen Andersen, B. et al (2008). Psychological intervention improves survival for breast cancer patients: a randomized clinical trial. _Cancer_, 113: 3450-8 [published on-line November 17, 2008]. Gigerenzer, G. et al (2008). Helping doctors and patients make sense of health statistics. _Psychological Science in the Public Interest_, 8: 53- 96. ----------------------------------------------------------------- Stephen L. Black, Ph.D. Professor of Psychology, Emeritus Bishop's University e-mail: [EMAIL PROTECTED] 2600 College St. Sherbrooke QC J1M 1Z7 Canada Subscribe to discussion list (TIPS) for the teaching of psychology at http://flightline.highline.edu/sfrantz/tips/ ----------------------------------------------------------------------- --- To make changes to your subscription contact: Bill Southerly ([EMAIL PROTECTED])
