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Rapid Responses: Rapid Responses published:
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Artificial Colouring in CT scans
- Andrew Slater (20 February 2004)
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Patients' preferences for the management of non-metastatic prostate cancer.
- Sashi Kommu (23 February 2004)
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Readers need more information on Discrete Choice Experiments
- Madeleine T King, Deborah Street, Leonie Burgess, and Jordan Louviere. (26 February 2004)
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Need for wider scope in study term of reference
- Mr. G.A. Bates (4 March 2004)
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Interesting, but hypothetical
- Anssi Auvinen (14 April 2004)
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Andrew Slater, SpR Clinical Radiology John Radcliffe Hospital, Oxford, OX3 9DU, UK
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I note that the CT image on the cover of the BMJ of 14th February has been coloured in. I have seen this often before in general practice magazines, but I am surprised that it is felt necessary in a scientific journal. Are CT scans not felt visually stimulating enough? To arbitrarily add colour to a black and white dataset is essentially manipulating data to fit the result one wishes to show. If the colours are intended to introduce clarity then use of green and brown together does not aid interpretation for the 10% of the male population who are colour blind. I note that the image has also been incorrectly labeled as an MRI scan. Future editions of the BMJ may benefit from the editiorial input of a radiologist. Competing interests: None declared |
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Sashi Kommu, Clinical Research Fellow in Urology/ Cancer Genetics The Institute of Cancer Research, Surrey. U.K. SM2 5NG.
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Editor— I read with great interest the article by Sculpher et al (1), it is indeed commendable. However, instructing their patients to assume a five year survival may lead to a feeling of ‘reconciliation and palliation’ on the part of the patient and hence bias them to choose the most comfortable option knowing that 'death is near'. Hence, the study perhaps should not have included the five-year survival assumption by the patient. Particularly so with the absence of concrete evidence in the literature that their grade and stage may put them in this specific survival time frame. In this study, it is unclear as to whether the patients were made fully aware of the implications of their choice on the survival benefit literature wise. Reziciner et al (2) showed in his study involving recurrence of cancer of the prostate after initial treatment with diethylstilbestrol (DES) in a homogeneous series, that practically all well differentiated prostatic cancers, regardless of their stage, responded remarkably well to first-line treatment with sufficient doses of DES. When correctly monitored, practically none of these cancers escaped and early stages of escape can be salvaged. It was also shown that true escape occurs all the earlier and evolves all the more rapidly for advanced, poorly differentiated cancers, but this is not constant. I am interested how the knowledge of the current literature may have influenced the patients’ decision in the study. They should have had at least a briefing of the current choices in more detail than the average counselled patient. The therapeutic dilemma that patients and clinicians face is the timing of androgen suppression and this study illustrates the difficulty of choice. Until we better understand and conquer the management of hormone escaped prostate cancer patients, the dilemma will continue to conquer us. The choices that patients make are most important in our management at present. Their choice, however, would be irrational if they were not presented with a reasonable cache of facts about their disease process. Respectfully, Sashi Kommu. 1)Sculpher M,Bryan S,Fry P,de Winter P,Payne H, Emberton M. Patients' preferences for the management of non-metastatic prostate cancer: discrete choice experiment. BMJ 2004; 328: 382-0. (2)Reziciner S.Recurrence of cancer of the prostate after initial treatment with diethylstilbestrol (DES) in a homogeneous series of 175 cases. Ann Urol (Paris) 1997;31(4):213-24. Competing interests: None declared |
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Madeleine T King, Lecturer in Health Services Research University of Technology, Sydney, Australia 2007, Deborah Street, Leonie Burgess, and Jordan Louviere.
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Discrete choice experiments (DCE), long used in marketing research (Louviere et al. 2003), are gaining popularity as a means of eliciting preferences for health services. If properly designed, such experiments allow efficient and independent estimation of the effects of interest. In the paper by Sculpher et al (2004), these effects are factors that may be important in a patient's decision about which treatment to choose for non- metastatic prostate cancer. While this is a useful and interesting application of stated preference methods, we have some concerns about the particular DCE used. The structure of the options presented in each choice and the set of all choice sets used in a DCE determine which effects can be estimated. Sculpher et al (2004) identify 8 attributes that may influence a patient’s decision making; 6 treatment side-effects plus survival benefit and cost. They then divide these into two “parts”, effectively creating two separate choice experiments. Each part has 5 attributes; survival and cost appear in both parts, while 3 side-effects appear in one part but not the other. This was done to “avoid overburdening patients with too many attributes”. While we agree that the effect of task complexity on respondent consistency may be an issue in some cases, dividing attributes into separate choice experiments creates four (related) problems: 1) the hypothetical choice fails to mimic the real choice that men face in trading off across the full set of treatment side-effects; 2) information about the correlation between estimates of attribute effects in the two parts of the DCE cannot be obtained; 3) the variance of the random components in the two parts may differ, which would affect estimates of the attribute effects and inferences; and 4) it may introduce bias due to omitted variables and/or context effects. Our concerns are based on a great deal of research summarized in Louviere, Hensher and Swait (2000, Chapter 8), and we are unaware of any theoretical or empirical work that would suggest that this is good practice. While it is good that the authors have chosen an orthogonal main effects design, several important details remain unclear. Which main effects plan was used? Which attribute levels were used in each version for each part? For example, although the “out-of-pocket expenses” attribute is described as having 16 levels, the authors state, “Each version of the questionnaire presented different levels of the cost attribute...” so we do not know how many levels were used in any particular design. Finally, how were the pairs chosen? It is not possible to assess the statistical efficiency of the design (Street and Burgess 2004) unless all the pairs used are displayed. We hope that in the future the journal will require that authors provide sufficient information about the DCEs used to better inform readers’ judgment and interpretation of results and conclusions. Louviere J, Street D and Burgess L (2003). A 20+ years retrospective on choice experiments. In Y Wind and PE Green, ed. Marketing Research and Modeling: Progress and Prospects, Kluwer, New York. Louviere JJ, Hensher DA and Swait JD (2000). Stated choice methods: analysis and applications Cambridge University Press, Cambridge, U.K. ; New York. Sculpher M, Bryan S, Fry P, de Winter P, Payne H and Emberton M (2004). Patients' preferences for the management of non-metastatic prostate cancer: discrete choice experiment. BMJ, 0, 379724972-379724970. Street D and Burgess L (2004). Optimal and Near-Optimal Pairs for the Estimation of Effects in 2-level Choice Experiments. Journal of Statistical Planning and Inference, 118, 185-199. Competing interests: None declared |
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Mr. G.A. Bates, Private Researcher Leicester LE2 3EE
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The boundary conditions of the present study are well defined: Prostate cancer has a majority age of diagnosis of 65-plus years and average age of survival of 5-plus years [1]. However, the diagnosis of prostate cancer for a younger man can spell an early death[4]. In the UK nearly 1000 men of working age die every year from prostate cancer[2]. In the USA [3] the number of pre-retirement deaths due to prostate cancer is about 5000. Treatment needs of this small but significant population requires attention because the chioces made will impact so much more on quantity and quality of life. Putting the same questions used in this study of 70 year olds to a 50 year old man, is quite a different matter. Following diagnosis at young age, decline traces a familiar pattern for these men[5]: Failing prostatic surgery or radiotherapy (or both) for the more aggressive type of prostate cancer, chemical castration or long term hormone block (HB) is generally prescribed (e.g. gonadorelin analogues goserelin, leuprorelin or triptorelin )[6]. I prefer the term "chemical castration" to the more euphemistic "hormone block", since this treatment effectively simulates physical castration with accompanying iatrogenic symptoms, the so-called androgen deficiency syndrome [7,8]. The younger man diagnosed with prostate cancer needs an entirely new approach to treatment that will challenge current medical thinking. References 1. WHO World Health Statistics Annual 1997; Geneva; ISBN 92 4 06 7960 X. p. B-636 2. ibid WHO World Health Statistics Annual 1997; p. B-435 3. ibid WHO World Health Statistics Annual 1997. 4. Dijkman GA, Debruyne FM. Epidemiology of prostate cancer. Eur Urol. 1996;30(3):281-95. Review. PMID: 8931959. Figure 3 p. 283 5. Cancer Causes Control 2002 Jun;13(5):435-43 ; Effect of young age on prostate cancer survival: a population based assessment (United States) ; Merril RM, Bird JS. PMID 12146848 6. Section 8.3.4.2 Prostate Cancer and Gonadorelin Analogues; British National Formulary, March 2003; ISBN 0 85369 555 5 7. Strum SB, McDermed JE, Scholz MC, Johnson H, Tisman G. Anaemia associated with androgen deprivation in patients with prostate cancer receiving combined hormone blockade. Br J Urol. 1997 Jun;79(6):933-41. PMID: 9202563 8. Strum SB, Scholz MC & McDermed JE: The Androgen Deprivation Syndrome: the incidence and severity in prostate cancer patients receiving hormone blockade. Proc Amer Soc Clin Oncol. 17: 316A, 1998. Competing interests: None declared |
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Anssi Auvinen, professor of epidemiology Tampere School of Public Health, FIN-33014 University of Tampere, FINLAND
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Sir, I found the paper by Dr Sculpher and collagues highly interesting and relevant, but what strikes me is the hypothetical nature of the decision making. I am afraid people tend to value things differently when they actually experience the situation - which is the shortcoming of utility assessment. A more relevant approach would be conducting a trial of actual patients choosing the treatment for themselves. We have tried to adopt such a strategy in a trial where the intervention was different level of guidance for choosing the treatment (Auvinen et al. BJU Int 2004;93:52- 56). Patients who received a treatment recommendation were more frequently treated surgically than those for whom no preference between treatment options was given by the physician. This result is in accordance with the findings by Sculpher and others. However, I feel more knowledge can be gained by applying a rigoristic study design in research into patient participation in decision-making ("empirical ethics"). Competing interests: None declared |
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