- Email: [email protected]
Breast-cancer prevention: is the risk-benefit ratio in favour of tamoxifen?
COMMENTARY
study data on the controversial topic of an association between dietary fat and breast cancer10,11 will unfortunately remain unclear until further objective information becomes available about the measurement properties of the dietary assessment methods used. Ross L Prentice Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA (e-mail: [email protected]) 1
US Department of Health and Human Services. Healthy People 2010 Objectives: secretary’s council draft. Washington, DC: US Department of Health and Human Services, Office of Public Health and Science, 1999; April 23. 2 The American Cancer Society 1996 Advisory Committee on Diet, Nutrition, and Cancer Prevention. Guidelines on diet, nutrition, and cancer prevention: reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin 1996; 46: 325–41. 3 Willett WC, Sampson L, Stampfer MJ, et al. Reproducibility and validity of a semiquantitative food frequency questionnaire. Am J Epidemiol 1985; 122: 51–65. 4 Day NE, McKeown N, Wong MY, Welch A, Bingham SA. Epidemiological assessment of diet: a comparison of a 7-day diary with a food frequency questionnaire using urinary markers of nitrogen, potassium and sodium. Int J Epidemiol 2001; 30: 309–17. 5 Heitmann BL, Lissner L. Dietary underreporting by obese individuals: is it specific or non-specific? BMJ 1995; 311: 986–89. 6 Hebert JR, Clemow L, Pbert L, Ockene IS, Ockene JK. Social desirability bias in dietary self-report may compromise the validity of dietary intake measures. Int J Epidemiol 1995; 24: 389–98. 7 Schoeller DA. Recent advances from application of doubly labeled water to measurement of human energy expenditure. J Nutr 1999; 129: 1765–68. 8 Bingham SA, Cummings JH. Urine nitrogen as an independent validatory measure of dietary intake: a study of nitrogen balance in individuals consuming their normal diet. Am J Clin Nutr 1985; 42: 1276–89. 9 Prentice RL. Future possibilities in the prevention of breast cancer: fat and fiber and breast cancer research. Breast Cancer Res 2000; 2: 268–76. 10 Greenwald P. Role of dietary fat in the causation of breast cancer: point. Cancer Epidemiol Biomarkers Prev 1999; 8: 3–7. 11 Hunter DJ. Role of dietary fat in the causation of breast cancer: counterpoint. Cancer Epidemiol Biomarkers Prev 1999; 8: 9–13.
Breast-cancer prevention: is the riskbenefit ratio in favour of tamoxifen? Breast cancer is the most common malignancy in the world among women: over a million women are diagnosed every year, and 370 000 will die due to breast cancer.1 Breast cancer incidence and mortality has marked regional and country differences. Unknown western lifestyle factors and the hormonal environment are strongly related to the risk of developing sporadic breast cancer, the most common form. Treatment of early breast cancer with tamoxifen and chemotherapy gives clinically meaningful and long-lasting survival improvements.2,3 The beneficial effects of adjuvant tamoxifen on oestrogen-receptor-positive breast cancers and the reduction in contralateral breast cancers, combined with the high incidence of breast cancer, stimulated investigators on both sides of the Atlantic to investigate whether the development of breast cancer could be prevented in at-risk women. Four randomised studies with tamoxifen and one with raloxifene have investigated the potential preventive effect of these drugs; raloxifene was actually tested for osteoporosis prevention (breast cancer prevention was a secondary endpoint). The women included in the trials had calculated risks of breast cancer varying from normal (a woman in the USA and other countries in the western world has a lifetime
risk of around 1 in 8 and up to 1 in 10, respectively) to different increased levels of risk, according to predefined risk-level strategies.4–9 The reduction of new breast cancers tended to be highest in the largest study. 36 111 women (28 406 in the four tamoxifen studies) were included in these prospective studies with active drug or placebo.9 In total, 289 patients were diagnosed with breast cancer in the tamoxifen-treated groups; the corresponding figure was 465 for those not receiving tamoxifen, including in-situ cancers. In the tamoxifen groups, 1 in 49 women developed breast cancer; in the placebo groups, 1 in 31 did so. The calculated reduction in breast cancer was 38% (48% for invasive oestrogen-receptor-positive breast cancers) after treating with tamoxifen for 5 years. Thus, by treating 14 192 women at different risk levels, 5 years of tamoxifen prevented, or deferred, 132 oestrogen-receptor-positive and invasive breast cancers. The gain also had an expense; 53 versus 22 women developed an endometrial carcinoma and 118 versus 62 had a thromboembolic event (tamoxifen versus untreated, respectively). 59 and 39 women, respectively, had a recorded diagnosis of a cerebrovascular accident or stroke. The opposite was found for transient ischaemic attacks. The other drug tested, the selective oestrogen-receptor modulator, raloxifene, was associated with a potentially larger reduction of breast cancer incidence and no increased risk for endometrial carcinoma, and raloxifene is being tested head to head with tamoxifen in the ongoing STAR (Study of Tamoxifen and Raloxifene) study.9 Using the prevention data from the largest study, NSABP-P1,10 Fisher estimated that 700 000 invasive and non-invasive breast cancers could be avoided over 5 years by giving tamoxifen prevention to 29 million women. Andrew Freedman and colleagues11 recently recalculated the potential impact using the data from the P1 study, modulated on almost 66 million US women aged 35–79 years. These investigators used a modified Gail model and estimated that 15·5% would be potentially eligible for prevention with tamoxifen, although with marked between-race differences (18·7% for white women, 5·7% for black women, and 2·9% for Hispanic women). The calculated risk-estimates will, in some other high-risk countries in the world, be almost as high as for the high-risk group of white women in the USA. However, when benefitrisk ratios for tamoxifen are applied, only 4·9%, instead of 18·7%, of white women in the USA would be potential candidates for tamoxifen prevention, according to Freedman and colleagues. For black women the corresponding figure is 0·6%; similar data cannot be properly estimated for Hispanic women. The health-economic consequences of this type of strategy must also be analysed. In almost all countries, the health sector has limited resources. We must therefore strive to increase resources, but also to make the best priorities and medical decisions, and include health-economic modelling. On such a basis, plus the current data on prevention, it is by no means obvious that prevention with present drugs is the way forward. However, with present knowledge, doctors can carefully discuss with women at risk for breast cancer the potential benefits and risks in relation to each individual’s risk level for breast cancer, other illnesses, and individual preferences.11 The lack of a benefit in overall survival in the prevention studies to date, with complicated benefit-risk relations and the fact that only oestrogen-receptor-positive tumours can be prevented or deferred, means that the task today is to find early oestrogen-receptor-positive breast cancers by surveillance strategies, including mammography. Modern
THE LANCET • Vol 362 • July 19, 2003 • www.thelancet.com
For personal use. Only reproduce with permission from The Lancet.
183
COMMENTARY
therapy of small oestrogen-receptor-positive breast cancers will result in survival expectations that are similar to an agematched population without breast cancer.12 Further follow-up of the current prevention studies is awaited, together with exploration of new prevention concepts and drugs, and a search for better and tailored markers of risk for later development of breast cancer. An ideal and more global prevention strategy for breast cancer must include positive cardiovascular effects, benefits on the central nervous system, uterine safety, and positive skeletal effects, in addition to breast cancer prevention, or, at least, no negative effects on other organ systems. Current selective oestrogen-receptor modulators and aromatase inhibitors, in standard doses and alone, will not fulfil this broader objective. However, the aromatase inhibitors may have an even more beneficial effect on present prevention of breast cancer, but skeletal and cardiovascular side-effects are likely and raise concern, although final answers will only be obtained from randomised studies.13 Jonas Bergh Radiumhemmet, Karolinska Institute and Hospital, S-171 76 Stockholm, Sweden (e-mail: [email protected]) 1
2
3
4
5
6
7
8
9 10
11
12
13
Schwartsmann G, Ratain MJ, Cragg GM, et al. Anticancer drug discovery and development throughout the world. J Clin Oncol 2002; 20 (suppl): 47S–59S. Early Breast Cancer Trialists’ Collaborative Group. Tamoxifen for early breast cancer: an overview of the randomised trials. Lancet 1998; 351: 1451–67. Early Breast Cancer Trialists’ Collaborative Group. Polychemotherapy for early breast cancer: an overview of the randomised trials. Lancet 1998; 352: 930–42. Cuzick J, Forbes J, Edwards R, et al. First results from the International Breast Cancer Intervention Study (IBIS-I): a randomised prevention trial. Lancet 2002; 360: 817–24. Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 1998; 90: 1371–88. Cauley JA, Norton L, Lippman ME, et al. Continued breast cancer risk reduction in postmenopausal women treated with raloxifene: 4-year results from the MORE trial—multiple outcomes of raloxifene evaluation. Breast Cancer Res Treat 2001; 65: 125–34. Veronesi U, Maisonneuve P, Sacchini V, Rotmensz N, Boyle P. Tamoxifen for breast cancer among hysterectomised women. Lancet 2002; 359: 1122–24. Powles T, Eeles R, Ashley S, et al. Interim analysis of the incidence of breast cancer in the Royal Marsden Hospital tamoxifen randomised chemoprevention trial. Lancet 1998; 352: 98–101. Cuzick J, Powles T, Veronesi U, et al. Overview of the main outcomes in breast-cancer prevention trials. Lancet 2003; 361: 296–300. Fisher B. National Surgical Adjuvant Breast and Bowel Project breast cancer prevention trial: a reflective commentary. J Clin Oncol 1999; 17: 1632–39. Freedman AN, Graubard BI, Rao SR, McCaskill-Stevens W, Ballard-Barbash R, Gail MH. Estimates of the number of US women who could benefit from tamoxifen for breast cancer chemoprevention. J Natl Cancer Inst 2003; 95: 526–32. Bergh J, Holmqvist M. Who should not receive adjuvant chemotherapy—international databases. J Natl Cancer Inst 2001; 30 (suppl): 103–08. Smith IE, Dowsett M. Aromatase inhibitors in breast cancer. N Engl J Med 2003; 348: 2431–42.
Dam medicine
to serve villages. The impact of a dam depends not only on its height and width and the size of the river behind it, but also on its location, and there will always be costs as well as benefits. The new Chinese dam is displacing more than 1 million people, but it will stop the river flooding (in 1998 at least 1000 people drowned), extend irrigation, and supply hydroelectric power. 2 years ago, Adrian Sleigh and Sukhan Jackson1 regretted the neglect, in the 2000 report from the World Commission on Dams, of assessment of the impact on health. Lately there has been a subtle change—too late to affect the Three Gorges project, but of possible significance to future dams and similar construction projects that are financed by international bank loans. The so-called equator principles are intended to ensure that loans are made only for projects that are socially and environmentally responsible. That is a very broad brush and may attract the cynical response that this declaration of principle is just an exercise in public relations. We can only speculate whether or not the controversial Three Gorges Dam would have been starved of money had these principles been in place earlier, but they do seem to be a step in the right direction and they do have the support of the private arm of the World Bank, the International Finance Corporation.2 Sleigh and Jackson1 also thought that the little publichealth impact assessment of dams that had been done was too focused on parasitic disease, to the neglect of the broader medicosocial effects of population displacement. The obvious example of this focus is “red water” disease— more still water means more snails and, in many parts of the world, more Schistosoma haematobium. Other examples are dracunculiasis, filariasis, and malaria. The disease burden can be long lasting. John Hunter has made a special study of smaller agricultural dams, and his most recent paper shows that in north-east Ghana, where over 100 dams were built in just 3 years, an early trebling from 17% to 51% in the prevalence of schistosomiasis has become permanent.3 Field surveys in 1997 showed a mean prevalence of 54% positivity for haemolysed blood in urine. In neighbouring Burkina Faso the trend has been much the same, and intestinal schistosomiasis (“almost unheard of until 1987”) has become a problem too.4 Transmission can be interrupted with a single dose of praziquantel followed by avoidance of exposure to risky water in future. But, as Hunter says, this is not as easy as it sounds, and it is generally true that populations affected by proximity to dams are those whose access to health services is already limited. If bankers really want to be socially responsible they could do a lot with what is known already. The increase in disease in Ghana’s Upper Region would have been significantly reduced, Hunter concludes “if even a tiny fraction of the original financial investment had been judiciously used in protective health measures”.3 David Sharp c/o The Lancet, London NW1 7BY, UK 1 2
The word dam conjures up some big names—the Hoover on the Colorado River and the Nile’s two at Aswan, for example. Last month, the Yangtze began to back up behind the vast Three Gorges Dam. The water should rise to no more than 135 m above sea level in this phase, and to 175 m in 2009. Most dams, however, are below 15 m in height; the world has over 45 000 of these, almost half of them in China. In northern Ghana, for example, soon after that country’s independence in 1957, 185 dams were built 184
3
4
Sleigh AC, Jackson S. Dams, development, and health: a missed opportunity. Lancet 2001; 357: 570–71. International Finance Corporation. The “equator principles”: an industry approach for financial institutions in determining, assessing and managing environmental and social risk in project planning. Washington, DC: International Finance Corporation, 2003: http://equatorprinciples.ifc.org/ifcext/equatorprinciples.nsf (accessed June 25, 2003). Hunter JM. Inherited burden of disease: agricultural dams and the persistence of bloody urine (Schistosomiasis hematobium) in the Upper East Region of Ghana, 1959–1997. Soc Sci Med 2003; 56: 219–34. Poda JN, Sondo B, Parent G. Impact of hydraulic installations on the distribution of schistosomiasis and its intermediary hosts in Burkina Faso. Santé 2003; 13: 49–53 (in French).
THE LANCET • Vol 362 • July 19, 2003 • www.thelancet.com
For personal use. Only reproduce with permission from The Lancet.
study data on the controversial topic of an association between dietary fat and breast cancer10,11 will unfortunately remain unclear until further objective information becomes available about the measurement properties of the dietary assessment methods used. Ross L Prentice Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA (e-mail: [email protected]) 1
US Department of Health and Human Services. Healthy People 2010 Objectives: secretary’s council draft. Washington, DC: US Department of Health and Human Services, Office of Public Health and Science, 1999; April 23. 2 The American Cancer Society 1996 Advisory Committee on Diet, Nutrition, and Cancer Prevention. Guidelines on diet, nutrition, and cancer prevention: reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin 1996; 46: 325–41. 3 Willett WC, Sampson L, Stampfer MJ, et al. Reproducibility and validity of a semiquantitative food frequency questionnaire. Am J Epidemiol 1985; 122: 51–65. 4 Day NE, McKeown N, Wong MY, Welch A, Bingham SA. Epidemiological assessment of diet: a comparison of a 7-day diary with a food frequency questionnaire using urinary markers of nitrogen, potassium and sodium. Int J Epidemiol 2001; 30: 309–17. 5 Heitmann BL, Lissner L. Dietary underreporting by obese individuals: is it specific or non-specific? BMJ 1995; 311: 986–89. 6 Hebert JR, Clemow L, Pbert L, Ockene IS, Ockene JK. Social desirability bias in dietary self-report may compromise the validity of dietary intake measures. Int J Epidemiol 1995; 24: 389–98. 7 Schoeller DA. Recent advances from application of doubly labeled water to measurement of human energy expenditure. J Nutr 1999; 129: 1765–68. 8 Bingham SA, Cummings JH. Urine nitrogen as an independent validatory measure of dietary intake: a study of nitrogen balance in individuals consuming their normal diet. Am J Clin Nutr 1985; 42: 1276–89. 9 Prentice RL. Future possibilities in the prevention of breast cancer: fat and fiber and breast cancer research. Breast Cancer Res 2000; 2: 268–76. 10 Greenwald P. Role of dietary fat in the causation of breast cancer: point. Cancer Epidemiol Biomarkers Prev 1999; 8: 3–7. 11 Hunter DJ. Role of dietary fat in the causation of breast cancer: counterpoint. Cancer Epidemiol Biomarkers Prev 1999; 8: 9–13.
Breast-cancer prevention: is the riskbenefit ratio in favour of tamoxifen? Breast cancer is the most common malignancy in the world among women: over a million women are diagnosed every year, and 370 000 will die due to breast cancer.1 Breast cancer incidence and mortality has marked regional and country differences. Unknown western lifestyle factors and the hormonal environment are strongly related to the risk of developing sporadic breast cancer, the most common form. Treatment of early breast cancer with tamoxifen and chemotherapy gives clinically meaningful and long-lasting survival improvements.2,3 The beneficial effects of adjuvant tamoxifen on oestrogen-receptor-positive breast cancers and the reduction in contralateral breast cancers, combined with the high incidence of breast cancer, stimulated investigators on both sides of the Atlantic to investigate whether the development of breast cancer could be prevented in at-risk women. Four randomised studies with tamoxifen and one with raloxifene have investigated the potential preventive effect of these drugs; raloxifene was actually tested for osteoporosis prevention (breast cancer prevention was a secondary endpoint). The women included in the trials had calculated risks of breast cancer varying from normal (a woman in the USA and other countries in the western world has a lifetime
risk of around 1 in 8 and up to 1 in 10, respectively) to different increased levels of risk, according to predefined risk-level strategies.4–9 The reduction of new breast cancers tended to be highest in the largest study. 36 111 women (28 406 in the four tamoxifen studies) were included in these prospective studies with active drug or placebo.9 In total, 289 patients were diagnosed with breast cancer in the tamoxifen-treated groups; the corresponding figure was 465 for those not receiving tamoxifen, including in-situ cancers. In the tamoxifen groups, 1 in 49 women developed breast cancer; in the placebo groups, 1 in 31 did so. The calculated reduction in breast cancer was 38% (48% for invasive oestrogen-receptor-positive breast cancers) after treating with tamoxifen for 5 years. Thus, by treating 14 192 women at different risk levels, 5 years of tamoxifen prevented, or deferred, 132 oestrogen-receptor-positive and invasive breast cancers. The gain also had an expense; 53 versus 22 women developed an endometrial carcinoma and 118 versus 62 had a thromboembolic event (tamoxifen versus untreated, respectively). 59 and 39 women, respectively, had a recorded diagnosis of a cerebrovascular accident or stroke. The opposite was found for transient ischaemic attacks. The other drug tested, the selective oestrogen-receptor modulator, raloxifene, was associated with a potentially larger reduction of breast cancer incidence and no increased risk for endometrial carcinoma, and raloxifene is being tested head to head with tamoxifen in the ongoing STAR (Study of Tamoxifen and Raloxifene) study.9 Using the prevention data from the largest study, NSABP-P1,10 Fisher estimated that 700 000 invasive and non-invasive breast cancers could be avoided over 5 years by giving tamoxifen prevention to 29 million women. Andrew Freedman and colleagues11 recently recalculated the potential impact using the data from the P1 study, modulated on almost 66 million US women aged 35–79 years. These investigators used a modified Gail model and estimated that 15·5% would be potentially eligible for prevention with tamoxifen, although with marked between-race differences (18·7% for white women, 5·7% for black women, and 2·9% for Hispanic women). The calculated risk-estimates will, in some other high-risk countries in the world, be almost as high as for the high-risk group of white women in the USA. However, when benefitrisk ratios for tamoxifen are applied, only 4·9%, instead of 18·7%, of white women in the USA would be potential candidates for tamoxifen prevention, according to Freedman and colleagues. For black women the corresponding figure is 0·6%; similar data cannot be properly estimated for Hispanic women. The health-economic consequences of this type of strategy must also be analysed. In almost all countries, the health sector has limited resources. We must therefore strive to increase resources, but also to make the best priorities and medical decisions, and include health-economic modelling. On such a basis, plus the current data on prevention, it is by no means obvious that prevention with present drugs is the way forward. However, with present knowledge, doctors can carefully discuss with women at risk for breast cancer the potential benefits and risks in relation to each individual’s risk level for breast cancer, other illnesses, and individual preferences.11 The lack of a benefit in overall survival in the prevention studies to date, with complicated benefit-risk relations and the fact that only oestrogen-receptor-positive tumours can be prevented or deferred, means that the task today is to find early oestrogen-receptor-positive breast cancers by surveillance strategies, including mammography. Modern
THE LANCET • Vol 362 • July 19, 2003 • www.thelancet.com
For personal use. Only reproduce with permission from The Lancet.
183
COMMENTARY
therapy of small oestrogen-receptor-positive breast cancers will result in survival expectations that are similar to an agematched population without breast cancer.12 Further follow-up of the current prevention studies is awaited, together with exploration of new prevention concepts and drugs, and a search for better and tailored markers of risk for later development of breast cancer. An ideal and more global prevention strategy for breast cancer must include positive cardiovascular effects, benefits on the central nervous system, uterine safety, and positive skeletal effects, in addition to breast cancer prevention, or, at least, no negative effects on other organ systems. Current selective oestrogen-receptor modulators and aromatase inhibitors, in standard doses and alone, will not fulfil this broader objective. However, the aromatase inhibitors may have an even more beneficial effect on present prevention of breast cancer, but skeletal and cardiovascular side-effects are likely and raise concern, although final answers will only be obtained from randomised studies.13 Jonas Bergh Radiumhemmet, Karolinska Institute and Hospital, S-171 76 Stockholm, Sweden (e-mail: [email protected]) 1
2
3
4
5
6
7
8
9 10
11
12
13
Schwartsmann G, Ratain MJ, Cragg GM, et al. Anticancer drug discovery and development throughout the world. J Clin Oncol 2002; 20 (suppl): 47S–59S. Early Breast Cancer Trialists’ Collaborative Group. Tamoxifen for early breast cancer: an overview of the randomised trials. Lancet 1998; 351: 1451–67. Early Breast Cancer Trialists’ Collaborative Group. Polychemotherapy for early breast cancer: an overview of the randomised trials. Lancet 1998; 352: 930–42. Cuzick J, Forbes J, Edwards R, et al. First results from the International Breast Cancer Intervention Study (IBIS-I): a randomised prevention trial. Lancet 2002; 360: 817–24. Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 1998; 90: 1371–88. Cauley JA, Norton L, Lippman ME, et al. Continued breast cancer risk reduction in postmenopausal women treated with raloxifene: 4-year results from the MORE trial—multiple outcomes of raloxifene evaluation. Breast Cancer Res Treat 2001; 65: 125–34. Veronesi U, Maisonneuve P, Sacchini V, Rotmensz N, Boyle P. Tamoxifen for breast cancer among hysterectomised women. Lancet 2002; 359: 1122–24. Powles T, Eeles R, Ashley S, et al. Interim analysis of the incidence of breast cancer in the Royal Marsden Hospital tamoxifen randomised chemoprevention trial. Lancet 1998; 352: 98–101. Cuzick J, Powles T, Veronesi U, et al. Overview of the main outcomes in breast-cancer prevention trials. Lancet 2003; 361: 296–300. Fisher B. National Surgical Adjuvant Breast and Bowel Project breast cancer prevention trial: a reflective commentary. J Clin Oncol 1999; 17: 1632–39. Freedman AN, Graubard BI, Rao SR, McCaskill-Stevens W, Ballard-Barbash R, Gail MH. Estimates of the number of US women who could benefit from tamoxifen for breast cancer chemoprevention. J Natl Cancer Inst 2003; 95: 526–32. Bergh J, Holmqvist M. Who should not receive adjuvant chemotherapy—international databases. J Natl Cancer Inst 2001; 30 (suppl): 103–08. Smith IE, Dowsett M. Aromatase inhibitors in breast cancer. N Engl J Med 2003; 348: 2431–42.
Dam medicine
to serve villages. The impact of a dam depends not only on its height and width and the size of the river behind it, but also on its location, and there will always be costs as well as benefits. The new Chinese dam is displacing more than 1 million people, but it will stop the river flooding (in 1998 at least 1000 people drowned), extend irrigation, and supply hydroelectric power. 2 years ago, Adrian Sleigh and Sukhan Jackson1 regretted the neglect, in the 2000 report from the World Commission on Dams, of assessment of the impact on health. Lately there has been a subtle change—too late to affect the Three Gorges project, but of possible significance to future dams and similar construction projects that are financed by international bank loans. The so-called equator principles are intended to ensure that loans are made only for projects that are socially and environmentally responsible. That is a very broad brush and may attract the cynical response that this declaration of principle is just an exercise in public relations. We can only speculate whether or not the controversial Three Gorges Dam would have been starved of money had these principles been in place earlier, but they do seem to be a step in the right direction and they do have the support of the private arm of the World Bank, the International Finance Corporation.2 Sleigh and Jackson1 also thought that the little publichealth impact assessment of dams that had been done was too focused on parasitic disease, to the neglect of the broader medicosocial effects of population displacement. The obvious example of this focus is “red water” disease— more still water means more snails and, in many parts of the world, more Schistosoma haematobium. Other examples are dracunculiasis, filariasis, and malaria. The disease burden can be long lasting. John Hunter has made a special study of smaller agricultural dams, and his most recent paper shows that in north-east Ghana, where over 100 dams were built in just 3 years, an early trebling from 17% to 51% in the prevalence of schistosomiasis has become permanent.3 Field surveys in 1997 showed a mean prevalence of 54% positivity for haemolysed blood in urine. In neighbouring Burkina Faso the trend has been much the same, and intestinal schistosomiasis (“almost unheard of until 1987”) has become a problem too.4 Transmission can be interrupted with a single dose of praziquantel followed by avoidance of exposure to risky water in future. But, as Hunter says, this is not as easy as it sounds, and it is generally true that populations affected by proximity to dams are those whose access to health services is already limited. If bankers really want to be socially responsible they could do a lot with what is known already. The increase in disease in Ghana’s Upper Region would have been significantly reduced, Hunter concludes “if even a tiny fraction of the original financial investment had been judiciously used in protective health measures”.3 David Sharp c/o The Lancet, London NW1 7BY, UK 1 2
The word dam conjures up some big names—the Hoover on the Colorado River and the Nile’s two at Aswan, for example. Last month, the Yangtze began to back up behind the vast Three Gorges Dam. The water should rise to no more than 135 m above sea level in this phase, and to 175 m in 2009. Most dams, however, are below 15 m in height; the world has over 45 000 of these, almost half of them in China. In northern Ghana, for example, soon after that country’s independence in 1957, 185 dams were built 184
3
4
Sleigh AC, Jackson S. Dams, development, and health: a missed opportunity. Lancet 2001; 357: 570–71. International Finance Corporation. The “equator principles”: an industry approach for financial institutions in determining, assessing and managing environmental and social risk in project planning. Washington, DC: International Finance Corporation, 2003: http://equatorprinciples.ifc.org/ifcext/equatorprinciples.nsf (accessed June 25, 2003). Hunter JM. Inherited burden of disease: agricultural dams and the persistence of bloody urine (Schistosomiasis hematobium) in the Upper East Region of Ghana, 1959–1997. Soc Sci Med 2003; 56: 219–34. Poda JN, Sondo B, Parent G. Impact of hydraulic installations on the distribution of schistosomiasis and its intermediary hosts in Burkina Faso. Santé 2003; 13: 49–53 (in French).
THE LANCET • Vol 362 • July 19, 2003 • www.thelancet.com
For personal use. Only reproduce with permission from The Lancet.