Correspondence to: Director, National Cancer Intelligence Centre, Office for National Statistics, B7/04, 1 Drummond Gate, London, SW1V 2QQ, U.K. (e-mail: mike.quinn{at}ons.gov.uk).
The fifth in the series of Annual Reports to the Nation on the Status of Cancer (1) focuses on the four most common cancerslung, female breast, colorectal, and prostatethat together account for more than half of both cancer cases and deaths in the United States. These four cancers have similar importance in most of Europe (2). A principal strength of the report is that it provides a wealth of information on the cancer trends in terms of both incidence and mortality. Incidence and mortality data each have their own advantages and disadvantages (Table 1).
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Mortality data never were free from bias or criticism (4). Death is not always correctly certified, nor is the underlying cause always correctly coded, even for cancer. Many studies have shown wide variability in the accuracy of death certification and coding, particularly among countries (5). For cancers with moderate or good survival, mortality trends give only a delayed indication of trends in new cases, because those dying in any one year may have been diagnosed and treated many years earlier. Mortality data are also an imperfect and fuzzy indicator of trends in the efficacy of treatment, reflecting earlier trends in both incidence and survival, and cannot be interpreted sensibly without them. Incidence and survival trends from cancer registries provide additional insight into the complex problems of cancer control (7). Over the past 30 years, survival from almost all cancers has genuinely improved, sometimes dramatically. The implication is that trends in incidence and mortality have been diverging. If this can be shown to be true, then this overall coherence in the results from what are largely independent systemscancer and death registrationinduces greater confidence in each of them. But none of incidence, survival, or mortality is perfect, and none is adequate on its own. It is somewhat surprising that no survival results were given in the Annual Report to the Nation (1).
In Europe, long established population-based cancer registration systems with national coverage (often regionally organized) and with virtually complete follow-up of cases exist in all the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden), in the United Kingdom, and in many of the Baltic and central European countries of the former Soviet bloc. Coverage in other parts of Europe such as France, Germany, Italy, and Spain is, however, relatively poor (6) and is unlikely to improve much, if at all, in the foreseeable future. In this context, the establishment in the United States of state cancer registries, in addition to the high quality SEER registries, is a major step forward in cancer control (7).
LUNG CANCER TRENDS
Lung cancer incidence and mortality in U.S. men has been declining for some time, and rates in women in the 1990s were increasing much less steeply than before. A recent analysis of lung cancer mortality trends in the 15 member states of the European Union (EU) (8) has shown declining trends for men in 11 member states (the earliest occurring in Finland and in the United Kingdom in the early 1970s), stable trends in France and Greece, but rising trends in Portugal and Spain. Although tobacco control in Europe has been highly effective in men, there has been almost complete failure in women (8). Lung cancer mortality trends in women have been rising since the 1950s in Austria, Belgium, Denmark, Finland, France, Germany, Italy, Luxembourg, The Netherlands (extremely steep increase), and Sweden; the rising trends have slowed in Greece, Ireland, Portugal, and Spain; and in the United Kingdom, the overall trend has begun to turn downward. Large differences exist in the levels and trends in both men and women within the United Kingdom, with very high mortality rates in Scotland.
The first point of the recently revised European Code Against Cancer (9) is "Do not smoke. If you smoke, stop. If you fail to stop, do not smoke in the presence of non-smokers." The risk of cancer rapidly decreases upon stopping smoking, and the benefit progressively increases over time (10). Large proportions of adult smokers want to quit smoking. Marked reductions in future lung cancer mortality could be achieved if more money and resources were devoted to smoking cessation programs, one of the most cost-effective public health interventions.
BREAST CANCER TRENDS
There is now almost universal consensus that mammography screening for women aged 5069 years is effective in reducing breast cancer mortality. The criticisms of the randomized controlled trials of breast screening in a review by two opponents of screening (11) have all been rebutted by several groups (12). The results of randomized controlled trials strongly suggest that mammography may well lead to a reduction in breast cancer mortality in younger women, but that the reduction is probably smaller (approximately 20%) than in older women (approximately 35%) (13). The balance of benefits and harms, however, is different if women are screened annually from the age of 40 years. In Europe, the evidence is considered too limited to reach a conclusion about the efficacy of screening women aged 4049 years (9). However, it seems increasingly likely that in a few years, with the accumulation of more deaths among younger women included in randomized clinical trials, the 20% reduction will become statistically significant.
The ninth point in the European Code Against Cancer (9) stresses that breast screening should be within programs with quality control procedures that are in compliance with the European Guidelines for Quality Assurance in Mammography Screening. The code stresses that screening is but one step in the total care of women with breast cancer, and emphasizes the importance of the role of the multidisciplinary teamas specified in the Guidelinesand the development of an integrated breast care center. The separation of mammographic screening from treatment, counseling, and other support services in the United States is widely viewed in old Europe to be inappropriate.
The decline in breast cancer mortality rates in the United States and in the United Kingdom (14) have been attributed in part to increased mammography screening. However, the general publics expectations of the effect of breast screening have not been met because it is not widely appreciated that for many years the effect will be far smaller than was seen in the randomized controlled trials, principally because approximately 50% of all women dying from breast cancer within 10 years of the introduction of screening will have been diagnosed before screening started. It was estimated that about one-third of the overall 21% reduction in breast cancer mortality in the United Kingdom by 1998 (10 years after screening began) was due directly to screening (14). Of the remainder, much of the reduction will have been due to indirect effects, including the establishment of treatment protocols and guidelines for women with screen-detected cancers that are also effective for women with symptomatic cancers. Some, although probably not a majority, of the reduction will have been due to the dissemination of multi-agent chemotherapy and tamoxifen.
What is striking about the U.S. results is that breast cancer mortality has decreased in every state (statistically significantly in almost 40 states). In Europe, few countries have introduced national breast screening programs (15). The biggest reduction in mortality has occurred in the United Kingdom, with reductions also in Austria, Germany, Ireland, Italy, Luxembourg, The Netherlands and, over a longer period than elsewhere, Sweden. Recent mortality has been stable in Belgium, Denmark, Finland, France, Portugal, and Spain, and mortality is increasing in Greece (8).
PROSTATE CANCER TRENDS
Randomized controlled trials are in progress evaluating the efficacy of prostate-specific antigen (PSA) testing for prostate cancer. The U.S. Preventive Services Task Force (USPSTF) has concluded that the current evidence is insufficient to make a recommendation, a statement that is echoed in the revised European Code Against Cancer (9). Mortality from prostate cancer has decreased in the United States, where, as with breast cancer, it is striking that it has decreased in every state (statistically significantly in more than 40 states). Mortality from prostate cancer has also decreased in Australia and Canada, in Austria, France, Germany, Italy, and the United Kingdom, but trends are rising in Belgium, Denmark, Finland, Greece, Ireland, The Netherlands, Portugal, Spain, and Sweden (8). Although PSA testing may explain part of the reduction in the United States, for it to explain all of it would require that the lead time be implausibly short (16). The smaller rise in 1-year survival than in 5-year survival in the United Kingdom supports a recent U.S. study that suggests that increased use of hormonal therapy may be having an impact on survival (17). The strong arguments against PSA testing are well known (Table 2; Fig. 1
).
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COLORECTAL CANCER TRENDS
The trends in colorectal cancer in the United States are quite different from those in Europe. In the United Kingdom, incidence has increased only slightly since 1971, whereas by the end of the 1990s, mortality had decreased by approximately 50% since 1950. This is consistent with 5-year survival rates improving from just over 20% in the early 1970s to almost 45% in the mid-1990s. Elsewhere in Europe, there have been generally greater declines in mortality in women than in men, which may be attributable to the increased use of oral contraceptives and hormone replacement therapy (8). Mortality has been falling recently in most EU countries, but is rising in Greece, Portugal, and Spain.
Despite the accumulating evidence, including from several randomized controlled trials of the efficacy of fecal occult blood (FOB) testing, that a worthwhile reduction in colorectal cancer mortality could be obtained from a population-based program, most people in developed countries have not been screened by any method (9). In this context, the proportions of Americans who have had an FOB test within the past 2 years (25% to 35% in most states) or who ever had sigmoidoscopy or colonoscopy (median around 50%) are quite high. The USPSTF supports the use of FOB and other screening tests, but, as noted, there could be problems associated with the medical infrastructure for both screening itself and subsequent treatment, and a reluctance to participate. In the United Kingdom, two large pilot studies, each covering a population of approximately 1 million, are under way to test implementation and delivery of treatment services. A randomized controlled trial of flexible sigmoidoscopy has shown encouraging early results (20), and the final results should be available in 2005. The tenth point of the European Code Against Cancer (9) is that "Men and women should participate in colorectal screening. This should be within programmes with built-in quality assurance procedures." There are, however, no current European guidelines.
Colorectal cancer has probably not gained the same level of public awareness as lung, breast, and prostate cancer, or indeed some of the less common cancers such as those of the cervix and testis. Effective screening could bring about further reductions in mortality from what is now the most common cancer in the European Union (9).
FUTURE REDUCTIONS IN CANCER MORTALITY
The rapid emergence of new technologies, including imaging, molecular typing of tissue, and intelligent drug design will have major impacts on cancer prevention, diagnosis, and treatment, but the application of such technologies will take another decade or so (9). It seems unlikely that cancer death and suffering will be completely eliminated by 2015 (21). In Europe, in parallel with the revised European Code Against Cancer (9), a more modest target has been set of a 20% reduction in the number of cancer deaths compared with the number expected if the rates in 2000 remained unchanged. Approximately half of this reduction is likely to occur given the forecasts of decreasing age-specific mortality trends in most EU countries and acceding countries with large populations (22). The remaining reduction will be achieved only if smoking prevention and cessation programs are expanded and are effective; if screening programs for breast and cervical cancer with quality control procedures in compliance with EU guidelines are quickly extended to countries and areas that currently do not have them; if screening for colorectal cancer is proven in various pilot studies and is effectively introduced across the European Union; and if future advances are made in treatment that substantially lower mortality for the major cancers. In addition, the results from the EUROCARE study of cancer survival in Europe (6,23) indicate (despite their limitations and some doubts about the geographical representativeness of some of the results) that there are extremely wide differences in cancer survival across Europe. There is clearly scope for large reductions in cancer mortality in some countries through eliminating these differences in survival using only existing knowledge and treatment regimens. There is similar potential from all the above factors for future reductions in cancer mortality in the United States.
NOTES
1 Editors note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the National Cancer Institute (NCI). Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research.
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