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What is the True Cure Rate of Cancer with Present methods?
At least half of all invasive cancers can now be cured permanently. Most commonly cured are primary (i.e. localized) solid cancers that are diagnosed before they have a chance to spread (metastasize) or invade vital structures. To these can be added many cases of leukemia, lymphoma and childhood cancer. Metastatic cancers still have the poorest cure rates.
How do we know all this? There has been extensive study of all common cancers showing that cure rates can range from virtually 100% to virtually zero, depending on cancer type, stage and aggressiveness . A middle of the range figure looks about right for all stages and types combined. For more direct evidence of overall cure rates we have to turn to the gatherings of national statistical agencies.
1. Incidence/mortality Statistics
United States of America
(From the American Cancer Society Journal -CA Jan/Feb 2002 Vol 52 No1 See also: http://www.cancer.org/downloads/STT/CancerFacts&Figures2002TM.pdf The large spike for cancer diagnosis in males in the early 1990s is due to PSA screening for prostate cancer. Declining incidence of lung cancer is probably the most important contributor to recent decline in overall death rates from male cancer).
The above graph shows that deaths from cancer (lower three lines) remained at or below about half that of the number of new cases of cancer (upper lines) over a thirty-year period. The time lag between between diagnosis and death in fatal cases is usually less than five years (see below) and can clearly account for little of the difference. N.B. easily cured skin cancers, benign tumors and non-invasive cancers (carcinoma in situ), except of the bladder, are NOT included.
In the year 2002 estimated cancer deaths in the USA were 555,500, and new cases of cancer 1,284,900, suggesting an overall cure rate of cancer approaching 57%.
The USA figures, although generally regarded as being of high quality <2>, involve extrapolation from incomplete population coverage. However, a very similar picture is seen in Australia, which has a nationwide cancer registry ---.
Trends in age-standardised incidence and mortality rates for all cancers (excluding non-melanoma skin cancers), Australia, 1983–2002 Source: Cancer in Australia 2001 (AIHW & AACR 2004). http://www.aihw.gov.au/publications/can/ca01/ca01-c02.pdf
In 2001 there were 36,913 deaths from cancer in Australia and 88,398 new cases, suggesting a cure rate running at about 58%, very close to the USA figure..
The most interesting results for any specific type of cancer are for breast cancer, by far the most common cancer in females. Death rates are distinctly falling, even as breast cancer rates continue to climb. UK figures are shown below, but American and Australian statistics show the same trends.
Age-standardised incidence of and mortality from female breast cancer, England and Wales, Rate per 100,000 (From: http://www.statistics.gov.uk/cci/nugget.asp?id=575 ) The advent of screening produced an upsurge in the diagnosis rate, and presumably contributes to the declining mortality.
Conclusion: Despite increasing rates of cancer, cancer mortality remains nearly constant or in decline. The most recent statistics of this type suggest that 55-60% % of all cancers can now be cured .
2. Another Perspective- Evidence from Survival Rates
Firstly, some important facts about survival rates. They are widely misunderstood and misrepresented.
Compare the following graphs. They show survival rates (percentage of cases remaining alive) over the first ten years after diagnosis for two common cancers, namely breast and colon.
From National Statistics: Cancer Trends in England and Wales 1950-1999: http://www.statistics.gov.uk/statbase/Product.asp?vlnk=4822&More=N (The different colored lines are for different years of diagnosis and show improving survival rates over time. These are UK figures for all stages (1-1V) of the cancers. US and Australian survival rates are somewhat higher but follow the pattern shown.)
With both cancers most deaths occur within in the first five years, but there is an obvious difference in the slope and shape of the curves between five and ten years. Deaths from breast cancer are clearly continuing to occur at ten years, albeit at a slowing rate. In contrast, the curve for colon cancer patients has virtually levelled out completely by five years. Essentially all deaths from the original cancer will have occurred by then (see also <1>).
Five year survivors with colon cancer thus have approximately the same life expectancy as persons without cancer of the same age and sex This is an adequate practical definition of "cure" for most types of cancer. (Even in cured patients deaths may occur at a higher rate than that of a comparable normal population due to a greater risk of second cancers, other adverse health effects of risk factors e.g. smoking, and rare late complications of treatment).
The message is that five year survival rates (5YSRs) provide an adequate approximation of the permanent cure rate of some cancers, but not of others.
For what it is worth, the American Cancer Society gives a 5YSR for all patients with invasive cancers in the USA of 63%. Comparable figures for a sampling of other countries are 60% from the Australian Bureau of Statistics, 59% from a Canadian source (British Columbia), and 58% for females and 43% for males over the somewhat earlier period of 1955-1994 in Finland.
Yet we have shown that the ultimate cure rate must be less. How much should we allow for cancer mortality occurring after five years? Let's look at Australian statistics listing the overall survival rate for invasive cancers in Australia for each year over the fifteen years beginning in 1982.
Such longer term relative survival rates have to be interpreted with some caution. They can involve large adjustments for the effect of age upon mortality in a disease where the majority of patients are elderly (survival figures would be meaningless without such adjustments). With that caveat, the figures suggest that deaths from cancer between five and fifteen years may reduce overall survival rates by as little as 5%, and that overall relative survival may decline by as little as 0.1% per annum after ten years. Overall relative survival will decline very slightly forever due to rare late recurrences of breast cancer and melanoma and the factors mentioned above .
On these figures, the true cancer cure rate for Australians may have been close to 50% even for patients diagnosed over twenty years ago. It would be higher today..
A somewhat similar picture emerges from from an analysis of US figures using a "period" method as opposed to the more usual cohort method <2>. Such an analysis makes allowances for improvement in outcomes over the period being examined. The following figure shows the estimated cancer survival rates in the USA for the twenty years from 1978 to 1998 using both methods. For the study author's explanation of the difference between the methods see <3>.
Perhaps more helpful for present purposes, is a graph constructed from the same data source--
Graphically, a normal life expectancy is reflected by a horizontal survival curve. The shape of the curves suggests that this is a approached at about a 40% survival rate for the earliest figures and about 50% for more recent ones. (The exclusion of lung and bronchus cancers from this graph will affect the shape of the curves little, since 98% of the deaths from this cancer occur within ten years. It would inflate the ultimate cure rate, since about a 10% but declining percentage of all cancer deaths are from this cancer. )
Conclusion: The overall permanent cure rate of cancer lies in the vicinity of 50%, and is improving.
1. McLeish JA, Thursfield VJ, Giles GG. Survival From Colorectal Cancer in Victoria: 10-year follow up of the 1987 management survey. ANZ J. Surg. 2002,72: 352-356)
2. Long-term survival rates of cancer patients achieved by the end of the 20th century: A period analysis
Hermann Brenner. The Lancet. London: Oct 12, 2002.Vol.360, Iss. 9340
3. Ibid: "One of the most widely used global measures of achievement in health is life expectancy, which is derived from population life tables. These tables can be regarded as a special type of survival analysis, because they quantify survival of newborn babies. Two main approaches are used to derive such tables. The first quantifies survival of a cohort of newborn babies. Although the conception and interpretation of this approach is very straightforward, its use is limited by the fact that it takes a human lifespan before the life table can be completed and life expectancy can be calculated. The second approach uses period life tables, which are based on mortality of a population within a recent period, such as a recent year. With this approach, survival data for various ages are obtained from cohorts of people born in different years. Although the interpretation of period life tables is slightly less straightforward than that for cohort life tables, they are widely used in health statistics because they provide much more up-to-date estimates of life expectancy than do cohort life tables.Up to now, long-term cancer survival statistics have almost always been calculated from cohorts of patients diagnosed many years ago,1,2 and they could therefore be quite out of date when they were derived. The idea to use the period principle to obtain estimates of long-term cancer survival rates was proposed a few years ago.3,4 Meanwhile, extensive empirical evaluation studies have shown that period analysis provides much more up-to-date estimates of long-term survival of cancer patients than does cohort-based survival analysis.5-7 Furthermore, period estimates for a particular time quite accurately predict long-term survival rates of patients diagnosed in that period.6,7"
Peter J Moran MB BS BSc(Med) FRACS FRCS(Eng)
Constructive comments to pmoranATinternode.on.net
January 2005 Back to Index