Good news about cancer?
Yes, the five-year survival of patients diagnosed with cancer has increased worldwide
Why is survival measured at five years?
“5-year survival has been recognised by clinicians as an index of the effectiveness of the treatment of cancer for more than 60 years. When applied to hospital case series, it has often been labelled as the 5-year cure rate, because “with so mortal a disease as cancer, those who survive for this length of time can be considered cured”. 5-year survival has increased for many cancers since the 1950s, but it remains a widely used benchmark, even though it cannot be directly interpreted as the proportion of patients who are cured”
That’s great and good news, is not it?
Yes effectively. It is the result of better diagnoses and treatments in all the countries of the world, rich and poor. For example, acute lymphoblastic leukemia (a cancer with generally poor prognosis in children) has increased survival at five years by 10%, or more, in fourteen countries, from Colombia to Finland, from China to Turkey and from Portugal to Spain.
Does survival at five years in all types of cancers measure the same?
Not at all. It is an excellent indicator in cancers such as those of the pancreas and brain or in the afore mentioned lymphoblastic acute leukemia, in which we do not screen. It is a misleading and deceptive indicator in the cancers in which we do screening, as in breast cancer.
With data, an example, please
In breast cancer, survival at five years is:
90% in the United States,
82% in Spain, and
66% in India.
That is, in the United States they do it better than in Spain, and in Spain better than in India
Not quite. What these data tell us is that in the United States more screening mammograms are done than in Spain, and in Spain more than in India. The cancers diagnosed by mammography are more “benign” and therefore it is easy to have a better survival at five years.
More screening mammograms, does not decrease the mortality from breast cancer?
No. Annual mortality from breast cancer is
of 21 women per 100,000 in the United States
of 16 women per 100,000 in Spain, and
of 13 women per 100,000 in India
That is, in the United States more women die from breast cancer than in Spain and Spain more than in India
Effectively, that’s right. Mortality from breast cancer is higher in the United States than in Spain, and in Spain greater than in India.
But does screening mammography not help to better diagnose breast cancers?
Yes, in theory. In practice it is not diagnosed better but more. Many more breast cancers are diagnosed where many more screening mammograms are done. This is “overdiagnosis” (true positives, but cancer of benign prognosis).
The annual number of new breast cancers is
of 126 per 100,000 women in the United States
of 88 per 100,000 women in Spain
of 26 per 100,000 women in India
|Annual new cases||126 per 100,000||88 per 100,000||26 per 100,000|
|Mortality||21 per 100,000||16 per 100,000||13 per 100,000|
That is, in the United States more diagnoses of breast cancer are made than in Spain and Spain more than in India
Exactly. As a result of screening mammograms, in the United States, breast cancer is an epidemic, greater than in Spain, but this does not lead to an improvement in mortality.
In the United States, as in Spain with respect to India, there are more diagnoses of breast cancer, there is greater survival at five years … and there is higher mortality from breast cancer!
So, what does all this mean?
- That women, professionals and society are deceived with the presentation of good results in five-year survival of women diagnosed with breast cancer in the countries where screening mammograms are done.
- That, in general, it is statistical illiteracy to believe that survival at five years is a good indicator of “cure” of cancers diagnosed by screening.
- That in the United States (and in Spain) are many women who believe they have been “saved” from dying from breast cancer when in fact they have been “condemned” to live with a diagnosis that does not help in anything positive.
- That what appears in the United States (and in Spain) is a real army of women treated unnecessarily with radiotherapy, chemotherapy and surgery, in many cases mutilated and all of them followed for life unnecessarily by a breast cancer that would never have killed them. It is estimated that in the United States this army is made up of 1,300,000 women (one million three hundred thousand women who believe they have been “saved”, and it is false because their cancer would never have killed them) out of an estimated three and a half million women alive after the diagnosis of breast cancer.
- Of course, life expectancy in low in India and most women died from cardiovascular, respiratory and infectious diseases so we can expect less cancer mortality, but this applies also to the breast cancer five year survival (lower in India because the impact of cardiovascular, respiratory and infectious diseases mortality). So the method to improve the future of women in India is to decrease the burden of cardiovascular, respiratory and infectous diseases and not to increase mammography uptake.
I do not get it
The deceit is constant. For example, in India the need to have a screening mammogram is promoted with a reasoning that says:
In the United States one out of every six women diagnosed with breast cancer dies of breast cancer.
In Spain, one in five women diagnosed with breast cancer die of breast cancer.
In China, one out of every four women diagnosed with breast cancer dies of breast cancer.
In India, one out of every two women diagnosed with breast cancer dies of breast cancer.
It seems like a tongue twister that makes people believe that in India it is diagnosed late and badly
Exactly! That is what is suggested. It seems that the method to improve the future of women in India is to increase the number of women diagnosed with breast cancer. An atrocities that would have no impact on mortality, would only form an army of women similar to that in the United States and Spain (women who believe they have been “saved” from dying from breast cancer when in fact they have “condemned ” to live with a diagnosis that does not help at all!)
To summarize, is it a manipulation to publish an article on cancer survival at five years without separating diagnostic cancers by screening for other cancers?
Yes, exactly, that’s it. It is a manipulation without ethics.
In the case of breast cancer, deceit and shame, the damage to society and to women does not occur in India but in the United States and Spain. However, it is in India where it is publicly presented as a failure, and in the United States and Spain as a success.
It is the “popularity paradox”: popularity of a bad cancer screening ->overdiagnosis (true positives) -> people don’t die of this cancer- think life saved -> 5-year survival % increased -> think screening great -> bad screening gets more popular-> “increased” cancer risk for relatives ->snowball of “needed” bad cancer screening.
Overdiagnosis is an extreme form of length-time bias and occurs when screening detects indolent tumors that meet diagnostic criteria for cancer but would not otherwise have come to clinical attention during the lifetime of the individual.
Overdiagnosis artificially inflates the 5-year survival rate.
Overdiagnosis does not change mortality.
Overdiagnosed patients obtain no benefit while being subjected to all of the harms of treatment.
The case analyzed reflects well the influence of the “experts” and their publications and the arrogance of a preventive medicine that damages without benefits. They take advantage of the statistical illiteracy of patients and professionals to promote their activities without science.
American Cancer Society. In 2015, there were an estimated 3,418,124 women living with female breast cancer in the United States.
Bleyer A, Welch HG. Effect of screening mammography on breast cancer incidence. N Engl J Med. 2013 Feb 14;368(7):679. doi: 10.1056/NEJMc1215494. http://www.nejm.org/doi/full/10.1056/NEJMoa1206809
Breast Cancer India.
Chandra Sharma N. India still has a low breast cancer survival rate of 66%: study. Feb 01 2018
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Gérvas J. Overdiagnosis as an extreme form of length-time bias. Breast cancer screening as an example. Madrid (Spain). October 2014
Gérvas J. Ovarian cancer screening: could you recommend it? No. J Evid Based Med. 2016. 10.1136/ebmed-2016-110385
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Gigerenzer G, Gaissmaier W, Kurz-Milcke E, Schwartz LM, Woloshin S. Helping Doctors and Patients Make Sense of Health Statistics. Psychol Sci Public Interest. 2007 Nov;8(2):53-96. doi: 10.1111/j.1539-6053.2008.00033.x. Epub 2007 Nov 1.
International Agency for Research on Cancer. WHO. GLOBOCAN 2012. http://globocan.iarc.fr/Pages/fact_sheets_cancer.aspx
Margaret McCartey. Patients deserve the truth: health screening can do more harm than good.
Ram U et al. Age-specific and sex-specific adult mortality risk in India in 2014: analysis of 0·27 million nationally surveyed deaths and demographic estimates from 597 districts.
SEOM . Las cifras del cáncer en España, 2017
Juan Gérvas, retired rural general practitioner, CESCA Team, Madrid, Spain
email@example.com www.equipocesca.org @JuanGrvas