Shares

Cancer remains the number 2 killer in the US, causing 22% of all deaths, just behind heart disease at 23%. The American Cancer Society carefully tracks all cancer statistics as a way of gauging how we are doing in all aspects of the fight to reduce the cancer burden in the population. The latest statistics are available for 2015 and they show that recent trends have continued:

Cancer incidence and mortality rates from 1975 to 2015 (click to embiggen).

There is a lot to unpack in these numbers, and they are interesting for science-based medicine beyond just telling us how we are doing in the war on cancer. It is also interesting what the numbers do not show, but we will get to that below.

Cancer incidence

Here are the main findings of these latest statistics:

Over the past decade of data, the cancer incidence rate (2005-2014) was stable in women and declined by approximately 2% annually in men, while the cancer death rate (2006-2015) declined by about 1.5% annually in both men and women. The combined cancer death rate dropped continuously from 1991 to 2015 by a total of 26%, translating to approximately 2,378,600 fewer cancer deaths than would have been expected if death rates had remained at their peak.

Let’s look first at cancer incidence – how many new cases of cancer are diagnosed each year. First we have to recognize that “cancer” is not one disease but a category of diseases, or a disease type. There are many different kinds of cancer, and the data does track them individually, so we will delve down a little into specific cancers as well.

Overall the incidence of all cancers was stable in women, and declined by 2% in men. For both sexes colorectal cancers have been steadily declining. This is likely not due to changes in risk factors, but mainly to increased screening. More people over 50 are getting colonoscopies (up from 22% to 60%), and more cancers are being prevented by removing precancerous polyps.

Lung cancer rates are also dropping, reflecting decreased tobacco use, and are dropping faster in men than in women.

These dropping rates are offset in women by small increases in breast, uterine, thyroid, and melanoma cancers. These increases are mostly in minority populations, and stable in non-Hispanic white women.

The decline in male cancer overall is largely driven by decreases in prostate cancer. This is probably entirely an artifact of screen procedures for prostate cancer. In the mid-1990s prostate specific antigen (PSA) testing started to be used extensively, finding many early prostate cancers. However, tracking these cases showed that many early prostate cancers would never cause problems, and we were probably overtreating these early cases. This led to a later decline in the use of PSA for routine screening.

Liver cancers have been increasing a bit, which is thought to be due to increases in hepatitis C, which in turn has been increasing partly due to the opioid epidemic.

So overall cancer incidence has been stable in women and declining steadily in men. Changes in specific cancers reflect known risk factors and the effect of screening methods. What is not seen in this data is any mysterious increase in any specific cancer or cancers overall.

This data does not fit the fearmongering narrative that we often confront on SBM, that the toxic bogeyman de jour is making us sick. There is no increase due to GMOs, vaccines, pesticides, or toxins in food. Cancer rates are driven by smoking and other tobacco use, hepatitis C, UV light, and other known risk factors.

The numbers also break the common “alternative medicine” narrative that mainstream medicine does not focus on prevention and wants to keep us sick – nonsense! When available, preventive measures like colonoscopy are reducing cancer incidence. Mainstream medicine has been engaged in a campaign to reduce real cancer risk factors like smoking for decades. Now we are confronting the hepatitis C increase and pushing for greater screening and early treatment to prevent liver cancer.

Deaths from cancer

There are two main ways to look statistically at deaths from cancer – the overall death rate from cancer, and the death (or survival, if we want to be positive) rate for those diagnosed with cancer.

The overall death rate from cancer has been steadily declining by 1.5% per year since 1991. This has resulted in a cumulative decrease in the cancer death rate by 26% (32% in men and 23% in women). This data is interesting because it is not affected directly by cancer screening or diagnostic artifacts. If you are going to die from your cancer, you are going to die, no matter when we diagnose it or how we categorize it.

The reduction in cancer deaths has two components: a reduction in cancer incidence (discussed above) and increased survival of those with cancer. The main challenge in determining cancer survival is what is called the lead-time bias. If we diagnose cancers earlier, then people will survive longer after their diagnosis, even if we did not extend their survival with treatment. We can, however, compensate for lead-time bias by tracking survival based upon the stage of the cancer (a measure of how advanced the cancer is).

Even when we look at the data accounting for stage at diagnosis, overall cancer survival has been steadily increasing. In 1975 the overall 5-year survival rate for cancer was 50%. In 2007 it was 68%. The data also shows a slow improvement in survival of cancer over this time, and this trend continues.

There are stark differences by cancer type, however. Some cancers are much harder to treat than others:

Progress has been especially rapid for hematopoietic and lymphoid malignancies due to improvements in treatment protocols, including the discovery of targeted therapies. For example, the 5-year relative survival rate for chronic myeloid leukemia increased from 22% for patients diagnosed in the mid-1970s to 68% for those diagnosed during 2007 through 2013. Based on a review of clinical trial data, most patients with chronic myeloid leukemia who are treated with tyrosine kinase inhibitors experience near normal life expectancy, particularly those diagnosed before age 65 years.

Cancer survival has increased at all stages, so this does not just reflect lead-time bias. However, early stages have benefited more than late stages.

By contrast improvement in lung and pancreatic cancer survival has been slow, which partly reflects the fact that these cancers tend to be diagnosed at more advanced stages.

The future

There are still some risk factors driving cancer rates that have significant room for improvement. The biggest is clearly smoking. While tobacco use has declined from 42% in the 1960s to about 17% now, this still is the largest preventable cause of death. Smoking correlates highly with less education and lower socioeconomic status. It is, essentially, a social problem, and can be addressed through education.

We also need more screening and early treatment for hepatitis C, and we need to address the underlying opioid epidemic that is driving hepatitis C rates.

There is actually a vaccine that can prevent some types of cancer – specifically the human papillomavirus (HPV) vaccine. This can prevent cervical and some oral cancers. Uptake of the vaccine has been limited by political and ideological opposition to this health measure, however.

In addition our ability to treat various forms of cancer has been steadily improving and will likely continue to improve. There will not be any sudden “cure for cancer.” It is too diverse and complex a disease for any one cure. Advances are likely to be incremental, but they add up over time. That is what has been happening, and is overwhelmingly likely to continue to happen. Cancer survival will slowly steadily improve, and each decade we will see significant improvements.

This also, of course, breaks the common alternative medicine narrative that mainstream cancer treatments are ineffective, even counterproductive. This claim is nothing but a cynical attack on effective medicine in order to sell snake oil to desperate patients with serious disease. It is difficult to overstate how malicious such behavior is. Dr. Gorski reported in August on a Yale study that found that patients who delay standard treatment in order to pursue alternative cancer treatments have a lower survival rate.

The alternative medicine fad is demonstrably eating into our improvements in cancer treatment by selling a harmful narrative that scares patients away from effective treatment or lures them with worthless ones. That is why it is so important to push back.

But numbers don’t lie, so we will continue to monitor and publish cancer statistics in order to tell the real story.

Shares

Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.