Each year the American Cancer Society publishes cancer statistics for the US. This is a massive set of data capturing the incidence of every type of cancer and deaths from cancer. This is an important window into how medical interventions for preventing, detecting, and treating cancer are doing. There are some important trends in the 2023 report worth highlighting.
The top line observation is that cancer deaths continued to decline:
Despite the pandemic, and in contrast with other leading causes of death, the cancer death rate continued to decline from 2019 to 2020 (by 1.5%), contributing to a 33% overall reduction since 1991 and an estimated 3.8 million deaths averted.
This is all observational data, so we can only infer cause and effect. But epidemiologists have been following and examining this data for decades, so we can make some fairly high-confidence conclusions. Cancer mortality can be reduced in three major ways. The first is by preventing cancer from occurring in the first place, through preventive measure. The second is through improved treatment for cancer when it occurs. The third is by changes in diagnosis of cancer – anything that might cause someone to die from cancer without being recorded as a cancer death. If anything our ability to properly diagnose cancer and cancer screening and surveillance has increased, so this factor would likely artificially increase the measured cancer death numbers. Also, failure to screen properly can increase cancer death by delaying treatment.
Just looking at total cancer deaths captures all of these factors. The big picture is that there has been a steady decline in cancer deaths of a little more than 1% each year for decades, adding up to 33% since 1991. This has mainly been accomplished through improved prevention and treatment. There has been a steady increase in available treatments, with newer technologies constantly coming online. Each one provides and incremental improvement in cancer survival with a steady cumulative effect.
For example, in 1997 the first monoclonal antibody drug to treat cancer was approved (Rituximab). In 2004 the FDA approved the first antiangiogenesis drug, drugs that reduce the growth of blood vessels to feed solid tumors. In 2017 the first car-t cell therapy, that uses the patient’s own immune cells to fight their cancer, was approved. And there are new technologies in the pipeline – such as using CRISPR to engineer tumor cells to kill the tumors themselves and function as a vaccine against cancer recurrence. There have been countless other advances over this time, but these are some of the exciting new technologies that have come into use.
The bottom line is that the steady improvement in cancer survival and reduction in cancer deaths is largely due to advances in science and medical technology. This is necessary because cancer is a difficult enemy. It is also not one disease, but a category containing many diseases. Cancer cells evolve to evade our treatments. This is SBM so I have to emphasize that these improvement are the result of science. Meanwhile, so-called “alternative medicine” approaches that try to avoid, deny, or change the rules of science are associated with increased death from cancer.
Preventive measures also made a huge impact on these numbers. Under this category, the biggest story is the success of the HPV vaccine. From 2012 to 2019 there was a 65% drop in cervical cancer incidence. The incidence had already been dropping due to increased screening and treatment of precancerous lesions, but this is now the first cohort of women who received the vaccine and they show a significant increase in the rate of decline.
HPV causes almost all cases of cervical cancer, and also increases the risk of cancer of the vulva, vagina, penis, anus, and oropharynx. The HPV vaccine is extremely effective at preventing HPV infection.
Other US studies have shown “surprisingly large” herd immunity, the study authors said. Sexually active females age 14 to 24 who were vaccinated showed a 90% reduction in infections with HPV-16 or HPV-18, and even those who had not been vaccinated had a 74% reduction in infections.
This is an opportunity to virtually eliminate cervical cancer, and significantly reduce the others listed above. The only thing that stands in the way is vaccine hesitancy. The authors also report:
In 2020, only 32% of boys and girls ages 13 to 17 in Mississippi were up to date with HPV vaccination and only 43% in West Virginia. States with high proportions of vaccinated teens include Massachusetts (73%), Hawaii (74%), and Rhode Island (83%). In the coming years, these differences will become apparent in incidence rates for cervical and other HPV-associated cancers.
We have the technology to eliminate a type of cancer with a safe and effective preventive measure. We now have data that the HPV vaccine not only works to prevent HPV infection but also cervical cancer. We need sustained efforts to make the public aware of these facts so as not to lose out on the potential benefits of this technology.
The other interesting result of this latest cancer data is that the story of screening for prostate cancer continues. The issue is using prostate specific antigen (PSA) levels in the blood to screen for early prostate cancer. This screening works, but does tend to have a lot of false positives, which can lead to unnecessary biopsy and surgery. For that reason in 2008 the US Preventive Services Task Force (USPSTF) changed their recommendation, to not use PSA for routine screening in men 75 and older, and then later for all men.
This change resulted in a decrease in prostate cancer diagnoses – but this was not a real decrease, just an artifact of decreased screening. Now we are seeing the downside to this decision – for the first time in 20 years, death from prostate cancer has increased in the US. Further, the proportion of prostate cancer that is diagnosed in a later stage when the cancer is harder to treat has doubled in the last 10 years.
This is all a balancing act between optimal screening of at risk populations while minimizing false positives and the negative effects that come from it. The same debate was had with regard to mammograms and breast cancer. More screening is not always better.
The recommendations on using PSA to screen for prostate cancer have therefore again shifted. Now the recommendation is for men 50 and older to have a conversation with their primary doctor about the risks and benefits of PSA screening, and to make an informed individual decision. The problem can also be mitigated by newer technology, using markers and imaging to stage prostate cancer. The PSA story is a good example of how cancer statistics are used to tweak medical practice and recommendations.
There is more in the full report, but these were the highlights. Overall the report is good news. Cancer treatment, starting with prevention, continues to improve. The reports estimates that 3.8 million cancer deaths have been averted since 1991. Cancer is still a scary diagnosis, but it is decidedly less scary than it was 30 years ago.