Is Cancer Progress Stagnating?
The War on Cancer began with the National Cancer Act of 1971, and continues to this day. The National Cancer Institute, the largest federally funded organization for cancer research, has a budget of $4.95 billion for 2015; the NIH’s total budget for cancer is $5.39 billion.
But the War on Cancer seems to have disappointing results. Cancer deaths haveonly fallen by 5% since 1950, at a rate of 200 deaths a year per 100,000 individuals. (By contrast, heart disease deaths are a third of what they were in 1950, thanks to innovations like statins, stents, and bypass surgery.)
Let’s dig into the cancer numbers to see if this represents real stagnation in medical progress. It’s possible, for instance, that we’re getting better at treating cancer and it’s just that more people get cancer in the first place, for lifestyle or environmental reasons.
Looking in more depth at the overall cancer numbers from the National Cancer Institute, we see that age-adjusted overall cancer mortality looks a bit better; a 15% decline since 1975, and a 22% decline from the peak of cancer mortality in 1991. So it looks like cancer deaths were getting worse from the 1950’s through early 1990’s.
Incidence rates also showed a rise from 1975 to a peak in 1991 in males, and a continuing rise in females. Cancer incidence data is sparse before the 1970’s — US population-level data were collected only three times during a period of more than 30 years before 1973. But cancer incidence was reported to have declined between 1947 and 1970. So the “stagnation” in cancer death rates from 1950 to the present is clearly somewhat confounded by the rise in cancer death rates between 1950 and the early 1990’s.
Now let’s subdivide into some common types of cancer.
Breast cancer has a solid 33% decline in death rates since 1975, beginning in the late 90’s, despite rising incidence. (It’s one of the most common cancers, at an incidence of 130 per 100,000.)
Prostate cancer, at an incidence of 114 per 100,000, had incidence rise sharply from 1975 to the 90’s, and has been dropping since. Death rates, likewise, rose and fell over the same timeframe, but are still 35% lower than they were in 1975.
Lung cancer, which has a current incidence of 41 per 100,000, rose dramatically in men to a peak in the early 90’s, and has been falling since; it is less common in women but steadily rising. (This may be a consequence of trends in smoking habits.) Lung cancer deaths, like overall cancer deaths, rise to a peak in the early 1990’s and decline thereafter; there has been no overall change in lung cancer deaths since the 70’s.
Melanoma, at 23 per 100,000, really does have stagnant death rates.
Kidney cancer, at 15 per 100,000, has been rising steadily in incidence since the 1970’s; death rates have been more or less steady. (Some of this may be due to earlier detection of less severe cases.)
Leukemia, at 14 per 100,000, has slightly increasing death rates
Pancreatic cancer, at 13 per 100,000, also has stagnant death rates.
Ovarian cancer, at 12 per 100,000, has declined somewhat in incidence since the 1970’s, and had a roughly comparable decline in mortality.
The overall peak and decline in cancer mortality seems to be an artifact primarily of lung cancer incidence, which tracks trends in smoking habits. Breast cancer is the only one of the most common types of cancer that looks like a strong “success story” for treatment — i.e. deaths dropped significantly faster than incidence. Childhood cancer is also a “success story” — deaths dropped in half while incidence slightly increased. Then there are cases like colon and cervical cancer, where incidence notably declined, perhaps due to the rise in early screening. But on the whole, the figures seem consistent with the hypothesis that the “war on cancer” has not been successful. In particular, if you look at our ability to treat cancer (as opposed to prevent it, through things like screening or anti-smoking campaigns) the progress looks worse than the raw death numbers would suggest. (A life saved is a life saved, no matter the means; progress in prevention is a major humanitarian gain. But it is in some sense less of a technological gain.)
The conventional hypothesis as to why cancer progress has been difficult is that cancer itself is complex and diverse and there is little low-hanging fruit. “Simplifying principles may not exist”, says an NPR interview with leading cancer researchers. More specifically, the discovery of oncogenes in the early 1970’s led molecular biologists to believe that the onset of cancer was a single “switch” that could be turned off; instead there turned out to be a wide array of oncogenes and tumor suppressor genes, activated in no particular order, and resulting in a great diversity of phenotypes.
This “low-hanging fruit” explanation is the usual one given to explain phenomena like “Eroom’s law”, in which the number of new drugs approved by the FDA per dollar of research spending has steadily declined since 1950. Biology is complex; progress is hard; that’s it.
The contrarian hypothesis is that cancer research is doing something avoidably wrong. Usually proponents say something in the vein of “cancer research is too traditionalist” — conservative, slow to innovate, wedded to unsuccessful strategies. One might assume that this is prima facie absurd — after all, with all the time, money, and human intelligence spent on cancer, if there was a cure out there wouldn’t somebody have found it? Cancer researchers can’t all be idiots!
In subsequent posts I’ll try to argue that the “cancer isn’t hard” position is at least plausible. This really divides into a negative case — that there are systematic biases in medical research and treatment that push against making progress on cancer — and a positive case — that there are plausible candidates for radical innovation in cancer treatment that deserve more attention. In an ideal world, this argument would be made by a science journalist or an experienced biologist; I am neither, and so I’ll simply present the facts I’m aware of, with the understanding that it’s pretty incomplete and somebody may come along later and either flesh it out or refute it.