CANCERS OF THE YOUNG

You must have heard that cancer incidence and mortality in the U.S. are decreasing, right?  For most types of cancer this is the case. However, there are a few types of cancer that are increasing in incidence, mortality, or both.

I found the data from the Surveillance, Epidemiology and End Results (SEER) database (a registry of cancer cases kept by the National Cancer Institute) informative. You can access the "search SEER" tool through this website, and if you are interested, you can obtain the breakdown of the data by gender and race.

I was interested in analyzing the data by age since there are reports that the younger U.S. population (< 50) has increased rates of incidence of colorectal cancer (I have previously discussed this). Therefore, I focused on the pattern of cancer incidence and mortality among different age groups. 

The SEER data confirmed that there is a distinct pattern of increased incidence and mortality of specific cancers.  For example, only for people younger than 50, the mortality from colorectal cancer has been increasing for the indicated five-year period; whereas, the mortality from uterine (endometrial) cancer has been increasing for all ages (see Table I). 

Cancer Site	Average Annual Percent Change in Mortality, 2009-2013
	Ages <50	Ages 50+	Ages 65+	All ages
Thyroid	0.5 (-0.2, 1.2)	0.8# (0.6, 1.0)	1.0# (0.7, 1.2)	0.8# (0.6, 1.0)
Brain & ONS	0.8 (-1.7, 3.3)	0.4 (0.0, 0.9)	0.6 (0.0, 1.3)	0.5 (-0.1, 1.1)
Colon & Rectum	1.3# (0.8, 1.8)	--	--	--
Uterus	1.5# (1.2, 1.9)	1.9# (1.1, 2.6)	1.1# (0.6, 1.6)	2.4# (1.6, 3.1)
Bladder	--	0.1# (0.0, 0.3)	0.2# (0.1, 0.4)	0.1 (0.0, 0.2)
Pancreas	--	0.3# (0.3, 0.4)	0.4# (0.3, 0.5)	0.3# (0.2, 0.4)
Liver & Bile Duct	--	3.4# (3.0, 3.7)	2.6# (2.3, 3.0)	3.0# (2.7, 3.4)
Melanoma of the Skin	--	--	1.2# (1.1, 1.4)	--
Oral Cavity/Pharynx	--	--	--	0.4 (-0.9, 1.7)

TABLE I.

95% confidence interval shown in parentheses

# - The annual percent change is significantly different from zero (p<0.05).

Stable (no increase): when the 95% confidence interval of annual percent change includes 0.

Rising (increase): when the 95% confidence interval of annual percent change is above 0.

The cancer incidence data (Table II) is even more intriguing. There are total of seven types of cancer that exhibit a trend of increasing incidence in younger adults (<50); albeit, only two types of these cancers have truly “increased” incidence according to statisticians (i.e., thyroid and kidney cancer).

Is there a unifying theme? It seems that most of the cancers that exhibit a trend of increase in incidence, mortality, or both, are associated with obesity. Since 70% of the adult US population and 30% of our children are now overweight/obese, the trends of increasing liver, pancreatic, kidney, colorectal, thyroid, uterine, and stomach cancers are probably going to be confirmed as statistically significant in another decade or so.

Cancer Site	Average Annual Percent Change in Incidence, 2009-2013
	Ages <50	Ages 50+	Ages 65+	All ages
Thyroid	2.7# (1.4, 3.9)	1.4# (1.0, 1.9)	1.1# (0.6, 1.7)	2.1# (1.5, 2.7)
Colon & Rectum	0.8 (-0.1, 1.7)	--	--	--
Uterus	0.3 (-0.1, 0.7)	0.6# (0.3, 1.5)	0.8# (0.5, 1.2)	0.6# (0.3, 0.9)
Pancreas	1.3 (-0.1, 2.7)	0.4# (-0.5, 0.4)	0.2  (0.3, 0.5)	0.5 (-0.4, 1.4)
Liver & Bile Duct	--	2.5# (1.5, 3.6)	2.3# (1.3, 3.2)	2.0# (0.9, 3.1)
Melanoma of the Skin	--	1.8# (0.6, 3.0)	2.5# (1.1, 3.9)	0.7 (-0.4, 1.9)
Oral Cavity/Pharynx	--	0.9# (0.1, 1.6)	0.9 (-0.1, 1.9)	0.5 (-0.2, 1.2)
Breast	--	--	0.1 (-1.0, 1.2)	--
Leukemia	0.1 (-1.2, 1.4)	--	--	--
Stomach	0.7 (-2.6, 4.1)	--	--	--
Kidney&Renal Pelvis	1.2# (0.3, 2.2)	--	--	--

Table II.

95% confidence interval shown in parentheses

# - The annual percent change is significantly different from zero (p<0.05).

Stable (no increase): when the 95% confidence interval of annual percent change includes 0.

Rising (increase0: when the 95% confidence interval of annual percent change is above 0.

There are also a few enigmas in these data. Note that the incidence of brain cancers is not increasing; however, there seems to be a trend of increased mortality (not according to the confidence interval, though) . One possible explanation is that the proportion of deadly brain cancers (e.g., glioblastomas) is increasing, but the total number of brain cancers does not change in a statistically significant manner. We should follow on whether the mortality of brain cancer will increase in a statistically significant manner in the next years. Gliomas, by the way, are also associated with obesity.

Another puzzling observation is that thyroid cancer incidence and mortality are both increasing (these data are statistically significant). There has been lots of noise in the media about this observation. The most prevalent explanation is that the current detection methods for thyroid cancer have become extremely sensitive, and most of the “increased” thyroid cancer burden is in fact due to the detection of very small lesions. According to the clinicians, such lesions may never develop into deadly cancers.  Well, if this is the case, why is the mortality of thyroid cancer increasing too? Is it possible that the patients with the less advanced lesions are over-treated and in fact, they die from the treatment, rather than from the neoplasm?

Questions, questions. There are too many of questions; however, no one has had the guts to address the fact that all of the cancer types on the rise are associated with increased body weight.