Geeking Out on Cancer: The Difference Between Incidence Rates From Screening and Types
Plus, Society of Actuaries paper and more Items
Recently, I came across this visualization of cancer incidence rates:
I know that’s a huge image, so let me clip out the extremes:
Okay, Australia and New Zealand are…. ok, this is not about the latitude they’re at, because lots of other places are at similar latitudes, and it’s not about a big ozone hole or anything over them, as far as I can tell.
It’s that it’s really nice to be outside and under the sun where they are. And lots of people do not wear sunscreen. (Or it washes off over time)
For the same reason, people go outside in the sun in Arizona and Florida and get skin cancer.
(And no, having darker skin doesn’t necessarily help you. More on that in a moment.)
Oh look! Sierra Leone has the lowest cancer incidence rate!
Let me give you some other facts about Sierra Leone:
GDP (using purchasing power parity) per capita: $3,550 [165th out of 186]
Human Development Index: 0.47 [185th out of 193]
“The CIA estimated that the average life expectancy in Sierra Leone was 57.39 years.” [from the Wikipedia entry - it’s a 2014 estimate]
I’m leaving that one with a quote; it’s an old estimate.
But this is the most relevant bit from the Wikipedia article:
Medical care is not readily accessible, with doctors and hospitals out of reach for many villagers. While free health care may be provided in some villages, the medical staff is poorly paid and sometimes charge for their services, taking advantage of the fact that the villagers are not aware of their right to free medical care.[214]
Again, the source is from 2012. It’s a little old. But. I don’t think Sierra Leone has necessarily changed that much in 13 years.
So, do you really think the base rate of cancer in Sierra Leone is low?
It’s probably only low because nobody is ever diagnosed… because it takes a lot before anybody is going to notice if you have cancer in Sierra Leone. They’re not sitting around doing mole checks for skin cancer, forget about regular colonoscopies.
About Dark Skin and Skin Cancer
This is an aside before I get into the really geeky stuff.
2022, Columbia University: Skin Cancer in People of Color
Dark skin does provide some protection against the sun’s ultraviolet rays, but it’s a myth that people with dark skin tones are immune to the harmful effects of UV radiation.
People of color have a lower risk of developing skin cancer than people with fair skin tones, but UV exposure raises the risk for everyone.
Studies show that Black and Hispanic Americans who live in sunnier parts of the country have greater rates of melanoma and that UV radiation also correlates with other types of skin cancer in people with darker skin tones.
UV radiation also ages the skin, leading to wrinkles, spots, and changes in skin texture in people of all skin tones.
We spoke with Dawn Queen, MD, a dermatologist at Columbia University Vagelos College of Physicians and Surgeons, to get the facts about skin color, skin cancer, and other effects of ultraviolet rays.
There are multiple points:
Dark skin is not sunscreen.
Dark skin does burn.
Melanoma survival rates are lower among people of color.
Melanomas in people of color are often hidden.
Watch for other types of skin cancer.
Get vitamin D through food or supplements.
The issue is that it can be difficult to see weird moles/spots on your skin if it’s darker.
But the big issue is whether people are getting cancer screening (whatever cancer) in general.
Society of Actuaries: The Trends of Cancer Incidence in the U.S.
Irene Schepp, Sept 2025, Reinsurance News: Heatmaps and the Development of Cancer Incidences
I titled it SOA above, but it’s Irene Schepp from the reinsurer Gen Re. I often read publications from Gen Re on trends in morbidity and mortality.
Schepp looks at breast cancer and colorectal cancer, and both of these cancers are important in terms of changes in recommendations for screening, as well as changes in cancer treatments.
Breast cancer
It took until 1976 for the American Cancer Society (ACS) to officially recommend yearly mammogram screening for women at average risk aged 50 and over. In the years following the screening introduction, a notable increase in the cancer incidence for the affected age groups, where more cancers were detected, was observed (see Figure 1B, Marker no. 1).
Starting in 1983, the ACS included younger women (age 40 to 49) in the regular mammogram screening program and recommended screening every one to two years. Starting in 1997, annual screening was advised—a change that is slightly indicated by Marker no. 2.[6] Awareness of the disease received another boost in the 1990s with the adoption of the pink ribbon symbol and the growth of the Susan G. Komen foundation.[7] Implementing a screening program can be valuable; however, it is equally important to raise awareness and encourage active participation among individuals.
We saw the success of the screening program in the decline of incidence rates in women aged 50 and above in the following years (see Marker no. 3). Since 2015, the ACS has recommended annual mammogram screening for women aged 45 to 54. Women aged 40 to 44 and those 55 and older can choose annual screenings. The older age group is advised to follow a biennial schedule. Screening mammograms should continue as long as a woman is in good health and is expected to live at least 10 more years.[8] Future data will show the effectiveness of the updated recommendations.
Early-onset Breast Cancer
In Figure 1B (see Marker no. 4), we see a negative development of higher cancer incidences for women below age 45. Especially the youngest age groups seem to be strongly affected in periods starting in 1992 followed by less high (but still positive) increases of incidences in the next periods, until 2012. The data indicates that the number of cases within this age group is low, with approximately 15 cases per year recorded between 1992 and 2017. Prior to utilizing these heatmap results for groups at the margins of the age range, they should be thoroughly examined to assess the impact of volatility (and smoothing).
This is the super-geeking out portion of this post. I’m going to be critical about the color choices used in this graph. Obviously, the author is not red-green colorblind (nor am I), but I believe many people who are would have difficulty looking at this graph.
As it is, even with full color vision, I think the odd triangular contours would be difficult for many to interpret.
The issue is that there are multiple overlapping age groups/time periods. There are other ways one could deal with this to smooth the experience — especially since it’s not like breast cancer is rare. This is incidence, not mortality, after all.
Something to indicate re: the reduction in breast cancer incidence, though, would not merely be due to regular screening — once regular screening is in place, a change in incidence rates would be due to actual rate changes, as opposed to changes in screening.
I would assume a reduction in breast cancer incidence rates after there was regular screening in the population, would be partly due to the reduction in various risk factors — I’m thinking smoking.
Colorectal cancer
I have something else to note here.
Since 2018 the ACS recommends that people at average risk of colorectal cancer start regular screenings at age 45. People at higher risk might need to start earlier.[12]
As we can see (from Markers no. 3) the screening initiative appears to have a positive effect on incidence rates for females and males in higher ages. Screening for colorectal cancer not only detects existing cases in participants who have no symptoms of the disease but also contributes to a long-term reduction in incidence rates.
The screening past the particular age (and yeah, I’ve had my first colonoscopy, and am due for my second at age 53), looks all peachy keen for trend.
Heatmaps can highlight the periods and age groups of notable shifts in incidence rates. Since the early 1980s, the data shows a significant increase in cancer incidences among younger adults in the U.S. (see Markers no. 4) which is steadily worsening over time, particularly among women. Although incidence rates for younger adults are on a lower level compared to older adults, in general, these trends are concerning.
That’s the incidence trend.
What about the mortality trend? I wrote about this earlier.
Early-onset colorectal cancer: a concerning trend
March 2024: Colorectal Cancer: Top Cancer With Concerning Trend in Younger Ages
This is a very long-term issue.
I didn’t split it out by sex, as in the incidence graphs above, but you can see that both sexes had a problem.
From the SOA article:
Mortality trends for CRC [colorectal cancer] are significantly worse than those for breast cancer. Both incidence and mortality are increasing among younger adults aged below 40. As a result, CRC has recently become the main cause of cancer-related death among males aged 20 to 49 years in the U.S., and current estimates indicate that by 2030 one-third of all CRC will be diagnosed in individuals younger than 50.[14]
Within the scientific community there are studies and discussions on the influences of various risk factors leading to a higher number of CRC diseases. What are the changes compared to the mid-1980s? Are the younger generations more exposed to some environmental factors? How did their diet change? Is the CRC progression different in younger adults and changing over time? The wide range of topics and the possible interactions between the risk factors present scientists with a complex field of work.
To me, it seems kind of rich to blame increased colorectal cancer deaths on those under age 50 on dietary changes. It seems to me it should take some rather extreme dietary changes for that to occur.
That said, we have found linkages to, for instance, viral infections and cancer, as with HPV and cervical cancer. Perhaps there is a viral or bacterial infection related to the increase in cancer.
There has been a long-term decrease in the older ages, which may be due to earlier detection of cancer and/or improved cancer treatment.
But there really is no good reason for the increases at younger ages.
That we know of.
Yet.