Korea's prostate cancer prevalence rose 170 percent in a decade. The men it accumulated are 73, and most of them are on hormone therapy

Every article in this coverage has arrived at the same question from a different direction. More than half of Korean prostate cancers are high-risk when found. Rural men fare worse than urban ones. Korean datasets record what was done and what it cost, but not what happened to the men. So what does happen to them?

There is one Korean dataset that answers a version of it, because prescriptions are recorded even when outcomes are not.

How many men, and how old#

A nationwide study covered every Korean who received medical care for prostate cancer between 2011 and 2021, using national claims. It is a prevalence study, so it counts men living with the disease rather than men newly diagnosed with it.

The mean age in 2021 was 73.07 years and more than 80 percent were 65 or older. Diabetes, pulmonary disease and mild liver disease were common. This is a population in which any treatment decision is also a decision about a man who has other things wrong with him.

What they are given#

Androgen deprivation therapy — suppressing testosterone, on which prostate cancer depends — remained the most common pharmacological treatment throughout the decade. Its share fell gradually as androgen receptor-targeting agents were introduced and their use rose steadily.

Androgen deprivation is the treatment for disease that has spread or is likely to, and it is given alongside radiotherapy in higher-risk localised disease. In a country where 53.9 percent of prostate cancers are high-risk at diagnosis, a great many men reach it. It is not a treatment men are on briefly.

What hormone therapy costs the skeleton#

Testosterone maintains bone. Removing it does what removing it would be expected to do, and a two-year study measured how much. It followed 115 men from the start of androgen deprivation, 43 of whom received zoledronic acid to protect bone under national guidelines and 72 of whom did not, using both standard DXA scanning and high-resolution peripheral CT.

• In the men not given zoledronic acid, areal bone mineral density fell significantly at every measured location — lumbar spine, hip, femoral neck, total body, both arms and both legs.
• Zoledronic acid prevented that loss of areal density at both central and peripheral sites.
• It did not prevent everything. Bone area, volumetric density, microarchitecture and calculated bone strength at the distal radius and distal tibia declined significantly even in the treated men.

The Alzheimer's signal, and what to make of it#

Whether androgen deprivation affects the brain has been argued for a decade without resolution. A Korean national cohort took 163,723 men with prostate cancer diagnosed between 2013 and 2017, narrowed to 24,456 eligible, and matched 10,168 men who received androgen deprivation against 10,168 who did not.

The pattern in that table is unusual enough to be worth stating rather than summarising. Alzheimer's disease was significantly more common. Overall dementia, which includes Alzheimer's disease, was not.

1. A subtype can be elevated while the category containing it is not, if the other subtypes run the other way or if the category is diluted by cases coded without a subtype. That is a plausible statistical explanation and it is not the same as a plausible biological one.
2. It can also happen because men on androgen deprivation are under more medical observation than men who are not, and a diagnosis that requires someone to look for it is recorded more often in the group being looked at. Vascular dementia, which is more often found incidentally on imaging, showed nothing.
3. The confidence interval for overall dementia, 0.97 to 1.19, does not exclude a real effect. It is a null result in the sense of not reaching significance, not in the sense of showing there is nothing.
4. The study is claims-based. It knows what was prescribed and what was coded, not what was measured in any man.

The authors' own conclusion is that their evidence reinforces a positive association between androgen deprivation and Alzheimer's disease while making vascular dementia and Parkinson's disease unlikely. That is a defensible reading of their data. A man being offered androgen deprivation should hear it as one input among several rather than as a settled harm, and the alternative to hormone therapy for advanced prostate cancer is not an unproblematic one.

What this closes and what it does not#

1. The prevalence study is cross-sectional and claims-based. It describes who was treated and with what, not whether the treatment helped.
2. The bone study is Dutch, 115 men, two years. It establishes the direction and rough size of bone loss on androgen deprivation, not what a Korean man's fracture risk is.
3. Neither the Korean prevalence data nor the Korean dementia cohort records hot flushes, fatigue, loss of libido, or the other effects that make androgen deprivation hard to live with. Those remain unrecorded in Korean data, as continence and sexual function are.
4. None of these studies compares androgen deprivation against not having it in men who needed it. Withholding effective treatment is not the counterfactual on offer.

This coverage began by establishing that Korea finds prostate cancer late. This is the first Korean evidence of what accumulates at the other end of that: half a million men per hundred thousand, mean age 73, most of them on a treatment that costs bone and may cost more than bone. What it still does not contain is any Korean record of how those men are actually doing.