"Men who struggle with infertility are at much greater risk of prostate cancer," reports the Sun.
In a new study, Swedish researchers used their databases to investigate what happened to almost all men who fathered a child over 20 years from 1994 to December 2014.
They found men whose babies were born after fertility treatment were more likely to have been diagnosed with prostate cancer in the years since, and more likely to have had prostate cancer at a young age (under 55).
The 2 types of fertility treatment considered were IVF, when sperm and eggs are put together in a laboratory to see if the sperm will penetrate and fertilise the egg, and ICSI (intracytoplasmic sperm injection), where sperm is injected directly into the egg.
ICSI is most commonly used when there's a problem with the man's sperm. For example, if a man does not produce many sperm or they do not swim well.
IVF is sometimes used when the cause of infertility is unknown, or when the problem is with the woman's fertility rather than the man's.
There's no suggestion that fertility treatment causes prostate cancer. But it may be that men who have problems with their sperm, leading to the need for treatment, are at a higher risk of prostate cancer.
This study has some limitations. It did not include men who had fertility treatment and did not become fathers, and the average age of men when they were followed up was 45.
And the overall number of men who developed prostate cancer in all 3 groups was small: 0.28% in the non-treatment group, 0.37% in the IVF group and 0.42% in the ICSI group.
Men with a history of fertility treatment should not be overly concerned.
Where did the story come from?
The researchers who carried out the study were from Lund University in Sweden.
It was funded by the Swedish Cancer Foundation, an ALF government grant, Malmö University Hospital Cancer Research Fund, the Swedish Prostate Cancer Research Foundation and the European Association of Urology.
The UK media mostly reported the study accurately. But The Times' headline, "Fathering an IVF baby is linked to double the risk of prostate cancer", suggests that it's the act of fathering the baby that increases the risk, which is incorrect.
Fertility treatment was simply used as a "marker" to identify men who were infertile, as this information is not routinely provided in medical records.
But the body of The Times' article was accurate.
What kind of research was this?
This was a cohort study of men who were registered as fathers of children born over 20 years in Sweden.
Cohort studies are useful ways to look for links between risk factors, such as the need for assisted conception, and outcomes, such as prostate cancer.
But they cannot explain the exact nature of the link between them.
What did the research involve?
The researchers used Swedish databases of births to trace all men registered as fathers from 1994 to 2014.
They then used additional databases to trace which men had undergone IVF or ICSI fertility treatment, leading up to the birth of the child, and which men had later been diagnosed with prostate cancer.
The researchers adjusted their figures to take account of the men's ages when their child was conceived (as prostate cancer risk rises with age) and their education level.
They also did a sensitivity analysis, removing all men who had any type of cancer prior to conception.
This is because some types of cancer treatment, such as radiotherapy and chemotherapy, may affect fertility and increase the risk of a second cancer.
The researchers also looked at the treatment men received for prostate cancer.
Androgen deprivation therapy (a type of hormonal treatment) tends only to be used in more serious cases of prostate cancer, so the researchers used it to assess the seriousness of cancer and cancer needing treatment (as opposed to small, slow-growing cancers that did not need treatment).
What were the basic results?
The researchers investigated 1,181,490 births with registered fathers.
Of these, the vast majority (1,145,990) did not result from fertility treatment: 20,618 followed IVF and 14,882 followed ICSI.
- 0.28% of men who had no fertility treatment were later diagnosed with prostate cancer, at an average age of 57.1
- 0.42% of men who had ICSI were later diagnosed with prostate cancer, at an average age of 55.1
- 0.37% of men who had IVF were later diagnosed with prostate cancer, at an average age of 55.9
Men who had IVF had a 33% increased risk of prostate cancer (HR 1.33, 95% CI 1.06 to 1.66).
Men who had ICSI or IVF were also more likely to be diagnosed with prostate cancer before the age of 55 (HR for ICSI 1.86, 95% CI 1.25 to 2.77, and HR for IVF 1.51, 95% CI 1.09 to 2.08).
The increased risks remained after taking out the men who'd had previous cancers or men who'd been on testosterone replacement therapy.
Testosterone therapy is sometimes used for men who have low levels of testosterone. It's been linked to prostate cancer, which is why the researchers looked at it.
Men with prostate cancer who'd had ICSI were most likely to be prescribed androgen deprivation therapy, with 19.2% having this treatment compared with 11.8% of men who had IVF and 13% of men who had no fertility treatment.
How did the researchers interpret the results?
The researchers said: "This work shows that men fathering children by assisted reproduction are a high risk group for prostate cancer at early ages."
They suggested that this group of men should be screened for prostate cancer early using the prostate specific antigen (PSA) test, a blood test used in prostate cancer screening.
The study suggests that there's something about the group of men who had IVF or ICSI treatment that raised their risk of prostate cancer at an earlier age, compared with men who did not need to have fertility treatment.
It's important to be clear that there's no suggestion fertility treatment itself raises the risk.
It's more likely that there may be a common cause for fertility problems and prostate cancer.
But this study cannot tell us what that cause is.
This type of study cannot tell us whether sperm abnormality or other problems in male fertility are a direct cause of prostate cancer.
And the study has a major limitation: it did not include information about men who had fertility treatment but did not become fathers.
It's possible that these men were at an increased risk of prostate cancer, but we cannot tell from this study.
The study also had a short follow-up period. The average age of men was 45 when the study concluded, so it may not give a clear picture of the long-term risk of prostate cancer for men who have had fertility treatment.
The researchers' suggestion that all men who have had fertility treatment are screened by PSA is controversial.
The PSA test is not particularly accurate, and extending screening to a big group of men might cause more men to undergo unnecessary investigations and treatment.
In a linked editorial, 2 researchers from Hammersmith Hospital warned: "In the absence of a plausible mechanism of action or proof of causation, justifying screening for prostate cancer in all infertile men is difficult."
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Sun, 25 September 2019
BBC News, 26 September 2019
Sky News, 26 September 2019
Mail Online, 25 September 2019
Links to the science
BMJ. Published online 25 September 2019