Nearly 200 children born from sperm of donor with cancer-causing mutation

Sperm from a donor who was unknowingly carrying a cancer-causing mutation has been used to conceive at least 197 children across Europe.

The sperm – originally donated in Denmark – has been used for 17 years in 67 clinics across 14 countries, including Denmark, Belgium, Spain, Greece, and Germany. While the donor passed genetic screening, the mutation – which is not present in all of his body's cells – was not detectable in blood tests.

'Screening for something de novo in testis will never work on blood. Each sperm in an ejaculate is slightly different, so screening these is also not simple,' said Professor Jackson Kirkman-Brown at the Centre for Human Reproductive Science, University of Birmingham.

Cancer doctors first expressed their concerns to the European Society of Human Genetics earlier this year (see BioNews 1291 and 1308). It was reported that 23 children out of 67 known to be conceived from the donor at the time carried the mutation. Ten of these children had already been diagnosed with cancer, and it is now known that some children have died.

Different countries have different rules about how many families or children can be created using a donor's sperm. For example, one donor's sperm can only be used to create up to ten families within the UK. However, that same donor's sperm could potentially be used to create additional families overseas (see BioNews 1222, 1240, 1241, 1253, 1278 and 1283).

'More needs to be done to reduce the number of families that are born globally from the same donors,' Sarah Norcross, director of PET (the Progress Educational Trust) told BBC News. 'We don't fully understand what the social and psychological implications will be of having these hundreds of half-siblings.'

In a follow-up article on BBC News, Norcoss added: 'Many recipients, and also donors, are unaware that a single donor's sperm can be lawfully used in many different countries. This fact should be better explained.'

Further investigation has revealed that up to 20 percent of this particular donor's sperm carry a mutation in a tumour suppressor gene called TP53. Those who are conceived from one of the donor's affected sperm will – unlike the donor – carry the mutation in almost every cell of their bodies. This results in a condition known as Li Fraumeni syndrome, which can increase the chance of developing cancer by 90 percent across a person's lifetime (including during their childhood).

'It is a dreadful diagnosis,' Professor Clare Turnbull, a cancer geneticist at the Institute of Cancer Research in London, said. 'It's a very challenging diagnosis to land on a family, there is a lifelong burden of living with that risk, it's clearly devastating.'

Deciding how to screen donor sperm involves many complex considerations. While it is possible to screen sperm for many genetic conditions, testing for gene variants which are not present throughout somatic tissues comes with practical challenges and increased costs.

Andrologist Professor Allan Pacey, from the University of Manchester, explained: 'You can't screen for everything. We only accept one percent or two percent of all men who apply to be a sperm donor in the current screening arrangement, so if we make it even tighter, we wouldn't have any sperm donors – that's where the balance lies.'