Scientists have long known that chemotherapy has the potential to interfere with a patient’s reproductive health, but a new study suggests that the effects of chemotherapy treatment could be passed on for many generations. According to the study, chemotherapy in adolescence may bring about permanent changes to the cells in the testes, causing molecular changes that can be passed to future offspring.

The study, conducted by researchers from Washington State University, found epigenetic changes in the sperm of men who had undergone chemotherapy in their teens that may affect how certain genes are turned on and off in future generations. When compared to the sperm of men who had never received chemo, the sperm of men who had received it all displayed the same pattern of molecular changes.

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For the small study, Skinner and his team looked at sperm samples from 18 men who had undergone chemotherapy as teens and 18 men who had never taken part in the procedure. Although the sample size was small, the same molecular changes were unanimously seen in all 18 samples from the chemo-treated men — a finding that shocked even Skinner.

"It was very reproducible," Skinner said in a recent statement. "That in and of itself was very surprising to me."

Women are born with all the eggs they will ever have, which means chemotherapy could pose a serious threat to their fertility. In fact, according to The American Cancer Society, most chemotherapy drugs do have the potential to damage a woman’s eggs, with effects varying on her age, the type of drugs, and dosage amounts. However, male fertility is different. The testes make new sperm cells every 75 days, and once made, these cells only stay alive for around 20 to 30 days.There are instances where chemotherapy can completely destroy a man’s ability to reproduce. The ACS explained that this occurs if chemo destroys all the spermatogonial stem cells (the immature cells in the testicles that divide to make new sperm) to the point that they can no longer produce maturing sperm cells.

The effects of chemotherapy on male reproduction beyond permanent infertility is less clear.

According to the new study, the fact that these molecular changes were seen 10 years after the men received chemotherapy means that the procedure was able to permanently alter how sperm cells were made.

At the moment, it's not clear what these molecular changes could mean, although mice experiments suggest they could increase risk for certain cancers and decrease fertility in future generations. Due to these risks, lead study author Michael Skinner insists that he is not suggesting patients opt out of chemotherapy. Rather, he urges young boys planning to undergo this treatment to save their sperm before the procedure. The researchers plan to study the offspring of men who had undergone chemotherapy in their youth.

Source: Skinner MK, Shnorhavorian M, Schwartz SM, et al. Differential DNA Methylation Regions in Adult Human Sperm following Adolescent Chemotherapy: Potential for Epigenetic Inheritance. Plos One . 2017

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