Survival rates of childhood cancer are now better than ever.
Today, more than 80% of children with cancer survive into adulthood.
This is, of course, a true triumph for medical science, but not the end of the road.
With the steady improvements in cancer therapy, there have been changes in its methodology.
Previous studies have found that some types of chemotherapy drugs, especially alkylating drugs, can negatively impact fertility. However, the effects of newer drugs, such as cisplatin and ifosfamide, have not been fully investigated in regards to their influence on reproduction in later life.
A fresh look at chemotherapy and fertility
The research team, led by Dr. Eric Chow at the Fred Hutchinson Cancer Research Center in Seattle, WA, used data from the Childhood Cancer Survivor Study (CCSS) to investigate this question in detail.
The CCSS followed children who developed cancer before the age of 21 and survived for at least 5 years. These individuals came from 27 institutions across the US and Canada between 1970-1999.
The researchers measured the rate of live births in 10,938 male and female cancer survivors and compared the sample to 3,949 of their siblings. They then investigated the impact of 14 commonly used chemotherapy drugs on their reproductive rates. (The team did not use individuals who had undergone radiotherapy to their pelvis or brain.)
By the age of 45, 70% of female cancer survivors had given birth, compared with 80% of the sibling group. For male survivors, the story is less positive: 50% had fathered a child, compared with 80% of the sibling controls.
In the males, as the doses of alkylating drugs (including cyclophosphamide, ifosfamide and procarbazine) and cisplatin increased, the chances of fathering a child decreased. This falls in line with previous research that has demonstrated a drop in sperm count and testicular volume with chemotherapy.
Findings and shortfalls
For the females, only busulfan and high doses of lomustine were matched with particularly low parenthood rates. Although female cancer survivors' rates of pregnancy were lower than the sibling control group, the effect was most pronounced in women who waited until after the age of 30 to conceive. This may be due to chemotherapy speeding up the natural depletion of eggs that occurs with age.
Overall, the study is in line with previous research; its results strengthen the earlier findings, thanks to the large size of the data sample. The findings are relatively good news for female survivors but not so for male survivors.
Having said that, the authors are quick to admit the shortfalls of the study; some factors were not included in the analysis, such as whether partners were cohabiting and how long conception took. And, although the total number of participants was high, some of the rarer drug groups were still relatively underrepresented.
Dr. Chow says:
"We think these results will be encouraging for most women who were treated with chemotherapy in childhood. However, I think we, as pediatric oncologists, still need to do a better job discussing fertility and fertility preservation options with patients and families upfront before starting cancer treatment."
He goes on to say that "all boys diagnosed post-puberty should be encouraged to bank their sperm to maximize their reproductive options in the future." For women, the solution is not so straight forward, but they could potentially be offered "oocyte and embryo cryopreservation."
Dr. Chow ends the paper by calling for further research, specifically into cisplatin, which significantly reduced fertility in males. He also hopes that the results "provide reassurance" to female cancer survivors.
Medical News Today recently covered research showing that the immune system takes time to recover after breast cancer chemotherapy.