A new registry study from Denmark covering 40 years of data shows that, while rates of fatherhood are increasing for men with cancer, the chances are much lower than for men in the general population – and particularly low when diagnosed in young boys and adolescents.
Parenthood among men after cancer may be increasing, but the odds are still stacked against survivors, despite advances in fertility preservation and a growing public awareness of freezing sperm and reproductive tissue. Such conclusions are borne out by nearly 40 years of data now analysed by a register-based cohort study from Denmark which shows the chances of having children remain significantly lower for males with a diagnosis of cancer than those without.(1) Men who develop the disease as boys or in adolescence have particularly poor success rates, a finding the authors suggest may be linked to an unavailability of services for this group in addition to the particularly intensive treatments they undergo.
No studies to date have examined such an extensive time period (1978 to 2016) for changes in the probability of becoming a father post-cancer. What’s reassuring is that this new research provides evidence of a marked rise in rates of fatherhood among those who overcome the disease during this time - especially so among patients diagnosed in recent years, men whose illness was discovered in their 20s, and those with solid tumours. The research, based on 9353 patients diagnosed from birth to age 29, provides ‘novel and updated’ information on important aspects about fatherhood after cancer, and the authors recommend that their results be used for counselling to ‘create awareness of their (men’s) chances of family creation’.
Small sample sizes, short follow-up times and lack of comparison with the general population have undermined the robustness of earlier studies. This latest analysis was undertaken by a group which includes those associated with Denmark’s successful fertility preservation group at Copenhagen University Hospital (Rigshospitalet).
Using the Danish Cancer Register, they matched each man randomly and according to time of diagnosis with 150 (total number = 1.4 million) who were undiagnosed, born in the same year and from the general population. Both groups were followed until their first child’s birth, the man’s death, migration or the end of the study (December 2017); all had to be childless at study entry to ensure the decision to become a parent was taken after diagnosis; cancer types were central nervous system (CNS), solid or haematological. Fatherhood rates were compared with the non-cancer group and classified according to age at diagnosis (0-9, 10-19, 20-29) and the timeframe when the disease was first discovered (1978-1989, 1990-1999, 2000-2009, 2010-2016).
The results show that over a third (36%) of cancer survivors became fathers during the study period compared with 42% in the control group. Overall, those with solid tumours had the greatest chance of paternity, with slightly increased odds (HR 1.16) than the control group, followed by haematological (HR 0.90) and CNS (HR 0.67). The chances of becoming a parent increased over the decades for all types of tumours: the HR rose from 0.78 to 1.08 for solid tumours; haematological cancers from 0.64 to 0.97; and CNS tumours from 0.44 to 0.98. A disease diagnosis for men between the ages of 20 to 29 meant they were more likely to become fathers (HR 0.80 to HR 1.08) whereas the HR did not increase for those diagnosed between birth and age 19.
Sadly, but inevitably, many patients died within the first five years post-diagnosis without the possibility of becoming fathers. All analyses in this study were adjusted for death as a competing risk (changes in survival rates influence the HR of fatherhood), and the authors recommend that future studies correct for death too.
Of course, this is an observational study. Many factors remain unknown, such as whether the men actually wanted to have children or not, if they could find a partner with whom to have children, if they used fertility preservation or ART, and if those who had children were actually the biological fathers. Nevertheless, say the authors, the findings are not prone to selection bias, can be extrapolated to similar populations, and provide new insights into an area of fertility of growing importance.
With cancer survival rates improving, the authors add that genetic parenthood after the disease is now ‘considered a major factor of quality of life’ and a goal for many men who survive the disease. On this basis, patients need information and education about fertility preservation and ‘their chances to create their own family’, and more should be done to help prepubertal boys or men with azoospermia whose only viable (but still experimental) option is testicular tissue freezing.
1. Sylvest R, Vassard D, Schmidt L, et al. Parenthood among men diagnosed with cancer in childhood and early adulthood: Trends over time in a Danish National Cohort. Human Reprod 2021; 36; 2576–2586; https://doi.org/10.1093/humrep/deab154