Partnership and fatherhood outcomes in young men diagnosed with cancer: a nationwide register-based study.

Purpose: A cancer diagnosis during young adulthood can impact identity, relationships, and family building. While young men with cancer face fertility risks, data on fatherhood and partnership outcomes remain limited. This study aimed to examine the hazard ratios (HRs) for fatherhood and partnership formation in young men diagnosed with cancer compared to age-matched comparisons.

Methods: This nationwide register-based study, based on the DANAC II cohort, included men diagnosed with cancer at 18-39 years (1978-2016) and age-matched male comparisons. Cox regression models estimated HRs of fatherhood and partnership formation, adjusting for time of diagnosis or study entry, immigration status, and pre-diagnosis children.

Results: Among 16,913 men with cancer and 1,353,040 comparisons, those with cancer had a lower HR of fatherhood (0.88 [95% confidence interval (CI) 0.86-0.91]), the lowest among men with lymphoma, central-nerve system (CNS), and gastrointestinal cancers. Fatherhood probabilities improved over time, with older men showing the greatest gains. Among men who were single at diagnosis or study entry, the HR for partnership formation was similar to the comparison group (1.03 [95% CI 0.99-1.07]), except for those with gastrointestinal or CNS cancers.

Conclusions: Fatherhood HRs were generally lower than in comparisons, varying by cancer group, age, and diagnosis period. However, single men diagnosed with cancer typically formed partnerships similar to the comparisons.

Implications for cancer survivors: The lower probability of fatherhood highlights the need for and importance of oncofertility counseling, timely fertility preservation referrals, and follow-up care tailored to cancer groups and age at diagnosis.