Subsequent breast cancer risk in childhood cancer survivors and survivorship care

Survival rates for childhood cancer have improved markedly over the last decades. Unfortunately, the life expectancy and quality of life of long-term survivors are compromised by long-term adverse effects such as subsequent neoplasms. Subsequent breast cancer represents one of the most common subsequent malignant neoplasms among childhood cancer survivors. In the first part of this thesis, we studied the risks of and risk factors for subsequent breast cancer in female and male childhood cancer survivors using internationally pooled data. Our findings demonstrated that doxorubicin and epirubicin were associated with an increased risk of female breast cancer in survivors. We also found that male childhood cancer survivors have an elevated risk of developing subsequent breast cancer compared to the general population. The findings from the first part of our thesis have led to novel insights into risks of and risk factors for subsequent breast cancer, which emphasize the need for awareness and will inform surveillance guidelines and developments of new childhood cancer treatment protocols. The second part of this thesis includes international COVID-19 guidelines and recommendations for childhood cancer survivors during the COVID-19 pandemic. Given that childhood cancer survivors are more vulnerable to chronic comorbidities than the general population, this raises concern that survivors may be at increased risk for severe COVID-19. Therefore, we established recommendations on conditions associated with the risk of a severe course of COVID-19 at the onset of the pandemic. The international COVID-19 guideline has been translated into 13 different languages and has provided guidance to healthcare providers and childhood cancer survivors worldwide during this unexpected and unique period.