Simple Summary Due to improvements in the treatment of childhood cancer, around 80%
of children are cured. However, childhood cancer survivors are at risk of developing
late effects, including subsequent malignant neoplasm; these are defined as histologically
different cancers, which appear after treatment for primary cancer. The risk of subsequent
malignant neoplasm formation is influenced mainly by previous anticancer therapy (chemotherapy,
radiotherapy, immunotherapy, and targeted therapy), genetic factors, and the length
of survival. For these reasons, at present, for the treatment of tumors with a good
prognosis, it is important to consider the possible risk of late side effects e.g.
use of radiotherapy in Hodgkin's lymphoma only if chemotherapy does not induce complete
remission or in nephroblastoma only in locally advanced stages. Therefore, we study
risk factors for the development of subsequent malignant neoplasm. In the review,
we present possible risk factors for the development of subsequent neoplasm. Advances
in medicine have improved outcomes in children diagnosed with cancer, with overall
5-year survival rates for these children now exceeding 80%. Two-thirds of childhood
cancer survivors have at least one late effect of cancer therapy, with one-third having
serious or even life-threatening effects. One of the most serious late effects is
a development of subsequent malignant neoplasms (histologically different cancers,
which appear after the treatment for primary cancer), which occur in about 3-10% of
survivors and are associated with high mortality. In cancers with a very good prognosis,
subsequent malignant neoplasms significantly affect long-term survival. Therefore,
there is an effort to reduce particularly hazardous treatments. This review discusses
the importance of individual factors (gender, genetic factors, cytostatic drugs, radiotherapy)
in the development of subsequent malignant neoplasms and the possibilities of their
prediction and prevention in the future.