Objective: Childhood cancers form 2% of all cancers, and identified familial and genetic factors are responsible for only 5-15%. Determining the hereditary conditions that cause predisposition enables early detection of cancer.

Methods: It was aimed to determine the patients with a genetic predisposition to cancer, treatment success and drug side effects among the patients diagnosed with a non-leukemia malignancy in Okmeydanı Training and Research Hospital between 2015-2017.

Results: A Cancer Predisposition syndrome was found in 7 (5%) of 121 cases diagnosed with non-leukemia malignancy. Cancer Predisposition syndromes were Ataxia telangiectasia, Beckwith Wiedemann syndrome, Neurofibromatosis type 1, Down syndrome, Gardner syndrome, and Rothmund Thomson syndrome. Cancers observed were Non-hodgkin lymphoma, Wilms tumor, malignant glial tumor, malignant peripheral nerve sheath tumor, testicular germ cell tumor, hepatoblastoma, and osteosarcoma. Malignancy was detected at an early stage in all three patients who were followed up regularly due to Cancer Predisposition syndrome. At the last follow-up, five cases were in remission. In two cases, drug dose reduction was required due to chemotherapy side effects.

Conclusion: Detection of malignancy at an early stage indicates the importance of regular follow-up. With this study, we wanted to emphasize the importance of recognizing Cancer Predisposition syndromes and the need for regular follow-up.