The contribution of hereditary factors for development of childhood tumors is limited to some few known syndromes associated with predominance of tumors in childhood. Occurrence of childhood tumors in hereditary cancer syndromes such as BRCA1/2 associated breast and ovarian cancer, DNA-mismatch repair (MMR) genes associated hereditary non polyposis colorectal cancer and CDKN2A associated familial malignant melanoma are very little studied. Herein we report the prevalence of childhood tumors (diagnosed

Background: Whether cancer predisposing familial factors are associated with childhood

Relatives of patients with childhood ACTs, CPTs, and RMSs showed no increased risk of LFS associated tumors. However, TP53 mutations could be found in these children irrespective of family history. Absence of LFS associated tumors may suggest the presence of other cancer syndromes. Improved knowledge about relatives' cancer risks could be helpful in counseling family members of children with cancer.

Background: Recently, we found a two-fold increased risk for childhood tumors among first- to third degree relatives of childhood cancer patients. Whether cancer predisposing familial factors are associated with childhood tumors is unclear. The purpose was to study the incidence of adult tumors in extended families of children with cancer and whether there are any differences in cancer incidence between families with single and multiple cases of childhood tumors. Methods: Family history of cancer was obtained through questionnaires, and the Swedish Population-, and Cancer Registries for 194 childhood cancer patients aged ≤18 years, diagnosed 1972-2009. Standardized cancer incidence ratios (SIR), and 95% confidence intervals (CI) were estimated by comparing with expected rates in the general population. Results: Overall, an increased incidences of adult tumors (179 observed cases vs. 121.3 expected; SIR=1.5; 95% CI: 1.3-1.7) was found among first- to third degree relatives. Highest incidence was found among first degree relatives (SIR=2.2; 95% CI: 1.2-3.5), while the incidence was somewhat lower for second degree relatives (SIR=1.4; 95% CI: 1.2-1.7). No increased risk was observed for third degree relatives (SIR=1.1; 95% CI: 0.1-3.9). A significantly increased risk for tumors in the prostate (SIR=2.7; 95% CI: 1.9-3.8) and breast (SIR=1.7; 95% CI: 1.2-2.4) were observed among first- to third degree relatives, both observed at earlier than average ages. Excess of breast cancer was especially found in first degree relatives, all observed cases were mothers (SIR=4.6; 95% CI: 1.7-10.1). The cancer incidence in relatives of first- to third degree were found to be similar for families with multiple cases (16 observed cases vs. 10.9 expected; SIR=1.5; 95% CI: 0.8-2.4) and with single cases (163 observed cases vs. 110.4 expected; SIR=1.5; 95% CI: 1.3-1.7) of childhood tumors. An excess of breast cancer was found in both subgroups. However, this was somewhat higher in families with multiple cases (SIR=2.6; 95% CI: 0.9-6.2) compared with families with single cases (SIR=1.6; 95% CI: 1.1-2.3). Moreover, families with single childhood cases also had an excess of lung cancer (SIR=1.7; 95% CI: 0.9-2.8), prostate cancer (SIR=2.8; 95% CI: 1.9-3.9), and Non-Hodgkin's lymphoma (SIR=2.5; 95% CI:1.2-4.8). There was no significantly increased incidence for these cancers in families with multiple childhood tumors. Conclusions: Familial factors may increase the risk for both childhood and adult cancers and modify the age of onset of common adult tumors. To identify common pathways that confers increased risk for both childhood and adult tumors and to assess the possible interplay between genetic susceptibility and environmental factors further molecular epidemiological studies are needed. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5512. doi:1538-7445.AM2012-5512

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