We carried out a cohort study in the Italian province of Trieste (2001 population, 242,000) to ascertain whether the risk of a subsequent primary cancer among 265 individuals diagnosed with a first malignancy at ages up to 25 years between 1971 and 1993 differed from that in the general population and to evaluate the effect of cancer family history, quantified by the family risk index (FRI), on the occurrence of second primaries. During the follow-up (median duration = 10 years; 25th-75th percentile = 2-16), 15 cohort members developed a second cancer vs. 1.60 expected for a standardized incidence ratio (SIR) of 9.4 (p < 0.0001). The overall SIR fell to 4.7 (p = 0.004) after excluding the 8 patients with wellknown cancer-predisposing conditions (SIR = 300.0; p < 0.0001) and the 50 with a positive family history (FRI ! 1.0) of malignant tumors (SIR = 20.0; p < 0.0001). Among 114 patients treated with radiotherapy and chemotherapy for their first neoplasms and not affected by predisposing disorders, 23 with a positive family history of cancer showed a 6.4-fold excess risk of second primaries (p = 0.008) compared with 91 with a negative history (FRI < 1.0). It is imperative that clinicians carefully and regularly evaluate cancer family history of young patients with malignancies. This would enable them to identify possible individual and familial features in patients at higher risk of multiple primaries and to adopt more suitable preventive and therapeutic measures. ' 2005 Wiley-Liss, Inc.Key words: second primary cancer; family risk index; children; adolescents; young adults Individuals who suffered from a first primary malignancy in childhood or adolescence exhibit an increased risk of developing a second primary in comparison with the general population. 1-5 The major determinants of subsequent primary cancer in the young are inherited susceptibility and initial cancer therapies, particularly ionizing radiation and chemotherapy with their carcinogenicity. 6 In spite of several studies substantiating the association between the occurrence of second malignant neoplasms in young patients and well-known hereditary predisposing disorders 7-12 and exposure to therapeutic radiation or antineoplastic drugs, 10,11,[13][14][15][16][17][18][19][20][21][22][23] only one epidemiologic study investigating the risk of second primaries in relation to the extent of cancer clustering in young patients' relatives has been published to our knowledge. 24 The present cohort study is based on young people living in the northeastern Italian province of Trieste who developed a first primary malignancy during the period 1971-1993. The study aims at determining the effect of cancer risk found in their nuclear families on the incidence of second malignant neoplasms.
Material and methodsAll permanent residents of the province of Trieste (2001 population, 242,000) diagnosed with a first primary cancer at ages 0-25 years between 1 January 1971 and 31 December 1993 were extracted from the file of the general population-based Cancer Registry ...