Abstract
To determine whether the occurrence of first and second primary malignancies in first‐degree relatives of cancer patients aged 0–25 years (probands) differed from that in the general population, a cohort study was carried out on 860 relatives of 265 probands living in the province of Trieste, Italy. During the follow‐up period (median duration = 28 years, 25th–75th percentile = 20–34), the relatives developed 103 first primary cancers vs. 88.9 expected for a standardized incidence ratio (SIR) of 1.2 (p = 0.2). Significantly elevated risks were found for melanoma in the parents of probands aged 15–25 years with melanoma (SIR = 15.0, p = 0.002), for hemolymphatic malignancies in the fathers of probands aged 0–14 years with brain tumors (SIR = 13.3, p = 0.0005) and for hemolymphatic cancers in relatives as a whole of probands aged 15–25 years with lymphomas (SIR = 4.5, p = 0.01). During the follow‐up period, 7 relatives with a first primary cancer had a subsequent malignancy vs. 4.2 expected for an SIR of 1.7 (p = 0.3). Our results indicate that young cancer patients per se should not to be considered as a factor that usually increases the risk of developing malignant tumors among their first‐degree relatives, except when a known cancer family syndrome or predisposition is recognized. © 2003 Wiley‐Liss, Inc.