Familial histology-specific risks for 22 rare solid cancers in Sweden

Abstract

Recognition of familial cancer has become increasingly important in oncology as it can help guide treatment and find individuals at risk. However, reliable data on the prevalence and risk of familial cancer are limited to the most common cancers. We use here Swedish population and cancer data resources on 16 million individuals to characterize risks of familial cancer (risk in those with a first-degree family member diagnosed with the same cancer compared to those without an affected relative) up to year 2021. Cancers include 22 solid cancers, excluding breast, prostate, colorectal and lung cancers. Familial risks between two relatives were significantly increased for 20 of 22 cancers, relative risk ranging from 1.56 (cervix and brain cancers) to 4.27 (thyroid cancer) and 5.46 (testis cancer). A total of 16 cancers had three affected family members, resulting in high familial risks, from above 3.0 for bladder, skin, brain and stomach cancers to those of the testis (24.7), gallbladder (31.9), thyroid (56.6), small intestine (67.0) and other nervous system (143). For many cancers, histology-specific cancers showed distinct familial risks, with thyroid cancer as a prime example: common adenocarcinoma, SIR 3.86 and rare medullary cancer, 465. Risks for concordant histology were higher than for discordant histology, suggesting contribution of genetic constitution on histology. The main conclusion is that familial clustering is common also for rare cancers which should alert oncology clinics to request information about affected family members at diagnosis of rare cancers and prepare for mutation analysis when genetic causes are likely.