People with a parent, sibling, or child affected by blood cancer are more likely to be diagnosed with the disease, a new study has shown.

The analysis—the largest and most comprehensive population study of its kind—offers strong evidence that the risk of developing blood cancer is partly inherited from DNA changes passed on from parents.

Estimating the family risk of blood cancer could help pick out people at highest risk, who could benefit from counseling, genetic testing, and surveillance.

Scientists at The Institute of Cancer Research, London, working with colleagues in Germany and Sweden, analyzed all individuals with a blood cancer diagnosis and their relatives in the Swedish population from 1958 onwards.

The study was published in the journal Blood and supported by the German Cancer Aid, the Swedish Research Council, ALF funding from Region Skåne, the German Cancer Research Centre, and Bloodwise UK.

Finding a genetic component

Researchers identified 153,115 blood cancer patients and 391,131 first-degree relatives in the Swedish Family-Cancer Database, and found that cases with a family link represented 4.1% of all blood cancer diagnoses— suggesting the risk has a genetic component.

The study looked at registered blood cancer diagnoses, as well as birth and death records and records of familial relationships. Certain subtypes of Hodgkin lymphoma (HL), lymphoplasmacytic lymphoma, and mantle cell lymphoma had the strongest familial link.

Factors such as the age at which a relative was diagnosed and the number of affected first-degree relatives affected the strength of the increased risk in certain blood cancers—including non-Hodgkin lymphoma and chronic lymphocytic leukemia (CLL).

For instance, individuals with a first-degree relative with CLL were six times more likely than the general population to be diagnosed with CLL. The risk was higher if the first-degree relative was a sibling, was diagnosed with CLL at a younger age, or if individuals had more than one first-degree relative with CLL.

The researchers have pointed out that the findings may only apply to Western countries, as economically developing countries have different tumor incidence rates and potentially diverse environmental and genetic risk factors.

Understanding how blood cancer develops

Study lead author Dr. Amit Sud, clinical research fellow at the ICR, said, “Our analysis provides strong evidence that inherited genetic changes influence the risk of developing blood cancers. For the first time, we looked at all blood cancer types instead of focusing on a single group, and included greater case numbers and a longer follow-up than previous studies. By improving our understanding of family risks, we may help people with blood cancers and their relatives through providing appropriate information, counseling, and, in the future, genetic testing. Our work could even underpin new ways of screening people for their risk of developing blood cancer, and help us understand how blood cancers develop—although more research is needed in this area. In the meantime, patients with blood cancers who are concerned about family risks should also discuss this with their treating doctor for guidance.”