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Colorectal cancer is the third most common form of cancer worldwide and is one of the most common types of cancer in Germany. If there are cases of colorectal cancer in your family, there is an increased risk that you will fall ill yourself. Heidelberg cancer researchers along with international colleagues have investigated the risk of this disease for first- and second-degree relatives in the world’s largest register-based cohort study on family members of over 170,000 colorectal cancer patients. In their study, they found that half-siblings of colorectal cancer patients have a similar increased risk of this cancer as their siblings.

The National Center for Tumor Diseases (NCT) Heidelberg is a joint institution of the German Cancer Research Center (DKFZ), Heidelberg University Hospital (UKHD), and German Cancer Aid.

Every year, approximately 1.8 million people worldwide develop colorectal cancer and about half of them die as a result. First-degree relatives, such as children or siblings, of colorectal cancer patients have an increased risk of developing colorectal cancer themselves. This cancer risk can be significantly reduced with timely and regular screenings. The current recommendation in Germany for anyone who has a history of colorectal cancer in their family is therefore: Begin the screening ten years before the youngest age at diagnosis of colorectal cancer in family members, but no later than 40 to 45 years of age. If the family history indicates the risk of hereditary colorectal cancer in the family, it is recommended that first-degree relatives regularly perform a colonoscopy as early as the age of 25 years.

“Even though we have for a long time been aware of the link between a family history and an increased risk of being diagnosed with colorectal cancer, the risk by type of relationships thus far have not been examined in detail, especially for half-siblings” reported Mahdi Fallah, head of the research group “Risk-adapted Prevention” in the Department of Preventive Oncology at the German Cancer Research Center (DKFZ) and the National Center for Tumor Diseases (NCT) in Heidelberg. Together with colleagues from Sweden, Japan, and the United States, scientists at the DKFZ and the NCT in Heidelberg evaluated the world’s largest database of individuals with a familial cancer risk. Over 16 million people from Sweden are included in this dataset. Among this group, 173,796 people were diagnosed with colorectal cancer during the period 1958-2015. Based on genealogical and family history, researchers were able to draw conclusions on the risk in various types of first- and second-degree relatives.  

The results of their investigation showed that siblings of colorectal cancer patients have a 1.7-fold increased risk of developing colorectal cancer compared with those without any colorectal cancer cases. The researchers found a similar risk for half-siblings. Having a half-sibling with colorectal cancer is associated with a higher risk of the disease than having it in other second-degree relatives, such as a grandparent or an aunt/uncle. The highest risk of colorectal cancer can be found in people whose family histories show several first- and second-degree relatives with the disease.

“We were able to prove that the familial risk for half-siblings of cancer patients was significantly higher than previously expected. As currently there is no screening recommendation for those with an affected half-sibling, for the time being, half-siblings should be classified as first-degree relatives in the family history for the risk assessment of colorectal cancer and risk-adapted screening,” advises Fallah. “At the same time, the results also show that, in addition to genes, common childhood living conditions and lifestyles shared in families play an important role in familial aggregation of colorectal cancer, since otherwise one would expect to see a clear difference in the risk between ‘full siblings’ and half-siblings,” added Hermann Brenner, head of the Department of Preventive Oncology at DKFZ.

Original publication:
Yu Tian, E. Kharazmi, K. Sundquist, J. Sundquist, H. Brenner, M. Fallah (2019). Familial colorectal cancer risk in half siblings and siblings: nationwide cohort study. BMJ 364:1803, https://doi.org/10.1136/bmj.l803

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National Center for Tumor Diseases Heidelberg (NCT)
The National Center for Tumor Diseases (NCT) Heidelberg is a joint institution of the German Cancer Research Center, Heidelberg University Hospital and German Cancer Aid. The NCT’s goal is to link promising approaches from cancer research with patient care from diagnosis to treatment, aftercare and prevention. This is true for both diagnosis and treatment, follow-up care or prevention. The interdisciplinary tumor outpatient clinic is the central element of the NCT. Here, the patients benefit from an individual treatment plan prepared in a timely manner in interdisciplinary expert rounds, so-called tumor boards. Participation in clinical studies provides access to innovative therapies. The NCT thereby acts as a pioneering platform that translates novel research results from the laboratory into clinical practice. The NCT cooperates with self-help groups and supports them in their work. In 2015, the NCT Heidelberg established a partner location in Dresden.

German Cancer Research Center (DKFZ)
The German Cancer Research Center (DKFZ) with its more than 3,000 employees is the largest biomedical research institute in Germany. At DKFZ, more than 1,000 scientists investigate how cancer develops, identify cancer risk factors and endeavor to find new strategies to prevent people from getting cancer. They develop novel approaches to make tumor diagnosis more precise and treatment of cancer patients more successful.
The staff of the Cancer Information Service (KID) offers information about the widespread disease of cancer for patients, their families, and the general public. Together with Heidelberg University Hospital, DKFZ has established the National Center for Tumor Diseases (NCT) Heidelberg, where promising approaches from cancer research are translated into the clinic.
In the German Consortium for Translational Cancer Research (DKTK), one of six German Centers for Health Research, DKFZ maintains translational centers at seven university partnering sites. Combining excellent university hospitals with high-profile research at a Helmholtz Center is an important contribution to improving the chances of cancer patients. DKFZ is a member of the Helmholtz Association of National Research Centers, with ninety percent of its funding coming from the German Federal Ministry of Education and Research and the remaining ten percent from the State of Baden-Württemberg.

Heidelberg University Hospital
Heidelberg University Hospital is one of the most important medical centers in Germany; Heidelberg University’s Medical Faculty is one of Europe's most prestigious biomedical research facilities. Their shared objective is the development of innovative diagnostics and treatments and their prompt implementation for the benefit of the patient. The hospital and faculty employ approximately 13,000 individuals and are involved in training and qualification. Every year approximately 65,000 patients are treated as inpatients and 56,000 as day patients in more than 50 specialized clinical departments with around 2,000 beds, with more than 1 million patients being treated as outpatients. Together with the German Cancer Research Center and German Cancer Aid, the Heidelberg University Hospital established The National Center for Tumor Diseases (NCT) Heidelberg as the leading oncology center of excellence in Germany. The Heidelberg Curriculum Medicinale (HeiCuMed) is at the forefront of medical training in Germany. At present 3,700 aspiring physicians and doctors are studying in Heidelberg.