First-degree relatives are parents, children, brothers or sisters – those who share one-half of the same genes. In the largest ever study that included men and women, researchers concluded lung cancer patients and their affected relatives share an inherited genetic susceptibility for cancer development.

Close to 5,000 persons took part in the study at the M.D. Anderson Cancer Center at the University of Texas. Families including lung cancer patients were compared with families without smokers or lung cancer. About 2,500 persons were included in each group.

The study group (“case”) looked at whether close relatives of 316 lung cancer patients who never smoked would develop cancer. The “control” group involved an equal number of patients who had never smoked and had not developed lung cancer and their close relatives. Average age of both case  and control group participants was 61, and each patient had approximately eight first-degree relatives taking part.

The study’s main conclusion was that familial factors are important in the general development of cancer because genes control pathways common to a number of cancers.

Researchers say their study strongly suggests the following conclusions:

• First-degree relatives of cancer “cases” had a 25% increased risk of developing any type of cancer, compared to controls. Cancers diagnosed in first degree relatives included melanoma, colorectal, head and neck cancer, lung, prostate and breast cancers.
• Case relatives were about 10 years younger when diagnosed with cancer, compared to control group relatives.
• A 44% excess risk of cancers occurring before the age of 50 took place among case relatives.
• A six-fold risk of developing lung cancer at an early age (before 50) was found in case relatives.
• A 68 percent increased risk of developing lung cancer was found in relatives of case patients.
• Mothers of case patients had more than twice the risk of developing breast cancer.

Cancer has long been found to occur in family clusters. This study involving a unique group of lung cancer patients and their relatives helps to explain why this is so.

Source:  ScienceDaily.Com