Is cancer hereditary?
For what concerns family history, there is also a lot of confusion between background noise and danger signals; in other words, when is it right to be worried? For example, if the mother and maternal grandmother of a 25-year-old woman both developed breast cancer at the ages of 40 and 50 years, respectively, this means that the 25-year-old has a high probability of developing breast cancer at an early age. This signal is so strong that genetic counseling and appropriate genetic tests must be carried out in order to calculate the risk for the young woman and other members of the family and to take preventive measures.
By contrast, the mere fact that a grandfather had lung cancer and an uncle had bladder cancer is no cause for alarm and does not mean that other family members need to be tested.
The difference between these two situations lies in the fact that there is a hereditary tendency to develop certain tumors, but not others. In some tumors, such as those of the breast, colon, uterus and ovary, hereditary plays a major role in a high percentage (5-20%) of cases in all other tumors, this percentage is very low and concerns very rare cases.
In general , the warning signal comes from the presence of at least one of the following conditions in family members:
- two or more cases of solid tumors (leukemias and lymphomas do not count) in the same side of the family
- one or more cases of solid tumor at young age
- more than one cancer in the same patient
In this field, the most skilled specialist is the medical geneticist (as yet, there are few in the health service), who has three tasks:
- to recognize the possibility of heredity, on the basis of family history, and to prescribe appropriate genetic tests (BRCA1, BRCA2, APC, MSI etc). These tests are very complex and time-consuming, and are carried out on the patient’s tumor or blood and on the blood of the family member;
- to interpret the result of the test. Results maybe positive or negative, and positivity may be manifested in various ways, each of which prompts different actions and preventive strategies. Naturally, it is always possible that the test might yield results that cannot be interpreted, and so prove useless;
- to communicate all of this effectively, which is no easy task, given the complexity of the issue.
As there are few specialists in the medical genetics of tumors, a good first step to take is to consult an oncologist. In every team of oncologists, there is usually someone who can point these individuals in the right direction, at least in the early phases.