If the body is under a lot of stress, ill or subjected to substances that alter the cells, such as smoking or smokers, large amounts of alcohol, or some industrial chemicals, then it is fighting a tough battle. The immune system is a well-organized defence mechanism, but like everything else, it can only take so much. As a person ages, the immune system becomes slower to respond to threats. It cannot deliver the punch as well as it could when it was only 18. This means that cancers develop and are not detected in time to be eliminated by the body.
Elimination requires surgery and medications.
The signs and symptoms of cancer are varied. In lung cancer, by the time there are symptoms, it is unfortuantely usually to late for medicine to be of much help except in pain relief. This is only one of the many reasons that it is important to have a yearly medical check up. An annual check-up will reveal any early warning signs. If there is a hint of something of concern, your family doctor will look into it further, ordering the required tests.