Bowel cancer is a general term for cancer that begins in the large bowel. Depending on where the cancer starts, bowel cancer is sometimes called colon or rectal cancer. Bowel cancer is one of the most common types of cancer diagnosed in the UK. Most people diagnosed with it are over the age. B causes A. A and B are both caused by a third variable, C. Chance (the correlation is spurious). So how was the causal link between cigarettes and lung cancer established? In the 50s and 60s a large number of studies came out that confirmed the correlation.