I have also reviewed the question of 2nd cancers in CLL.

The most recent papers conclude that there is an increased risk of other cancers in CLL, putting the risk at 1.2 times normal, but with very small confidence intervals, which means that there is a small but definite risk of a second cancer.

However, there are some grounds for doubting this. 1. Many of these cancers were diagnosed co-incidentally with the CLL. We know that the commonest reason for diagnosing CLL is that the patient has a blood test for some other reason. If he or she had not had the test the CLL would not have been diagnosed. Consequently there must be many people out there who have never had a blood test who have got CLL, but because many cases of CLL never become clinically relevant, they will never find out that they have CLL. Now everybody diagnosed with cancer gets a blood tests. So comparing patients with cancer with the general population for the incidence of CLL is unfair since only the former will definitely have a blood test. 2. Patients developing cancer often fel ill for months or years before the cancer is diagnosed. During this time they are likely to have a blood test. 3. Patients with CLL are more likely to have a physical than the general population and therefore if there is any cancer to find, it will be picked up. this is particularly true with skin cancer (especially basal cell cancer) which often goes undiagnosed unless a physician's attention is drawn to it.

But some cancers seem to have a specially high risk in CLL. This includes, skin cancers including melanoma, kidney cancer and Hodgkin's disease. These cancers are also commoner in patients who have had transplants or on immunosuppressive drugs. People have suggested that they might have a viral origin. One cancer with a definite viral origin, Kaposi's sarcoma, is definitely commoner in CLL than in the general population.