The association of a second primary malignancy with CLL is well known. Epidemiological studies were carried out on large series of CLL patients enrolled in tumor registries participating in the National Cancer Institute Surveillance, Epidemiology, and End Results program. CLL patients were found to have a significantly increased risk, constant over time, of developing second cancers, with an overall observed/expected ratio of 1.2 (46,47). In our series, we recorded an overall incidence of 8.3% with a nonstatistically different rate of second primary cancers in the old and young age groups of (9). The rate of second cancers did not appear to be influenced by therapy. This finding suggests that the disease-related immunodeficiency state of CLL that most likely predisposes to the development of second malignancies is independent of treatment and age. The simultaneous occurrence of a leukemia of the elderly and of a second cancer at a younger age strongly suggests that some patients may have an increased risk of developing a tumor early because of individual predisposing factors.
The incidence of Richter's syndrome in CLL patients recorded in our series (9) and reported by Robertson et al. (48) and by Morrison et al. (49) ranges between 1 and 2.8%. No predictive risk factors for the occurrence of Richter's syndrome have been identified so far. In the Cancer and Leukemia Group B study (47), age did not have a predictive effect on the occurrence of Richter's syndrome. In our series, younger patients showed a Richter's syndrome rate fivefold higher than that of older patients. However, it should be recalled that the rate of lymphomas in the older age group is possibly underestimated, since very old patients with advanced and unresponsive disease are not always surgically biopsied, for ethical reasons. Most of Richter's syndrome occur as a consequence of a clonal transformation from the original CLL cells; a small proportion of cases may occur as a consequence of an immunosuppressive state.
Since younger patients are usually treated with purine analogs, an important point to analyze is whether the immunosuppression caused by purine analogs therapy may facilitate the occurrence of both second cancers and Richter's syndrome. An absence of a relationship between fludarabine and 2-chlorodeoxyadenosine (2-CDA) therapy and a higher occurrence of Richter's syndrome has been reported by Robertson et al. (48), whereas other authors (50) have reported a higher risk of Richter's syndrome in patients receiving fludarabine. In a large study reported by Cheson et al. (51), the rate of second malignancies in CLL patients treated with fludarabine was not increased compared with those never treated with purine analogs. However, the value of these findings is limited by two factors: the immunosuppressive state related to CLL itself and the short patient follow-up.
No information is yet available about the rate of Richter's syndrome and second malignancies occurring after autologous and allogeneic stem cell transplantation.
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