What is changing in the natural history of chronic lymphocytic leukemia?

In the last few years there has been a trend towards an improvement in overall survival of patients with chronic lymphocytic leukemia (CLL). Studies based on tumor registries of the general population or including patients referred to hematologic institutions have analyzed reasons for these changes. However, results need to be validated on independent series.

We retrospectively evaluated 518 CLL patients diagnosed at our institution between January 1970 and December 1998. In this cohort of patients we looked at characteristics affecting natural history such as age and sex distribution, stage at diagnosis, survival probability and impact of the disease status on the actuarial survival. Trends in these variables were analyzed after splitting the whole series into three groups according to the period in which the diagnosis was made. Group I consisted of 75 patients diagnosed between 1970 and 1979, group II consisted of 149 patients diagnosed in the period 1980--1989, group III was composed of 293 patients diagnosed between 1991 and 1998.

Age and sex distribution did not reflect different periods of diagnosis. The proportion of patients in whom diagnosis was established in low clinical stage (stage A) was higher in the group III (72%) than in groups I or II (26.3% and 50.3%, respectively) (p < 0.0001). Differences in the stage distribution affected life-expectancy which was longer for patients diagnosed in the nineties (median survival, 93 months) than in those diagnosed in the eighties (median survival, 54 months) or in the seventies (median survival, 38 months) (p < 0.0001). Finally, survival analyses by stage showed an improvement of life-expectancy when dealing with patients of high risk category (p =0.005).

CLL patients diagnosed in the last decade enjoy the best clinical outcome, mostly as a result of a greater proportion of patients in the low-risk clinical stage and a relatively longer survival of the high risk group. It is not clear whether these changes represent true modifications of the natural history of CLL. At the beginning of the third millennium CLL continues to be a fatal disease with a significant impact on life-expectancy.