Prior Treatment Relates More Strongly to Richter’s Transformation Than ZAP-70, CD38, IgV_H Gene Mutation Status, and Cytogenetic Abnormalities: Findings of an Observational Cohort Study of 962 Patients with CLL.

BACKGROUND: Studies have suggested that patients with CLL are at a significantly increased risk of developing other lymphoid malignancies. Whether the risk of developing a 2^nd lymphoproliferative disorder (LPD) is more strongly related to characteristics of the leukemia cell or to other factors such as prior chemotherapy is unknown. This distinction is important given increasing momentum to pursue early treatment of CLL patients based on recently identified prognostic markers, e.g. ZAP-70, IgV_H mutation status. We used the Mayo Clinic CLL Database (DB) to conduct an observational cohort study to evaluate the relationship between clinical, biologic, and treatment characteristics and the risk of secondary LPD.

METHODS: The Mayo Clinic CLL DB was established in 1999 and included 962 patients at the time of the present analysis. Clinical information regarding date of diagnosis, prognostic parameters, treatment history, disease-related complications, and co-morbidities was abstracted from clinical records on all patients at the time of study enrollment and maintained on an ongoing basis. For the present study, cases of secondary LPD were identified by chart review and cross referencing patient clinic numbers from the CLL DB with the Mayo Clinic Lymphoma and Leukemia/Myelodysplasia databases. Additionally, all clinic numbers were cross-referenced with an electronic hematopathology database that has recorded results of all bone marrow and lymph node biopsies of all Mayo Clinic patients since 1992.

RESULTS: A second LPD was identified in 26 (2.7%) of the 962 CLL patients during a median follow-up of 7.12 years (range 0.1–21.0). The median time from diagnosis to development of secondary LPD was 4.4 years (range 0–19 years). Diffuse large B-cell lymphoma was the most common subtype of secondary LPD (12 of 26 cases). Gender was associated with increased risk of developing 2nd hematologic cancer where 1% of women compared to 3.4% of men (p=0.051) developed a 2nd LPD. Treatment history was also related to development of a 2^nd LPD. 2nd LPD developed among 4% of previously treated CLL patients compared to 2% of untreated patients (p=0.08). Among the 362 patients who were treated for CLL prior to developing a second LPD, the median time to first treatment was shorter for those who developed a 2^nd LPD (2.43 years vs. 6.22 years; p<0.001). No statistically significant association was observed between other clinical or biologic leukemia cell characteristics and development of 2nd LPD including IgV_H gene mutation status, ZAP-70 status, CD38 status, cytogenetic abnormalities by FISH, B2M, stage at diagnosis, or ALC at diagnosis.

CONCLUSIONS: In this observational cohort study, prior treatment demonstrated a stronger correlation with the risk of developing a 2nd LPD than did leukemia cell characteristics including IgV_H gene mutation status, FISH, ZAP-70, B2M, and CD38. This finding suggests Richter’s transformation may relate more to therapy than characteristics of the leukemia cell itself. Until the results of clinical trials evaluating the role of early treatment based on prognostic parameters are available, this result underscores the importance of delaying administration of chemotherapy until patients meet established criteria for treatment.