Second cancer risk in hairy cell leukemia: analysis of 350 patients.

Purpose: The discovery of effective therapy for hairy cell leukemia (HCL) has increased the relevance of long-term outcome. We have therefore examined the incidence of second cancers.
Patients and Methods: Data on 350 HCL patients was obtained from the M.D. Anderson Cancer Center Cancer Registry's computerized data base and from chart review. Standardized incidence ratios (SIRs) and standardized mortality ratios (SMRs) (observed/expected [O/E]) were calculated with the expected number determined using age, sex, and calendar-year-specific rates from the Connecticut Tumor Registry and from national mortality data, respectively.
Results: The median age of the patients was 50 years and the median follow-up duration was 6 years. Twenty-six patients developed a second cancer at least 6 months after the HCL diagnosis (O/E ratio, 1.34; P = .08). There was no excess of malignancy among patients treated with interferon alfa (IFN-alpha; P = .27), 2-chlorodeoxyadenosine (2CDA; P = .37), or deoxycoformycin (DCF; P = .7). However, an excess of myeloma-related neoplasms (O/E, 13.04; P < .001) and lymphomas (O/E, 8.7; P = .03) was observed. Survival from the advent of systemic therapy for HCL was better than before this time (P = .0009). Nevertheless, mortality remained excessive (O/E, 6.17; P < .001), mainly because of HCL-related infections and secondary malignancy.
Conclusion: Among 350 patients with HCL, there was an increase in the number of second cancers; however, it did not reach statistical significance and was not associated with therapy. The incidence of lymphoid neoplasms was significantly higher than expected. Survival since the advent of effective systemic therapy was excellent, although excess mortality was still observed.