Patients with chronic myeloid leukaemia (CML) who use the tyrosine kinase inhibitor (TKI) imatinib may be three to four times more likely to develop non-Hodgkin's lymphoma (NHL) than the general population, study findings indicate.
The researchers could not, however, find an increased incidence of any other secondary malignancies in their analysis of 1525 patients with chronic phase CML who took part in the CML Study IV.
Susanne Sauẞele (Medizinische Fakultä̈t Mannheim der Universitä̈t Heidelberg, Germany) and team undertook the study to address growing concerns over long-term carcinogenicity associated with TKIs and contradictory reports on the incidence of secondary malignancy in CML patients.
They identified 67 secondary malignancies in 64 CML patients treated with TKIs (n=61) and interferon-α only (n=3) during a median follow-up period of 67.5 months.
Of these patients, eight were in complete cytogenetic remission and 31 were in major molecular remission when the secondary malignancy was diagnosed, a median of 2.4 years after the initial CML diagnosis.
The most common secondary malignancies identified were prostate cancer (n=9), NHL (n=7), colorectal and lung cancer (n=6 each), malignant melanoma (n=5), non-melanoma skin tumours (n=5) and breast cancer (n=5).
The researchers report in Leukemia that the rates of prostate, colorectal, breast, pancreatic and kidney cancers and malignant melanoma did not differ significantly between the CML patients and the general German population, with standardised incidence ratios (SIRs) ranging from 0.49 for colorectal cancer in men to 3.33 for kidney cancer in women.
However, the number of cases of NHL observed in the CML study IV cohort was significantly higher than the expected number of NHL cases in the matched German population. Specifically, the SIR was 3.33 for men and 4.29 for women.
Sauẞele et al note that one of the seven NHL cases was a recurrence after 7 years, while another occurred in a patient with a previously documented prostate cancer. They also point out that three of the seven cases were low-grade lymphomas that could easily be missed in the general population not undergoing the same degree of monitoring as the study cohort.
The authors conclude that "[o]verall, our data do not support an increased risk for secondary malignancies in CML patients treated with imatinib".
However, they add that "the increased SIR for NHL has to be considered and long-term follow-up of CML patients is warranted, as the rate of secondary malignancies may increase over time."
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