Secondary Malignancies in CML Patients – Data From the German CML Study IV

The increase of overall survival in chronic myeloid leukemia (CML) requires closer long-term observation in the face of a potential carcinogenicity of tyrosine kinase inhibitors (TKIs). Preclinical studies with imatinib in rats showed neoplastic changes in kidneys, urinary bladder, urethra, preputial and clitoral glands, small intestine, parathyroid glands, adrenal glands, and nonglandular stomach. Two epidemiologic studies on patients with chronic myeloproliferative neoplasms (CMPN) and CML (Frederiksen H et al., Blood 2011; Rebora P et al., Am J Epidemiol 2010) found an increased risk of secondary malignancies compared with the general population independent of treatment. In contrast, in a recent analysis of patients with CML and CMPN treated with TKI (Verma D et al., Blood 2011) a decreased risk of secondary malignancies was reported.

To further elucidate the risk of TKI treated CML patients for the development of secondary malignancies we analysed data of the CML study IV, a randomized 5-arm trial (imatinib 400 mg vs. imatinib 800 mg vs. imatinib 400 mg in combination with interferon alpha vs. imatinib 400 mg in combination with AraC vs. imatinib 400 mg after interferon failure).

From February 2002 to April 2012, 1551 CML patients in chronic phase were randomized, 1525 were evaluable. Inclusion criteria allowed the history of primary cancer if the disease was in stable remission. Forty-nine malignancies were reported in 43 patients before the diagnosis of CML. If relapses occurred within 5 years after diagnosis of primary cancer they were not considered for further analysis. Median follow-up was 67.5 months. Age-standardized incidence rates were calculated from the age-specific rates using the European standard population (1976).

In total, 67 secondary malignancies in 64 patients were found in CML patients treated with TKI (n=61) and interferon alpha only (n=3). Twelve of these patients developed neoplasms after diagnosis of a primary cancer before diagnosis of CML, 5 patients with metastases or recurrence of the first malignancy (range of diagnosis 5–19 years after primary cancer). Median time to secondary malignancy was 2.5 years (range 0.1–8.3 years). The types of neoplasms were: prostate (n=9), colorectal (n=6), lung (n=6), non Hodgkin's lymphoma (NHL; n=7), malignant melanoma (n=5), skin tumors (basalioma n=4 and squamous cell carcinoma n=1), breast (n=5), pancreas (n=4), kidney (n=4), chronic lymphocytic leukemia (n=3), head and neck (n=2), biliary (n=2), sarcoma (n=2), and esophagus, stomach, liver, vulva, uterus, brain, cancer of unknown origin (each n=1). With these numbers the age-standardized incidence rates of secondary malignancies in CML patients were calculated: 534 cases per 100,000 for men (confidence interval [350;718]), and 582 for women (confidence interval [349;817]). The incidence rates of the general population in Germany were 450 and 350 cases, respectively (“Krebs in Deutschland 2007/2008”, 8^th ed., Robert Koch Institute, 2012). The incidence rate of NHLs was higher for CML patients than for the general population but this is not significant.

In our cohort, the incidence rate of secondary neoplasms in CML patients was slightly increased compared to the general population. The most common secondary malignancies in CML patients under treatment were cancers of the skin, prostate, colon, lung and NHL. Since the occurrence of secondary neoplasia increases over time, long-term follow-up of CML patients is warranted.

Müller:Novartis, BMS: Consultancy, Honoraria, Research Funding. Hochhaus:Novartis, BMS, MSD, Ariad, Pfizer: Consultancy Other, Honoraria, Research Funding. Hehlmann:Novartis: Research Funding.