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Original Contribution
December 14, 2011

Cancer Risk Among Patients With Myotonic Muscular Dystrophy

Author Affiliations

Author Affiliations: Clinical Genetics Branch (Drs Gadalla, Mueller, and Greene), Biostatistics Branch (Dr Pfeiffer), Infections and Immunoepidemiology Branch (Dr Shebl), Division of Cancer Epidemiology and Genetics, Medical Oncology Branch (Dr Landgren), Center for Cancer Research, Cancer Prevention Fellowship Program (Dr Gadalla), National Cancer Institute, National Institutes of Health, Bethesda, Maryland; Division of Epidemiology, Department of Epidemiology Research, Statens Serum Institut, Denmark (Drs Lund, Wohlfahrt, and Melbye and Ms Gørtz); Department of Neurology, Neuromuscular Disease Center, University of Rochester Medical Center, Rochester, New York (Dr Moxley and Mr Hilbert); and Division of Hematology, Department of Medicine, Karolinska University Hospital Solna and Karolinska Institutet, Stockholm, Sweden (Drs Kristinsson and Björkholm).

JAMA. 2011;306(22):2480-2486. doi:10.1001/jama.2011.1796

Context Myotonic muscular dystrophy (MMD) is an autosomal-dominant multisystem neuromuscular disorder characterized by unstable nucleotide repeat expansions. Case reports have suggested that MMD patients may be at increased risk of malignancy, putative risks that have never been quantified.

Objective To quantitatively evaluate cancer risk in patients with MMD, overall and by sex and age.

Design, Setting, and Participants We identified 1658 patients with an MMD discharge diagnosis in the Swedish Hospital Discharge Register or Danish National Patient Registry between 1977 and 2008. We linked these patients to their corresponding cancer registry. Patients were followed up from date of first MMD-related inpatient or outpatient contact to first cancer diagnosis, death, emigration, or completion of cancer registration.

Main Outcome Measures Risks of all cancers combined and by anatomic site, stratified by sex and age.

Results One hundred four patients with an inpatient or outpatient discharge diagnosis of MMD developed cancer during postdischarge follow-up. This corresponds to an observed cancer rate of 73.4 per 10 000 person-years in MMD vs an expected rate of 36.9 per 10 000 person-years in the general Swedish and Danish populations combined (standardized incidence ratio [SIR], 2.0; 95% CI, 1.6-2.4). Specifically, we observed significant excess risks of cancers of the endometrium (n = 11; observed rate, 16.1/10 000 person-years; SIR, 7.6; 95% CI, 4.0-13.2), brain (n = 7; observed rate, 4.9/10 000 person-years; SIR, 5.3; 95% CI, 2.3-10.4), ovary (n = 7; observed rate, 10.3/10 000 person-years; SIR, 5.2; 95% CI, 2.3-10.2), and colon (n = 10; observed rate, 7.1/10 000 person-years; SIR, 2.9; 95% CI, 1.5-5.1). Cancer risks were similar in women and men after excluding genital organ tumors (SIR, 1.9; 95% CI, 1.4-2.5, vs SIR, 1.8; 95% CI, 1.3-2.5, respectively; P = .81 for heterogeneity; observed rates, 64.5 and 47.7 per 10 000 person-years in women and men, respectively). The same pattern of cancer excess was observed first in the Swedish and then in the Danish cohorts, which were studied sequentially and initially analyzed independently.

Conclusion Patients with MMD identified from the Swedish and Danish patient registries were at increased risk of cancer both overall and for selected anatomic sites.