medwireNews: Among patients with systemic lupus erythematosus (SLE), the risk for cancer may be increased in older patients, men, and those who smoke, suggests an analysis of data from an international cohort.
Sasha Bernatsky (McGill University, Montreal, Quebec, Canada) and co-authors investigated the factors influencing the risk for cancer among 1668 patients who presented with new-onset SLE, between 1999 and 2011, to one of 33 centers spanning across North America, Europe, and Asia.
Over a median follow-up of 9 years, 65 patients developed cancer, equating to 4.3 events per 1000 patient–years, with the most common types being breast (n=15), non-melanoma skin (n=10), lung (n=7), and hematologic (n=6) cancer.
In multivariate analysis, older age at SLE diagnosis was associated with a significantly elevated risk for any type of cancer, at a hazard ratio (HR) of 1.05, and female patients were significantly less likely to develop any type of cancer than male patients, at an HR of 0.47.
The fact that older patients and men had a higher risk for cancer “may be, at least in part, because these demographic groups are at greater cancer risk in the general population,” note the investigators.
Half of the cancers occurred in smokers, including all of the patients who developed lung cancer. This meant that the effects of never smoking could not be compared in lung cancer patients, but the researchers calculated that smoking at least 15 cigarettes a day significantly increased the risk, at an HR of 6.64. The authors emphasize that smoking “is a key modifiable risk factor for lung cancer in SLE.”
Patients who had previously received cyclophosphamide were at a significantly increased risk for non-melanoma skin cancer (HR=15.3), consistent with existing knowledge that “non-melanoma skin cancers may be triggered by immunosuppressive drugs, for example in organ transplant populations.”
On the other hand, patients who received antimalarial drugs were significantly less likely to develop non-melanoma skin cancer (HR=0.23) and breast cancer (HR=0.28).
Bernatsky et al looked at whether other drugs, including methotrexate, mycophenolate, and biologic DMARDs, were associated with cancer risk, and although “[n]o other drug effects were clearly seen,” they point out that “confidence intervals around many estimates were relatively imprecise.”
They add: “Interestingly, none of the lung cancer cases had been exposed to cyclophosphamide or methotrexate, and all had been exposed to antimalarial agents for at least 5 years; this precluded us being able to calculate specific estimates of risk for lung cancer for these agents.”
High disease activity, specifically scoring within the highest quartile on the SLE Disease Activity Index, significantly decreased the risk for breast cancer, at an HR of 0.10, whereas it significantly increased the risk for hematologic cancer, at an HR of 7.14.
“These findings not only help us better understand cancer risk in SLE, but also suggest potential approaches to improve the cancer risk profile in SLE, and provide future directions for research,” say Bernatsky et al in Arthritis Care & Research.
They continue: “Longer follow-up would also allow more precise estimation of the effect of multiple sequential or combined immunosuppressive drug exposures and new drug exposures, including biologic therapies.”
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