Cancer incidence in patients with systemic lupus erythematosus (SLE) is higher compared with the general population, especially in younger women, according to research results published in Arthritis Care and Research.
Researchers conducted a retrospective, multicenter study using patient data from the SLE Registry of the Spanish Society of Rheumatology. With these data, investigators aimed to estimate cancer incidence in patients with SLE and to analyze the factors associated with cancer onset, differentiating between hormone-sensitive and nonhormone-sensitive cancers.
The study cohort included 3539 patients (90.4% women; mean age at diagnosis, 35 years; mean disease duration, 143 months). In total, 154 patients (4.35%) within the cohort had a cancer diagnosis; 91.0% of these patients were women with a mean age of 40.37±15.70 years. Overall, age at diagnosis, association with Sjogren syndrome, Katz index score, Systemic Lupus International Collaborative Clinics/American College of Rheumatology (SLICC/ACR) Damage Index, and Charlson index were all higher in patients with cancer.
The accumulated rates of incidence of cancer in patients with SLE were 6.31 cases per 1000 patients (95% CI, 4.00-9.45). After stratification by age and sex, the group with women aged >64 years showed the highest number of first cancers (16 cases per 1000 patients; 95% CI, 6.45-32.65). The standardized incidence ratio for cancer was 1.37 (95% CI, 1.15-1.59); the group with women <65 years had the highest standardized incidence ratio rate of 2.38 (95% CI, 1.84-2.91). Among women, the standardized incidence ratio for hormone-sensitive cancer was 1.02, compared with 1.93 for nonhormone-sensitive cancers (95% CI, 0.13-1.91 and 0.98-2.89, respectively).
Breast and gynecologic cancers were the most frequently noted types of cancer (23.4% and 20.1%, respectively), followed by hematologic (75% non-Hodgkin lymphoma) and nonmelanoma skin cancers (11.7%). Colorectal, thyroid, and lung cancers had the lowest rates of incidence (5.20%, 5.20%, and 3.25%, respectively). In a subgroup analysis of patients with SLE and associated Sjogren syndrome, the most frequent cancers were breast (29%), gynecologic (16.1%), and hematologic (16.1%).
Median time to cancer onset was 10 years (interquartile range [IQR], 5.75-17.00 years), which was significantly shorter in women compared with men (9.5 vs 12.5 years; IQR, 5.0-17.0 and 8.75-17.5 years, respectively). In addition, median time was also significantly lower in patients <45 years (8.0 vs 10.9 years; IQR, 5.0-16.0 and 7.0-18.6 years).
Multivariate analysis indicated that SLE diagnostic age and the period of disease evolution were significantly associated with the onset of hormone-sensitive cancers (odds ratio [OR], 1.4 and 1.01; 95% CI, 1.01-1.07 and 1.00-1.01; P =.002 and P <.001, respectively). For nonhormone-sensitive cancers, significant associations were noted between SLE diagnostic age, disease evolution period, SLICC/ACR damage index, and prescription of angiotensin-converting enzyme inhibitors (ORs, 1.04, 1.00, 1.27, and 2.87, respectively.)
Cancer was the fourth leading cause of death (5.5%) in this patient population, after SLE, cardiovascular disease, and infection. Within the study cohort, cancer-related deaths accounted for 10.66% of deaths (19% hematologic cancers, 19% breast cancers, 14.3% lung cancers, and 9.5% colorectal cancers).
One major study limitation was the retrospective nature of the study design.
“Further studies confirming our findings on the difference between [hormone-sensitive and nonhormone-sensitive] cancers are greatly warranted, as is a renewed search for factors that most clearly determine the risk [for] such cancers,” the researchers concluded.
Disclosure: This clinical trial was supported by GlaxoSmithKline, Roche, UCB, Lilly, and Novartis. Please see the original reference for a full list of authors’ disclosures.
Cobo-Ibáñez T, Urruticoechea-Arana A, Rúa-Figueroa I, et al. Hormonal dependence and cancer in systemic lupus erythematosus [published online September 17, 2019]. Arthritis Care Res. doi:10.1002/acr.24068