- The frequency of cancer in patients with SLE is between 2.5 and 13.8%. A literature review has identified nine full-length studies that estimated the overall risk of cancer in SLE patients compared with the general population. Five of them have not noted an increased risk for the development of overall cancers among SLE patients compared with the general population. One study identified a 30% increased risk (SIR or 1.3) for occurrence of cancer among 1585 SLE patients followed over 10,807 patient-years. Taken together, it is controversial whether the risk of all cancers is increased in SLE patients compared with the general population. Increased risk of lymphatic malignancies has been shown in multiple large series of SLE patients, but SLE is not associated with an increased risk for the development of most of the solid tumors. Pathogenic mechanisms involved with the development of lymphoproliferative malignancies in association with SLE include a common etiologic agent for both diseases, environmental factors as the use of cytotoxic or immunosuppressive agents, genetic variables, and immunologic factors as immunoregulatory disturbances of the immune system.