Malignancy Risk in IgG4-RD: Interpreting Conflicting Evidence

"Malignancy Risk in IgG4-RD: Interpreting Conflicting Evidence" takes up a question that has divided the field.

Dr. Katz explains that the malignancy debate is heated because the answer remains unknown. Several cohorts show higher malignancy prevalence, meaning patients more often have a cancer history than people without the disease. Less clear is whether patients face higher risk after disease onset. A previous cancer does not change disease management. Future risk, however, matters greatly to them.

Data on post-onset risk are mixed, and many studies have important limitations. Detection bias is a major concern. Extensive imaging at diagnosis may uncover cancers that would otherwise have remained hidden for years. Some studies do not separate existing cancers from new ones. Claims-based studies showing higher incidence cannot easily separate the disease itself from treatment effects. Some treatments used in IgG4-related disease, such as cyclophosphamide, are known to increase cancer risk.

His center studied malignancy risk from the first clinical signs of disease rather than diagnosis. Reassuringly, it found no increased risk. He notes that it is the largest study of its kind but is single-center. Given conflicting results, larger longitudinal studies are needed.

In his practice, imaging monitors disease activity only. Evidence does not support extra cancer surveillance. He recommends routine, age-appropriate cancer screening. Pancreatic imaging is an exception in practice. Some data suggest autoimmune pancreatitis may raise pancreatic cancer risk, though findings conflict. Chronic gastrointestinal inflammation is linked to local cancer, which supports continued pancreatic imaging, as most clinicians already do.

Dr. Della Torre agrees about study limitations. His retrospective cohort showed a slight increase in malignancy in the 3 years around diagnosis. Notably, his team has never seen cancer arise in an organ affected by IgG4-related disease. He suggests that treatment may suppress local inflammation that might otherwise promote cancer. He has seen no dominant tumor type, so he does not use disease-specific cancer screening.

In "New International IgG4-RD Guidelines and the Road Ahead," the panel will close the series with a look at new international guidelines and what may make the greatest difference for patients.