A patient's remarkable recovery from the common blood cancer multiple myeloma several years ago has drawn the attention of researchers, who were stunned by the fact the patient was treated for a completely different disease.

Interest in the potential connection has now led a Spanish and French team to discover that hepatitis B virus (HBV) and hepatitis C virus (HCV) are linked to the development of multiple myeloma and earlier non-cancerous stages known as monoclonal gammopathies.

Their recent study confirms that detecting hepatitis B and C early could help doctors prevent monoclonal gammopathies from progressing into cancer by treating these viral infections.

"We demonstrate that antiviral therapy improves the survival of HBV-positive multiple myeloma patients," biomedical scientist Alba Rodríguez-García from the Hematological Malignancies Clinical Research Unit in Spain and colleagues write in their published article.

"Our study also confirms in a large cohort that antiviral treatment improves multiple myeloma outcome for HCV-infected patients."

Multiple myeloma is a cancer that develops in the bone marrow from abnormal plasma cells – a type of white blood cell that normally makes antibodies to fight infections. The disease is characterized by multiple tumors.

Abnormal plasma cells proliferate and make too much of one antibody, which varies in each case. Called a myeloma protein, this antibody can be used as a biomarker to indicate the cancer, or a similar condition, is present.

Before multiple myeloma, there are earlier stages called monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM).

Research and treatment for multiple myeloma have progressed, but the disease is still considered incurable.

Some studies have linked chronic exposure to specific substances (viral byproducts, for instance) to MGUS and multiple myeloma. Chronic lymphocytic leukemia and lymphoma – two diseases that involve receptors which are needed to recognize antibodies – have also been linked to long-term infections.

Researchers have also found links between multiple myeloma and infections with other viruses such as HIV, or Epstein-Barr virus. Figuring out what the patient's antibodies are trying to attack can help control the disease.

The same group previously published a study in 2022 involving nine hepatitis C patients with monoclonal gammopathy. Those who were treated with antiviral medication showed greater improvement in multiple myeloma or monoclonal gammopathy compared to those who were not.

Even more encouraging – antiviral medication put one of those multiple myeloma patients into long-term complete remission, reportedly for at least four years at the time.

Rodríguez-García and team's new study involved 45 patients with monoclonal gammopathy and hepatitis B. In 36.7 percent of cases where they were able to detect the type of excessive antibodies being produced, it specifically targeted HBV, which suggests their gammopathy was driven by HBV. Upon receiving antiviral treatment, two of those patients' gammopathy did not progress.

They then looked at a larger group of over 2,500 multiple myeloma patients with either hepatitis B or C. In both groups, they found that those who received antiviral treatment had a higher chance of survival.

"This study demonstrates the importance of antiviral treatments for patients with HBV-or HCV-driven clonal gammopathies, including multiple myeloma," the authors conclude.

"Anti-viral therapy should be prescribed as early as possible in the development of HBV- or HCV-linked clonal gammopathies, ideally at the MGUS stage."

The research has been published in Haematologica.