A review of the clinical studies in which
interferons have been involved has shown that they may have a role in the treatment of
multiple myeloma. Twelve studies, each of which involved at least 10 evaluable cases (352 in total) with various dose schedules involving leukocyte, lymphoblastoid and recombinant alpha-IFNs, reported 8-33% objective responses. The response duration was rather short but, in a few cases, it lasted for more than a year. In addition to a decrease in the levels of M-
protein and/or urine
Bence-Jones protein, a decrease in the number of plasma cells in the bone marrow, disappearance of bone
pain, healing of bone lesions, increase of
hemoglobin and/or restoration of normal
immunoglobulins were observed. Higher doses of recombinant alpha-
interferons seemed to exert a stronger effect. No clear difference in response rate was observed between myeloma which had been previously treated and that which was not treated. At least clinically, therefore, there seems to be no cross-resistance between alpha-
interferons and conventional anti-
tumor drugs. A randomized study comparing low-dose
leukocyte interferon with intermittent high-dose
melphalan-
prednisone has given a lower response rate for
interferon. Beta- and gamma-
interferons have not yet been extensively studied. They have been used at low doses producing an objective response in 7% of 68 and 2% of 45 evaluable cases, respectively. Since the myelosuppression of
interferons is transient and, after discontinuation of
interferon therapy, peripheral blood cells usually recover within a week, it may be possible to use
interferon in combination with agents that have strong myelosuppressive effects provided there is no synergism.