Phase I-II trial on natural beta interferon in chemoresistant and relapsing multiple myeloma

One Waldenström's disease and 16 multiple myeloma patients were administered IFN-beta I.V. at the dose of 6 x 10(6) IU/m2 over 6 hours for 7 days on alternate weeks for a total of 3 cycles, and then continued at the same dose, twice a week, for an additional 24 weeks. Four patients had initially proved to be, and 6 became, resistant to chemotherapy. Disease progressed after chemotherapy was discontinued in another 7 patients: 3 SD and 4 PR. One of the 16 evaluable patients achieved an MR, and 11 experienced brief stabilization of disease (median 14 weeks, range 6-34). In addition, cellular response to IFN-beta was documented by increased B2-microglobulin and neopterin levels, even as early as 24 hours after the 1st IFN injection of the 1st and 2nd cycles. Hemtological and extrahematological toxicity was low despite the fact that 8/16 patients had severely or moderately reduced bone marrow reserve at the beginning of treatment. Since vincristine-adriamycin-dexamethasone and etoposide-dexamethasone-cytarabine-cisplatin combinations achieve high response rates in resistant and relapsing multiple myeloma patients, IFNs alone should be reserved as third-line therapy for those subjects who are resistant to, or not candidates for, these chemotherapeutic regimens. The low toxicity and the modulation of B2-microglobulin and neopterin should encourage studies aimed at defining the optimal antitumor dose of IFN-beta that could be used in combination with conventional chemotherapeutic regimens to improve the response rate in multiple myeloma patients.