Multiple myeloma can be regarded as model disease for quantification of
tumor mass, investigation of
tumor cell kinetics and of
tumor response to
therapy. The quantification of the
tumor cell number allows evaluation of prognosis and monitoring of disease as well as of
therapy induced responses. Treatment of
multiple myeloma is primarily based on the alkylating drugs
cyclophosphamide and
melphalan. In recent years other
cytostatic substances, also effective in the treatment of this disorder have been introduced. However, the sensitivity determination of the individual myeloma stem cells seems to be the only possible method which possibly increases the response rate significantly. In accordance with these considerations we have, in preliminary clinical investigations, observed a good correlation between the in vitro determined
cytostatic drug sensitivity and the in vivo response to
therapy. Further progress in the treatment of
multiple myeloma is to be expected with the introduction of
interferon into the therapeutic regimen. Administration of this
glycoprotein has resulted in significant reduction of
tumor mass in more than half of all patients treated up to this time.