The aim of this study was to assess the effect of systemic chemotherapy
on the monoclonal protein levels of patients with solid tumors who also
have a monoclonal gammopathy of undetermined significance (MGUS). All
patients with solid tumors who were referred to our department for
consideration of systemic chemotherapy were evaluated with serum protein
electrophoresis (SPEP) for the presence of MGUS. When MGUS was confirmed
with immunofixation, serial SPEP was performed during and after
completion of chemotherapy. Over a 6-year period, 21 patients with solid
tumors and MGUS were prospectively identified and assessed. At least
50% reduction of serum monoclonal protein was noted in 4 of 11 patients
treated with paclitaxel or docetaxel with a platinum analogue and in 5
of 7 patients who received an irinotecan-containing regimen. Our data
indicate that in MGUS patients treated with irinotecan-containing
chemotherapy regimens, a high incidence of reduction in their monoclonal
protein levels is observed. Since topotecan, another topoisomerase I
inhibitor, has some activity in multiple myeloma, further evaluation of
irinotecan may be warranted. Evaluation of larger numbers of MGUS
patients treated with chemotherapy for their underlying malignancy may
help identify “in vivo” potentially active agents and regimens for
patients with overt myeloma