Cereblon (CRBN) has been identified as a primary target of immunomodulatory drugs and is considered a biomarker for the prediction of outcomes after thalidomide- or lenalidomide-based treatments. In this study, we evaluated CRBN expression in bone marrow (BM) tissue at diagnosis and investigated the relationship between CRBN expression and treatment outcomes after thalidomide- or bortezomib-based front-line therapies in 89 elderly patients with multiple myeloma (MM). CRBN expression at the time of diagnosis was evaluated with immunohistochemical (IHC) staining for myeloma cells in paraffin wax-embedded BM tissue. CRBN-immunostained slides were scored by intensity and diffuseness, and a total score of >6 was defined as CRBN-positive (CRBN(+)). Thirty-eight patients (45.2 %) were CRBN(+). Among patients treated with thalidomide-based regimens, CRBN(+) patients showed a better treatment response than did CRBN-negative patients (35.0 vs. 11.8 % complete response rate, respectively; HR = 4.038, P = 0.137). During a median follow-up of 31.8 months, patients treated with bortezomib-based regimens had a longer time to progression (TTP) than did patients treated with thalidomide-based regimens (15.6 vs. 13.2 months, respectively; P = 0.047), but early mortality occurred frequently in patients treated with bortezomib-based regimens. Additionally, there was no significant difference in survival outcomes between thalidomide- and bortezomib-based regimens in CRBN(+) patients (median TTP, 13.8 vs. 15.6 months, respectively; P = 0.842 and median OS, 39.3 vs. 30.1 months, respectively; P = 0.074). These data suggest that thalidomide-based regimens are as effective as bortezomib-based regimens in elderly patients with MM who are CRBN(+). Thus, CRBN positivity, by IHC staining, may be useful in deciding appropriate treatment options in elderly patients with MM.
Keywords: Cereblon; Elderly; Multiple myeloma.