Higher incidence of injection site reactions after subcutaneous bortezomib administration on the thigh compared with the abdomen.

Subcutaneous (sc) rather than intravenous administration of bortezomib (Bor) is becoming more common for treating multiple myeloma (MM) because scBor results in lower incidence and severity of peripheral neuropathy and has equivalent efficacy. Bor is an irritant cytotoxic agent when it leaks out; therefore, it is recommended that injections of scBor should be rotated among eight different sites on the abdomen and thigh. However, detailed information about injection site reaction (ISR) has not been sufficiently documented. We retrospectively analyzed the incidence and severity of ISR following scBor administration in 15 Japanese patients with MM. Grade 1 ISR occurred following 40 of 158 (25.3%) scBor injections in ten patients, whereas grade 2 ISRs occurred following seven injections (4.4%) in five patients. Five patients did not develop ISR. Of note, grade 2 ISR was documented in 6 of 65 (9.2%) thigh injections but only in 1 of 93 (1.1%) abdominal injections. These data show that grade 2 ISRs were more common in the thigh compared with the abdomen possibly because the thigh contains lesser adipose tissue than the abdomen. Grade 2 ISRs resolved without any sequela within a median of 7 d. scBor administration on the abdomen instead of the thigh should be considered, especially for emaciated patients, because ISR rapidly resolves within the interval before the next injection even if it occurs.