Impact of Plerixafor Use at Different Peripheral Blood CD34+ Thresholds on Autologous Stem Cell Collection in Patients with Multiple Myeloma.

Patients with multiple myeloma (MM) scheduled for autologous stem cell transplantation must undergo autologous stem cell mobilization; unfortunately, however, many do not obtain an adequate collection yield. Despite the availability of plerixafor, its widespread and uniform use is limited by its cost, and consequently, many institutions have adopted various risk-adapted algorithms. We report our mobilization experience as we have modified our plerixafor algorithm to a more liberal one, with the expectation of greater collection efficiency and mobilization success with higher plerixafor use. A total of 344 mobilization attempts were analyzed over 3 time periods and using 3 different peripheral blood CD34+ cell counts to guide plerixafor use: <15/µL (n = 66), <20/µL (n = 130), and <40/µL (n = 148). The primary endpoints were evaluation of changes in mean plerixafor utilization and apheresis days and assessment of the impact on overall mobilization costs. Secondary endpoints were a description of the impact of lenalidomide use on mobilization and evaluation of the rate of mobilization failure. We found that mean plerixafor use increased from 1.32 to 1.65 to 1.74 doses per mobilization (P = .026) and the mean days of apheresis decreased from 2.15 to 2.17 to 1.89 days per mobilization for the <15/µL, <20/µL, and <40/µL cohorts, respectively (P = .011). The combined cost of plerixafor and apheresis procedures at a threshold of 40/µL is close to that at a threshold of 15/µL, while saving 26 apheresis days per 100 patients. In general, there were low rates of mobilization failure across all thresholds. Patients who received more than 6 cycles of lenalidomide demonstrated impaired mobilization and required more apheresis sessions (P < .013) and greater plerixafor use (P < .001) to achieve target stem cell yields. Overall, using plerixafor in patients with MM, with a day 4 pCD34 count of <40/µL is a reasonable and cost-effective strategy to optimize apheresis utilization.

Intestinal pseudo-obstruction caused by diltiazem in a neutropenic patient.

OBJECTIVE: To describe a case of diltiazem-induced intestinal pseudo-obstruction in a neutropenic patient. CASE SUMMARY: A 74-year-old male with newly diagnosed acute myelogenous leukemia developed atrial fibrillation on day 12 of induction chemotherapy. He was initially treated with diltiazem 5 mg intravenously every 5-10 minutes for 5 doses and an amiodarone 150-mg loading dose intravenously. Diltiazem 30 mg orally 4 times daily and amiodarone continuous infusion were started thereafter. Amiodarone therapy was discontinued after one day due to an untoward adverse effect. The diltiazem dose was then escalated. By day 14, the patient was receiving diltiazem 120 mg orally 4 times daily. On day 15, he developed increasing abdominal distention with hyperactive bowel sounds. On day 16, a radiographic examination showed multiple dilated loops of both the small and large bowel representing possible intestinal pseudo-obstruction; diltiazem was discontinued that day. Starting on day 18, the patient showed recovery of intestinal pseudo-obstruction without intervention. No further GI complications developed during his remaining hospital course. DISCUSSION: Intestinal pseudo-obstruction is usually associated with underlying medical conditions such as trauma, infection, cardiac disease, and after surgery. Medications rarely cause such a condition. Detailed examination of the patient's record indicated neither infection nor other medications contributed to the development of intestinal pseudo-obstruction. Additionally, a radiographic examination ruled out neutropenic enterocolitis, a common gastrointestinal complication in neutropenic patients. Use of the Naranjo probability scale indicated a probable relationship between pseudo-obstruction and diltiazem in this patient. CONCLUSIONS: Although calcium-channel blockers rarely cause intestinal pseudo-obstruction, clinicians must be aware of this serious but reversible adverse effect.