Pharmacokinetics of melphalan in myeloma patients undergoing an autograft

Development of a method for clinical pharmacokinetic testing to allow for targeted Melphalan dosing in multiple myeloma patients undergoing autologous transplant

AIMS

High dose melphalan (HDM) and autologous stem cell transplant (ASCT) is standard of care for multiple myeloma (MM), but there is significant variability in melphalan exposure (area under the plasma drug concentration-time curve, AUC) when using body surface area-based dosing. Our aim was to establish a method of pharmacokinetic (PK) testing for real-time melphalan dose adjustments.

METHODS

We performed a prospective PK study of melphalan 140 or 200 mg/m2 in MM patients undergoing ASCT. Twenty MM patients were administered HDM on days -2 and - 1, with PK sampling at 8-10 time points. PK testing was performed on day -2 in all patients, and on day -1 in 5 patients.

RESULTS

Less than 20% interpatient variation in the day -2 and - 1 AUC was observed. The day -2 range in AUC (4.95-11.28 mg h/L) confirmed significant interpatient variability. The hypothetical total dose ranged from 133-302 mg/m2 to achieve the total median AUC. A 4-time point AUC (0, 30, 150 and 240 min) highly correlated with the AUC from the 8-time point schedule. A higher AUC correlated with increased risk of febrile neutropenia (P = .05).

CONCLUSION

Here we outline the methods to establish novel melphalan dosing using PK testing in MM patients undergoing ASCT to target a desired melphalan AUC.

Predictors of increased melphalan exposure correlate with overall survival, nonrelapse mortality, and toxicities in patients undergoing reduced-intensity allogeneic stem cell transplantation with fludarabine and melphalan

The reduced-intensity conditioning regimen, fludarabine and melphalan 140 mg/m² (FM140), is widely adopted in practice. Pharmacokinetic studies report 10-fold interpatient variability in melphalan exposure. We identified low hemoglobin (Hb) and/or creatinine clearance (CrCl), determinants of melphalan pharmacokinetic, as strong predictors of outcomes after high-dose melphalan and autologous transplant. We hypothesized that these variables could predict for outcomes after FM140. Overall survival was shorter in patients with a lower Hb (113 vs. 2536 days; p = 0.004), due to an increased rate of nonrelapse mortality (NRM) (p = 0.0005). Overall survival was also worse in patients with lower CrCl (75 vs. 317 days; p = 0.003), with a significantly worse nonrelapse mortality (p = 0.0023). In a multivariate analysis, a higher Hb and CrCl predicted for better overall survival (p = 0.017). In patients with a lower Hb, the median duration of hospitalization (p = 0.02) and the mean duration of diarrhea (p = 0.008) were longer. In patients with a lower CrCl, the median duration of hospitalization (p = 0.06) and the mean duration of diarrhea (p = 0.0009) longer, and the rate of infection was higher (p = 0.02). We show for the first time that Hb and CrCl represent important determinants of outcomes after FM140, suggesting that pharmacokinetic-directed dosing may be beneficial in achieving optimal outcomes.

Pretransplant hemoglobin and creatinine clearance correlate with treatment-free survival after autologous stem cell transplantation for multiple myeloma

Melphalan is given at a dose of 200 mg/m² (Mel200) prior to ASCT for multiple myeloma (MM). Pharmacokinetic (PK) studies show a high degree of interpatient variability. We aimed to test the impact of clinical factors previously shown to affect melphalan PK such as hemoglobin (Hgb), fat-free mass (FFM), and creatinine clearance (CrCl) on outcomes. Median Hgb (from day -2 to -1) and FFM were grouped as low or high relative to their sample medians, and CrCl was divided into ≥60 or <60 ml/min. In 133 MM patients, median TFS (defined as time from ASCT to initiation of next subsequent line of therapy or death) was longer in patients with lower Hgb (35 vs. 16 months, p = 0.02). Patients with both lower Hgb and CrCl experienced longer TFS compared to those with higher Hgb and CrCl (35 vs. 13 months, p = 0.03). In multivariate analysis, lower hemoglobin, lower CrCl, and a combined low hemoglobin and CrCl were strongly associated with improved TFS. Patients with a lower hemoglobin or creatinine clearance experienced significantly more toxicity. We show for the first time that Hgb and CrCl are important predictors of outcomes after Mel200. PK-directed melphalan dosing may be beneficial in achieving optimal outcomes.

Contribution of Clostridium difficile infection to the development of lower gastrointestinal adverse events during autologous stem cell transplantation

BACKGROUND

Lower gastrointestinal (GI) adverse events (LGAE) are common afflictions of patients undergoing stem cell transplantation (SCT). Unfortunately, the pathophysiology remains poorly characterized. Emerging data suggest a prominent role of intestinal microbiota; however, contributions of pathogenic gut microbiota such as Clostridium difficile are not well defined. We performed a genome-wide association study (GWAS) to investigate clinical and genetic factors associated with development of LGAE.

METHODS

A total of 972 patients undergoing autologous SCT were graded for LGAE based on Common Terminology Criteria for Adverse Events (v 4.0). Germline DNA material was obtained from leukapharesis products and genotyped using Illumina(®) Whole Genome Genotyping Infinium chemistry and HumanOmni1-Quad Bead chips containing over 1.1 million single nucleotide polymorphisms (SNPs) (Illumina, San Diego, California, USA). Statistical models incorporating clinical factors, genetic factors, and a combination of clinical plus genetic factors were utilized to compare patients who developed severe LGAE (grade 2 or above) and others.

RESULTS

Among 972 patients, 459 (47.2%) developed severe LGAE. Baseline hemoglobin and hematocrit, estimated glomerular filtration rate, β2-microglobulin, protocol type, and C. difficile infection (CDI) were associated with severe LGAE on univariate analysis, Genomic comparisons between groups did not reveal any SNPs associated with severe LGAE and neither did incorporation of genetic factors into the clinical model. In addition, 11 candidate SNPs associated with upper GI mucositis were evaluated, alongside clinical factors in a multivariate model. Only CDI was found to be associated with severe LGAE in all models.

CONCLUSION

CDI is a prominent factor in the development of LGAE in patients undergoing autologous SCT.

Incidence and risk factors for lower alimentary tract mucositis after 1529 courses of chemotherapy in a homogenous population of oncology patients: clinical and research implications

BACKGROUND

Lower alimentary tract mucositis is a serious complication of chemotherapy. The aim of the study was to determine the incidence, risk factors, and mortality of lower alimentary tract mucositis in a homogeneous population of patients with newly diagnosed myeloma receiving similar antineoplastic therapy and standardized supportive care.

METHODS

Lower alimentary tract mucositis was evaluated among 303 consecutive patients with myeloma (2004-2007) enrolled in a clinical trial consisting of induction chemotherapy, tandem melphalan-based autologous stem cell transplantation (ASCT), and consolidation. Lower alimentary tract mucositis was defined as neutropenia-associated grade II-IV enteritis/colitis. Pretreatment risk factors were examined including body surface area (BSA), serum albumin (albumin), and estimated creatinine clearance (CrCl). Multiple logistic regression model was used to compute adjusted odds ratio (OR) and 95% confidence intervals (CI).

RESULTS

Forty-seven (15.5%) patients developed lower alimentary tract mucositis during 1529 courses of chemotherapy (including 536 melphalan-based ASCT). Pre-enrollment BSA <2 m² (OR, 2.768; 95% CI, 1.200-6.381; P = .0169) increased the risk for lower alimentary tract mucositis, whereas higher albumin was protective (OR, 0.698; 95% CI, 0.519-0.940; P = .0177). Pretransplant variables associated with lower alimentary tract mucositis were BSA <2 m² (OR, 4.451; 95% CI, 1.459-13.58, P = .0087) and estimated CrCl <60 mL/min (OR, 3.493; 95% CI, 1.173-10.40; P = .0246). Higher albumin level conferred protection (OR, 0.500; 95% CI, 0.304-0.820; P = .0061). No lower alimentary tract mucositis-related death was observed.

CONCLUSIONS

Lower alimentary tract mucositis is not uncommon among a homogenous population of oncology patients undergoing sequential courses of chemotherapy including melphalan-based ASCT but does not contribute to mortality. Lower BSA, renal function, and albumin are associated with increased risk for lower alimentary tract mucositis.