Worse capecitabine treatment outcome in patients with a low skeletal muscle mass is not explained by altered pharmacokinetics

Laura Molenaar-Kuijsten*, Bart Albertus Wilhelmus Jacobs, Sophie Alberdine Kurk, Anne Maria May, Thomas Petrus Catharina Dorlo, Jacob Hendrik Beijnen, Neeltje Steeghs, Alwin Dagmar Redmar Huitema

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Background: A low skeletal muscle mass (SMM) has been associated with increased toxicity and shorter survival in cancer patients treated with capecitabine, an oral prodrug of 5-fluorouracil (5-FU). Capecitabine and its metabolites are highly water-soluble and, therefore, more likely to distribute to lean tissues. The pharmacokinetics (PK) in patients with a low SMM could be changed, for example, by reaching higher maximum plasma concentrations. In this study, we aimed to examine whether the association between a low SMM and increased toxicity and shorter survival could be explained by altered PK of capecitabine and its metabolites. Methods: Previously, a population PK model of capecitabine and metabolites in patients with solid tumors was developed. In our analysis, we included patients from this previous analysis for which evaluable abdominal computed tomography (CT)-scans were available. SMM was measured on CT-scans, by single slice evaluation at the third lumbar vertebra, using the Slice-o-Matic software. The previously developed population PK model was extended with SMM as a covariate, to assess the association between SMM and capecitabine and metabolite PK. Results: PK and SMM data were available from 151 cancer patients with solid tumors. From the included patients, 55% had a low SMM. No relevant relationships were found between SMM and the PK parameters of capecitabine and, the active and toxic metabolite, 5-FU. SMM only correlated with the PK of the, most hydrophilic, but inactive and non-toxic, metabolite α-fluoro-β-alanine (FBAL). Patients with a low SMM had a smaller apparent volume of distribution and lower apparent clearance of FBAL. Conclusions: No alterations in PK of capecitabine and the active and toxic metabolite 5-FU were observed in patients with a low SMM. Therefore, the previously identified increased toxicity and shorter survival in patients with a low SMM, could not be explained by changes in pharmacokinetic characteristics of capecitabine and metabolites.

Original languageEnglish
Pages (from-to)4781-4789
Number of pages9
JournalCancer Medicine
Volume10
Issue number14
DOIs
Publication statusPublished - Jul 2021

Keywords

  • body composition
  • capecitabine
  • pharmacokinetics
  • skeletal muscle mass
  • Humans
  • Middle Aged
  • Neoplasms/drug therapy
  • Fluorouracil/pharmacokinetics
  • Male
  • Tomography, X-Ray Computed
  • Treatment Outcome
  • Prodrugs/administration & dosage
  • beta-Alanine/analogs & derivatives
  • Capecitabine/administration & dosage
  • Sex Factors
  • Adult
  • Female
  • Aged
  • Muscle, Skeletal/diagnostic imaging
  • Antimetabolites, Antineoplastic/administration & dosage

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