A retrospective analysis of plasma concentration monitoring of fluorouracil in patients with advanced colorectal cancer

Determining acceptance and perceptions of chemotherapy dose banding in an ambulatory cancer centre

INTRODUCTION

Despite the advantages of dose banding (DB) and numerous plans to adopt this practice, uptake of DB is still poor. As opinions of healthcare professionals were deemed essential in DB's acceptance, this study surveyed key stakeholders to determine the acceptance, facilitators, and barriers of DB in chemotherapy to improve its implementation.

METHODS

A cross-sectional study at the National Cancer Centre Singapore, involving physicians, nurses, and pharmacy staff, was conducted in February 2022. The Theory of Planned Behaviour was adapted to design a survey questionnaire to obtain the acceptance, facilitators, and barriers of DB. Additional questions on maximum acceptable dose variance and essential criteria for selecting drugs for DB were included.

RESULTS

A total of 93 participants responded, with a mean 9.75  ±  7.37 years of clinical experience. Less than half have heard of DB while few had prior experience. Drug cost was the top selection criteria for DB, followed by toxicity, therapeutic index, frequency of use and drug wastage. Acceptance rate of DB was 41.9%, with majority agreeing to use DB in various drugs but to determine patient suitability before usage. Being greatly affected by subjective norms, having a positive outlook for DB's impacts, and no effect on toxicity significantly influenced acceptance.

CONCLUSION

Prior to implementing DB at the institutional level, educational training addressing concerns over toxicity, and providing technological support can help improve acceptance. Future studies can involve patients' perspectives and more institutions for greater diversity in opinions.

5-fluorouracil therapeutic drug monitoring and adverse events in a Romanian population

Fluoropyrimidines represent the backbone of many chemotherapy protocols and the standard treatment for many types of tumors. Toxicity associated with fluoropyrimidines can occur in up to 40% of cases.

Background and purpose

The objective of this study was to analyze the correlation between the plasma concentration of 5-fluorouracil and the adverse events that patients might experience during this therapy.

Methods

A total of 58 patients received 5-fluorouracil-based chemotherapy. A blood sample was collected from each patient during the drug infusion, in order to assess the area under the curve for 5-fluorouracil. The occurring adverse events were evaluated through medical recordings of the patients' reported symptoms, clinical and paraclinical examinations.

Results

In our study, the majority of patients experienced some type of toxicity. Moreover, we found a correlation between 5-FU plasma concentration (expressed as AUC) and adverse events, a stronger one with hematological adverse reactions and a weaker one with gastrointestinal and cardiovascular toxicity.

Conclusion

Determining the plasma concentration of 5-FU in patients with severe toxicities could represent a method of individualizing the treatment and improving the safety profile.

Implementation of pharmacogenetic testing in oncology: DPYD-guided dosing to prevent fluoropyrimidine toxicity in British Columbia

Background: Fluoropyrimidine toxicity is often due to variations in the gene (DPYD) encoding dihydropyrimidine dehydrogenase (DPD). DPYD genotyping can be used to adjust doses to reduce the likelihood of fluoropyrimidine toxicity while maintaining therapeutically effective drug levels. Methods: A multiplex QPCR assay was locally developed to allow genotyping for six DPYD variants. The test was offered prospectively for all patients starting on fluoropyrimidines at the BC Cancer Centre in Vancouver and then across B.C., Canada as well as retrospectively for patients suspected to have had an adverse reaction to therapy. Dose adjustments were made for variant carriers. The incidence of toxicity in the first three cycles was compared between DPYD variant allele carriers and non-variant carriers. Subsequent to an initial implementation phase, this test was made available province-wide. Results: In 9 months, 186 patients were tested and 14 were found to be heterozygous variant carriers. Fluoropyrimidine-related toxicity was higher in DPYD variant carriers. Of 127 non-variant carriers who have completed chemotherapy, 18 (14%) experienced severe (grade ≥3, Common Terminology Criteria for Adverse Events version 5.0). Of note, 22% (3 patients) of the variant carriers experienced severe toxicity even after DPYD-guided dose reductions. For one of these carriers who experienced severe thrombocytopenia within the first week, DPYD testing likely prevented lethal toxicity. In DPYD variant carriers who tolerate reduced doses, a later 25% increase led to chemotherapy discontinuation. As a result, a recommendation was made to clinicians based on available literature and expert opinion specifying that variant carriers who tolerated two cycles without toxicity can have a dose escalation of only 10%. Conclusion: DPYD-guided dose reductions were a feasible and acceptable method of preventing severe toxicity in DPYD variant carriers. Even with dose reductions, there were variant carriers who still experienced severe fluoropyrimidine toxicity, highlighting the importance of adhering to guideline-recommended dose reductions. Following the completion of the pilot phase of this study, DPYD genotyping was made available province-wide in British Columbia.

3D-Printed Tumor-on-Chip for the Culture of Colorectal Cancer Microspheres: Mass Transport Characterization and Anti-Cancer Drug Assays

Tumor-on-chips have become an effective resource in cancer research. However, their widespread use remains limited due to issues related to their practicality in fabrication and use. To address some of these limitations, we introduce a 3D-printed chip, which is large enough to host ~1 cm3 of tissue and fosters well-mixed conditions in the liquid niche, while still enabling the formation of the concentration profiles that occur in real tissues due to diffusive transport. We compared the mass transport performance in its rhomboidal culture chamber when empty, when filled with GelMA/alginate hydrogel microbeads, or when occupied with a monolithic piece of hydrogel with a central channel, allowing communication between the inlet and outlet. We show that our chip filled with hydrogel microspheres in the culture chamber promotes adequate mixing and enhanced distribution of culture media. In proof-of-concept pharmacological assays, we biofabricated hydrogel microspheres containing embedded Caco2 cells, which developed into microtumors. Microtumors cultured in the device developed throughout the 10-day culture showing >75% of viability. Microtumors subjected to 5-fluorouracil treatment displayed <20% cell survival and lower VEGF-A and E-cadherin expression than untreated controls. Overall, our tumor-on-chip device proved suitable for studying cancer biology and performing drug response assays.

Current status and future outlooks on therapeutic drug monitoring of fluorouracil

INTRODUCTION

: Therapeutic drug monitoring (TDM) of the anticancer drug fluorouracil (5FU) as a method to support dose adjustments has been researched and discussed extensively. Despite manifold evidence of the advantages of 5FU-TDM, traditional body surface area (BSA)-guided dosing is still widely applied.

AREAS COVERED

: This review covers the latest evidence on 5FU-TDM based on a literature search in PubMed between June and September 2021. It particularly highlights new approaches of implementing 5FU-TDM into precision medicine by combining TDM with pharmacogenetic testing and/or pharmacometric models. This review further discusses remaining obstacles in order to incorporate 5FU-TDM into clinical routine.

EXPERT OPINION

: New data on 5FU-TDM further strengthen the advantages compared to BSA-guided dosing as it is able to reduce pharmacokinetic variability and thereby improve treatment efficacy and safety. Interprofessional collaboration has the potential to overcome the remaining barriers for its implementation. Pre-emptive pharmacogenetic testing followed by 5FU-TDM can further improve 5FU exposure in a substantial proportion of patients. Developing a model framework integrating pharmacokinetics and pharmacodynamics of 5FU will be crucial to fully advance into the precision medicine era. Model applications can potentially support clinicians in dose finding before starting chemotherapy. Additionally, TDM provides further assistance in continuously improving model predictions.