Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

Incidence, Extent, and Management of Hypomagnesemia in Colorectal Cancer Patients During Epidermal Growth Factor Receptor Inhibitor (EGFRI) and Fluorouracil (5FU) Based Therapy at Ipswich Hospital: A Retrospective Audit (141825)

Guru Sule 1 , Lesley Dawson 1
  1. Cancer Services, Ipswich hospital, , Queensland health, Ipswich, QLD, Australia

Background: Hypomagnesemia is an effect of Epidermal Growth Factor Receptor inhibitor (EGFRI) and fluorouracil (5FU) based therapy1. Appropriate magnesium supplementation is important to reduce symptoms associated with hypomagnesemia and enhance compliance for colorectal cancer patients2. Current Queensland Health (QH) prescribing guidelines for HYPO-Electrolyte disturbances in adults classified mild hypomagnesemia as 0.9-0.71 mmol/L, moderate hypomagnesemia as 0.7-0.4 mmol/L, and severe hypomagnesemia as less than 0.4 mmol/L3. 

Aims: To quantify the incidence of hypomagnesemia in the study population, assess compliance with local guidelines of magnesium supplementation to determine the need to consider further development of current guidelines, compare the choice of pharmacotherapy prescribed with oral versus parenteral magnesium supplementation, and examine the effect of proton pump inhibitor use on serum magnesium levels for this patient cohort.

Methods: A retrospective audit was conducted; patients were identified by data extraction from Pharmacy Oncology Information Management Systems (POIMS/CHARM). Adult patients who received greater than one cycle of treatment with an EGFRI plus 5FU based chemotherapy were included in this study. A sample size of 34 patients was audited. Serum magnesium levels prior to EGFRI and 5FU based therapy, and at each cycle of therapy were recorded from patient pathology reports. Patients who received magnesium supplementation or a (Proton Pump Inhibitor) PPI were identified through electronic medication records (ieMR)

Results: All patients studied experienced hypomagnesemia at early cycles of treatment and PPI usage resulted in lower magnesium serum concentrations4,5. Intravenous supplementation achieved better outcomes in comparison to oral supplementation6.

Conclusion: Hypomagnesemia remains a common issue for colorectal cancer patients undergoing EGFRI and 5FU based therapy. Effective management of hypomagnesemia is important to decrease associated symptoms such as fatigue and tremors1,7. Thereby, development of further guidelines should be based on elemental magnesium content to include prophylactic magnesium supplementation. 

 

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  3. 3. Queensland Health. Prescribing Guidelines for HYPO-Electrolyte Disturbances in Adults. Queensland (AU): Queensland Government; 2023. 2 p.
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  8. 7. Pietropaolo G, Pugliese D, Armuzzi A, Guidi L, Gasbarrini A, Lodovico Rapaccini G, et al. Magnesium absorption in intestinal cells: Evidence of cross-talk between egf and trpm6 and novel implications for cetuximab therapy. Nutrients. 2020;12(11):1–11. https://doi.org/10.1021/mp300323q