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DGI-041 Hypomagnesemia as a Possible Marker of Effectiveness in Patients Treated with Panitumumab
  1. J Megías Vericat,
  2. J Ruiz Ramos,
  3. J Reig Aguado,
  4. C Borrell García,
  5. MJ Esteban Mensua,
  6. E López Briz,
  7. Poveda JL Andrés
  1. Hospital Universitario La Fe, Servicio de Farmacia, Valencia, Spain

Abstract

Background Panitumumab is a human monoclonal antibody indicated in the treatment of colorectal carcinoma (CRC) that is currently being tested in otolaryngology (ENT) tumours. Recent studies suggest that hypomagnesaemia (<1.7 mg/dL) during treatment with panitumumab may be related to greater anti-tumour efficacy.

Purpose To review the effectiveness of panitumumab and its possible relationship with hypomagnesaemia.

Materials and Methods Retrospective observational study that included all patients treated with panitumumab in a tertiary hospital. The primary endpoint of effectiveness was overall survival (OS), calculated using the Kaplan Meier method. We examined anthropometric data, diagnosis, treatment duration and, in patients whose magnesium had been determined during panitumumab treatment, we also studied the causes of termination and adverse reactions.

Results During the study period (August 2008–October 2012) 72 patients were treated, who had an average baseline age of 63 (SD:11) years and were mostly male (56%). At the end of the study 47% of patients were alive and 44% of them are still being treated with panitumumab. Diagnosis of 89% of patients was CRC, while 8 ENT cancer patients were enrolled in a clinical trial. The average length of treatment was 4.9 (SD:5.7) months and 7.7 (SD:6.4) cycles/patient were administered.

Magnesium levels were only determined in 13 patients, hypomagnesaemia being detected in 6 patients (ENT:3, CCR:3) and normomagnesaemia in the remaining 7 (ENT:5, CCR:2). Treatment with panitumumab was stopped in 6 patients due to disease progression. Two patients had to reduce the dose due to severe skin toxicity. The OS was calculated in all patients [hypomagnesaemia: 9.5 (95CI:4.9–14.0) vs. normomagnesaemia 8.2 (95CI:4.2–12.3) months (p:0.703)] and in the ENT tumours subgroup [hypomagnesaemia: 13 (95CI:9.3–16.7) vs. normomagnesaemia 4.8 (95CI:2.9–6.8) months (p:0.127)].

Conclusions Despite the low magnesium determinations we observed a trend to greater OS in hypomagnesaemic patients. Further studies are needed to confirm this trend.

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Abstract DGI-041 Table 1

No conflict of interest.

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