Acquired Fanconi Syndrome After Treatment with Capecitabine, Irinotecan, and Bevacizumab

Abstract

Objective: To describe a case of acquired Fanconi syndrome after treatment with capecitabine, irinotecan, and bevacizumab. Case Summary: A 77-year-old female with metastatic colon cancer presented with vomiting and diarrhea. The patient had been diagnosed with stage IIIC (T3, N2, M0) colon cancer 18 months earlier and was initially treated with FOLFOX6 (regimen of oxaliplatin, fluorouracil, and leucovorin) after her hemicolectomy. She was switched to a capecitabine/oxaliplatin regimen after 4 cycles due to central access problems. She did well until 10 months after her cancer diagnosis, when metastasis was discovered. She was started on reduced doses of capecitabine, irinotecan, and bevacizumab. After her eleventh cycle, she presented to the hospital with the above symptoms. Laboratory test results showed hypokalemia, hypocalcemia, hypophosphatemia, and hypouricemia. The patient had not been started on any new medications other than chemotherapy for over 1 year. The electrolyte derangements were new, since the patient had laboratory values checked every 3 weeks. Despite daily intravenous replacements, the electrolyte abnormalities persisted. Laboratory evaluations demonstrated the presence of euglycemic glucosuria and a high fractional excretion of phosphorus in the setting of hypophosphatemia. Fanconi syndrome was confirmed by demonstration of aminoaciduria. Discussion: Fanconi syndrome is a disorder characterized by proximal tubular dysfunction resulting in electrolyte wasting. In the acquired form, medications and multiple myeloma are the most common causes. Based on the Naranjo probability scale, a drug was the probable cause of Fanconi syndrome in our patient. However, because multiple drugs were involved, it was not possible to determine which one was the culprit. Conclusions: This is the first case of Fanconi syndrome reported after the administration of capecitabine, irinotecan, and bevacizumab. More studies are needed to confirm this association.