BackgroundIn Malawi, preoperative chemotherapy for Wilms tumour is a logical strategy, but detailed information on toxicity and efficacy in such a resource limited setting has been unavailable.ProcedurePatients diagnosed with a unilateral Wilms tumour received preoperative chemotherapy—a two‐drug 4‐week regimen for localized disease and 6 weeks of a three‐drug regimen for metastatic disease. Estimated maximum tumour diameter, decrease in tumour size, resectability, stage distribution and haematological toxicity during therapy were documented.ResultsAt diagnosis, 28% of 72 patients had an estimated maximum tumour diameter of more than 25 cm; 29% of patients had metastases. Eight children (11%) died during preoperative chemotherapy. More than half (59%) of the patients developed moderate neutropenia (neutrophils <1.0 × 109/L; CTC grade 3) and 27% severe neutropenia (CTC grade 4 neutrophils <0.5 × 10.9/L). Grade 4 neutropenia occurred significantly more frequently in children receiving the three‐drug regimen compared to the two‐drug regimen; 50% (10/20) versus 15% (6/40) (P = 0.004). Fifty‐seven percent of all patients had CTC grade 4 anaemia (Hb < 6.5 g/dL) during treatment. Most tumours (92%, 56/61) showed a response to chemotherapy but 14% (8/58) remained unresectable.ConclusionPreoperative chemotherapy for Wilms tumour causes considerable haematological toxicity and treatment‐related mortality in malnourished Malawian children. A significant number of children have unresectable disease despite preoperative chemotherapy. To reduce treatment related mortality, consideration should be given to starting treatment with reduced doses in acutely malnourished patients. Pediatr Blood Cancer 2012;59:636–641. © 2012 Wiley Periodicals, Inc.