"Histological response of Wilms tumour to preoperative chemotherapy in children in Rwanda’’

Abstract

Renal tumours constitute about 8% of all tumours in the first 15 years of life. In this age range, Wilms tumour is the most common occupying 85% of all cases. Currently in Rwanda, Wilms tumour is the most common paediatric renal tumour. It comprises 6% of all paediatric malignancies and 90% are diagnosed before the age of three. The survival rates of Wilms tumour are still low in most African countries Rwanda included. Its histological responsiveness is known to affect prognosis. The aim of our study was to obtain accurate data regarding this histological response of Wilms tumour after administration of preoperative chemotherapy in children in our country by determining the frequency of the viable tumour, its subtypes and if sex and age influence the tumour’s histological response to the preoperative chemotherapy.

After acquiring the ethical approval from the Institutional review board (IRB) of the University of Rwanda (UR) College of Medicine and health sciences (CMHS), permissions from the institutions involved in the study were also obtained before data was collected. A total of 96 cases were found over a period of 7 years, from 2013 to 2020. Their haematoxylin and eosin (H&E)-stained glass slides were retrieved and reviewed by two independent pathologists for confirmation of the diagnosis including the presence of the viable tumour, its type, its subtypes as well as the histological response. We also looked at the degree of necrosis, risk group and stage. The recorded data was analysed using statistical product and service solutions (SPSS) 26.0, p<0.05 was considered as showing a statistically significant association.

Of the 96 cases collected, 51 (53.1%) were females while 45 (46.9%) were males. The 2–5 age group was the most represented (65.6%) with a median of 3 years. Viable tumour was seen in 81 cases (84.4%) and almost all of them were solid (96.3%). The mixed subtype was the most predominant with 45.7% while the epithelial subtype was seen the least at 7.4%. Necrosis was present in almost all cases (99%) and the estimated degree of necrosis of 10-30% was the most seen (44.2% of cases). The intermediate risk group predominated at 62.5% as well as stage I at 64.5%. We found that males were more likely to have a higher stage (III and above) compared to females (p-value=0.022, OR=4.85, 95% CI= 1.25-18.76).

Our study showed that, in our settings, the degree of necrosis in Wilms tumours after administration of preoperative chemotherapy is insufficient. This merits further investigations for validation and eventually review of the existing treatment protocols.