Nephroblastoma Definition and Overview
Nephroblastoma, also known as Wilms tumour, is a childhood cancer that starts in the kidneys. Named after the doctor who first described it (Dr. Max Wilms), it is very rare and most commonly occurs in children between the ages of three and four.
Wilms tumours can develop in one or both kidneys but in the majority of patients, only one kidney is affected. Doctors suspect that the condition develops when some cells that are meant to form into a kidney malfunction. These cells, which are supposed to disappear soon after birth, act abnormally and remain in their early form resulting in the formation of tumours.
Every year, approximately 500 children in the United States are diagnosed with nephroblastoma. Although 25per cent of them have other birth or inherited gene defects, doctors say that Wilms tumours are not the result of any known inherited syndromes.
Due to the recent advances in the methods used to treat the condition, up to 90% of patients are able to make a complete recovery after undergoing multimodality therapies (surgical treatment and chemotherapy or radiotherapy). This is in stark contrast to 50 years ago when only 10% of diagnosed patients survive.
Causes of the Condition
Cancer develops when there’s an error in the cells’ DNA. It is characterised by the uncontrollable growth and division of cells that were supposed to die and be replaced by new cells. When these cells accumulate, they form a tumour.
Nephroblastoma, just like other types of cancerous tumours, does not have a known cause. However, it is worth nothing that a small number of Wilms tumour patients also have other congenital malformations and certain syndromes. These include aniridia in which the coloured portion of the eye does not fully form and hemihypertrophy in which one side of the body is larger than the other side. However, doctors are yet to confirm if there's a link between Wilms tumours and other developmental abnormalities.
Wilms tumour can also occur as part of rare syndromes, including:
Beckwith-Wiedemann syndrome – An overgrown syndrome that results in an unusual growth pattern in which one side of the body is noticeably bigger than the other side.
WAGR syndrome – This stands for Wilms tumour, aniridia, and genital and urine system abnormalities.
Denys-Drash syndrome – Other than Wilms tumour, this also includes kidney disease and pseudohermaphroditism in which a baby boy exhibits female characteristics.
Nephroblastoma does not normally cause any symptoms other than the presence of a firm lump in the abdomen. However, in some cases, children may experience the following:
Blood in the urine
High blood pressure
Loss of appetite
Shortness of breath
Who to See and Types of Treatments Available
Children with a firm lump in their abdomen must be taken to their doctor even if they do not show other symptoms listed above. To make a diagnosis, doctors will perform a physical examination and order blood and urine tests, which can help determine if the kidneys are functioning well. If kidney problems are suspected, doctors will order imaging tests including computed tomography (CT) scan, ultrasound, and magnetic resonance imaging (MRI). These tests are quick, painless, and create clear images of the kidneys making it easier for doctors to spot any abnormalities.
If a child has been diagnosed with Wilms tumour, doctors will proceed with staging in which they determine the extent of cancer. Additional tests including chest CT and bone scans will be performed to assess if cancer cells have already spread to other parts of the body. The stage of nephroblastoma dictates the most appropriate treatment for the patient.
Stage I - Cancer is localised to the kidney
Stage II – The tumour extends beyond the kidney and there’s already renal capsule and sinus involvement
Stage III – The tumour has penetrated the peritoneal surface
Stage IV – Hematogenous or lymph node metastases beyond the pelvis
Stage V – Both kidneys have malignant growths
Stages I – IV nephroblastoma are treated with radical nephrectomy, a surgical procedure that removes the kidney, the tumour, surrounding lymph nodes, and the adrenal glands. Nephrectomy can be performed using traditional open surgery or laparoscopic method. Open surgery involves making a long incision in the abdomen, lower back, or the patient’s side to access and remove the kidney. Although this is more invasive when compared to the laparoscopic method, it allows surgeons to thoroughly examine the kidney. This is deemed important when other abnormalities in the structures surrounding the kidneys are suspected.
Laparoscopic radical nephrectomy, on the other hand, uses multiple smaller incisions and is typically recommended for smaller, localised tumours. In this procedure, the surgeon inserts a tiny camera (laparoscope) and specialised surgical tools to remove the kidney and tumour using an imaging technology as a guide. Since this is less invasive, patients are able to recover faster. They also experience less pain and scarring than those who undergo open surgery. Following radical nephrectomy, patients undergo chemotherapy or radiation therapy to kill remaining cancer cells.
For patients with bilateral nephroblastoma, surgeons exhaust all means to remove cancer cells without removing both kidneys as this would result in kidney failure. This is a life-threatening condition that may lead to abnormal heart rhythms and sudden death.
Prior to administering any form of treatment, doctors explain all treatment options to the patients’ parents or guardians. This is important as surgery, chemotherapy, and radiation therapy can result in a range of complications including cardiac and pulmonary dysfunction. Women who have undergone radiation therapy in childhood can also suffer from ovarian failure while male patients are at risk for testicular failure. In addition, radiation therapy can affect the skeletal system and the growth of any given bone.
Approximately 90% of patients with less complicated nephroblastoma are able to make a full recovery after they undergo surgery and chemotherapy. However, for patients with anaplastic Wilms tumour, the four-year survival rates are 33% for stage IV, 65% for stage III, and 83% for both stages I and II.
Patients who have undergone nephrectomy usually do not suffer from impaired renal function. They also do not typically develop serious long-term complications. However, renal failure is a serious risk for patients with bilateral nephroblastoma.
Coppes MJ, Huff V, Pelletier J. Denys-Drash syndrome: relating a clinical disorder to genetic alterations in the tumor suppressor gene WT1. J Pediatr. 1993 Nov. 123(5):673-8. [Medline].
Grundy PE, Breslow NE, Li S, et al. Loss of heterozygosity for chromosomes 1p and 16q is an adverse prognostic factor in favorable-histology Wilms tumor: a report from the National Wilms Tumor Study Group. J Clin Oncol. 2005 Oct 10. 23(29):7312-21. [Medline].