Kidney cancer is a rare condition, accounting for 7% of all childhood cancers. It occurs when the organ’s cells begin to grow and divide uncontrollably, impairing function and leading to tumour formation.

Childhood kidney cancer can be effectively managed, allowing children to reclaim their health and lives. Awareness provides the best possible outcome for a child: while hospitals provide expert care and treatment, parents can offer their child comfort and support.

In conjunction with Rare Disease Day last week on Feb 28, here’s what you need to know about childhood kidney cancer.

Wilms’ tumour

Wilms’ tumour is the most common type of paediatric kidney cancer. It is caused by mutations in kidney cells that typically occur after birth, and usually affect one kidney. That said, in 5-7% of cases, it can be found in both kidneys.

The cause of most childhood cancers is unknown. There are, however, certain inherent genetic disorders that increase a child’s risk of developing Wilms’ tumour.

There are isolated risk factors such as aniridia (absence of iris in the eye) or hemihypertrophy (overgrowth of one side of the body). It could also occur because of a syndrome (signs and symptoms that occur collectively), among them being WAGR – Wilms’ tumour, aniridia, genitourinary malformation, and range of developmental delays.

Patients with this syndrome have a 45-60% chance of developing the tumour.

According to Dr Eni Juraida Abdul Rahman, paediatric haematologist and oncologist at a medical centre in Sunway City, Wilms’ tumour usually occurs in children below age five.

“As the child grows older, the risk of them developing Wilms’ tumour is reduced, and we hardly ever see Wilms’ tumour in adults,” she said.

Symptoms include:

• painless swelling in the abdomen, often noted by parents while bathing the child, as the tumour may cause the abdomen to swell and cause discomfort;
• haematuria, or blood in the urine;
• hypertension, as Wilms’ tumour can cause high blood pressure;
• fever;
• loss of appetite leading to weight loss;
• pain in the abdomen, especially if bleeding within the tumour causes a sudden increase in mass size;
• cough and shortness of breath if the tumour has spread to the lungs; and
• generally feeling unwell.

Treatment

In most cases, by the time the child arrives for a diagnosis, the tumour would have grown to a large size and the kidney would be rendered non-functional.

If a tumour is suspected, the patient will undergo blood tests to look into his or her general health, haemoglobin levels and kidney function. Radiological examination will also be performed, including an ultrasound of the abdomen and CT scan to further define the tumour and determine staging:

• Stage one: tumour within the kidney.
• Stage two: tumour within the kidney has involved surrounding fatty tissue and blood vessels, but can still be completely removed.
• Stage three: very large tumour that has crossed the midline of the body.
• Stage four: tumour has spread to distant sites, usually the lungs, liver or bone.
• Stage five: tumour involving both kidneys.

Depending on the stage of the tumour, the patient will undergo:

• Surgery or nephrectomy to remove the affected kidney

This is usually done upfront for stage-1 or -2 tumours, or delayed for stage-3 disease. All children will undergo surgery as there is a risk of the tumour growing back if it is not done after chemotherapy.

• Chemotherapy

These are drugs that kill cancer cells, and can either be adjuvant (given after surgery for stage-1 and -2 tumours), or neoadjuvant (given before surgery to reduce tumour size and kill cells).

Chemo is given upfront for stage-3 cancer as the tumour would be big. The aim is to shrink the growth to allow the procedure to be carried out safely.

• Radiotherapy

This is done on some patients depending on what the tumour looks like microscopically, how far it has spread outside the kidney, or if it has spread to distant organs such as the lung and has not been completely resolved with chemotherapy.

“For stage-1 Wilms’ tumour, the cure rate is 95%,” Eni said. “For stages 2 to 4, if there are no unfavourable features in the histology, a four-year survival rate of 90% can be expected.”

Prevention

Since the cause of Wilms’ tumour is unknown, it is difficult to take preventive measures. For children with symptoms such as WAGR, surveillance ultrasound of the abdomen is carried out periodically to detect the occurrence of any tumours.

Parents are also counselled to be more vigilant concerning signs and symptoms. Here are some things to look out for:

• Most tumours are discovered incidentally, and parents should keep an eye out for lumps when bathing or dressing their child. It will be obvious when one side of the stomach looks bigger than the other.
• Presence of blood in the urine, which indicates that bleeding could be coming from the kidney, prostate, or bladder.
• Loss of appetite and weight. Tumours that arise from the left kidney will compress the stomach as it grows, leading to a sense of fullness.
• Big-birth weights with hemihypertrophy. These individuals have a higher chance of developing a renal tumour and, therefore, should be screened periodically.