Kidney cancer

What is kidney cancer?

The kidney is a vital organ whose primary role is filtering blood and producing urine. This function allows for the elimination of waste from the bloodstream. Kidney cancer is therefore a tumor derived from a cell that has acquired the ability to multiply indefinitely. It most often originates from the renal parenchyma.

It is a disease with a steadily increasing incidence worldwide, particularly in industrialized countries. In 2020, approximately 431,288 new cases of kidney cancer were recorded globally, making it the 14th most common cancer worldwide (Global Cancer Observatory, IARC).

Interview with Professor Stéphane Oudard

Different types of kidney cancer

There are many subtypes of kidney cancer, but the most common (80% of cases) is called clear cell renal carcinoma. The other most frequent histologies (i.e., the categories of kidney cancer based on the type of cells affected) are papillary carcinoma (type I and type II) and chromophobe carcinoma. In total, there are more than 50 different subtypes.

Parfois, le cancer du rein peut entrer dans le cadre de maladies génétiques héréditaires. Il peut également s’accompagner de pathologies extra-rénales (exemple de la maladie de Von Hippel Lindau). Bien que rares, des analyses génétiques doivent reconnaître et confirmer ces situations. C’est pourquoi on sollicitera une consultation génétique dédiée, en cas de diagnostic avant 45 ans, pour les tumeurs bilatérales et/ou multifocales. Le généticien effectuera alors ces consultations pour les personnes apparentées au 1er degré.

Causes et risk factors

There are non-modifiable risk factors for kidney cancer:

• Age : the risk increases with age, particularly after 70 years
• Gender : twice as many cases in men
• Tobacco use : 6% of cases
• Overweight and obesity : 25% of cases
• Occupational exposure to carcinogens
• Certain conditions themselves increase the risk of developing renal carcinoma: hypertension (HTN)
• Chronic kidney disease : especially dialysis/transplant patients
• Hereditary diseases as mentioned above, accounting for 2% to 8% of cases

Screening

There is no mass screening strategy for kidney cancer. Additionally, systematic monitoring is only performed for individuals with hereditary predispositions to this cancer.

Symptoms

In the majority of cases, kidney cancer is discovered incidentally without any symptoms (65% of cases).

• Fatigue
• Weight lost
• Loss of appetite
• Hematuria
• Lower back pain
• Palpable mass in the abdomen
• Fever

Diagnosis

The essential examination to confirm the diagnosis is a CT urogram with and without contrast injection. Abdominal MRI also allows for clear visualization and characterization of the lesion. Contrast-enhanced ultrasound can also be used.

Unlike most tumors, it is rare to perform a confirmatory biopsy. Indeed, it will only be done if it can change the treatment strategy. Finally, the diagnosis of kidney cancer is made through imaging.

Given that 20% of kidney tumors are metastatic, meaning they have spread beyond the kidney, a staging workup will always be performed using a complete CT scan +/- a brain MRI. Additionally, a bone scan may also be performed depending on the symptoms present at diagnosis.

Treatments

The therapeutic strategy mainly depends on the stage of the disease.

In the localized stage

A focal treatment will be preferred (i.e., aimed at removing or neutralizing malignant cells).

Additionally, depending on the context (size and location of the tumor, initial kidney function, hereditary disease, etc.), different options exist and will be presented to you by a specialized urologist and/or an interventional radiologist.

Surgery

• Total nephrectomy (in the majority of cases): the affected kidney, surrounding fat, and the ipsilateral adrenal gland are removed.
• Partial nephrectomy if the tumor is on the kidney's periphery, small in size, or in the context of hereditary disease with a risk of multiple tumors.

Interventional radiology treatments:

• Radiofrequency ablation: a probe is placed percutaneously in contact with the tumor, causing tumor cell death by heat (between 50 and 100°C).
• Cryoablation: also percutaneously, but this time the probe destroys the lesion by freezing (-47°C).

There is no reimbursement yet, but immunotherapy might soon be offered as an adjuvant, meaning after an ablative treatment of a localized tumor.

In the metastatic stage

When kidney cancer is or becomes metastatic, the oncologist has a significantly expanded therapeutic arsenal in recent years.

Kidney cancer is not sensitive to chemotherapy, so your oncologist will not propose it. The treatment is based on oral targeted therapies or immunotherapy by infusion, or a combination of both. Finally, if the metastatic lesions are few, focal treatment (radiotherapy, surgery, interventional radiology) may be proposed.