Role of radiation in oligometastatic and advanced renal cell cancer
Renal cell cancer (RCC) is the most common type of kidney cancer, originating in the cells lining the tiny tubes within the kidneys. These tubules return nutrients and fluid back into the bloodstream while expelling unwanted waste as urine.
In some cases, both kidneys can be affected at the same time with tumors appearing in different areas within them.
Unfortunately, early RCC usually does not exhibit any warning signs of the disease, with most patients unaware of the disease’s presence. It is estimated that 20% to 40% of patients will eventually become symptomatic manifesting symptoms such as blood-stained urine (hematuria), lower back or flank pain, or even high blood pressure (hypertension). At this point, the RCC is likely already at an advanced stage, meaning that the cancer has spread (metastasis).
Metastatic RCC requires aggressive management to control further progression, as these patients often have an unfavourable outcome. Advanced and refined imaging techniques (scans) have proven invaluable in identifying and categorizing patients with metastatic RCC, particularly those with oligometastatic RCC. Oligometastatic RCC is defined when the number of detectable lesions at presentation is typically five in number or fewer.
There have been significant advances in the surgical, medical and radiological management of RCC in the past decade. The management approach to RCC is tailored to fit the patient’s risk profile. Surgical treatment is curative in localized RCC, while systemic therapy is administered in patients with metastatic disease.
In recent years, radiotherapy has had a major role to play in metastatic RCC. It is important to recognize that not all metastatic RCC should be considered alike.
Oligometastatic disease, characterized by low-volume and limited metastatic lesions is significantly responsive to stereotactic ablative body radiation (SAbR). SAbR is defined by the American Society of Therapeutic Radiology and Oncology guidelines as a “treatment method to deliver a high dose of radiation to the target, utilizing either a single dose or a small number of fractions with a high degree of precision within the body.”
Although early studies suggested that RCC cells were radioresistant, subsequent research established that a higher single dose of radiation significantly enhanced RCC cell death. A systematic review of literature has corroborated that the early use of SAbR with high-dose irradiation appears to be safe, feasible, and effective in achieving excellent local control in patients with oligometastatic RCC.
Furthermore, guidelines have now begun recommending the use of SAbR for recurrent and metastatic RCC. SAbR might play a role in selected patients either as a means to delay the initiation of systemic therapy, or as a means of palliative care for terminally ill patients.
Remarkably, half of the patients may not need additional systemic therapy at the two-year mark following SAbR indicating that this approach can prolong the time to progression and potentially improve survival.