Stereotactic body radiation therapy for kidney cancer. Where do we stand?
At present, surgery is still the gold standard for the local treatment of renal cancer. Nonetheless, in several clinical scenarios, stereotactic body radiation therapy (SBRT) also known as stereotactic ablative body radiotherapy (SABR) is emerging as a highly effective ablative technique in fragile patients and those with significant comorbidities, as well as in cases where percutaneous therapy (cryoablation or radiofrequency) is not viable. However, considering the intrinsic radioresistance of renal tumors, the optimal treatment schemes have not been established. In oligometastatic patients, it has been reported that the control of the oligometastases can be a potentially curable approach. Being a technique than can be administered exclusively or in combination with systemic therapy, treatment individualization based on patient characteristics is key. Another scenario under investigation is oligoprogression, where SBRT offers the possibility of delaying further lines of systemic therapy by eliminating subclones of resistant tumor with ablative doses, with the additional opportunity of stimulating the immune system (immunomodulatory role). In this review, we have conducted an analysis of recently published studies that test the role of this technique in different clinical scenarios of this disease. We have found promising results that make SBRT a potent therapeutic approach with low toxicity. We also comment on ongoing studies that will generate the necessary evidence needed for the implementation of this technique in our daily clinical practice.
Renal SBRT seems to be an effective and safe approach for the treatment of renal lesions in patients who are unfit for surgery. While there are no comparative studies with other ablative therapies, results suggest similar local control and toxicity rates. But, in contrast to cryoablation and radiofrequency, tumor size >4 cm and proximity to the renal pelvis are not exclusion criteria for SBRT. There are currently multiple ongoing studies in different clinical scenarios that will provide us with more information of the role of this technique in the short and medium term. Therefore, the treatment approach must be agreed by a multidisciplinary team. Nonetheless, this therapy will probably gain a more important role in the near future.