Stereotactic Body Radiation Therapy Demonstrates ‘Exceptional Control’ in Primary Renal Cell Carcinoma
Although surgery remains the standard of care for primary renal cell carcinoma, a novel, noninvasive approach has yielded positive results that could pave the way for future treatment strategies, according to data presented at the 2023 American Society for Radiation Oncology (ASTRO) Annual Meeting.1
FASTRACK II, the first multicenter, nonsurgical phase II trial for primary kidney cancer, demonstrated “exceptional outcomes” with stereotactic body radiation therapy (SBRT), including a local control rate of 100% and no cancer-related deaths. Over a 43-month median follow-up, freedom from distant failure was also encouraging at 99%.
“Our study demonstrated that a novel treatment delivered in an outpatient setting is able to achieve unprecedented efficacy for patients with inoperable kidney cancer,” said lead study author Shankar Siva, PhD, a radiation oncologist at the Peter -MacCallum Cancer Centre and Professor at the University of Melbourne in Australia. “There’s an unmet need for curing this type of cancer, and our findings point to the potential of radiation therapy to address that need.”
“Our study demonstrated that a novel treatment delivered in an outpatient setting is able to achieve unprecedented efficacy for patients with inoperable kidney cancer.”— Shankar Siva, PhD
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Kidney cancer is the ninth most common cancer worldwide, with increasing incidence over the past 3 decades. The traditional standard of care involves surgery, but surgery presents limitations for patients who carry other medical conditions that amplify their risk for major surgery or for dialysis after surgery. Existing alternative treatments, such as thermal and radiofrequency ablation, involve invasive techniques and are ineffective for larger tumors.
Stereotactic radiotherapy, on the other hand, is a noninvasive novel treatment that not only avoids the need for a general anesthetic but also allows the treatment of deep centrally located kidney tumors, which are difficult to treat with other methods without removal of the entire kidney. Stereotactic radiotherapy can also manage larger tumors and works by targeting them directly with high doses of radiation delivered in a small number of outpatient sessions.
FASTRACK II Trial
The TransTasman Radiation Oncology Group (TROG) FASTRACK II study is the first multicenter phase II trial of any nonsurgical therapy in primary kidney cancer. Spanning seven centers in Australia plus one in the Netherlands, the trial recruited 70 patients from diverse backgrounds (70% male, 30% female) between 2016 and 2020 to evaluate local control, with a target of no less than 80% control.Patients enrolled on study had confirmed biopsy results of kidney cancer and were either medically inoperable or had a risk of dialysis postsurgery. Dr. Siva and colleagues divided participants into two treatment approaches, depending on the size of their tumor.
‘Remarkable’ Local Control
According to Dr. Siva, treated tumors were relatively large, with an average of 4.7 cm. Patients with tumors smaller than 4 cm received a single fraction of radiation (n = 23), and those with tumors larger than 4 cm received three fractions (n = 47).
The use of SBRT demonstrated promising results, said Dr. Siva, including a “remarkable” local control rate, which accounts for the decrement in the progression of tumors. “We were quite surprised with the outcomes,” Dr. Siva continued. “The local control rate was 100% after the treatment, which is considerably higher than the minimum benchmark of 80% that we were aiming for.”
In addition, with a median follow-up of 43 months, no patients died from cancer and only one patient experienced a distant recurrence of cancer. Overall survival was 99% at 1 year after SBRT and 82% at 3 years.
- A novel treatment approach for kidney cancer involving stereotactic body radiation therapy has demonstrated a local control rate of 100% in a cohort of medically inoperable patients.
- Outcomes from the phase II study support the design of a future randomized clinical trial of SBRT vs surgery for primary renal cell carcinoma.
Treatment with SBRT was associated with mild impairment of kidney function, which was assessed by measuring patients’ estimated glomerular filtration rate (GFR). Average estimated GFR declined by 10.8 mL/min at 1 year and by 14.6 mL/min at 2 years after treatment, indicating “mild-to-moderate kidney stress,” said Dr. Siva, who reported that all patients had some baseline preexisting kidney dysfunction. One patient required dialysis, he added, and “this patient had a large, complex tumor with low kidney function to begin with.”
Underscoring the importance of these findings, Dr. Siva concluded: “SBRT offers a novel treatment approach that stands as an attractive alternative to general anesthetics and invasive techniques. With such exceptional control rates and only a modest decline in kidney function, SBRT is clearly setting a new standard of care for primary kidney cancer that’s not suited to surgery.”
According to the study authors, the impressive outcomes of the FASTRACK II study should support the design of future randomized trials, where either surgery or SBRT should be considered as a treatment option.
DISCLOSURE: Dr. Siva reported financial relationships with AstraZeneca and Telix Pharmaceuticals; and institutional funding from Varian Industries, Merck Sharp & Dohme, and Bayer Pharmaceuticals.
1. Siva S, Bressel M, Sidhom M, et al: TROG 15.03/ANZUP international multicenter phase II trial of focal ablative stereotactic radiotherapy for cancers of the kidney (FASTRACK II). 2023 ASTRO Annual Meeting. Abstract 5. Presented October 3, 2023.
Rohann J.M. Correa, MD, PhD
Abstract discussant Rohann J.M. Correa, MD, PhD, a radiation oncologist at London Health Sciences Centre and Assistant Professor at Western University, Canada, shared his insights on this landmark clinical trial for the treatment of kidney cancers.