SABR Yields ’Exceptional‘ Outcomes in Older Patients With Inoperable Renal Cell Carcinoma

Shankar Siva, PhD, MBBS, FRANZCR

Stereotactic ablative radiotherapy (SABR) led to an “exceptional” disease control rate in older patients with renal cell carcinoma (RCC) who were ineligible for surgery, according to findings from the Dutch and Australian phase 2 TransTasman Radiation Oncology Group (TROG) FASTRACK presented during the 2023 ASTRO Meeting.

According to Shankar Siva, PhD, MBBS, FRANZCR, a radiation oncologist with the Peter Mac MacCallum Cancer Centre in Australia, the results of this study clearly position SABR as the new standard of care for primary kidney cancer that is not suited for surgery. Further, he argued that these findings support the design of a future, phase 3, randomized clinical trial to compare it against surgery for primary RCC.

“Our research clearly defines a new population of patients who will benefit from stereotactic radiation,” Siva said in a presentation of the findings. “These patients often don’t have other viable treatment options, so we are excited to see that radiation therapy can be effective for them.”

Key Findings

The local disease control rate, or lack of any tumors growing back, was 100% at a median follow-up of 43 months.

The freedom from distance failure was 99% at 3 years and 92% at 5 years. In other words, patients did not have their disease coming back in any other forms, Siva explained.

In addition, the rate of cancer-specific survival was 100% throughout the duration of the trial, meaning no patient died from their cancer.The loss of kidney function was 14.6 mLs/min, which, according to Siva, is mild kidney dysfunction. Only 1 patient required dialysis—and this patient had a large tumor and preexisting kidney dysfunction at baseline.

“These are quite exceptional and unexpected outcomes,” Siva remarked.

Methodology

The trial’s primary outcome was local control after radiation. A total of 70 patients were recruited from July 2016 to February 2020 across 1 center in the Netherlands and 7 centers in Australia.

The median patient age was 77 years. All participants had a biopsy-confirmed diagnosis of primary RCC with a single lesion within a kidney and were considered either medically inoperable or at high-risk with surgery. Their tumors could be no larger than 10 cm and could not be touching the bowel. For all of these patients, their multidisciplinary team had concluded that active treatment was warranted. Most patients had a Charlson comorbidity index score of 7.

Of note, one third of the patients had smaller tumors (T1a; golf ball sized or smaller); this group of patients could potentially all also undergo treatment with thermal ablation. However, for the rest of the patients who had larger tumors, there were not many curative treatment options.

For patients whose tumors were less than 4 centimeters in size, a single treatment with 26 Gy was used.

“That is basically 1 visit for treatment that might last an hour,” Siva said. “The patient drives themselves in, drives themselves home, has dinner with their family, [etc,] and that’s it. That’s their cancer treatment done.”

For those with tumors larger than 4 centimeters, 3 treatments (42 Gy) were given over the course of a week. Again, as Siva explained, this is an outpatient-based treatment with no anesthetics and no knives.

Significance

Kidney is the ninth most common cancer worldwide, and the incidence of kidney cancer is rapidly increasing—specifically in patients over the age of 70.

Surgery is the standard of care for patients with kidney tumors; however, this approach is not always suitable for older patients. Comorbidities, such as diabetes or high blood pressure—that are more common in older populations—also increase the risk of complications from surgery. Additionally, tumors may be in difficult-to-operate areas, in which case surgery may lead to dialysis.

Alternative options can include thermal ablation and radiofrequency ablation, or inserting a needle which “heats” the tumor, but this approach is still invasive and cannot treat larger tumors. According to investigators, SABR is a totally non-invasive treatment that can treat both large tumors and peri-hilar tumors, and avoids the use of general anesthetic. In this way, it can be an attractive option for patients.

“This is a novel treatment approach,” Siva concluded. “It has some specific advantages that may tick all of the boxes as the ideal treatment for kidney cancer.”

References

1. Siva S, et al. TROG 15.03/ANZUP international multicenter phase II trial of focal ablative stereotactic radiotherapy for cancers of the kidney (FASTRACK II). Presented at: 2023 American Society for Radiation Oncology Annual Meeting (ASTRO); September 30 to October 4, 2023; San Diego, CA. Abstract 5.
2. High-dose radiation offers new treatment option for older patients with inoperable kidney tumors. News release. ASTRO. October 1, 2023. Accessed October 12, 2023. https://www.astro.org/News-and-Publications/News-and-Media-Center/News-Releases/2023/High-dose-radiation-offers-new-treatment-option-fo