Primary renal cell carcinoma (RCC) is a challenging cancer to treat, especially for patients who are not suitable candidates for surgery. However, a promising new study, the FASTRACK II trial, has shown that stereotactic ablative body radiotherapy (SABR) may be an effective and noninvasive alternative for these patients. Led by Shankar Siva, PhD, at the Peter MacCallum Cancer Centre in Melbourne, Australia, the study revealed impressive outcomes, suggesting that SABR could potentially become a new standard of care for primary kidney cancer. This article aims to delve into the key findings of the study and discuss the implications of this innovative approach.
The FASTRACK II trial was a prospective, phase II study involving 70 patients with primary RCC. Throughout the trial’s median follow-up of 43 months, none of the patients experienced local progression of kidney cancer. Moreover, the study reported a remarkable 100% cancer-specific survival over the same period. These outcomes suggest that SABR could potentially be a game-changer for patients who are not suitable candidates for surgery.
The study also revealed that freedom from distant failure at 1 and 3 years was an impressive 99% (95% CI 90-100%). Additionally, the overall survival rates at 1 and 3 years were 99% (95% CI 90-100%) and 82% (95% CI 70-89%) respectively. These results are highly encouraging, raising the possibility that SABR could become the new standard of care for primary kidney cancer patients who cannot undergo surgery.
Traditionally, surgery, including total and partial nephrectomy, has been the standard treatment for primary kidney cancer. However, there are limitations for patients who are medically inoperable or at high risk, such as the potential need for post-surgical dialysis. This is where SABR offers significant advantages.
SABR, also known as stereotactic body radiotherapy (SBRT), is a noninvasive procedure that avoids general anesthesia. Unlike thermal ablation, it has the capacity to treat perihilar and large tumors. SABR’s noninvasive nature is a critical advantage over both thermal ablation and surgery. It provides a viable alternative for patients who cannot undergo surgery due to medical reasons.
The FASTRACK II trial focused on patients with primary RCC who were considered medically inoperable, high risk, or had declined surgery. The median age of the patients was 77, with 70% being male. The trial included patients with a median BMI of 32 and a median Charlson comorbidity score of 7.
The treatment protocol varied based on tumor size. Patients with tumors up to 4 cm received a single fraction of 26 Gy, while those with tumors larger than 4 cm were prescribed 42 Gy in three fractions. Remarkably, the trial included patients with a median tumor size of 4.6 cm, larger than that typically seen in partial nephrectomy versus radical nephrectomy trials. However, despite the larger tumor size, the trial demonstrated comparable renal function loss to that observed in surgical trials.
Safety is a critical concern when evaluating any new treatment. In the FASTRACK II trial, 10% of patients experienced grade 3 treatment-related adverse events (TRAEs), most predominantly transient pain or nausea and vomiting. Notably, prophylactic antiemetics or steroids were not mandated during the trial. However, the authors recommend considering their use in the future.
There were no grade 4 or 5 TRAEs reported during the trial, indicating that SABR is a relatively safe procedure. Additionally, only 16% of patients reported no adverse events, further highlighting the promising safety profile of this innovative treatment.
The FASTRACK II trial provides exciting evidence to suggest that SABR could be an effective and noninvasive approach for treating primary renal cell carcinoma in patients who are not suitable candidates for surgery. With impressive outcomes, including no local progression of kidney cancer and 100% cancer-specific survival, SABR could potentially become the new standard of care for these patients.
Further research is needed to validate these findings and compare SABR to surgery through randomized clinical trials. Nevertheless, the trial’s results are promising and offer hope for patients who previously had limited treatment options. SABR has introduced a novel therapeutic avenue that could significantly improve the outcomes and quality of life for primary kidney cancer patients.
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