Although only a small minority of the audience would consider radiotherapy RT for this patient, Dr. So went on to discuss whether RT is a valid option in this setting.
There are many potential uses of RT in the management of both metastatic and primary RCC. In metastatic RCC, RT can be used for palliation of symptoms or, at a high dose, to treat metastatic disease to improve outcomes. RCC has been explored in the localized setting as adjuvant therapy, neoadjuvant therapy, or monotherapy in patients who either have unresectable disease or are unsuitable for surgery.
There is a common misconception that “RCC is radioresistant.” Dr. So sought to dispel this myth by focusing on the efficacy of stereotactic ablative radiotherapy (SABR) in localized RCC. SABR delivers an ablative dose of at least 6-8 Gy per fraction in 1 to 5 fractions. A pooled analysis of SABR in RCC demonstrated a favorable safety profile with preserved renal function and only 1.3% of patients having a Grade 3 or 4 adverse event. The same analysis demonstrated a two-year local control rate of 97%. Data on whether SABR reduces distant progression and overall survival is lacking.
In the setting of tumor thrombus, case reports have demonstrated safety and potential benefit. More data is available in the hepatocellular carcinoma literature, where portal vein and IVC thrombus is common, which demonstrate safety of 45-50 Gy given in 4 to 5 fractions with relatively good local control of the thrombus. A Phase 2 trial utilizing SABR in RCC with Level II or higher tumor thrombus is ongoing (NCT02473536).
SABR is frequently considered as a less invasive treatment than surgery for oligometastatic disease. A meta-analysis of 28 studies of SABR in patients with oligometastatic RCC demonstrated a one-year local control rate of 89.1% and only 0.7% of patients experienced a Grade 3 or 4 adverse event.1 A consideration of SABR for oligometastatic RCC is whether it delays time to systemic therapy. In the study below, time from SABR to disease progression was as long as 96 months. In the overall cohort, SABR significantly improved freedom from systemic therapy. Whether SABR for oligometastatic disease remains to be seen.
Dr. So concluded with the following take home points:
- Although not considered “standard of care,” SABR can provide good local control of primary and oligometastatic RCC
- SABR to primary RCC is associated with low toxicity and good local control rates
- SABR to oligometastatic RCC has the potential to delay time to systemic therapy
- There are many ongoing clinical trials to show safety and additive benefits of SABR when combined with systemic therapy
Following Dr. So’s talk, the audio was polled to answer the question “Is radiotherapy a reasonable option for control of primary tumor?” 40% agreed or strongly agreed compared to only 28% who disagreed or strongly disagreed.
Presented by: Alan So, MD, Urologist at the Vancouver Prostate Centre, University of British Columbia
Moderated by: Sumanta Pal, MD, Medical Oncologist at City of Hope Comprehensive Cancer Center and Robert Uzzo, MD, MBA, Urologist at Fox Chase Cancer Center
Written by: Jacob Berchuck, MD, Medical Oncology Fellow at the Dana-Farber Cancer Institute (Twitter: @jberchuck) at the 2020 Genitourinary Cancers Symposium, ASCO GU #GU20, February 13-15, 2020, San Francisco, California
1. NG Zaorsky, et al. Stereotactic ablative radiation therapy for oligometastatic renal cell carcinoma (SABR ORCA): a meta-analysis of 28 studies. Eur Urol Oncol. 2019 Sep;2(5):515-523