Targeted Radiotherapy Before Surgery Improves Control of Kidney Cancer Thrombus

Inferior vena cava tumor thrombus occurs when kidney cancer extends into the body’s largest vein, potentially obstructing blood flow, progressing toward the heart, and making surgery more complex. Standard treatment often involves kidney removal and thrombectomy, but some patients face substantial operative risk. To improve management in these cases, researchers have evaluated targeted radiation before surgery as a potential treatment strategy.

The phase 2 clinical trial at UT Southwestern Medical Center (Dallas, TX, USA) evaluated neoadjuvant stereotactic ablative radiotherapy for kidney cancer with inferior vena cava tumor thrombus. The technique, also known as stereotactic body radiation therapy, delivers precisely focused, high-dose radiation to the tumor thrombus. The approach was followed by surgery to remove the kidney and extract the tumor from the vein.

The trial included 23 patients treated at UT Southwestern and Parkland Health between July 2015 and January 2024. Patients received radiation in either three or five sessions. Of these patients, 22 completed kidney removal and thrombectomy four to 14 days after radiotherapy, and median follow-up was about nine years.

At one year after treatment, 71.4% of patients remained free of recurrence. This exceeded the trial’s prespecified historical benchmark of 55.7%. The findings were published in JAMA Oncology on October 15, 2026.

Researchers also observed regression of tumors outside the radiation field in two of three patients whose cancer had already spread before treatment. This response, known as the abscopal effect, occurred without direct radiation to those tumors or other drug therapy. The team is proposing a national randomized trial to test whether radiation alone can control the thrombus while kidney removal is performed with less extensive laparoscopic or robotic surgery.

“What surprised us was seeing tumors outside the radiation field regress without systemic therapy, which is fairly rare. We suspect the location matters: Blood continually brings immune cells into a tumor growing inside a vein. By damaging that tumor, radiation may help teach the immune system to recognize cancer elsewhere, the so-called abscopal effect. That possibility is exciting and deserves further study,” said Raquibul Hannan, professor of radiation oncology, immunology and urology, and chief of the Genitourinary Radiation Oncology Service at UT Southwestern.

“Combining radiation and surgery gives us a new way to approach one of the most challenging complications of kidney cancer. Our goal is to determine whether this strategy can reduce the burden of treatment and expand options for patients who face substantial risks from extensive surgery,” said Vitaly Margulis, professor of urology.

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