SAN DIEGO—Hypofractionated image-guided radiation (HIGRT) can achieve good local disease control with minimal toxicity in patients with metastatic renal cell carcinoma (RCC).

Selected use of HIGRT may delay or avoid the requirement of systemic therapies, according to new data presented at the 52nd Annual Meeting of the American Society for Radiation Oncology.

Historically, RCC has been thought to be a radio-resistant malignancy. Among RCC patients who have intracranial metastases, data support the use of stereotactic radiosurgery. The usefulness of hypofractionated treatments to other sites of metastatic disease has not yet been fully investigated. Researchers at The University of Chicago analyzed the use of HIGRT in the treatment of metastatic RCC in various locations throughout the body.

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From October 2006 to March 2010, patients with RCC and a limited burden of metastatic disease were referred for HIGRT. All subjects received computed tomography (C)-based treatment planning with the use of respiratory gating, as well as a 4D CT scan as appropriate.  All the subjects were treated with 3D conformal radiotherapy. A variety of fractionation schemes were used, with the most common being 10 treatments of 5 Gy doses or three treatments of 10-16 Gy doses. Image-guidance in the form of orthogonal kilovoltage imaging and cone beam CT scanning were performed prior to radiation treatments to ensure accurate radiation delivery. 

Eighteen patients with metastatic RCC received treatment to 39 metastatic lesions using a HIGRT technique; 12 of them received treatment to all sites of known disease. The mean follow-up period was 10.6 months and the median number of treated lesions was two per patient. As many as seven sites of disease were treated in a single patient. The most commonly treated sites were bone (11 lesions), abdominal lymph nodes (10 lesions), mediastinal lymph nodes (seven lesions), and lung nodules (four lesions).

The treatment was well tolerated. Mild fatigue, which occurred in 61.1% of patients, was the most common acute toxicity. Local control was 97.4% at 18 months for all treated lesions. In the patients treated to all sites of known disease, the mean follow-up was 12.2 months. At 18 months, local control was 100% and distant control was 34.3%.

“There are several medications that are approved for metastatic renal cell carcinoma, but those medications can be quite toxic so if we can identify some patients who may benefit from local treatment with radiation it may be able to delay them from having to go on these medications,” said study investigator Mark Ranck, MD, a radiation oncology resident at the University of Chicago.

He noted that late toxicity was limited, consisting of only one case of radiculitis and one rib fracture. At two years, overall survival was 77.9%. No patient who received treatment to all disease sites had died.

The researchers say HIGRT may be seen as a type of “bridge” because it could delay the need to start systemic therapy. “We also think there is a certain subset of renal cell carcinoma patients, who even though they have growth of their disease, radiation therapy can salvage them and lead to the disease not interfering with their life,” said co-investigator Joseph Salama, MD, now Assistant Professor of Radiation Oncology at Duke University in Durham, N.C. “Surprisingly the side effects are quite mild. That is one of the reasons this is promising as a bridge therapy; it doesn’t have side effects like the hand-foot syndrome you get with sorafenib and sunitinib. It also doesn’t lower blood counts as those medications do.”