Expert Discusses Success of Stereotactic Radiation in RCC

Raquibul Hannan, MD, PhD

A recent study demonstrated that treatment with a focused form of stereotactic radiation led to a greater than 90% rate of local control in patients with metastatic renal cell carcinoma (RCC), according to findings published in the International Journal of Radiation Oncology, Biology, and Physics.

“We have data that show that RCC responds very well to this stereotactic radiation. By giving high doses during treatment days, we can potentially cure RCC more effectively than with conventional treatments,” said senior study author Raquibul Hannan, MD, PhD.

OncLive: Can you please discuss this study?

In an interview with OncLive, Hannan, an assistant professor and radiation oncologist at The University of Texas Southwestern Medical Center, discussed the benefits of using stereotactic radiation for patients with RCC and highlighted ongoing trials examining the modality.Hannan: This is a retrospective study, where we viewed our experience over the past 5 to 7 years. We were one of the pioneers in studying stereotactic radiation, which is a very focused form of radiation. Because of this, we can deliver a dose without creating normal tissue damage, making the side effects very good.

This form of radiation allows us to treat the tumor anywhere in the body. With old conventional forms of radiation, you couldn't give a very high dose to the tumor that is right next to the spinal cord or the stomach because they are very radiosensitive structures.

Essentially, the tumor can be anywhere in the body and we can effectively treat it. This is especially important for patients with RCC because it is known to be resistant to the conventional forms of radiation. With conventional forms, you're giving small amounts of doses which can last from 5 to 7 weeks, whereas the stereotactic radiation lasts from 3 to 5 days.

We have data that shows that RCC responds very well to this stereotactic radiation. By giving high doses during treatment days, we can potentially cure RCC more effectively than with conventional treatments.

We've been studying stereotactic radiation in our institution for quite some time now. This study shows that in more than 90% of cases, we can cure the tumor when we use stereotactic radiation in the setting of kidney cancer.

The only times where the patients failed was when the tumor was in the spinal setting. Another area that saw failure was in patients that had prior multiple lines of systemic therapy since this has made the tumor more resistant. Those were the few failures we’ve seen which we have analyzed to determine how to apply stereotactic radiation to patients more appropriately.

How do the side effects of stereotactic radiation compare to conventional treatments?

Based on this study, if a patient has already failed multiple lines of systemic therapy, the patient needs to receive higher doses of stereotactic radiation to cure these patients. In this study, we were able to develop specific dose recommendations based on our analysis. Additionally, I have 4 ongoing prospective clinical trials to apply stereotactic radiation effectively to patients with kidney cancer.The chances of side effects were much lower with stereotactic radiation compared to conventional treatments. The conventional radiation is a bigger field of radiation, meaning radiation is given to normal tissue and is not able to spare it with a more focused application, such as what we have with stereotactic radiation. Overall, there were only a few grade 3 toxicities.

What patient population saw the most beneficial response to stereotactic radiation?

The side effects are so low, making the quality of life much better. Patients are able to enjoy their daily activities, whereas chemotherapy and systemic therapy see side effects of high blood pressure, tiredness, fatigue, rashes, and other effects ultimately decreasing the quality of life. In one of the current clinical trials, we want to see if we can safely delay the start of the systemic therapy by treating metastatic sites with stereotactic radiation. We applied stereotactic radiation in patients with metastatic RCC limited to 1 to 5 sites of disease. If a patient has completely widespread metastatic disease, we cannot possibly treat all of those sites with stereotactic radiation. If they have a limited number of metastatic disease, then we can treat each of those with stereotactic radiation. This is one of the reasons we are calling this a noninvasive form of surgery. If a patient has 1 to 5 sites, we can still effectively treat them, hopefully giving these patients somewhat of a curative chance.

What are the next steps regarding stereotactic radiation?

Ideally, patients who underwent surgery for their primary kidney tumor but saw the cancer come back in 1 to 2 sites are going to have the best chance of being cured with radiation.We hope to integrate it properly in the care of patients with kidney cancer. Since the high success rates are a relatively new finding, we are hoping to integrate it into the overall management of patients with kidney cancer.

For example, for patients with stage I kidney cancer, we now have a phase II clinical trial where we are bringing this stereotactic radiation to small kidney tumors, completely curing the patients. So far, every single patient who has been treated on this study has been cured from this cancer. We only need 15 patients to complete accrual of the trial. The standard of care for patients with stage I kidney cancer is surgery, and not every patient is a candidate for surgery, either due to age or other health factors. The non-candidates for surgery can now easily have an alternative that is completely noninvasive and will give them a very good chance of being cured.

We have another clinical trial for patients with stage III kidney cancer, focused on treating the tumor thrombus right before the patient goes into surgery. The goal of this study is to determine if stereotactic radiation is going to decrease the chance of a patient coming back with metastatic disease. We are hoping to improve the very poor outcome of patients with that stage III kidney cancer that go through surgery. That trial is also accruing and we hope to have the results soon.

In stage IV kidney cancer, stereotactic radiation does a very good job in terms of controlling the disease and improving a patient’s outcome. In this setting, we have 2 ongoing clinical trials. In one of the trials, we are looking to see if we can delay the start of systemic therapy by giving stereotactic radiation.

Wang CJ, Christie A, Lin M-H, et al. Safety and efficacy of stereotactic ablative radiation therapy for renal cell carcinoma extracranial metastases [published online May 1, 2017]. Int J Radiat Oncol Biol Phys. http://dx.doi.org/10.1016/j.ijrobp.2017.01.032.