Dr Hayes said the next big hurdle that needs to be overcome is tumor resistance to certain treatments. It is now hoped that combination therapies that act on different targets given simultaneously may help minimize drug resistance. Dr Hayes said SBRT can also be used in this setting to allow for a break from systemic therapy in patients for whom there is only one or few sites of progression that can be treated adequately with SBRT.

“This has the potential for not only improving patients’ quality of life, but also potentially prolonging the time to resistance to systemic therapies and improved response rates when the patient is rechallenged with the same systemic therapy later on in their disease course,” said Dr Hayes.


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She expects radiation’s role will change as more targeted systemic therapies come on the market. However, targeted therapies and radiotherapy are not mutually exclusive and although they have overlapping roles, they are not distinctly separate, but rather, complementary modalities.

“Most cancers require optimal local and distant control and therefore both targeted therapies and radiation will be paramount to improving outcomes,” said Dr Hayes.

Patrick Kupelian, MD, vice president of clinical affairs at Varian Medical Systems, Palo Alto, CA, said in the context of systemic targeted therapies, radiation is being investigated as an appropriate and maybe desired combination modality. He said ablative local therapy is still often needed with radiation being an established and effective method.

“There are currently a multitude of trials using modern radiation therapy techniques and schedules with immune modulation drugs, or other systemic agents. The next hurdles will be establishing the best combinations of drugs and radiation, in addition to identifying best responder patient subsets through well-designed clinical trials,” Dr Kupelian told Cancer Therapy Advisor.

He said it is highly unlikely that targeted therapies would completely replace radiotherapy in front-line therapy in any specific tumor type. Most targeted therapies produce durable responses in a small minority of cases.

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“Most commonly, drug combinations are required, again producing infrequent responses that are often only temporary. It is more likely that combination targeted therapies and short-course high-dose radiation therapy will be studied, and expanded into novel indications, such as in patients with metastatic or at least oligometastatic disease in melanoma, breast, prostate, lung, and kidney cancers amongst many. This will possibly require novel ways of sequencing and delivering radiation therapy,” said Dr Kupelian.   

Editor’s Note: Dr Hayes’ affiliation was updated on February 26, 2016.

               

Reference

  1. American Cancer Society. Types of targeted therapies used to treat cancer. American Cancer Society website. http://www.cancer.org/treatment/treatmentsandsideeffects/ treatmenttypes/targetedtherapy/targeted-therapy-types. Updated December 11, 2014. Accessed February 21, 2016.