The Maryland Proton Treatment Center (MPTC) has become the first in the world to bring the benefits of deep-tissue external thermal therapy (hyperthermia) to high-precision proton therapy.

Looking to boost survival chances for patients, the Baltimore-based facility plans to administer hyperthermia in combination with proton therapy for treating difficult to reach cancers in the abdomen and pelvic region, based on supporting evidence and studies that suggest the addition of heat sensitizes tumors to radiotherapy and chemotherapy, allowing both to significantly reduce the size of tumors.

“We can offer this treatment to patients, in particular the ones that previously failed at radiation and have to be re-radiated again. In those cases, you are limited in how much radiation can be delivered because of the risk of damage to surrounding organs. That’s why protons are extremely useful," Zeljko Vujaskovic, a professor of radiation oncology and director of the division of translational radiation sciences (DTRS) in the department of radiation oncology at the University of Maryland School of Medicine (UMSOM), told HCB News. "Protons minimize the radiation spillover to critical structures and healthy tissue. If you combine with heat, you can really get more out of this limited dose of radiation that you are trying to deliver a second time."

With a range of 104° F to 110° F, hyperthermia has been proven to sensitize tumor cells to radiotherapy and chemotherapy, as well as enhance anti-tumor immune response. Though applied by radiation oncologists to treat a range of cancers at the University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center (UMGCCC), their use of hyperthermia has not extended to cancers deep in the body.

Using deep-tissue thermal therapy equipment made by Pyrexar, clinicians at MPTC will raise the temperature of the tissue of tumors to 108° F, distributing the heat with internal and external probes that enable continuous temperature monitoring. A water-filled applicator will be put in place over the area that requires treatment, directing non-invasive radio frequency energy at the tumor, with the heat dilating blood vessels and bringing more oxygen into the mass, which makes the cancer cells more vulnerable to radiation therapy.

The application of thermal therapy is a time-consuming, laser intensive treatment with a relatively modest reimbursement that makes it difficult for some facilities to incorporate it. It also requires expertise and training, making it even less widespread, especially outside academic hospitals.

But Vujaskovic says the combination of both thermal and proton therapies, in theory, is equivalent to carbon ion therapy, which is able to kill more cancer cells due to its high linear energy transfer (LET). The therapy, however, is not available in the U.S.

"You need oxygen to kill tumors with radiation, whether you use protons or photons. But one of the properties of carbon ions is that they are completely oblivious to the fact that a cancer has hypoxia, or a deficiency in oxygen, which is one of the major reasons that tumors are radioresistant to treatment," said Vujaskovic. "The notion is that if you use protons that have a similar capability as carbon ions and use heat that is well-known to re-oxygenize tumors and increase blood flow, you could, in theory (there are not enough clinical trials but some preclinical information), mimic carbon ion therapy. In other words, proton and thermal therapy can be a 'poor man’s' carbon therapy."

MPTC is deploying the approach to treat cancers of the bladder, rectum, cervix, ovaries, pancreas and connective tissue, known as sarcomas, administering the therapy twice a week typically for an hour before or after patients undergo radiotherapy or proton therapy.

CPT codes are available to cover both superficial and deep thermal therapy under insurance, with Vujaskovic reporting positive reimbursement from Medicare and other payors at MPTC.

Purchase of the deep-tissue thermal therapy system was funded through donations from Jack and Emily Howell and the Middendorf Foundation Inc.