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Fighting tumors with brain implants

El Camino doctors turn to radiation 'tiles' in the fight against reoccurring brain tumors

El Camino Hospital physicians are taking a new approach to stubborn brain tumors that keep coming back, debuting a surgical treatment last month that plants a radioactive device directly into the patient's brain.

The treatment, called GammaTile Therapy, involves removing a malignant tumor and implants radioactive material in its place to finish off any residual cancer cells that, if left alone, could bring the tumor right back. The small implant is just 2 centimeters in size, and is outfitted with a low-energy isotope that decays in about a month.

Neurosurgeons have long grappled with recurrent brain tumors, removing malignant growths in a patient only to find a new tumor develop in the same spot within weeks. So-called primary brain tumors, which originate in the brain tissue rather than metastasizing from other organs, have a high chance of growing right back after removal, said Dr. Robert Sinha, a radiation oncologist at El Camino Hospital in Mountain View.

Hitting the affected area with chemotherapy and other targeted and biological treatments can reduce the chance of it coming back, but it's hardly a guarantee, he said.

"They almost always recur, and that is a very significant problem," Sinha said.

The frustrating recurrence rate is rooted in the fact that healthy brain tissue surrounding cancerous tumors is too important to lose. Residual cancer cells left behind after a malignant growth is removed are the culprit behind recurrent brain tumors, but they are invisible to neurosurgeons, even under a microscope. Physicians can't take out what they can't see, Sinha said, and what they can't see is leftover abnormal cells.

Carving out an extra layer of healthy tissue just to be on the safe side is out of the question when you're talking about brain tissue, said Dr. James Doty, a neurosurgeon at El Camino. He said anything removed beyond the tumor itself can have "dire consequences," particularly if it's near a part of the brain that controls motor function.

"We don't want to remove normal brain which could be part of a critical structure," Doty said.

The new tech, designed by the Arizona-based company GT Medical Technologies, is a small collagen plate containing four "seeds" of cesium-131, commonly used in the medical field for cancer treatments. The low-energy element is ideal for penetrating a couple millimeters of the brain without harming surrounding tissue, Sinha said, and it decays quickly. The half-life of cesium-131 is only 9.7 days.

The first patient to receive the treatment at El Camino Hospital in Mountain View last month was, in many ways, an ideal candidate for the treatment, Sinha said. She had esophageal cancer that was in remission and a brain tumor that had previously been taken out. Despite being treated with radiation, the tumor had returned. The growth was located near the motor cortex, meaning any damage to nearby healthy tissue could cause serious problems.

"This is a case that was ideal," Sinha said. "She really did not have any other options."

Though it will take many months to determine whether the GammaTile was a success, early MRIs are showing she is completely free of cancer, Sinha said.

The implant is the result of years of research and development by GT Medical Technologies, and is the flagship product of the medtech startup company. The venture was founded by a group of brain tumor treatment specialists who were frustrated with the limitations of treating brain tumors, said Ashley Hupman, marketing director for the company.

The treatment is particularly useful for patients whose brain tumors have returned more than once and can no longer be safely treated with standard radiation treatment, Hupman said. Although external "beam" radiation therapy can target the site of brain cancer, it still has to go through healthy tissue. There's a maximum amount of radiation patients can be exposed to before it risks killing off important brain functions, and that's when physicians have to candidly tell patients there's nothing more they can do, she said.

Hupman described how one patient had a glioblastoma tumor that was removed and came back within a month. The neurosurgeon took it out a second time and treated the area with external radiation only for it to return in full -- in the same spot -- within a month. The third time the tumor was removed, a GammaTile was implanted, and the tumor has yet to return, she said. Gliobastoma is the aggressive and incurable type of cancer that killed Sen. John McCain.

Whether or not the treatment will work for patients is dependent on how old they are and, more importantly, the location of the tumor. If it's right up against the optic nerves or the brain stem, it may not be safe to remove the tumor and treat the area with radiation, even low-grade radiation.

GammaTile's flagship product cleared FDA approval in July 2018, but only for treating patients whose tumors have regrown after being removed. The company has slowly rolled out the treatment to a select group of hospitals including El Camino, which is the first location on the West Coast to carry out the procedure. Hupman said El Camino was targeted by the company for fostering a strong relationship between its neurosurgeons and radiation oncologists.

Doty credited El Camino for being supportive of medical innovation and quick to streamline approval of the device, particularly when he had a patient at the ready who was a perfect fit for the treatment.

"You could not pick more of an ideal candidate, in that this is the exact patient that this therapy was designed for," he said.

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