Brain tumors have traditionally been managed with surgical intervention. Advancements in technology and radiation therapy have led to drastic changes in the management of many brain tumors with knife-less procedures. So, how do doctors perform brain surgery without making an incision?

If you take a walk into nearly any major medical center around the world, you will see brain surgery being conducted without typical surgeon’s tools. Instead of an operating room, Radiation Oncologists and Neurosurgeons treat patients in heavily shielded rooms with a therapy known as “Stereotactic Radiosurgery,” or “SRS.” SRS is a technique of delivering incredibly precise, high-intensity radiation to well-circumscribed targets, working to ablate brain tumors without the need for direct access and minimizing injury to surrounding areas.

The overall concept of SRS is to deliver multiple low-dose rays of radiation through different points of entry, to accumulate to one central high-dose area on to a tumor to destroy it . The radiation used in SRS is far more powerful than those used for diagnostic imaging, such as in x-rays used to look for broken bones, and employs the use of highly specialized machines. Typically, “Linacs” are the machines of choice due to their wide availability. These machines output electromagnetically-produced high-energy radiation with the use of a linear accelerator, which accelerates electrons to collide with heavy metals to produce high energy photons that can be directed at a target.

These Linacs also have the ability to rotate 360 degrees around a patient, allowing for multiple angles of radiation dose entry. However, the production of SRS-specific machines have helped to bolster radiosurgery further. Machines such as the Cyberknife, a compact linear accelerator attached to a robotic arm, similar to those automated to build cars, as well as the Gamma Knife , a half-spherical array of 200 Cobalt-60 radiation-emitting sources, have allowed for higher precision and increased range of delivery of radiation.

For patients, the process for SRS treatment begins with 3D mapping and treatment planning. Highly-trained physicists and dosimetrists calculate the doses and angles of entry, simulating customized treatment on a computerized program, to best understand how to maximize tumor dose while minimizing surrounding healthy brain dose.

In order to accurately and safely deliver these high-doses of radiation, patients undergoing SRS are stabilized with the use of tight-fitting customized plastic masks, or metal head frames that are bolted directly to the skull, as the slightest movement can endanger irradiation of a healthy portion of the brain. Once the doctors and physicists determine the best way to target the brain tumor, treatment can begin. Treatments are completely painless and can last anywhere from 30 minutes to several hours, depending on the size and number of tumors to be treated. Sometimes, radiosurgery is fractionated, a process where the total dose is divided into several smaller doses of radiation treated on separate days, up to 5 days. Fractionation is often reserved for tumors that are near other critical healthy portions of the brain, allowing these tissues to better tolerate treatment. Those receiving SRS often see their doctors from home, undergo the procedure, and leave for home the very same day.

Stereotactic radiosurgery has been such an incredible advancement in the treatment of brain tumors that its concepts and techniques are being used throughout the field of radiation oncology, the treatment of cancers with the use of radiation, to other tumors of the body. This type of treatment, often referred to as Stereotactic Ablative Radiotherapy or “SABR ” has exhibited profound effects in tumors of the lung, liver, pancreas, and so on, and in many cases, seen to increase tumor control rates and further sparing morbidity.

Learn more about Stereotactic Radiotherapy here.

The future of non-invasive treatments are bright. Progression in technology have allowed for even further advancements, where now, doctors can better visualize tumor movement and account for breathing in real time, even using MRI imaging technology in conjunction with treatment. Newer techniques such as FLASH radiotherapy, with report of the first patient treated in 2019, allows for ultra high rates of radiation, and has shown to vastly reduce toxicity while preserving tumor ablation. Although the pain of a cancer diagnosis can be devastating, advancements in painless, non-invasive procedures are paving a gentle pathway for cure.

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