In the Milman-Kover Cancer Pavilion of the Brian D. Jellison Cancer Institute at Sarasota Memorial, radiation oncologists utilize the latest in medical technology to command invisible forces against an implacable foe, strategists in a war fought on the microscopic level.
“Radiation oncology is by no means a ‘one size fits all’ branch of medicine,” says Radiation Oncologist Kunal Saigal, MD, Director of Radiation Oncology at the Brian D. Jellison Cancer Institute at Sarasota Memorial.
Here’s how it works.
What is External Beam Radiation Therapy?
Radiation Therapy, more formally defined as External Beam Radiation Therapy, or EBRT, is the use of targeted, high-energy radiation beams to destroy cancer cells in the body, while sparing surrounding tissue.
Non-invasive and low risk but still highly effective, it is a rapidly growing field in modern oncology, with technological advancements that enable radiation oncologists to wield gamma rays like a scalpel.
At the Brian D. Jellison Cancer Institute, oncologists have access to as many as six different types of radiation therapy, each with its own strengths and applications. These include:
But what is radiation therapy?
“It’s like virtual surgery,” Saigal says.
Turning a Linear Accelerator into a Virtual Scalpel
From a physics perspective, all of these radiation therapy techniques use the same basic technology: a linear accelerator to produce beams of radiation and a means to manipulate those beams. The real science—and art—of radiation therapy lies in directing that energy, accurately and consistently, exactly where it needs to go. And nowhere else.
That’s where the doctor comes in, and their tools.
At the Milman-Kover Cancer Pavilion, radiation oncologists treat patients with the Edge, a high-precision linear accelerator designed for image-guided radiotherapy and equipped with a micro-MLC for submillimeter precision.
An MLC, or Multi-Leaf Collimator, is the device that modulates the radiation beams coming from the linear accelerator, using tungsten leaves that move to shape or block the radiation. “Think about the water that comes out of your shower head in all those thin little beams,” Saigal says. “We can basically turn those little beams on or off.”
The Edge has 120 tungsten leaves ranging from 2.5mm to 5mm, computer-controlled to mold the radiation beam into a perfect match for the shape of the tumor, even as the machine rotates around the patient.
“This gives us that necessary precision to treat very small targets, sometimes even less than 5 millimeters, which we often do with small brain metastases,” says Saigal. “That's one of the advantages and one of the reasons that we invested in this technology.”
But this precision means little, if the physician is not armed with equally precise imaging of the cancer and the surrounding anatomy, in order to target the radiation.
Aiming an Invisible Scalpel at a Microscopic Enemy
With the opening of the Milman-Kover Cancer Pavilion comes even more investment in state-of-the-art imaging technology, including:
- The TrueBeam targets tumors with sub-millimeter precision, utilizing real-time 4D imaging and motion management to compensate for breathing and organ movement. It can deliver treatments in as little as 2 to 4 minutes, often keeping sessions under 10 minutes total.
- The Edge has built-in CAT scan capabilities, as well as the ability to track metallic markers implanted before treatment, so that the tiniest movement is detected and the radiation therapy can stay on target.
- AlignRT uses 3D stereo cameras and infrared to provide real-time imagery of the patient’s anatomy and position. “You basically have a virtual cutout of a patient,” says Saigal. And if the patient moves or the accuracy is off for any reason, the radiation automatically cuts off, sparing damage to healthy tissue.
- DoseRT uses Cherenkov imaging (detection of visible light emitted when high-speed radiation passes through human tissue) to precisely map exactly where the radiation is delivered, relative to the patient. “It’s something that very few centers in Florida have,” says Saigal.
“This technology is another way to ensure perfect setups every time,” says Saigal. “We can see exactly where we want to target—not just when we're planning, but in real time—to make sure the treatment is delivered as precisely as possible.”
“That's always an excellent question,” Saigal says. “Most patients think of radiation therapy as physical destruction of the cancer cell, which is very intuitive to think, but that's actually not what's happening.” In reality, radiation therapy is targeting the cancer cell’s DNA, not the structure of the cell itself. “So it's more of a biologic process than it is a physical destruction.”
Cancer cells divide at an uncontrolled pattern and rate. That's why tumors grow and that's why they spread and that’s why they’re a big problem. But if a treatment could inhibit their ability to divide, the cancer cells would eventually die off. Radiation therapy does just that—bombarding cancer cells with harmful radiation until their DNA is too fried to replicate.
Fortunately, cancer cells, by their nature, are highly susceptible to this form of treatment. Their natural mutations give them poor DNA fidelity, meaning they already struggle to accurately replicate themselves, and their poor DNA repair mechanisms are too inefficient to withstand repeated radiation therapy sessions.
“Eventually, there's so much DNA damage that the cells just die off,” says Saigal. “On the other hand, normal tissues have very efficient DNA repair mechanisms, so they’re able to heal very efficiently.”
This is why radiation therapy is often spread out over a long period of time, with regular weekend breaks that give healthy tissue time to repair.
“The joke is always that radiation doesn't work on the weekend,” Saigal says. “It's not that the radiation doesn't work on the weekends, but the body needs some time to recover.”
Why Radiation Therapy Instead of Surgery?
If physicians know exactly where the cancer is and have a perfect 3D model of the tumor, why go through weeks or months of radiation rather than surgery? There are a few reasons.
- 1)It’s non-invasive. Not all patients are good surgical candidates, whether that be due to age, co-morbidities, or location of the cancer. Radiation therapy gives these patients an option.
- 2)It preserves organ function. During surgery, the goal is to eradicate the cancer, not necessarily preserve organ function, Saigal says, while radiation therapy largely preserves normal organ function.
- 3)Surgery isn’t always enough. “Unfortunately, there are very few cancers that can be eradicated completely with surgery alone,” says Saigal. “In most cases, patients need some form of additional therapy, whether that's radiation therapy to clean up microscopic disease or something like anti-estrogen therapy for early-stage breast cancer.”
In fact, a large amount of what radiation oncologists do is in conjunction with surgical oncologists and others.
“The different disciplines work together and go over every case together, exploring every possibility,” says Saigal. “It's important that patients have access to a full multidisciplinary cancer team, so they know all of their options and can make their own informed decision.”
To hear more from Dr. Saigal about using radiation therapy to treat non-cancerous conditions, watch the HealthCasts video below.
Written by Sarasota Memorial copywriter Philip Lederer, MA, who crafts a variety of external communications for the healthcare system. SMH’s in-house wordsmith, Lederer earned his Master’s degree in Public Administration and Political Philosophy from Morehead State University, KY.