Radiation Therapy: Making Inoperable Cancers Operable

Three techniques—one that protects vulnerable organs from toxicities, one that delivers radiation inside tumors and another that delivers radiation only to cancer cells—are among new approaches radiation oncologist Amol Narang, M.D., is using to improve pancreatic cancer survival.

Which technique is right for each patient is a matter of precision medicine and a key component of the Multi-Disciplinary Clinic in the Skip Viragh Center for Pancreas Cancer Clinical Research and Patient Care. All of the experts involved in the treatment of pancreatic cancer analyze all available information and partner with patients to recommend a treatment plan best suited to the unique characteristics of each patient’s cancer. Narang’s focus is using advanced technologies and discoveries to make inoperable pancreatic cancers operable to give more patients a chance to be cured.

Building upon research using a very precise, high-dose form of radiation therapy, known as stereotactic radiotherapy, Narang can get high doses of radiation to pancreatic tumors that have attached to nearby blood vessels, making surgical removal of the entire tumor difficult or even impossible. These cancers are referred to as locally advanced and borderline resectable (operable) cancers.

“There are a number of very important blood vessels near the pancreas, and as it grows outside of the organ, the cancer attaches to these vessels. It’s hard to do surgery when these blood vessels are involved,” explains Narang. Surgeons must peel the cancer away from these delicate vessels, adding to the complexity of the already complicated surgery and increasing the chances that a few cancer cells will be left behind that can later result in the cancer spreading and coming back.

Stereotactic radiation therapy is focused radiation that reduces exposures to surrounding tissue and organs and makes it possible to deliver higher doses of radiation to tumors over a relatively short period of time—five days versus six weeks with conventional radiation therapy. Combing chemotherapy and stereotactic radiation therapy in patients with pancreatic cancers that have attached to blood vessels, shrinks the tumor, pulling it away from these critical vessels and making surgery possible for more patients.

“Surgery offers patients the best chance of cure. If we can get the tumors removed in these patients with locally advanced and borderline resectable cancers, their survival is similar to those who had surgery as a first treatment,” says Narang.

There is also evidence that radiotherapy may make cancer cells more responsive to subsequent treatment with immunotherapy. The damage it does to the DNA of cancer cells makes the cells more recognizable to the immune system and may prime them to respond better to new drugs that give the immune system an upper hand on cancer. The potential of this immune-boosting component in pancreatic cancer is the focus of clinical trials being led by Lei Zheng, M.D., Ph.D., Co-Director of the Precision Medicine Center of Excellence for Pancreatic Cancer.

Narang is also studying a new material, known as hydrogel, that could make even higher does of radiation therapy possible for pancreatic cancer. The risk of harming the bowel during treatment currently limits the dose of radiation that can be given, Narang says. This new product may solve that problem.

“The pancreas is surrounded by bowel, but if we can inject hydrogel to increase the distance between the pancreas and the bowel, we may be able to deliver higher doses of radiation to the pancreas without harming the bowel,” says Narang.

It is currently being used successfully in prostate cancer patients to protect the rectum from radiation toxicity. The first Kimmel Cancer Center trial for pancreatic cancer testing the ability of the product to reduce radiation exposure to the bowel is expected to begin soon.

Narang says the new Johns Hopkins Proton Therapy Center at Sibley Memorial Hospital, scheduled for completion in 2019, offers another opportunity to improve care for pancreatic cancer patients. Proton therapy uses a precisely targeted, single beam of protons to go directly into tumors where they deposit all of their energy rather than multiple beams of targeted X-rays that hit the tumor and some surrounding tissue as they enter and exit the cancer. The ability of proton therapy to treat pancreatic cancers will be researched in the new center.

Finally, Narang says improvements in endoscopic procedures are allowing radiation oncologists to deliver radioactive seeds internally to pancreatic tumors. Using endoscopy-guided ultrasound to direct the placement of the seeds, Narang can inject radioactive material directly into the pancreas tumor, increasing the radiation dose directly to the tumor without harming other tissues and organs.

“New technologies are allowing us to safely get higher doses of radiation to pancreatic tumors to reduce their size and ability to spread, providing more patients with an opportunity for a surgical cure,” says Narang.