Overview: Pancreas

Located at the T12 to L2 vertebral bodies, the pancreas lies retroperitoneally in the upper portion of the abdomen. It is divided into the head, body, and tail. The pancreas is in direct contact with the duodenum, jejunum, stomach, major vessels (IVC), spleen, and kidney. The tail of the pancreas is the most superior portion, while the head is the most inferior portion located in the C-loop of the duodenum. The main lymph node groups of the pancreas include the superior and inferior pancreaticoduodenal, porta hepatis, suprapancreatic, and paraaortic nodes. Most patients have advanced local or metastatic disease at the time of diagnosis due to the abundance of regional lymphatics. Most pancreatic cancers are adenocarcinomas and carry a very poor prognosis.

Patient simulation & Special Considerations: Pancreas

The simulation process is consistent with the typical abdomen in treating pancreatic cancer. Please refer to Patient Simulation: Abdomen section. The patients pancreas is highly moveable and can shift locations depending on the fullness or emptiness of surrounding structures. The physician may request patients may be NPO 2-3 hours before treatment.

Treatment Volume Localization: Pancreas

Lymph nodes associated with pancreatic cancer include the pancreaticoduodenal, porta hepatis, suprapancreatic, and celiac nodes. When treating the head of the pancreas, the nodal areas above and the entire duodenum must be treated. When the tumor is in the tail or body of the pancreas, the splenic hilar lymph nodes and paraaortic lymph nodes are at risk.

Historically, a 4-field box was used (opposed anterior and posterior fields and opposed lateral fields) to treat pancreatic cancer. The problem with this field arrangement is that the dose delivered to the spinal cord, right kidney, and liver section are higher. Wedges and beam weights are also necessary for treatment planning. Treatment borders for pancreatic irradiation are as follows:

Treatments today still follow these general borders but are more conformal to targeted tissues, sparing normal tissues and reducing toxicity. Because of the difficulty in determining tumor margins, radiologists and radiation oncologists should consult closely to delineate from scans the GTV, including any enlarged regional lymph nodes of 1.5 cm or greater. The CTV should include the visible tumor and the surrounding edema. This area is of considerable uncertainty, and margins must be individually designed. PTV margins are anisotropic with 5-10 mm in the AP direction, 2-4 mm in the transverse plane, and 15- 30 mm craniocaudal for organ movement with respiration or abdominal motion and set-up variations. If breath hold techniques or gating is used (ITV), craniocaudal margins may be reduced.

Treatment Techniques: Pancreas

Traditional fractionation for pancreatic cancers is 200-220 cGy with 25-28 fractions. Resectable tumors are usually treated with 45 Gy to the tumor bed, surgical anastomosis, and regional lymph nodes. If critical structure tolerances are not exceeded, a boost to 50-65 Gy may be delivered. Nonresectable cases have a target dose of 50-60 Gy. The typical energy that provides adequate skin sparing on the lateral aspects of the patient while still evenly distributing the requested dose to the tumor is 10 MV photons. This energy may vary based on patient thickness.

Today, VMAT and MR-Linac are used to treat pancreatic cancer due to their ability to conform to the pancreas and spare surrounding healthy tissue. Common VMAT treatments for the pancreas will consist of two to three complete 360-degree arcs. Studies have shown that IMRT and VMAT treatment techniques further reduce the liver, kidneys, stomach, and small bowel dose compared to 3D conformal treatment.  MRLinac SBRT pancreas fractionation consists of a total dose of 40 Gy delivered in 5 fractions with 8 Gy per fraction. This technique utilizes a treatment every other day, so there should be 40 hours minimum between treatments.

Emerging Technologies & Treatments: Pancreas

A pancreaticoduodenectomy, also called the Whipple procedure, is a potentially curative surgical procedure consisting of the resection of the head of the pancreas, entire duodenum, distal stomach, gallbladder, and common bile duct. Reconstruction is done to maintain the continuity of the biliary GI system. The remaining pancreas, bile ducts, and stomach are anastomosed onto various sites of the jejunum. This highly invasive procedure requires lots of recovery time, making it one of the most challenging surgeries for patients but it does offer the best chance of cure. Newer surgical techniques allow this surgery to be complete laparoscopically.

The TIGER-PaC Clinical Trial uses RenovoRX’s innovative therapy platform to evaluate RenovoGem. This clinical trial treats locally advanced pancreatic cancer through intra-arterial delivery of gemcitabine, a systemic chemotherapy agent often used to treat pancreatic cancer. Systemic chemotherapy associated with debilitating side effects may be ineffective in treating pancreatic cancer due to pancreatic tumors lacking blood vessels. The chemotherapy for the TIGER-PaC trial is delivered via an incision in the leg to give the chemotherapy to the targeted tissue across the vessel wall. The primary goal of this clinical trial is to improve overall survival and quality of life for patients with pancreatic cancer.

Proton Therapy: Can help reduce dose to surrounding organs at risk through a reduction in entrance and exit dose. However, organ motion may present a challenge for proton therapy.

Magnetic Resonance-guided Radiation Therapy (MRgRT): Due to abdominal organs’ movability and placement, a popular emerging treatment option is to treat these patients with MRgRT. The radiation delivery via a magnetic resonance linear accelerator (MR-Linac) uses magnetic resonance imaging with radiation to treat cancer patients. A significant benefit of this treatment technique is the ability to provide motion management and real-time imaging during treatment to ensure the target remains in the treatment field and sparing healthy tissue. It also allows the treatment to “Adapt to Shape” or “Adapt to Position” before each fraction. This is ideal for these cancers because the pancreas may be in a slightly different position each day.

Back to top. ↑