Condition:
Pancreatic Cancer
Contents:
What is pancreatic cancer?
What are the symptoms associated with pancreatic cancer?
How is pancreatic cancer diagnosed?
What treatment options are available?
What is CyberKnife® stereotactic radiosurgery and how might it help patients with pancreatic cancer?
What is the patient process for pancreatic radiosurgery using the CyberKnife?
What are the side effects of CyberKnife treatment?
What results have been seen with CyberKnife radiosurgery for pancreatic tumors?
Are clinical trials with the CyberKnife available?
What is pancreatic cancer?
Pancreatic cancer is an abnormal growth of malignant cells that originates from one of the many parts of the pancreas. The pancreas, a 6-inch organ located behind the stomach in the upper abdomen, produces both enzymes for digesting food and hormones, such as insulin, that regulate multiple bodily functions.
Because the pancreas is composed of a variety of cell types, there are many forms of pancreatic cancer. Unfortunately the most common pancreatic cancer, adenocarcinoma (which arises from the pancreatic duct and gland cells), is also the most difficult to treat. Pancreatic adenocarcinoma, which comprises approximately 95% of all pancreatic cancer, is the main reason there are almost as many deaths from pancreatic cancer each year as there are newly diagnosed cases (about 30,000 each year). The survival rate is generally better for the 5% of pancreatic cancers that are not adenocarcinomas.
There are basically two reasons why pancreatic cancer is so difficult to cure. First, it grows silently with very few symptoms until the tumor is quite advanced or has already spread outside of the pancreas. Secondly, this type of cancer generally does not respond well to many of the available treatments.
What are the symptoms associated with pancreatic cancer?
The earliest signs of pancreatic cancer are often so vague and mild that they are overlooked. The most common early symptoms typically include loss of appetite with mild weight loss and a vague, mild discomfort in the upper abdomen or occasionally in the middle-back area (the pancreas is positioned in the back of the abdomen directly over the spine). Because there are so many other potential, and relatively minor, explanations for this spectrum of symptoms, the earliest signs of pancreatic cancer are often ignored. However, as the cancer progresses, it causes increasingly more noticeable symptoms, such as yellow jaundice (often with little or no associated pain), which stems from the obstruction of the main duct that drains the liver's bile. As the tumor continues to grow, other digestive problems such as bloating or nausea from obstruction of the stomach are also common. Although pancreatic cancer is difficult to detect on physical exam in initial stages, firmness is some times felt in the upper middle abdomen late in the course of the disease.
How is pancreatic cancer diagnosed?
Despite ongoing research to diagnose pancreatic cancer earlier, no effective blood test has been developed to screen for this cancer. Although the presence of blood tumor marker "CA 19-9" may sometimes be used to help confirm a diagnosis of pancreatic cancer or follow a patient after treatment, this relatively simple test has not proven effective as a screening tool. Instead, radiologic tests such as an abdominal ultrasound or CAT scans are used to arrive at a presumptive diagnosis of pancreatic tumor. A definitive diagnosis of pancreatic cancer is most frequently established through subsequent endoscopy and appropriate biopsies. During endoscopy, a lighted fiber-optic tube is passed through a patient's mouth and into the stomach and duodenum (upper intestine). Using an ultrasound probe, it is sometimes possible to biopsy the tumor under direct visualization. The endoscope allows a specially trained doctor to visually inspect this portion of the gastrointestinal tract as w ell as the region in and around the junction with the pancreatic duct. In those patients who suffer from jaundice, a special tube called a stent will oftentimes be inserted into the bile duct at the time of endoscopy to open up this passageway and thereby permit more normal drainage of bile. It is not unusual to use all three of these tests (CAT scan, ultrasound, and endoscopy) when working up suspicious symptoms. Another frequently used method of diagnosis is to pass a needle into the tumor using a CAT scan to direct the placement of the needle. A small sample of the tumor is removed by this method and visualized under a microscope to confirm the presence of a tumor and to identify the type of tumor.
What treatment options are available?
Treatment for pancreatic cancer, as with all cancers, may involve a combination of surgery, radiation, and chemotherapy. To determine the best option(s) for an individual, the cancer is first evaluated and "staged". Staging determines how far a cancer is believed to have spread from its site of origin. Early stages generally have a more favorable prognosis and a much better chance of cure. Unfortunately, most pancreatic cancers when diagnosed usually already display some evidence of either growing into the organs directly surrounding the pancreas ("local invasion"), or have spread to other body sites away from the pancreas ("metastasis"). Metastases can occur to nearby lymph nodes or to more distant sites such as the liver or lining of the abdominal cavity. Treatment for such advanced cancer is rarely successful. In most advanced cases, much of the current treatment is directed at simply making patients more comfortable and improving quality of life.
For earlier stage malignancies, and especially those without metastatic disease, surgical resection (removal) through a procedure called a "pancreaticoduodenectomy" or "Whipple procedure" has been the mainstay of pancreatic cancer treatment. Despite the difficulty and risk associated with this surgery, it has been considered the only real chance for curing pancreatic cancer and offers the best chance of long-term survival. However, some patients with tumors confined to the pancreas are not good candidates for this procedure. If the cancer appears to involve critical blood vessels going to the small bowel (the superior mesenteric arteries), this operation is not feasible. Other patients may have serious medical problems that prohibit such a major operation.
In general, only a small percentage of all pancreatic cancer patients qualify as candidates for surgery, and many receive surgery only as a palliative measure (to relieve symptoms and make them more comfortable). Nevertheless, recent advances in other treatment modalities, such as radiation therapy and chemotherapy, have lead to other promising therapies, especially in situations where the pancreatic tumor cannot be removed surgically. One such development is the use of stereotactic radiosurgery to treat pancreatic tumors.
What is CyberKnife stereotactic radiosurgery and how might it help patients with pancreatic cancer?
Stereotactic radiosurgery is a technique for delivering highly accurate, very large focused doses of radiation to tumors while minimally irradiating surrounding normal tissues. Radiation oncologists and neurosurgeons have been using this technique for almost two decades to effectively treat brain tumors. Improvements in targeting and radiation delivery now allow physicians to treat tumors outside the brain with radiosurgery for the first time. In particular, some radiation oncologists and surgeons are using CyberKnife radiosurgery to treat abdominal tumors. The aggressive doses of focused radiation utilized in pancreatic cases are similar to those that have been shown in prior studies to be very effective in destroying brain and spinal tumors. Multi-institutional clinical studies are presently underway to test the effectiveness of CyberKnife radiosurgery for treating localized, non-metastatic pancreatic cancer. Preliminary studies conducted at Stanford University Medical Center in patients with relatively advanced disease suggested that CyberKnife radiosurgery was both well tolerated and that treatment was associated with some clinical benefit.
What is the patient process for pancreatic radiosurgery using the CyberKnife?
Prior to radiosurgery, 3-5 small gold seeds are implanted in the tumor to serve as fiducial markers
These markers are visible to normal diagnostic x-rays and are tracked by the CyberKnife to determine the precise position of the tumor throughout radiosurgery. The markers are placed through a needle under CT guidance by an interventional radiologist in an outpatient procedure that takes about 1 hour.
Approximately 1 week after the seeds are placed, a treatment planning session is scheduled. At this time, a custom mold (called an alpha cradle) will be made to hold the body in place during the radiosurgery. Next, a specialized pancreatic protocol CT scan will be completed with the patient lying in this custom alpha cradle. The CT images are downloaded to a treatment planning computer and a customized radiosurgery plan is developed according to each patient's anatomy and the shape/location of the tumor.
A team including a radiation oncologist, a pancreatic surgeon, an interventional radiologist, a diagnostic radiologist, a physicist, an oncology nurse, and a radiation therapy technician will all be involved in different aspects of patient care. Bringing together a team of highly trained individuals with different areas of expertise will benefit patients by providing them with the highest quality of care possible.
On the day of radiosurgery, patients receive an anti-nausea pill to take 1 hour before the scheduled treatment. The actual radiosurgery procedure takes place over a period of 3-5 hours. Patients are allowed to eat a normal meal and take all of their normal medications. Following radiosurgery treatment, patients are instructed to eat a light dinner and take another anti-nausea pill later in the evening.
What are the side effects of CyberKnife treatment?
In patients that have been treated thus far, the majority have no side effects related to radiosurgery. They are able to carry out all of their normal activities without interruption. In a minority of patients (approximately 10%), transient episodes of mild nausea and increased abdominal pain have been reported. These symptoms, which all responded successfully to medication, lasted less then 24 hours and all resolved spontaneously.
What results have been seen with CyberKnife radiosurgery for pancreatic tumors?
In a recently completed study at Stanford University Medical Center, patients were treated with radiosurgery using a "low," "middle," and "high" radiation dose. In 100% of patients treated at the "high" dose, all patients had their pancreatic tumors controlled for the remainder of their lives. In other words, these tumors either stopped growing or decreased in size following radiosurgery. In most patients, there was also a corresponding decrease in the level of detectable CA 19-9 (serum tumor marker for pancreatic cancer).
None of these patients suffered any significant treatment-related acute toxicity. As an unexpected benefit, most patients who had pain prior to radiosurgery had a decrease in their pain within a few weeks following treatment. Some patients had such dramatic reduction in their pain that they were able to stop taking all pain medications. Radiosurgery for pancreatic cancer has had a significant impact on improving the quality of life for these patients.
Are there clinical trials with the CyberKnife available?
Yes. Stanford University Medical Center has recently opened a phase II study for pancreatic cancer patients with locally advanced/unresectable (inoperable) tumors. Eligible patients must have tumors that have not spread beyond the pancreas. In this study, patients will be treated with conventional chemoradiotherapy followed by radiosurgery to the pancreatic tumor. Following this treatment, patients will be restaged (re-assessed) and can receive either additional chemotherapy or undergo surgical resection if their tumor regresses enough to be removed surgically.