Overview                                                                   

The Gastrointestinal (GI) tract consists of a wide variety of organs extending from the esophagus to the anus.  Major components include the stomach, liver, pancreas, large and small intestines (bowels), rectum and anus.

GI tumors may arise from any part of the GI tract.  Colorectal tumors are the most common comprising over 100,000 cases per year in the United States.  Pancreatic and gastric (stomach) cancers arise in approximately 30,000 and 22,000 patients per year.  Other GI tumors are more uncommon including esophageal cancer (14,000 cases/year) and anal cancer (4,000 cases/year).  

Primary cancers of the liver are rare in the United States, but are a major cancer worldwide.  Most liver cancers in this country are metastases from other tumor sites, notably the pancreas and colon.

Interested in learning more about specific gastrointestinal tumors? Click here to visit the American Cancer Society website.

Role of Radiation Therapy                                     

A wide variety of GI tumors are treated with Radiation Therapy, notably cancers of the stomach, pancreas, and rectum. In many of these tumor sites, radiation is used in conjunction with chemotherapy either prior to (preoperative radiotherapy) or following surgery (postoperative radiotherapy).  Preoperative chemoradiotherapy is also commonly used prior to surgery in patients with esophageal carcinoma. 

While the mainstay of treatment in most GI tumors, surgery is intentionally avoided in anal cancer by the use of concurrent chemoradiotherapy (view paper).  Such an approach avoids the need for a permanent colostomy improving patient quality of life.

Radiation Therapy Techniques                              

A variety of radiation therapy techniques are used in the treatment of patients with GI tumors.  The most common approach is 3-dimensional conformal radiation therapy (3DCRT).  The 3DCRT technique uses multiple shaped beams which help reduce the dose to the surrounding normal tissues.

3DCRT plan in a patient with rectosigmoid cancer

Depending on the tumor site treated, 2, 3 or even 4 radiation beams are used.  The tumor site also determines how the beams are configured.  In pancreatic cancer patients, 3 beams are used, entering anteriorly and from the right and left sides (lateral fields).  This technique helps reduce dose to the posteriorly located kidneys.  In rectal cancer patients, while 3 beams are also used, two lateral beams and a posterior beam are selected.  This configuration reduces the dose to the anteriorly located small bowel.

Intensity Modulated Radiation Therapy (IMRT)

In recent years, however, a sophisticated form of 3DCRT known as intensity modulated radiation therapy (IMRT) has been increasingly used in GI tumor patients.  Unlike conventional approaches, IMRT using highly modulated beams designed using sophisticated computerized optimization planning. Such beams conform the radiation dose to the shape of the tumor in 3D, reducing the volume of normal surrounding tissues receiving high doses (and thus the risk of treatment related sequelae).

Multiple investigators have reported promising results using IMRT in GI tumor patients (view paper 1 and paper 2).

IMRT plan in a patient with pancreatic cancer

IMRT is particularly appealing in patients with anal cancer (view paper).  In such patients, conventional approaches result in the irradiation of large volumes of normal tissues, exposing patients to a wide range of toxicities.  IMRT helps minimize the dose to these structures reducing the risk of treatment toxicities (view paper). 

IMRT plan in a patient with anal cancer

TNFerade Biologic                                                               

Pancreatic cancer patients treated at UCSD may be eligible for a noverl treatment approach. An adenovector (or DNA carrier), TNFerade (view paper) contains the gene for tumor necrosis factor alpha (TNFα), an immune system protein with potent and well-documented anti-cancer effects, for direct injection into tumors. 

The TNFα gene is turned on when the tumor is exposed to radiation therapy, resulting in high doses of chemotherapy within the tumor.  TNF not only leads to direct tumor killing, it also enhances the ability of radiation to destroy the tumor cells. 

If you are interested in learning more about TNFerade and the nation wide study of its use in pancreatic cancer, check out the GenVec website (manufacturers of TNFerade).

TNFerade was invented by Ralph Weishselbaum, M.D., a mentor to UCSD Radiation Oncologists Drs. Arno Mundt  and Kevin Murphy.  Dr. Mundt was the principal investigators on one of the first clinical trials evaluating TNFerade performed in the United States ( view paper).

UCSD Gastrointestinal (GI) Tumor Team                        

The UCSD GI Cancer Team is comprised of dedicated professional with considerable experience in the care of patients with GI cancers. 

Catheryn Yashar M.D. is the Chief of the GI Tumor Service in the UCSD Department of Radiation Oncology.

Catheryn Yashar, M.D. Chief, GI Tumor Service Department of Radiation Oncology

Dr. Yashar has considerable expertise in a wide variety of radiotherapy techniques used in GI cancer patients, including 3DCRT and IMRT.

Fiona Nasseraddin, R.N. Radiation Nurse Department of Radiation Oncology

Treatment of GI Cancers is a team approach. Dr. Yashar thus works closely with a number of professionals from other UCSD Departments including Surgical Oncologists Sonia Ramamoorthy, M.D. and Michael Bouvet, M.D., and Medical Oncologist Tony Reid, M.D., Ph.D.

Sonia Ramamoorthy, M.D. Surgical Oncologist

Michael Bouvet, M.D. Surgical Oncologist

Tony Reid, M.D., Ph.D. Medical Oncologist

Andy Lowy, M.D. Chief, Surgical Oncology

Gastrointestinal (GI) Tumor Publications by UCSD Radiation Oncology Faculty       

Listed below are Gastrointestinal (GI) Tumor Articles published by members of the UCSD Department of Radiation Oncology.  For a full list of published articles by UCSD Radiation Oncology faculty see Research section

Salama JK, Mell LK, Devisetty K, Jani AB, Mundt AJ, et al. Multicenter Outcome of Anal Canal Cancer Patients Treated With IMRT.  Int J Radiat Oncol Biol Phys 2006;66:S273

Mell LK, Salama JK, Roeske JC, Devisetty K, Jani AB, Mundt AJ et al. Dosimetric Predictors of Acute Hematologic Toxicity in Anal Cancer Patients Treated With Concurrent Chemotherapy and Intensity Modulated Radiation Therapy (IMRT). Int J Radiat Oncol Biol Phys 2006;66:S277

Devisetty K, Mell LK, Salama JK, Jani AB, Mundt AJ et al. Anal Cancer Treated With Intensity Modulated Radiation Therapy (IMRT) and Concurrent Chemotherapy: A Dosimetric Analysis of Acute Gastrointestinal Toxicity. Int J Radiat Oncol Biol Phys 2006;66:S287

Sandhu APS, Symonds RP, Robertson AG et al: Interstitial Iridium-192 implantation combined with external radiotherapy in anal cancer: Ten years experience. Int J Radiat Oncol Biol Phys 1998;40:575

Dobelbower RR, Merrick HW, Khuder S, Battle JA, Herron LM, Pawlicki T. Adjuvant radiation therapy for pancreatic cancer: a 15-year experience. Int J radiat Oncol Biol Phys 1997;39:31