Radiation Therapy for Colorectal Cancer

Radiation therapy is very often used, often in combination with chemotherapy and surgery, in a large fraction of patients with newly diagnosed rectal cancer. There is strong evidence to suggest that the combination of treatments improves the likelihood of cure in patients compared with surgery alone, particularly in more advanced tumors.
Radiation therapy is a form of therapy that directs a highly-focused beam of x-rays to the area or areas of the body that we know or suspect of harboring cancer cells. External beam radiation therapy (EBRT) is by far the most common type of radiation therapy used for rectal cancer.  We utilize a variety of approaches and technologies, customized to each individual patient and situation, so that we can deliver the correct radiation dose precisely where it is needed.  Treatment plans are carefully selected only after discussion between each patient and their other physicians.  Here at the Department of Radiation Oncology at Northern Light Eastern Maine Medical Center, we have only the most advanced technologies to deliver EBRT.  Our physicians, physicists, therapists, and nurses are highly trained and experienced in the management of colorectal cancer.
Some terms that you may hear:
Neoadjuvant radiation therapy = Radiation therapy that is given BEFORE surgery
Often given in order to shrink a tumor before surgery and improve the odds that the surgeon can completely remove the tumor.
Sometimes given in order to permit the surgeon to attempt a less aggressive surgery (for instance, perhaps to avoid a permanent colostomy).
Adjuvant radiation therapy = Radiation therapy that is given AFTER surgery
Often given in order to eliminate microscopic tumor cells that may not be able to be completely removed from the pelvis with surgery.
Definitive radiation therapy
For patients who are not candidates for surgery, or who decline to have surgery, we can consider treating with radiation therapy alone.  In some situations, this can be potentially curative.
Palliative radiation therapy
This is radiation therapy, often delivered in a short period of time, that is given in order to help relieve symptoms of advanced / incurable cancer.  Radiation therapy can be very effective in relieving bleeding, pain, or obstruction.
Simulation = Planning session
This is the process by which we initially plan out the radiation therapy.  We use a CT-scanner to precisely determine the areas we want to treat with the radiation beam, and just as importantly, to determine the areas that we want to protect from the radiation beam (normal tissues and organs).
3DCRT = 3-dimensional conformal radiation therapy
A method of delivering radiation therapy tailored to the patient’s specific anatomy, which reduces the likelihood of injuring nearby normal tissues and organs, such as the bowels, bladder, bones, etc.
IMRT = Intensity-modulated radiation therapy
A more-specialized method of delivering 3DCRT that permits us to even more precisely sculpt the radiation dose, and often permits us to use higher doses of radiation to tumors while reducing doses to normal tissues.
IGRT = Image-guided radiation therapy
A method of using advanced imaging techniques such as a CT scanner moments before delivering each daily treatment, to guide each days’ treatment, and make them more accurate.  This is important because people’s anatomy can change over the course of treatment (for instance, weight gain or loss, organs can shift, etc.), and this allows us to shift the treatment beam to account for these small changes that can occur from day-to-day.
Chemoradiotherapy = Chemotherapy and Radiation Therapy
We often combine the two cancer-killing technologies (Chemotherapy and Radiation Therapy) at the same time.  The chemotherapy can make the cancer cells more sensitive to radiation therapy.  In other words, the radiation therapy is often more effective in patients who are also receiving chemotherapy.