Colorectal Cancer Treatment

Colorectal cancer is the third most commonly diagnosed cancer in the United States. Radiation therapy is used in all stages from stage I to stage IV (metastatic disease). Radiation therapy is used in neoadjuvant treatment (before surgery), adjuvant treatment (after surgery), and palliative treatment.

Colorectal Cancer Symptoms

• Change in bowel habits (diarrhea, constipation, or narrow stools lasting >2 weeks)
• Blood in stool (bright red or dark, tarry black)
• Persistent abdominal discomfort (cramps, gas, pain)
• Unexplained weight loss
• Fatigue or weakness
• Feeling that the bowel doesn’t empty completely
• Iron deficiency anemia (without obvious blood loss)

Causes / Risk Factors

• Age >50 years (though increasing in younger adults)
• Personal or family history of colon cancer or polyps
• Inherited genetic syndromes
• Inflammatory bowel disease
• Low‑fiber, high‑fat diet
• Sedentary lifestyle and obesity
• Smoking and heavy alcohol use
• Type 2 diabetes

Rectal Cancer

Rectal cancer is grouped under colorectal cancer. Radiation therapy is a standard part of the treatment protocol and utilized commonly. For stage II–III rectal cancer (T3–T4 or node‑positive), radiation therapy is utilized prior to surgery to help reduce the risk of a locoregional recurrence. It is typically given with chemotherapy (under a medical oncologist’s care) and delivered over 5-6 weeks, daily (Monday-Friday). For some patients, a shorter course may be utilized over 1 week.

Medically Inoperable Rectal Cancer/Organ Preservation

For patients who are not candidates for surgery (medically inoperable or who refuse surgery), definitive chemoradiation to the primary rectal tumor can achieve long‑term local control in approximately 60‑70% of carefully selected patients. Additionally, for eligible patients seeking organ preservation, total neoadjuvant therapy combined with close surveillance enables a safe watch-and-wait strategy aimed at preserving the rectum without surgery.

Stage IV (Metastatic) Colon Cancer

Up to 20% of patients are initially diagnosed with synchronous metastases, most commonly in the liver. Surgical resection of liver metastases offers the best chance of cure, but not all patients are candidates due to the number, size, or location of metastases or poor liver reserve. SABR, or stereotactic ablative radiation therapy, for oligometastatic disease (up to 5 metastases, each ≤5 cm) can be utilized with excellent rates of local control.

The same SABR technique is used for lung metastases (up to 3-4 cm) and retroperitoneal lymph node metastases from colon cancer. For lung lesions, we use respiratory gating or abdominal compression to account for breathing motion.

Palliative Radiation Therapy for Stage IV Symptoms

For patients with symptomatic metastatic colon cancer, short‑course palliative radiation therapy can offer some relief with:

• Tumor bleeding – radiation therapy delivered over 1-5 treatments can control bleeding in over 90% of cases within 1‑2 weeks.
• Bone metastases pain – radiation therapy delivered over 1-10 treatments provides durable pain relief in 60-70% of patients.
• Bowel obstruction from a pelvic or abdominal mass—a short course of radiation therapy in some cases reduces the mass and allows for bowel function recovery.
• Ureteral compression causing hydronephrosis—radiation therapy may relieve obstruction in select cases

Colon Cancer Treatment: Side Effects and How We Manage Them

Common temporary side effects of pelvic or abdominal radiation include:

• Nausea – typically controlled with modern antiemetics
• Diarrhea – managed with loperamide, dietary changes, and hydration.
• Proctitis (inflammation of the rectum/anus) —usually resolves 2‑4 weeks after treatment ends.

To minimize side effects, we position patients prone (on the stomach) with a bladder-filling protocol (empty bladder, then drink 300 mL of water) and a belly board to push the small bowel out of the radiation field. These techniques reduce the volume of the small bowel receiving high doses. We can also treat patients supine (on their back) and use intensity‑modulated radiation therapy with daily cone‑beam CT to spare the small bowel, kidneys, and spinal cord.

Call 847-698-0600 ext. 112 to schedule a consultation. Our team will evaluate your imaging, discuss all options, and design a personalized treatment plan—whether you need neoadjuvant, adjuvant, ablative, or palliative radiation.