Based on PubMed | Is diarrhea a common side effect of endometrial cancer treatments like chemotherapy or pelvic radiation, and what can patients do to prevent and manage it?

Diarrhea is a fairly common side effect during treatment for endometrial cancer, especially with pelvic radiation and with certain chemotherapy combinations, and it ranges from mild loose stools to more severe, frequent watery bowel movements. ^[1] Many people receiving radiation to the pelvis develop diarrhea within the first few weeks of therapy, along with cramping or rectal discomfort. ^[2] With pelvic radiation alone, any‑grade diarrhea can occur in a large proportion of people, and the risk of moderate to severe diarrhea increases when chemotherapy is given at the same time. ^[1]

How common is it?

• Pelvic radiation: Acute diarrhea is very common during treatment; studies report that a majority develop gastrointestinal symptoms, and any‑grade diarrhea rates can be high. ^[1] Many individuals start noticing loose, watery stools in the first 2–3 weeks of pelvic radiation, and symptoms can persist for several weeks after treatment ends. ^[2]
• Chemotherapy: Several chemotherapy regimens used in gynecologic cancers may cause diarrhea, though the risk varies by drug and dose. ^[3] When chemotherapy and pelvic radiation are combined (chemoradiation), the likelihood and severity of diarrhea are higher than with radiation alone. ^[1]

Why does it happen?

• Radiation to the pelvis can inflame the lining of the small and large bowel (radiation enteritis), reducing the intestine’s ability to absorb fluid and causing faster transit, which leads to diarrhea. ^[2]
• Chemotherapy can injure the rapidly dividing cells of the intestinal lining and alter gut motility and microbiome balance, which can also result in diarrhea and cramping. ^[3]

What symptoms should you watch for?

• More frequent or more liquid stools, sometimes with urgency, cramping, bloating, or rectal pressure. ^[2]
• Signs of dehydration such as dry mouth, dizziness, dark urine, or reduced urination, which may occur if diarrhea is persistent. ^[3]

First-line self-care and diet strategies

• Follow a temporary low‑fiber, low‑fat, and low‑lactose diet while symptoms are present, then gradually reintroduce foods as stools normalize. ^[4]
• Drink plenty of fluids daily, including water and electrolyte-containing liquids (for example, oral rehydration solutions or broths) to replace fluid and salts lost in stool. ^{[5] [6]}
• Eat small, frequent meals, which can be gentler on the intestine during flares. ^[4]
• Limit foods that commonly worsen diarrhea, such as spicy foods, high‑fat foods, caffeine, carbonated drinks, raw high‑fiber produce, and dairy if lactose sensitive. ^{[4] [6]}
• Protect the skin: gentle cleansing with lukewarm water and patting dry can reduce irritation around the anus if stools are frequent. ^[4]

Medications that can help

• Over‑the‑counter loperamide can be used at the first sign of treatment‑related diarrhea unless your care team advises otherwise, as it slows intestinal movement and can reduce stool frequency. ^{[5] [6]}
• If diarrhea does not improve within about 48 hours, your team may add other agents (for example, prescription antidiarrheals) and check for other causes; this stepwise escalation is commonly used in oncology practice. ^[3]
• Octreotide can be effective for refractory chemotherapy‑related diarrhea in some settings, but it did not prevent acute diarrhea when given prophylactically during pelvic radiation in a randomized trial and is not indicated for prevention in that context. ^{[3] [7]}

Professional guidance during pelvic radiation

• Expect that bowel patterns may change during the second to third week of pelvic radiation and can take 2–4 weeks after the last treatment to return toward baseline. ^[4]
• Following the low‑fiber/low‑fat/low‑lactose diet and starting antidiarrheal therapy early when loose stools begin can help limit severity and dehydration risk. ^{[4] [5]}

When to call your care team urgently

• Four or more loose stools above your usual per day, blood in the stool, fever, severe cramping, inability to keep fluids down, dizziness, or signs of dehydration warrant prompt evaluation to prevent complications and to consider IV fluids or medication adjustments. ^[3]
• Persistent diarrhea despite loperamide and dietary measures should be assessed, as medication changes (including dose modifications of cancer therapy) or additional treatments may be needed to keep you safe and on track with therapy. ^[3]

Can it be prevented?

• Routine prophylaxis with octreotide during pelvic radiation is not effective and is not recommended for prevention. ^[7]
• Thoughtful supportive care hydration, early use of antidiarrheals, and diet adjustments can often reduce severity and duration. ^{[4] [5]}
• There is emerging but not definitive evidence that probiotics and soluble fiber may help in chemotherapy‑ or radiation‑related diarrhea; if considered, they should be discussed with your oncology team to ensure safety and appropriate selection. ^{[3] [8]}

Practical checklist

• Start fluids with electrolytes at the first sign of loose stools, aiming for steady sips throughout the day. ^[5]
• Switch temporarily to low‑fiber, low‑fat, low‑lactose foods; choose simple starches (such as rice, bananas, toast), lean proteins, and broths. ^[4]
• Use loperamide as directed by your team; seek help if there is no improvement within 48 hours. ^{[5] [3]}
• Protect skin with gentle cleansing; consider a barrier cream if irritation develops. ^[4]
• Keep a simple diary of stool frequency, consistency, associated cramps, and what you eat and drink, and share it with your care team to guide adjustments. ^[4]

Key takeaways

• Diarrhea is common with pelvic radiation and can occur with some chemotherapy regimens used for endometrial cancer, and it often begins within weeks of starting treatment. ^{[1] [2]}
• Most cases can be managed with hydration, diet changes, and antidiarrheals, but persistent or severe symptoms need prompt medical attention to avoid dehydration and keep cancer treatment on schedule. ^{[3] [5]}