What cancer do you have?
Bowel obstruction can be complete or incomplete.
If you have complete bowel obstruction (100% occlusion of the bowel lumen), then surgery should be performed despite that it may cause cancer spreading. If no surgery is done, then you would die from the complete bowel obstruction.
If the bowel obstruction is not complete, then it can be treated medically. Fasting (no eating) could help a lot. Your doctor will give you medicine and fluids through a vein (intravenous or IV). They may also run a thin tube through your nose and into your stomach. This is called a nasogastric (NG) tube. It lets out fluids and gas to ease your symptoms.
Enemas of air or fluid can help clear blockages by raising the pressure inside your bowels.
A mesh tube called a stent is a safe option for people who are too sick for surgery. Your doctor puts it in your intestine to force the bowel open. Some people may not need anything more than a stent. Others may need surgery after they become stable.