Richard Whittington, MD
Last Modified: November 1, 2001
Dear OncoLink "Ask the Experts,"
I have a question for your panel regarding my father. He is 75 years old and is currently undergoing treatment for a Stage 3 colorectal cancer. The pathology report indicated the tumor to involve the full thickness of the mucosal wall, 2 of 25 local lymph node involved, and the tumor's position just below the peritoneal reflection.
He has been administered 3 cycles of 5FU/ Leukovorin. His oncology team is now suggesting that he combine his next cycle of chemo with radiotherapy, due to the tumor's anatomical position relative to the peritoneal reflection. Can you tell me [approximately, based on current research] the recurrence rate for stage 3 colorectal cancer "just below" the peritoneal reflection when treated with combined surgery/chemo/radiation versus surgery/ chemo alone.
My dad is trying to weigh the potential decrease in cancer recurrence against the additional side effects of the radiotherapy and their effects on his quality of life.
Richard Whittington, MD, Associate Professor of Radiation Oncology at the University of Pennsylvania School of Medicine, responds:
The purpose of radiation is to try to clean up the radial margin (area around the bowel that was taken out) that has a 50 to 60% risk of having microscopic residual tumor. The extra peritoneal colon does not have a serosa (lining) like the peritoneum that slows the dissemination of the tumor. This colon is surrounded by fat that allows tumor cells to migrate freely and there is a higher risk of something microscopic being left behind.
The risks of radiation are diarrhea, perianal irritation (Sunburn), bladder irritation (urinary frequency & urgency) and the risk of a bowel obstruction. The skin clears up a week after radiation; the bladder symptoms improve about 4 to 6 weeks after radiation; the diarrhea gets better when chemotherapy ends, and a bowel obstruction can happen up to 1 year after radiation. The overall risk of the bowel obstruction is only about 4%, but it is heavily affected by the prior history of diabetes, prior abdominal surgery, peritonitis, diverticulitis, the skill of the surgeon, and the skill of the radiation oncologist.
The upside to the radiation is that chemotherapy alone will reduce the risk of pelvic recurrence to about 40% and chemotherapy + radiation will reduce it to about 5%. The morbidity of a recurrence is severe with intractable pain refractory to narcotics, incontinence of bowel and bladder and possible fistulae.