Preoperative chemo-radiotherapy: is there an associated distal resection margin in rectal cancer?

This study examined what constitutes an acceptable length of distal resection margin when performing sphincter saving surgery for rectal cancer in patients receiving preoperative chemo-radiotherapy.

A resection margin is the edge or border of normal tissue removed with a tumor during surgery. A sufficient distal resection margin has to be attained to ensure complete removal of the tumor and achievement of better treatment outcome. However, the optimal length of distal margins required remains to be controversial in sphincter saving surgery of the rectum. This surgery involves removal of the cancer without sacrificing the anal sphincter (the ring of muscle surrounding the anus).

This study evaluated the optimal length of distal margins in patients with rectal cancer treated with preoperative radiation therapy plus chemotherapy.

This study involved 368 patients who underwent preoperative chemo-radiotherapy and restorative surgery. These patients were divided into two groups by a cut-off value of 3 mm based on the length of their distal margin and were followed up for an average period of 48 months.

Overall, the 5-year pelvic recurrence was 15.2% for patients with a margin of 3 mm or less and 8.7% for those with a distal margin of more than 3 mm.

Results showed that in patients with late-stage rectal cancer, a distal resection margin of 3 mm or less was significantly related to higher 5-year pelvic recurrence (return of cancer to the pelvis) rates. The 5-year pelvic recurrence rate was 86.2% in patients with a distal resection margin of 3 mm or less compared to 66.7% in patients with a distal margin of more than 3 mm.

Patients who did not respond to chemo-radiotherapy with a distal resection margin of 3 mm or less had a pelvic recurrence rate of 89.1% compared to 70.0% in those with a margin of more than 3 mm. In patients who did respond to chemo-radiotherapy the distal margin did not relate to pelvic control.  

Late-stage rectal cancer patients with a distal margin of greater than 3 mm had a 5-year disease free survival (period after surgery in which there is no appearance of the symptoms or effects of the disease) rate of 63.3% versus 55.6% in those with a distal margin of 3 mm or less. Chemo-radiotherapy non-responders with a distal margin of greater than 3 mm had a 5-year disease free survival rate of 66% versus 60% in those with a distal margin of 3 mm or less.  However, the differences were not statistically significant.

In summary, this study concluded that a distal margin of more than 3 mm was associated with better disease outcome in patients with late-stage cancer and in those who did not respond to chemo-radiotherapy.

This study included a small number of patients and from a single institution.