Background & objective: The optimal distal molecular clearance margin of rectal cancer hasn't been confirmed. This study was designed to explore the molecular margin of distal intramural spread (DIS)in rectal cancer, and its prognostic value, and to further clarify the required distal margin of radical surgery for rectal cancer.
Methods: Sixty-one P53 positive specimens,resected from patients with rectal cancer from Aug.1996 to Oct. 1997, were collected. Microscopic DIS was examined by P53-immunohistochemistry (P53-IHC),comparing with conventional hematoxylineosin (HE)staining in consecutive large slice. Tissue shrinkage ratio,comparing the distal clearance margin measured in fresh specimens to that measured in large slice after fixed in each case,was used to convert macroscopically measured extent of distal spread to its actual extent. After long-term follow-up, the survival curves of 4 DIS groups were estimated by Life-table method.
Results: With P53-IHC,DIS was observed in 50 cases (82.0%), DIS extents were 0.11-3.50 cm with the mean of 0.59 cm, DIS extent of > 3.00 cm was detected in 1 case only. Meanwhile,DIS was observed in 29 cases (47.5%)by HE staining, DIS extents were 0.10-1.39 cm with the mean of 0.13 cm. There was significant difference between the 2 means (P< 0.0001). The long-term result indicated that the survival rate of DIS extent of >1.00 cm group was lower than those of non-DIS group,and DIS extent of < 0.50 cm group (P< 0.05).
Conclusions: DIS was more exactly detected by P53-IHC than by HE. Most of DIS extents were less than 1 cm in rectal cancer. For over 95% cases, 3 cm distal to the rectal cancers was relatively safe in radical operations. The poor prognosis can be predicted in cases with DIS extent of >1 cm.