Abstracts
1998 Digestive Disease Week
#1004
RECTAL CANCER: THE IMPACT OF HIGH DOSE PREOPERATIVE IRRADIATION ON DISTAL SURGICAL MARGINS. J. Marks, J. Cotter, G. Marks, M. Mohiuddin,* Dept. of Surgery, Allegheny University Hospital, Philadelphia, PA; *Dept. of Radiation Medicine, University of Kentucky, Lexington, KY.
Traditional data regarding an adequate distal margin of resection in rectal cancer has been based on surgical treatment alone. With the advent of preoperative radiation therapy, a better understanding is needed as to what is an acceptable distal margin. We examined our experience with high dose preoperative external irradiation and sphincter preservation surgery between 1976 and 1994. Using a four field box technique, patients were treated with 1.8-2.5 Gy fractions to a total of 45-60 Gy over 4.5-6 weeks. Following a period 4.5-8 weeks, to allow for maximal downstaging, surgery was performed. Decisions regarding sphincter preservation were based on the cancer after radiation. In 226 patients (mean age 62 y.o.; 85 women) local recurrence rates and distal margins were evaluated in 222 patients. In four patients, data on the distal margin was unavailable, but none had a local recurrence. There were no positive distal margins. There was no operative mortality or major radiation-related morbidity. The average follow up was 59 months. Local recurrence rates are shown below.
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Distal Margin of Resection (cm)
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0.1-0.5
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> 0.5-1
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> 1-2
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2-3
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> 3-4.5
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> 4.5-6
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> 6
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Local
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12%
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0
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16%
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9.5%
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12%
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0
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12%
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Recurrence
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(2/16)
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(0/10)
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(10/61)
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(4/42)
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(6/52)
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(0/16)
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(3/25)
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Using a Chi-Square test for trend, we found no significant differences in local recurrence as the distal margin varied. By comparing groups with margins
> vs. _ 6 cm, 4.5 cm, 2 cm, 1 cm, and 5 mm, there was no statistical difference in local recurrence even when stratified by stage of disease.
Our experience indicates that lesser distal margins are acceptable in rectal cancer treated with high dose preoperative external irradiation. It appears safe to base decisions regarding an acceptable distal margin for sphincter preservation on the characteristics of the cancer after radiation, allowing for the maximal benefit of tumor downstaging.
Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.
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