May Abdel-Wahab MD, PhD, Abstract Co-Author: Nothing to Disclose

Chandana A. Reddy MS, Abstract Co-Author: Nothing to Disclose

Luca Stocchi MD, Abstract Co-Author: Nothing to Disclose

I. Emre Gorgun MD, Abstract Co-Author: Nothing to Disclose

Matthew Kalady MD, Abstract Co-Author: Consultant, Precision Therapeutics, Inc Speaker, Precision Therapeutics, Inc

Ravi Kashyap MD, Presenter: Nothing to Disclose

David W. Dietz MD, Abstract Co-Author: Nothing to Disclose

Purpose/Objective(s):The poor prognosis for rectal melanoma has prompted the use of adjuvant radiation as a treatment approach. The purpose of this study is to determine if a survival benefit is seen when radiation therapy is administered after surgical resection in rectal melanoma patients in a large population-based database.Materials/Methods:Analysis of rectal melanoma cases in the SEER Registry between 1973 and 2008 who either underwent surgery alone (S) or surgery and radiation (S+RT) was done. Chi-square and unpaired tests were used to compare cases that did and did not receive radiation. Overall survival (OVS) and cause specific mortality (CSM) were analyzed. For CSM, a competing risk regression was done, where death from causes other than rectal melanoma were treated as competing events. Multivariate analysis (MVA) included treatment arm, extent of disease (regional vs Localized vs distant), age at diagnosis, race, and gender.Results:One hundred and fifty-five patients with melanoma of the rectum were studied (S 130; S+RT 25). The median follow up was 14 months for all patients, with median survival of 15 months in both groups. There were more localized tumors in the S group (43.8%) than the S+RT group ( 36%) (p=0.0108). No differences in age, race, gender, grade and geographic location were seen between S vs S+RT. Median survival was 15 months in both groups. One and 3-year OVS were 73.6% and 35.1% for the S arm versus 70.8% and 24.8% in the S+RT arm. The addition of radiationdid not significantly influence OVS on MVA-only stage was significant (p<0.001); the only significant factor for Cause Specific Mortality was the presence of distant disease- there was no significant difference between regional versus localized disease.Conclusions: In our series of resectable rectal melanoma patients, adjuvant treatment with radiation therapy led to a similar OVS and CSM to surgery alone inspite of the more advanced stages seen in the S+RT group. Further investigation of this approach may be warranted.

Abdel-Wahab, M, Reddy, C, Stocchi, L, Gorgun, I, Kalady, M, Kashyap, R, Dietz, D, The Impact of Radiation Therapy after Resection on Survival in Rectal Melanoma.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14044205.html