The role of postoperative PET-CT in the evaluation of patients with high-risk stage III colorectal cancer (CRC).

Abstract

566 Background: Routine PET-CT evaluation is still not indicated for stage III CRC patients; however accumulating data suggest that it may modify these patients' staging and treatment. We hence evaluated the role of PET-CT in high risk stage III CRC patients and to characterize positive predictors. Methods: Retrospective chart review of stage III CRC patients who underwent PET-CT for being at high risk for systemic disease attributable to: early T stage (T < 3), grade > 3, < 12 lymph-nodes examined, > 3 involved lymph-nodes, elevated postoperative CEA and/or CA-19.9. The demographic and clinicopathological characteristics of patients found to have metastatic disease were compared to those who were negative. Results: Seventy-three patients (33 males [45%], median age 67 years [range: 29-88 years]) were included. Pathologic FDG-uptake was observed in 33 (45%) patients. Of them, 16 (22%) were upstaged with altered treatment protocol, 13 (18%) required further work-up and 4 (5%) were found to have post operative changes. Elevated post-operative CEA and CA-19.9 levels correlated with positive PET-CT (p = 0.002 and p = 0.015, respectively). None of the other examined parameters differed between the groups. With a median follow-up of 26 months (range:1-63 months), overall survival was 88% in patients with positive PET-CT and 92% in patients with negative PET-CT. Eight patients in the positive group were disease free following metastectomy, five were alive with disease, two patients died of disease and one patient died of other cause. Conclusions: Selective postoperative PET-CT influenced staging/therapy in 22% of high risk stage III CRC patients. Postoperative CEA and CA-19.9 levels may play a role in selecting eligible patients. Failure to identify other parameters may be related to the preexisting selection bias and the small cohort. No significant financial relationships to disclose.