R. J. Straker1, C. E. Sharon1, S. Grinberg1, A. B. Shannon1, D. L. Fraker1, S. Shanmugan1, J. T. Miura1, G. C. Karakousis1 1Hospital Of The University Of Pennsylvania, Department Of Surgery, Philadelphia, PA, USA
Introduction: Full oncologic resection via right hemicolectomy (RHC) to obtain appropriate lymph node staging is currently recommended for patients with non-mucinous adenocarcinoma of the appendix (NMACA). However, it is unclear whether a group of patients exist with early NMACA who may be at low risk of developing LN metastases, and thus might be amenable to a less extensive resection without compromising outcomes.
Methods: The National Cancer Database was used to perform a retrospective analysis (2004-2016) of patients with NMACA without distant metastases who underwent margin negative surgical resection via either an RHC or appendectomy/partial colectomy (A/PC) and had at least 1 lymph node evaluated. Patients with lymph node metastases were compared to those without lymph node metastases to identify factors prognostic for nodal spread. Multivariable survival analysis was performed using Cox proportional hazards analysis. Five-year overall survival (OS) outcomes were compared between patients who underwent RHC versus A/PC using the Kaplan-Meier method and log-rank test.
Results: Of the 2,866 patients evaluated, 842 (29.4%) had nodal metastases. T4 T-stage (odds ratio [OR] 3.4, p=0.012), poorly/undifferentiated histology (OR 1.9, p=0.045), and lymphovascular invasion ([LVI], OR 4.3, p<0.001) were significantly associated with nodal metastasis. Forty-nine patients had tumors at low-risk for lymph node positivity (T1 T-stage tumors with well-differentiated histology and without LVI), and among this low-risk group, the rate of lymph node positivity was 2.0% (95% confidence interval [CI] 0.36%-10.69%). Conversely, among the 2,817 non-low-risk patients, the rate of lymph node positivity was 29.9% (95% CI 28.19%-31.57%). Twelve (24.5%) and 619 (22.0%) patients with low risk and non-low-risk tumors, respectively, underwent A/PC. No significant difference was observed between RHC and A/PC patients in regard to likelihood of treatment with adjuvant systemic therapy (OR 0.97, p=0.811). On multivariable survival analysis of the entire cohort incorporating patient, tumor and treatment factors, performance of A/PC as compared to RHC was associated with a survival disadvantage (hazard ratio 1.47, p=0.047) However, among patients with low-risk disease, 5-year OS did not significantly differ based on the type of surgical resection performed (83.3% A/PC vs. 88.9% RHC, log-rank p=0.726) (Figure 1).
Conclusions: Early NMACA with favorable features (T1 T-stage, well-differentiated tumors without LVI) appears to be associated with a very low risk of lymph node positive disease. These patients may be spared the morbidity of more extensive surgery without compromising outcomes.
