DISCORDANCE OF CLINICAL AND PATHOLOGIC STAGING IN LOCALLY ADVANCED GASTRIC ADENOCARCINOMA
Susanna W.L. de Geus, Boston Medical Center, Boston, MA
Background: With recent advances in systemic therapy, the approach to locally advanced gastric cancer is leaning more towards neoadjuvant therapy, as has been the standard of care for esophageal cancer for decades. Clinical staging guides decisions about optimal treatment sequence, although its preoperative accuracy is not strongly established. The present study investigates concordance of clinical and pathologic stage as well as its impact on survival in T2-4 gastric adenocarcinoma.
Methods: Patients with stage T2-4, N0, M0 gastric adenocarcinoma who underwent operations without neoadjuvant therapy were identified from the National Cancer Database (2010-2014). Multivariable logistic regression analysis with backward selection was performed to predict upstaging (cT < (y)pT, (y)pN1-3, and/or (y)pM1). Propensity scores were created for the odds of (y)pT upstaging. Patients were matched based on propensity-score.
Results: In total, 2,908 patients were identified. Stage breakdown was as follows: cT2: 47.9%, cT3: 38.9%, and cT4: 13.2%. cT stage was discordant with (y)pT stage in 42.6% of cases, with 23.7% clinically under-staged and 18.9% clinically over-staged. Stage T4 was misclassified in 12.4% of cases. On multivariable analysis, poor tumor differentiation (vs. well/moderate: OR, 2.59; p<0.001), cT2 (vs. cT3-4: OR, 4.34; p<0.001), and tumor location in the fundus of the stomach (vs. other: OR, 1.87; p=0.009) were predictive of (y)pT upstaging. Undergoing an operation > 4 weeks after diagnosis (vs. £ 4 weeks: OR, 1.03; p=0.783) and low-volume treatment center (vs. high-volume: OR, 1.04; p=0.735) did not significantly impact the likelihood of (y)pT upstaging. After matching, patients who demonstrated (y)pT upstaging had a lower survival compared to patients who were accurately staged, even after controlling for pT-stage (median survival, 30.1 vs. 51.4 months; log-rank p<0.001). In addition, 47.0% of cN0 patients demonstrated positive nodes on pathological examination. Age (OR, 0.99; p=0.002), male (vs. female: OR, 1.30; p<0.001), poor tumor differentiation (vs. well/moderate: OR, 2.60; p<0.001), and time to surgery > 4 weeks (vs. £ 4 weeks: OR, 1.22; p=0.012) were predictive of (y)pN upstaging. However, treatment at a low-volume center did not impact nodal upstaging (vs. high-volume: OR, 1.11; p=0.215). Distant metastases were discovered on pathology evaluation in 2.4% of cases.
Conclusion: This study demonstrated discordance between clinical and pathologic staging of potentially resectable gastric adenocarcinoma in patients who did not receive neoadjuvant therapy. These data may further support using neoadjuvant therapy in all but the earliest stage gastric adenocarcinoma patients, as has been the standard of care in esophageal cancers. Under-staging may misguide treatment decisions.
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