Is presumed clinical stage I endometrial cancer using PET-CT and MRI accurate in predicting surgical staging?

OBJECTIVE: To evaluate upstaging, lymph node (LN) metastasis, and recurrence in patients with presumed stage I endometrial cancer using preoperative magnetic resonance imaging (MRI) and positron emission tomography-computed tomography (PET-CT). METHODS: Retrospective review of 422 patients with presumed clinical stage I endometrial cancer diagnosed via MRI and PET-CT (July 2014-June 2023). Surgical staging included pelvic lymph nodes (PLNs) and para-aortic lymph nodes (PALNs), classifying patients as low/intermediate- or high-risk groups. RESULTS: Post-operative upstaging rate was 14.5% (8.8% low/intermediate-risk vs. 22.8% high-risk, p<0.001). LN metastasis occurred in 5.5% of patients (2.0% low/intermediate-risk vs. 10.5% high-risk, p<0.001), with a dual imaging negative predictive value of 0.945. PLN metastasis was 4.5% (2.0% low/intermediate vs. 8.2% high-risk, p=0.003), and PALN metastasis was 2.6% (0.4% low/intermediate-risk vs. 5.8% high-risk, p=0.001). In low/intermediate-risk group: tumors ≤2cm had 1.1% LN metastasis rate, endometrium-limited 0.8%, and ≤2cm with endometrium-limited 0.9%. Deep myometrial invasion (odds ratio [OR]=4.4; 95% confidence intervals [CIs]=1.6-12.4) and tumor size >2 cm on MRI (OR=2.9; 95% CI=0.8-9.9) increased LN metastasis risk. Median 48.5-month follow-up showed an 8.1% overall recurrence rate (4.0% low/intermediate-risk vs. 14.0% high-risk, p<0.001), with 2.4% nodal recurrences (1.2% low/intermediate-risk vs. 4.1% high-risk). CONCLUSION: High-risk patients had significant upstaging, LN metastasis, and recurrence rates. Even in low/intermediate-risk groups, some patients exhibited LN metastasis and nodal recurrence, underscoring the importance of comprehensive surgical staging, including PALN evaluation, for precise diagnosis and treatment.