RT Journal Article SR Electronic T1 476 Incidence of lymph node metastasis in cervical carcinoma with ≤5 mm depth of invasion and >7 mm horizontal spread JF International Journal of Gynecologic Cancer JO Int J Gynecol Cancer FD BMJ Publishing Group Ltd SP A28 OP A28 DO 10.1136/ijgc-2021-ESGO.35 VO 31 IS Suppl 3 A1 L Nicolai A1 R Yigit A1 MCG Bleeker A1 J Bart A1 J Van der Velden A1 CH Mom YR 2021 UL http://ijgc.bmj.com/content/31/Suppl_3/A28.1.abstract AB Introduction/Background*According to the 2018 International Federation of Gynecology and Obstetrics (FIGO) staging system, cervical cancer with ≤5 mm depth of invasion (DOI) and >7 mm horizontal spread, first classified as FIGO stage IB, are now classified as stage IA. For this group of cervical cancers, it is unclear what the risk of lymph node metastases (LNM) is, and consequently, what treatment is recommended. This study aims to determine the incidence of LNM in patients with tumors confined to the cervix, with ≤5 mm DOI and with >7 mm horizontal spread, and to study the association between histological type, diameter, lymph-vascular space invasion (LVSI) and LNM in this group.Methodology In this retrospective study, we selected all women diagnosed with FIGO (2009) IB cervical cancer between 1985 and 2020, with a tumor with ≤5 mm DOI and >7 mm diameter from patient records of the Amsterdam University Medical Center (Amsterdam UMC) and the University Medical Center Groningen (UMCG). All cases with LNM were revised by an expert pathologist. The incidence of LNM was calculated with 95% confidence interval (CI) for the whole population. The associations between histological type, DOI, diameter and LVSI with LNM were evaluated by calculating odds ratios (OR) with 95% confidence intervals (CI) using logistic regression.Result(s)*Of the 398 patients included, 16 had pathologically confirmed LNM (4%, 95% CI 2.3% – 6.4%). No difference in LNM incidence was found between histological types. The incidence of LNM in our cohort was not significantly increased in the presence of LVSI, OR 3.61 (95% CI 0.97-7.4). More LNM were seen in patients with a tumor diameter of ≥20 mm compared to the group of patients with a tumor <20 mm, OR 5.0 (95% CI: 1.81-13.82, p=.002). No cases with LNM were found in the tumors with a DOI of ≤3 mm without LVSI.Conclusion*Lymph node assessment is recommended for patients in 2018 FIGO stage IA with a diameter >7 mm, because of a 4% incidence of LNM. Since no LNM were found in the subgroup of patients in FIGO stage IA1 with a diameter > 7mm without LVSI, lymph node assessment is not recommended for this specific group.