Lymphovascular space invasion (LVSI) - the presence of cancer cells within the lymphatic or blood vessel channels of the uterus - is one of the most important prognostic factors in endometrial cancer. It predicts lymph node involvement, cancer recurrence, and overall survival.
LVSI is used in clinical decision-making to classify patients as high-intermediate risk, determining whether they should receive adjuvant radiation therapy. The landmark GOG 99 trial established LVSI as a key criterion for this risk classification, alongside high-grade histology and deep myometrial invasion.
Over the past decade, robot-assisted laparoscopic surgery has largely replaced open abdominal hysterectomy as the preferred approach for endometrial cancer, offering reduced blood loss, shorter recovery, and fewer postoperative complications. However, a concern arose: could the uterine manipulator used during robotic procedures artificially push cancer cells into the lymphovascular space, creating false LVSI readings?
The manipulator, inserted through the cervix into the uterine cavity, creates a closed pressure system. Researchers theorized this pressure could initially release cancer cells into surrounding lymphovascular spaces, with additional mechanical forces displacing them further during surgical removal. This so-called "pseudo-LVSI" could cause patients to be unnecessarily classified as high-risk and overtreated with adjuvant therapies.
Researchers at the University of Colorado Hospital conducted a retrospective review of 105 endometrial cancer patients who underwent surgery between February 2010 and June 2012. Of these, 104 had complete LVSI and/or peritoneal cytology data available.
The cohort included 54 robot-assisted hysterectomies and 45 open abdominal hysterectomies, plus 5 cases where robotic procedures were converted to open surgery mid-operation due to complications. LVSI was defined following GOG Protocol 99 criteria: any adenocarcinoma present in endothelial-lined channels.
For every case initially reported as LVSI-positive, two pathologists independently reviewed the slides to identify pseudo-LVSI. The pseudo-LVSI criteria were specific: disaggregated tumor cells in thick-walled vessels, lack of attachment to vessel walls, absent perivascular lymphocytic response, lack of fibrin within tumor cell clusters, and the presence of inflammatory debris.
Statistical analysis used chi-square tests for categorical variables and Student t-tests for continuous data. The study was powered to detect a clinically significant 30% increase in LVSI rates over a baseline of approximately 20%, requiring 45 patients per group.
Overall, LVSI was reported in 37.5% of all 104 patients. When comparing the two surgical approaches, LVSI appeared in 27% of robotic surgeries versus 48% of open procedures - a statistically significant difference (OR 0.39, 95% CI 0.17-0.92, p=0.03).
However, this difference was largely explained by case selection bias rather than a true surgical effect. Open surgeries involved patients with significantly larger average tumor size (4.9 vs 3.5 cm), greater depth of myometrial invasion (40.1% vs 22.6%), and a higher proportion of high-grade tumors (66.7% vs 30.6%). In other words, more advanced and aggressive tumors were preferentially treated with open surgery.
When the analysis was restricted to early-stage patients (stage I and II), the difference in LVSI rates disappeared: 20% in robotic versus 28% in open surgery (OR 0.64, 95% CI 0.22-1.85, p=0.43). This confirmed that surgical approach itself does not influence LVSI rates.
Peritoneal cytology was positive in only 6 patients (4.8% of the total cohort). The rate was slightly higher in open procedures (8.3% vs 4.8%), but this difference was not statistically significant (p=0.50), consistent with prior research showing cytology is not affected by surgical technique.
Of 38 cases initially reported as LVSI-positive, 36 had slides available for pathology review. The two reviewing pathologists found that 26 were true LVSI, 8 showed features of pseudo-LVSI, and 2 were classified as indeterminate.
Pseudo-LVSI - artificial displacement of tumor cells by the uterine manipulator - was confirmed in 8 cases. However, on closer examination, most had other markers of aggressive disease. Four pseudo-LVSI cases had distant lymph node metastases, and 2 had cervical stromal invasion, indicating genuine disease spread was present even if LVSI was artifactual.
Only 2 pseudo-LVSI cases occurred in patients without these other high-risk features - 1 in the robotic group and 1 in the open group. These were patients where the pseudo-LVSI designation may have incorrectly triggered high-intermediate risk classification and adjuvant brachytherapy treatment under GOG 99 guidelines.
Importantly, removing these 2 ambiguous pseudo-LVSI cases from the analysis did not change the statistical significance of any of the study's findings, confirming that pseudo-LVSI did not meaningfully distort the overall results.
This study provides reassuring evidence that robot-assisted hysterectomy with uterine manipulator use does not increase the rate of LVSI in endometrial cancer patients. The findings align with prior retrospective studies that found no relationship between minimally invasive surgical technique and elevated LVSI rates.
The clinical significance of this finding is substantial. LVSI drives treatment decisions about adjuvant radiation therapy under GOG 99 criteria. If robotic surgery were truly creating artificial LVSI, many patients would receive unnecessary adjuvant therapy with its associated toxicities and costs.
Peritoneal cytology was similarly unaffected by surgical approach, consistent with prospective evidence from other institutions that laparoscopic techniques do not alter cytology results.
The study's limitations include its retrospective design at a single tertiary referral center, where selection bias may have influenced which patients received robotic versus open surgery. Larger, prospective studies with more balanced patient populations between surgical groups would strengthen these conclusions. Nonetheless, the data support continued use of robotic approaches as the preferred surgical option for appropriate endometrial cancer patients.