Accurate clinical staging is a cornerstone in the management of early-stage cervical cancer. In particular, precise evaluation of tumour size, parametrial invasion and lymph node involvement determines treatment direction, including the feasibility of surgery and the need for chemoradiotherapy. While magnetic resonance imaging (MRI) is often regarded as the reference standard, it remains inaccessible in many low-resource settings. The SENTIX study, a large prospective multicentre trial, provided a valuable opportunity to evaluate the reliability of ultrasound as an alternative imaging modality to MRI in preoperative pelvic staging.
Comparative Accuracy of Tumour Size Assessment
One of the critical elements in staging early-stage cervical cancer is tumour size, influencing both surgical planning and the potential for fertility preservation. The SENTIX post-hoc analysis involved 690 patients, nearly equally distributed between those evaluated preoperatively by MRI (46.7%) or ultrasound (43.2%). When comparing preoperative imaging results with final pathology, a tumour size discrepancy of ≥10 mm occurred in 13.1% of ultrasound cases and 16.5% of MRI cases. This difference was not statistically significant, indicating comparable accuracy between modalities.
In most cases, the discrepancy remained below 10 mm, suggesting that both methods offer acceptable precision in tumour measurement. Despite this, both imaging approaches demonstrated a tendency to underestimate tumour size in a significant subset of patients. Since tumour size helps determine the extent of surgery and eligibility for less invasive procedures, underestimation may lead to suboptimal surgical strategies. Nevertheless, the findings confirmed that ultrasound, when conducted by experienced practitioners, is as effective as MRI in measuring tumour dimensions.
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Parametrial Involvement and Diagnostic Reliability
Assessment of parametrial invasion is essential in selecting candidates for surgery versus chemoradiotherapy. In this cohort, 536 patients underwent parametrectomy, enabling analysis of imaging accuracy for this parameter. Final pathology identified parametrial involvement in 25 patients. Of these, preoperative ultrasound missed nine cases and MRI missed fifteen, resulting in negative predictive values (NPVs) of 97.0% and 95.3%, respectively. Again, the difference in NPV between the two imaging modalities was not statistically significant.
These results underscore the high reliability of both imaging techniques in ruling out parametrial spread, a crucial step in planning curative surgery. Although parametrial invasion was relatively rare in the analysed cohort, the impact of misclassification is clinically significant. Patients with true parametrial involvement may face increased morbidity if incorrectly selected for surgery. Given the strong NPV for both ultrasound and MRI, either modality can provide confidence in proceeding with a surgical approach in appropriately staged cases.
Lymph Node Staging and Predictive Consistency
Lymph node involvement serves as a major determinant for treatment choice, as the presence of macrometastases typically precludes surgery in favour of chemoradiation. All patients in the SENTIX trial underwent sentinel lymph node biopsy with ultrastaging, enabling accurate pathological verification of imaging results. Among the 690 patients, 41 were found to have macrometastatic nodal disease. Preoperative imaging failed to identify these in 6.0% of ultrasound cases and 5.9% of MRI cases, yielding NPVs of 94.0% and 94.1%, respectively.
The comparable performance of both imaging techniques in detecting macrometastases reinforces the validity of ultrasound as a staging tool. However, both methods missed nodal metastases in approximately 11% of cases when broader definitions of nodal involvement (including micrometastases and isolated tumour cells) were considered. This limitation highlights the challenge of imaging-based lymph node staging and underscores the value of intraoperative assessment and ultrastaging protocols.
The findings from the SENTIX post-hoc analysis support the integration of ultrasound examination into standard preoperative staging protocols for early-stage cervical cancer. Ultrasound demonstrated equivalent performance to MRI in assessing tumour size, parametrial invasion and macrometastatic lymph node involvement. These results have important implications for global oncology practice, particularly in settings where MRI is unavailable or unaffordable.
While the operator-dependence of ultrasound remains a consideration, the SENTIX study design mitigated this concern by allowing each participating centre to use its preferred modality, maximising expertise. The rigorous standardisation of imaging protocols and pathology assessment further strengthened the study’s conclusions.
Incorporating ultrasound into clinical pathways can improve access to timely and appropriate care, reduce costs and maintain diagnostic accuracy. As cervical cancer remains a significant burden in resource-limited regions, leveraging ultrasound as a reliable staging tool may help expand the reach of life-saving surgical interventions.
Source: Ultrasound in Obstetrics & Gynecology
Image Credit: Freepik
