Diagnostic Utility of Diffusion-Weighted MRI and Apparent Diffusion Coefficient Values in Differentiating Metastatic...

In cervical carcinoma, lymph node involvement is a key indicator of disease progression and a critical prognostic factor that influences staging and treatment. Accurate identification of metastatic lymph nodes is essential for optimal management. Diffusion-weighted MRI combined with apparent diffusion coefficient (ADC) mapping provides a non-invasive approach for evaluating tissue cellularity and may enhance the identification of metastatic lymph nodes, surpassing traditional size-based criteria.

The purpose of the study is to assess the effectiveness of diffusion-weighted imaging (DWI) and ADC values in differentiating between metastatic and non-metastatic lymph nodes in patients with cervical cancer. The study focuses on imaging findings without histopathological confirmation, aiming to determine whether ADC measurements can reliably indicate nodal metastasis.

Thirty patients with histologically confirmed cervical cancer (International Federation of Gynecology and Obstetrics (FIGO) stage IB to IIIC) were prospectively enrolled in a study with a duration of three months. All patients underwent pre-treatment pelvic MRI including DWI on a 1.5 T scanner (b-values: 50, 400, and 800 s/mm²). ADC maps were obtained, and the ADC values of lymph nodes were quantitatively analyzed. Lymph nodes were categorized as suspicious for metastasis based on MRI features, including a short-axis diameter of ≥10 mm, round shape, or the presence of necrosis. Nodes lacking these characteristics were considered benign. Histopathological confirmation of lymph nodes was not conducted. A sample size of 30 was calculated via Fisher's z-test formula for correlation (assuming r = 0.685, 99% confidence, 90% power).

Of 30 patients (mean age -63.5 years, range 51-80), one-third had radiologic evidence of lymph node involvement on MRI (stage IIIC1 by the FIGO 2018 criteria), while the remainder had no enlarged nodes. DWI showed qualitatively restricted diffusion in nodes suspected of metastasis. Quantitatively, ADC values were markedly lower in suspicious (metastatic-appearing) nodes compared to non-suspicious nodes. The mean ADC of nodes deemed metastatic was approximately 0.90 × 10^-3 mm²/s, versus ~1.30 × 10^-3 mm²/s for benign nodes (p < 0.001). Notably, all nodes with ADC < 1.0 × 10^-3 mm²/s were in the metastatic-suspect group, whereas nodes with ADC > 1.0 × 10^-3 mm²/s were benign, suggesting a clear separation. Using an ADC threshold of ~1.0 × 10^-3 mm²/s to define positive nodes, the sensitivity for detecting metastatic nodes was ~93% and specificity ~100% in this cohort.

DWI and ADC mapping demonstrated strong potential in differentiating metastatic from non-metastatic lymph nodes in cervical carcinoma patients. Metastatic nodes showed significantly lower ADC values (around or below 1.0 × 10^-3 mm²/s) compared to non-metastatic nodes. These findings indicate that ADC measurements can augment conventional MRI assessment of lymph nodes, providing a non-invasive indicator of nodal metastasis. This could be especially valuable when surgical nodal sampling is not performed.