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Invited Commentary |
Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania
Lee et al (1) report their experience using MR imaging to stage endometrial carcinoma. Specifically, they found that gadolinium-enhanced T1-weighted imaging revealed the depth of myometrial invasion by the carcinoma more accurately than did T2-weighted imaging in postmenopausal women, whereas the latter sequence was more accurate in premenopausal women. An accuracy of approximately 80% was achieved with this schema by using the histopathologic depth of invasion as the standard for comparison. Therefore, this study refines diagnostic criteria for determining the depth of penetration in patients with endometrial carcinoma by using T2-weighted images in premenopausal patients, in whom the junctional zone is more well defined, and gadolinium-enhanced T1-weighted images in postmenopausal patients.
It behooves radiologists to understand the results of this study when interpreting MR images of women with endometrial carcinoma. In my view, however, it is an error to regard these results as support for the concept that MR imaging is generally useful in women with endometrial carcinoma. This study is one of a long line purporting to show that MR imaging has a clinically useful level of accuracy in staging endometrial carcinoma. Many of these studies focused on predicting depth of myometrial penetration, for two reasons. First, most endometrial carcinomas are stage I at diagnosis. The depth of penetration of the carcinoma, together with the tumor grade, allows stratification of patients into levels of risk for nodal metastases (2–4). Patients with higher-grade tumors or greater depth of myometrial penetration require nodal dissection for accurate staging, although lymphadenectomy in these patients has not been shown to improve survival (5). Second, the layered uterine anatomy on T2-weighted images appears to make assessment of the depth of invasion straightforward. The accuracy for determining the depth of invasion with MR imaging varies from 66% to 85% (6–10). MR imaging appears to be less accurate in the assessment of peritoneal, adnexal, and nodal metastases, which are all frequently microscopic (9,11,12).
If MR imaging provides information as to the depth of myometrial invasion (albeit far from perfectly), how does this information help guide the patient evaluation? In practice, this information means little. The critical determinants of the risk of nodal disease (histologic type, grade, stage, and depth of myometrial invasion) can be determined in the surgical suite by means of gross inspection of the hysterectomy specimen, microscopic analysis of frozen sections, and inspection of the pelvis (13). These findings can then be used by the surgeon to determine whether nodal dissection is indicated. If nodal metastases are discovered at surgery or if the patient is at high risk based on the histopathologic findings, postoperative radiation therapy to the affected areas (pelvic or periaortic) is performed. Therefore, in the average patient, MR imaging offers little to change this treatment algorithm. Because endometrial carcinoma is surgically staged and surgically treated in the same procedure, the value of determining the depth of myometrial invasion preoperatively seems slight.
However, there may be stronger reasons for determining the stage of the disease preoperatively in selected patient groups. These include patients with advanced tumors and patients who are poor surgical risks. Approximately 4%–9% of women with endometrial carcinoma are poor surgical risks (14). These patients are typically treated with primary radiation therapy instead of surgery (14). In these patients, MR imaging might provide information as to the risk of nodal metastases. Patients with clinically suspected advanced-stage tumors may benefit from preoperative staging with MR imaging to assess the extent of the tumor and determine resectability (15). Preoperative radiation therapy offers no proved advantage in patients with endometrial carcinoma but is performed at some institutions (16). Because of the difficulty of histopathologic staging after radiation therapy, staging with MR imaging could be performed before radiation therapy in these cases. In these special situations, MR imaging might therefore be useful, but its value still needs to be demonstrated in prospective studies.
In summary, endometrial cancer is primarily a surgically staged and surgically treated disease. The surgical treatment of early-stage carcinoma probably accounts for the excellent prognosis in these patients. The information that MR imaging can provide in the average patient is neither required nor accurate enough to help in surgical planning. The critical determinants of histologic findings and depth of penetration into the myometrium can be established at surgery. MR imaging is of value primarily in certain subgroups of patients, such as those who are poor surgical risks. For this reason, radiologists need to become familiar with staging of endometrial carcinoma with MR imaging. In this regard, the study of Lee et al (1) refines the criteria for staging the primary tumor.
References
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