Uterus

Cervical Cancer

Cervical carcinoma is staged according to the International Federation of Gynecology and Obstetrics (FIGO) staging system. Accurate staging of cervical cancer is crucial in determining the mode of treatment. Routine clinical staging incorporates gynecologic pelvic examination under anesthesia, chest X-ray, lesion biopsies, cystoscopy, and, if indicated, renal sonography for detection of hydronephrosis.92 In most centers, stage IB (confined to the cervix) and stage IIA (extends beyond the cervix but within upper two-thirds of the cervix, no parametrial invasion) disease are treated with hysterectomy with pelvic lymph node dissection. Radiation therapy is the treatment of choice with parametrial involvement (stage IIB or higher).49 However, clinical staging was shown to be inaccurate, and discrepancy between clinical staging and surgical staging, ranging from 34% to 39%, has been reported.92

MRI is the modality of choice to image cervical masses that are greater than 1.5 cm or presumed to extend beyond the cervix.93 On MRI, cervical carcinoma most often appears as an intermediate signal or high-signal-intensity mass distorting or disrupting the normal cervical zonal anatomy of the cervix (Figure 31.12). The size of the tumor measured by MRI correlates well with surgical measurement of the tumor size. When the hypointense ring of the cervical stroma is preserved on MRI, parametrial extension can be virtually excluded.93 Parametrial extension is suggested when there is full-thickness invasion of the cervical stroma associated with irregularity or asymmetry of the lateral cervical margin, parametrial mass, or stranding within the parametrial fat (Figure 31.12). However, when full-thickness stromal invasion occurs, microscopic parametrial extension may be present despite a smooth lateral cervical margin and the absence of abnormality in the parametrial fat.

Boss et al. performed meta-analysis of 12 studies published between 1986 and 1995 describing the staging accuracy of MRI in cervical carcinoma.92 The mean percentage of overall staging accuracy of MRI without use of contrast agents was 79% (range, 47%-90%), in comparison with the accuracy of the clinical examination of 72% (range, 55%-85%) and that of CT of 62% (range, 32%-80%). The mean percentage of accuracy in detecting parametrial invasion with MRI was 88%, with clinical examination 86%, and with CT 72%. Some studies indicated higher staging accuracy of gadolinium-enhanced T1-weighted94 or dynamic enhancement studies.95-97 Another meta-analysis study including 57 articles from 1985 to 2002 showed higher sensitivity and specificity in evaluating bladder invasion by MRI (75% and 91%) compared to CT (64% and 73%), but the specificity of rectal invasion was comparable between MRI and

CT.98

CT has been used to assess patients with tumors of advanced cervical cancer and evaluating patients for recur-rence.49 The use of CT in early disease has been limited due to prior reports of low sensitivity and specificity for local invasion.99 However, major advances in CT technology during the past few years may broaden the use of CT.99 Accuracy of

figure 31.12. Cervical cancer. (A) Axial T2-weighted image with fat suppression shows a large mass obliterating the entire cervix, extending anteriorly into the myometrium and the left pelvic side wall (large arrow). The mass obstructs the endometrial canal, which is dilated and filled with secretion and debris (small arrows). (B) Axial T1-weighted gradient echo image with fat suppression obtained after gadolinium contrast agent injection. There is heterogeneous contrast enhancement of the mass. The central area is not enhanced, representing necrosis. (C) Sagittal T2-weighted image with fat suppression shows large mass arising from the cervix, extending superiorly into the myometrium (large arrow). The mass obstructs the endometrial canal, which is dilated and filled with secretion and debris (small arrows). (D) Sagittal T1-weighted gradient echo image with fat suppression obtained after gadolinium contrast agent injection. There is heterogeneous contrast enhancement of the mass with areas of necrosis. The International Federation of Gynecology and Obstetrics (FIGO) staging was IIIB.

CT staging is greater with advanced disease and is reported as 92% for stage IIIB to IVB cervical cancers.100

The presence of pelvic lymph node metastases is not part of the FIGO staging criteria; however, it is the most important prognostic factor and findings may be crucial for treatment planning.92 Yang et al. reported that central necrosis of pelvic lymph nodes had a positive predictive value of 100%

in the diagnosis of metastastic adenopathy in patients with cervical cancer.101 They reported that spiral CT and MRI are roughly equivalent with accuracy in detecting metastatic pelvic lymph nodes, with accuracy rate of spiral CT and MRI being 89.5% and 85.5%, respectively, when a node of greater than 10mm in maximal axial diameter or a node with central necrosis was defined as a metastasic node.101 Meta-analysis studies also showed similar performance in the detection of lymph node metastasis from cervical cancer,102 with mean accuracy of detection of lymph node metastasis being 86% with nonenhanced MRI and 81% with CT.92

Local recurrence of cervical cancer occurs centrally in the pelvis or at the side wall. CT is an effective diagnostic tool for detection of recurrent cervical cancer, but it may be difficult to differentiate recurrence from postoperative and postirradiation fibrosis.103 Gadolinium-enhanced MRI is useful to detect recurrent tumor, which shows increased signal intensity on T1-weighted images, whereas radiation fibrosis remains low in signal intensity if imaged more than 12 months after radiation therapy.103 Dynamic contrast-enhanced MRI has been reported to be more accurate in depicting postoperative recurrent tumor compared to pre- and postcontrast T1-weighted images and T2-weighted images.104

Endometrial Cancer

Endometrial carcinoma is staged according to the FIGO staging system. The prognosis is related to the histologic tumor grade, depth of myometrial invasion, stage of the tumor, and presence of lymph node metastasis. Metastasis to the paraaortic and paracaval lymph nodes may occur without involvement of pelvic lymph nodes if the tumor spreads along the lymphatics accompanying the ovarian vessels. The probability of extrauterine disease and risk of nodal involvement is related primarily to tumor grade and depth of myometrial invasion.

Endometrial carcinoma often presents with vaginal bleeding in postmenopausal women and is usually diagnosed by a combination of ultrasound and endometrial biopsy, which provides the tumor grade and histologic type. Most women with endometrial carcinoma do not require imaging studies93 as surgical staging with the FIGO staging system is performed. However, knowledge of the extent of endometrial cancer spread before undertaking surgery can be of value because myometrial invasion of more than 50% may require more extensive surgery, including pelvic and paraaortic lymphadenectomy.105 MRI is recommended when locally advanced disease is expected based on physical examination findings and in patients with a difficult physical examination because of obesity or prior radiation or surgery.106 Hardesty et al. performed a cost analysis study and reported that staging with MRI has similar cost and accuracy compared to the current method of staging with intraoperative gross dissection of the uterus and that MRI decreases the number of unnecessary lymph node dissections.107

Kinkel et al. performed a meta-analysis in the preopera-tive assessment of myometrial invasion and demonstrated that contrast-enhanced MRI of the pelvis performed significantly better than ultrasound, CT, and noncontrast MRI.108 Because MRI can more clearly demonstrate the primary neoplasm and more accurately determine the depth of myome-trial invasion than CT, MRI is often used as the imaging procedure of choice in the preoperative evaluation of patients with high-grade endometrial carcinoma,49 although advanced extrauterine disease may be assessed with either MRI or contrast-enhanced CT scan.93

Noninvasive endometrial carcinoma may be identified within the uterine cavity on T2-weighted MR images and is seen as a signal intensity mass intermediate between that of normal endometrium and that of myometrium.49 In some cases, the endometrial stripe may appear homogeneously widened. Preservation of the low-signal-intensity junctional zone usually implies the absence of myometrial invasion, with negative predictive value close to 100%. When myome-trial invasion occurs, the interruption of the low-signal-intensity junctional zone on T2-weighted images109 or the interruption of the subendometrial enhancing line on early dynamic T1-weighted images110 is seen. The depth of myome-trial invasion can also be assessed to differentiate stage IB and IC disease. The accuracy of MRI in differentiating noninva-sive carcinoma (stage 1A) from invasive carcinoma has been reported to range from 74% to 85%, and in distinguishing deep invasion (stage 1C) from superficial disease (stage 1A and 1B) accuracy ranges from 75% to 95%. Dynamic contrast-enhanced MRI improved the accuracy of assessing myo-metrial invasion from about 83% to 91%.108 When patients have thinning of the myometrium due to distension of the endometrial cavity,111 when the junctional zone is not entirely visualized, or when the zonal anatomy is distorted by uterine abnormalities, such as leiomyoma or adenomyosis, MRI is less accurate for assessing myometrial invasion.49 For patients with a thickened or indistinct junctional zone from adenomyosis or other reasons, dynamic contrast-enhanced MRI improves the accuracy of staging.112,113

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