The Uterus Malignant Conditions Cervical Cancer

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Patients with cervical cancer are staged according to the classification of the International Federation of Gynecology and Obstetrics (FIGO) (Table 1). Unfortu nately, FIGO staging is based primarily on clinical exam (neither cross-sectional imaging, nor lymph node status is routine), and staging errors of 15-24% for patients with Stage IB disease and 45-58% for patients with Stages IIA and IIB disease have been reported [19, 20]. MRI is the best single modality for the pre-operative staging of cervical cancer: it is cost minimizing and it can alter therapy [21-23]. In a retrospective study, Hricak et al. found that women with cervical cancer > 2 cm whose initial staging examination was MR required fewer tests and fewer procedures compared to the standard work-up [22]. MR imaging correlates for FIGO staging have been developed and are summarized in Table 1.

T2-W images consistently demonstrate the relatively high SI tumors, and are 93% accurate in determining tumor size compared with surgical specimens [24]. The overall staging accuracy of MR imaging ranges from 8792% [24, 25].

Moreover, the negative predictive value for parametrium invasion, 95%, makes MR imaging an attractive modality for selecting appropriate therapy [21, 24, 25].

The morbidity associated with radiation therapy (RT) is increased after surgery, resulting in a preference for pre-operative RT followed by surgery. Moreover, conventional RT in combination with brachytherapy is as effec-

Table 1. Cervical cancer: FIGO staging with corresponding MR imaging findings1

Stage Findings

FIGO Stage

Stage 0 Carcinoma in situ

Stage I Tumor confined to cervix

Stage IA Microscopic tumor (preclinical tumor)

Stage IB Clinically visible invasive tumor > 5 mm

Stage II Tumor invades beyond uterus but not to pelvic wall or lowest third of vagina

Stage IIA Vaginal invasion

Stage IIB Parametrial invasion

Stage III Tumor extends to pelvic wall and/or involves lowest third of vagina and/or hydronephrosis, non-functioning kidney

Stage IIIA Invasion of lowest third of vagina

Stage IIIB Pelvic sidewall invasion, hydronephrosis, non-functioning kidney

Stage IV Tumor invades outside true pelvis and/or invades bladder or rectal mucosa

Stage IVA Invasion of bladder or rectal mucosa

Stage IVB Distant metastasis

MR imaging findings2 Stage 0

Stage IA Stage IB

Stage IIA Stage IIB Stage IIIA Stage IIIB

Stage IVA Stage IVB

No tumor present

No tumor present or localized widening of the endocervical canal with a small tumor mass Partial or complete disruption of low-signal-intensity stromal ring, intact tissue surrounding tumor

Segmental disruption of low-signal-intensity stromal ring with tumor extending into parametrium Complete disruption of low-signal-intensity stromal ring with tumor extending into parametrium Segmental disruption of low-signal-intensity vaginal wall (lowest third) Tumor extends to obturator internus, piriformis, levator ani muscles; dilated ureter

Signal loss of low-signal-intensity bladder or rectal wall Tumor in distant organs

1 T2-weighted or contrast-enhanced Tl-weighted images.

2 Modified from [26]

tive as surgery for FIGO stage IB (2) disease [27]. That is, patients with less than 5 mm stromal invasion (Stage IAI/2), or patients without evidence of a bulky tumor (> 4 cm) confined to the cervix (Stage IB1) may be amenable to surgical cure. Patients with bulky tumors (> 4 cm) confined to the cervix (Stage IB2) or patients with parametrial invasion (Stage IIB, tumor extends beyond the low SI cervical stroma and smooth muscle into the parametrium), or patients with more advanced disease are better treated with RT (Fig. 4). As a practical issue, when trying to distinguish Stage IB tumors from IIB tumors, it is better to overcall, sparing patients the added morbidity of RT after surgery [28]. The National Cancer Institute recommends that many patients with cervical cancer benefit from concurrent chemotherapy [29-31]. Chemotherapy decreases the relative risk of death, decreases tumor bulk and controls micrometastases.

There is some debate concerning the need for gadolinium in the evaluation of cervical cancers. Some reports found that delayed gadolinium-enhanced T1-W sequences were less accurate in depicting stromal invasion compared to T2-W sequences, while others have found that dynamic gadolinium-enhanced images are superior to both T2-W and delayed contrast-enhanced studies for assessing stromal invasion [32-34]. For the most part, cervical cancers enhance more than adjacent fibrocervical stroma immediately following contrast administration. This relationship reverses with delayed imaging. Dynamic contrast-enhanced MRI has also been advocated to predict tumor response to therapy, both prior to the institution of therapy and during the course of treatment [35].

Fig.4. Cervix cancer: stage IB vs IIB. Coronal T2 FSE of the cervix with effacement of normal zonal anatomy. While it is difficult to identify direct extension into the parametrium, upstaging is preferred in cases where the distinction between IB (1) and IIB tumor is controversial. An incidental simple right adnexal cyst is seen

For lymph node assessment, MR relies on size criteria. For para-aortic, iliac and obturator lymph nodes, a short axis of more than 1 cm is used to detect disease. For parametrial lymph nodes, most experts agree that those lymph nodes greater than 5 mm are suspicious for metastatic disease. While SI has no predictive value, central necrosis may imply involvement. Unfortunately, relying on lymph node size is imperfect. Using a 1 cm short axis as indicative of involvement has a modest sensitivity (45-60%). Ultra-small paramagnetic iron-oxide particles (USPIO) MR or positron emission tomography computed tomography (PET CT) will likely change lymph node assessment in patients with cervical cancer.

Conditions where MR imaging should be recommended in women with cervical cancer include:

- Transverse diameter > 2 cm, based on physical exam

- Tumor that is endocervical or predominantly infiltra-tive that cannot be accurately assessed clinically

- Tumor that is clinically suspected to be stage II disease

- Patients who are pregnant or have concomitant uterine lesions (e.g., leiomyomas), making assessment by other means difficult.

Endometrial Cancer

MRI has been gaining widespread acceptance for the evaluation of women with diagnosed endometrial cancer. MR correlates of surgical FIGO staging have been described (Table 2). The overall staging accuracy of MRI ranges from 83-92% [36-38]. Studies have found MRI to be 74-91% accurate for differentiating early superficial endometrial cancer (stages IA and IB) from cancers with deep myometrial invasion (stage IC). MRI examination of women with endometrial cancer should include dynamic intravenous gadolinium administration. Intravenous contrast improves the following: (1) detection of endometrial abnormalities; (2) distinguishing viable tumor from debris; and (3) assessment of depth of myometrial and cervical invasion [39-41]. A recently published meta-analysis comparing the utility of CT, US and MR for staging endometrial cancer found that contrast-enhanced MRI tended to perform better than CT or US in assessing depth of myometrial invasion [40]. This has important economic implications for the identification of a subset of patients that might benefit from referral to a tertiary care center for more aggressive management by a gynecologic oncologist.

Endometrial cancer images on T2-W sequence as either diffuse or focal widening of the endometrial canal [1, 37, 38 ,42] (Fig. 5). The hormonal milieu determines the normal endometrial width (approximately 13 mm for reproductive age women or post-menopausal women on hormone replacement therapy (HRT) vs 3 mm for postmenopausal women not on HRT). Disruption or irregularity of the junctional zone signifies myometrial invasion. Invasion is further classified as superficial, < 50%,

Parametrial Invasion Mri Pelvis

Fig.4. Cervix cancer: stage IB vs IIB. Coronal T2 FSE of the cervix with effacement of normal zonal anatomy. While it is difficult to identify direct extension into the parametrium, upstaging is preferred in cases where the distinction between IB (1) and IIB tumor is controversial. An incidental simple right adnexal cyst is seen

Table 2. Endometrial cancer: FIGO staging with corresponding MR imaging findings1

Stage Findings

FIGO Stage

Stage 0

Carcinoma in situ

Stage I

Tumor confined to corpus

Stage IA

Tumor limited to endometrium

Stage IB

Invasion < 50% of myometrium

Stage IC

Invasion > 50% of myometrium

Stage II

Tumor invades cervix but does not extend beyond uterus

Stage IIA

Invasion of endocervix

Stage IIB

Cervical stromal invasion

Stage III

Tumor extends beyond uterus but not outside true pelvis

Stage IIIA

Invasion of serosa, adnexa, or positive peritoneal cytologic findings

Stage IIIB

Invasion of vagina

Stage IIIC

Pelvic or para-aortic lymphadenopathy

Stage IV

Tumor extends outside true pelvis or invades bladder or rectal mucosa

Stage IVA

Invasion of bladder or rectal mucosa

Stage IVB

Distant metastases (includes intra-abdominal or inguinal lymphadenopathy)

MR imaging findings2

Stage

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