Magnetic resonance imaging is excellent for preoperative staging of gynecologic neoplasms. Not only lymphadenopathy, but also local tumor extension is well seen by MRI. Magnetic resonance imaging is the study of choice for preoperative staging of cervical cancer. Bowel, bladder, and pelvic sidewall involvement can be shown to advantage using MRI, enabling identification of tumor invasion and penetration.
Although the mortality rates have declined over the last several decades due to screening and early detection, cervical carcinoma is still the third most common gynecologic malignancy in the United States. Worldwide, cervical cancer is the fifth most common cause of cancer deaths.39,40
Most cervical carcinomas are squamous cell carcinomas and occur at the squamocolumnar junction. They can be infiltrative or polypoid. On MRI, cervical cancer typically appears solid with a signal intensity brighter than myometrium that stands out in sharp contrast to the low-signal junctional zone. The International Federation of Gynecology and Obstetrics (FIGO) staging system is used to clinically stage cervical carcinoma, but it has limitations. FIGO does not account for deep lymphadenopathy, assessment of tumor volume, or local extension beyond the fibrous stroma or into the uterus—all findings that can be demonstrated to advantage with MRI.41
Imaging is performed in the long and short axes of the uterus and cervix to show the tumor extent to best advantage. If the tumor extends beyond the fibrous stroma outside the cervix into the parametrium (stage IIB or greater), the lesion is usually not considered amenable to curative surgery (Figure 48-15).42 Such patients almost always undergo chemoradiation.43 Other findings such as invasion of surrounding organs (bladder or rectum), adenopathy, and invasion of the pelvic sidewall (obturator internus, pyriformis, or levator muscles) are well demonstrated on MRI. Magnetic resonance imaging for radiation treatment planning, tumor volumetry, and monitoring response to therapy helps to guide the duration of radiation therapy and to permit addition of adjunctive therapy. In addition, if patients have received a prior maximal dose of radiation, then they may be candidates for pelvic exenteration, unless there is invasion of the pelvic sidewall. After radiation therapy, MRI has been used for surveillance to search for recurrence.44
Cervical carcinoma. A: A 50-year-old patient with vaginal bleeding. Axial T2-weighted scan shows evidence of this stage III cervical carcinoma invading beyond the dark-signal fibrous stroma into the parametrium both anteriorly and posteriorly (arrows). B: T2-weighted sagittal scan shows the barrel-shaped cervix. This patient had radiation therapy.
Endometrial carcinoma is the most common gynecologic malignancy and the fourth most common cancer in females.40 It usually presents with postmenopausal bleeding resulting in the observation that most endometrial cancers are found at an early stage—an important point because the survival rates are greater than 95% for localized disease.40
Most endometrial cancers are adenocarcinomas. The patient's prognosis depends on the histologic grading, the presence of myometrial invasion (which carries a poorer prognosis), local extension (involving the cervix, vaginal canal, and tissues outside the uterus), and the presence of lymph nodes (which implies extrauterine spread). MRI has been a valuable addition to preoperative evaluation of patients with endometrial carcinoma in order to identify the primary site of the lesion as corpus or cervix, show deep myometrial invasion, invasion of the cervical fibrous stroma, assess risk of adenopathy requiring lymphadenectomy, and to guide subspecialty referrals.45
On MRI, endometrial carcinoma usually is isointense to myometrium on T1-weighted scans and bright on T2-weighted scans. After contrast administration, myometrial invasion is best identified on imaging performed after a 2- to 3-minute delay.46,47
FIGO staging of endometrial carcinoma is based only on the surgical and histologic findings and does not incorporate imaging findings. Surgical staging is performed for endometrial carcinoma with total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAHBSO), and lymph node dissection usually performed for patients with stage I disease confined to the endometrium (Figure 48-16). If there is an extremely high-grade tumor, preoperative radiation may be added. Pretreatment MRI is valuable because contrast-enhanced MRI can show myometrial invasion, which is associated with a greater risk of adenopathy, worse tumor grade, extension of tumor to the cervix, and a worse prognosis.41 With dynamic enhanced MRI with a fast gradient echo technique, the inner muscle layer in patients can be detected, even those who are postmenopausal with poor visualization of the junctional zone on T2-weighted images.48
Myometrial invasion from stage IB endometrial carcinoma in a 31-year-old female with vaginal bleeding. Coronal (A) and axial (B) T2-weighted MR scans showed dilated heterogeneous endometrial canal (E). Note that the junctional zone is mildly thinned and indistinct at the left upper uterine corpus (arrow). C: Gadolinium-enhanced fat-suppressed T1-weighted gradient echo scan shows bright signal-enhancing tumor in the dilated endometrial canal with early myometrial invasion, ie, tumor extending no further than the inner half of the myometrium (arrow).
Otherwise, it can be difficult or impossible to find myometrial invasion. If occult adenopathy or deep myometrial invasion by endometrial carcinoma is discovered preoperatively by MRI, then the patient may require more extensive nodal dissection and surgical exploration. Although the treatment of choice may still be radical surgery with hysterectomy and oophorectomy, the use of preoperative MRI is a useful predictor of more extensive disease that may require consultation from trained gynecologic oncologists.
Patients with stage II endometrial carcinoma usually undergo surgery and postoperative external beam radiation. If MRI shows a bulky lesion, it may be irradiated before surgery. Instead of administering preoperative intracavitary radiation, surgery is sometimes performed to remove as much of the tumor as possible, and the entire pelvis is irradiated afterward.
With stage III disease, which is unexpected preoperatively, surgeons will try to remove as much of the tumor as they possibly can with a TAHBSO and a node dissection, and then perform radiation postoperatively. If stage III tumor is known ahead of time, usually only radiation is administered. With stage IV disease, radiation and other adjuvant therapies are usually employed, because most patients do not do any better with radical surgery than with palliative therapy. Diagnosis of stage IV disease by preoperative MRI avoids unnecessary surgery (Figure 48-17).
Endometrial carcinoma stage IV. A: A 52-year-old patient with right abdominal pain, vomiting, and vaginal bleeding. Endometrial biopsy showed adenocarcinoma. T2-weighted sagittal scan shows an enlarged uterus with a markedly invasive malignancy extending into the myometrium and to the serosal surface of the uterus (arrows). Note the variable signal intensity in the multinodular mass. The endometrial canal (e) is distended. B: T2-weighted axial scan. Note the bright signal malignant ascites (a). The junctional zone is breached, indicating a deeply invasive lesion (arrows). C: T1-weighted axial scan in the abdomen. Lymphadenopathy is in the retroperitoneum (arrow). D: T1-weighted axial scan at the lung base. There is lymphangitic spread of tumor in the lungs and a malignant right pleural effusion. This patient has stage IV cancer and is not a candidate for curative radical surgery.
Although it is the second most common gynecologic cancer after endometrial cancer with an estimated 22,400 new cases in the United States in 2007, ovarian cancer is the most common cause of cancer death from the female reproductive system, with 15,280 deaths from ovarian cancer in 2007.40 This is because ovarian cancer is usually discovered late in its course since there is no good screening mechanism and symptoms are nonspecific. Ovarian cancer is most commonly of epithelial origin. Seventy percent of women will have advanced disease at the time of diagnosis. The 5-year survival rate for advanced disease is 15% to 20%, whereas for early disease (stage I) the 5-year survival is as high as 90%.49 Although cancer antigen 125 (CA-125) can be a used as a tumor marker, especially in postmenopausal women, there is no documented cost-effective, accurate screening method to detect ovarian cancer at the time of this writing.
The use of MRI for evaluation of ovarian cancer is controversial. Magnetic resonance imaging does not have a place in screening patients because it is too expensive, but it may be helpful for lesion characterization when US is inconclusive, such as with identification of dermoids or endometriomas.28 However, MRI can be used for preoperative staging. With ovarian cancer, the diagnosis is established histologically and surgical treatment is given at the same time. Regardless of initial clinical staging, almost all patients undergo surgery or surgery with adjuvant therapy. The exceptions are advanced stage III and stage IV tumors. Moreover, understaging at surgery can occur in up to a third or more of cases in some series.
Magnetic resonance imaging can be used to stage ovarian cancer and determine resectability, although spiral CT is more widely used.50 Unfortunately, the implants from ovarian cancer may be so small that cross-sectional imaging has been of limited value for detection of tiny implants, which are only apparent from laparotomy and tissue sampling. These include lesions in the peritoneum and lesions in the omentum (Figure 48-18). Gadolinium enhancement optimizes the contrast of the lesion in relation to surrounding tissue. Fast scanning with gadolinium using fat-suppression techniques (eg, spoiled gradient echo sequence or fast multiplanar spoiled-grass scans) is helpful in cases of abdominal disease to cut down on motion artifact from bowel peristalsis and to better identify enhancing tumor on a background of dark fat (Figure 48-19). Tumor implants are shown to best advantage even in the omentum or peritoneum.
Ovarian carcinoma. A: A 73-year-old patient with a pelvic mass. T1- weighted sagittal scan shows a huge complex cystic abdominal pelvic mass (m). There is ascites (a). The serosal implants cannot be distinguished from the bowel dorsal to the mass. B: Gadolinium-enhanced T1-weighted axial scan shows that this stage III ovarian carcinoma is associated with enhancing papillary fronds peripherally within the mass (m) itself and with enhancing serosal implants (s).
Vaginal apex recurrence. A 50-year-old patient previously underwent TAHBSO for stage III ovarian carcinoma. Note the enhancing vaginal apex lesion on this T1-weighted fat-suppressed gadolinium-enhanced scan. (B, bladder; R, enhancing rectal wall; V, Vaginal apex mass)
The features suggestive of ovarian malignancy that can be recognized on MRI or CT are complex lesions greater than 4 cm in size or greater than 3-mm wall thickness, septations, vegetations and frond-like projections, solid elements, necrosis, omental and peritoneal implants, adenopathy, and ascites.51
The argument for cross-sectional imaging is that one can predict the extent of disease from preoperative cross-sectional imaging. This assists in planning surgery and identifying nonresectable disease. In addition, MRI and CT permit referral to gynecologic oncologists for optimal treatment.52
Staging with the FIGO system is surgical and includes total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, peritoneal washings and biopsies, and pelvic and para-aortic lymph node dissection.
Chemotherapy is probably preferable to initial surgical cytoreduction in patients with nonresectable disease. Computed tomography has been used for this purpose for a very long time, is widely available, and is well accepted by radiologists and referring physicians. Shortened scan times with fast imaging and enhanced techniques on MRI afford better evaluation of extent of disease.
Second-look laparotomy has fallen out of favor because surgical cytoreduction tends not to be any better than chemotherapy, particularly if residual disease exceeds 1.5 to 2 cm in size. MRI and CT have both been reliable in finding lesions of 2 cm or larger. Patients with lesions of this size are the very ones in whom surveillance can make a difference. MRI and CT have both been used to scan patients with a history of ovarian cancer, but CT is probably more commonly used because it is better understood and accepted by both radiologists and clinicians. MRI may have some advantages due to its superior soft tissue contrast, especially with use of enhanced fast scans with fat-suppression techniques to demonstrate smaller lesions on serosal surfaces, which are difficult to detect. Whether MRI or CT is used, cross-sectional imaging can play an important role in lesion characterization, preoperative staging, and follow-up, often directing appropriate therapy for recurrence in ovarian cancer. Molecular imaging with positron emission computed tomography using F-18 fluorodeoxyglucose positron emission tomography (FDG-PET/CT) (Figure 48-20).
FDG-PET/CT of stage IIIC ovarian carcinoma in a 58-year-old patient with metabolically active primary cancer and peritoneal and liver metastases on PET-CT fused images. A: Axial fused images of the primary ovarian malignancy (arrow). B: Coronal fused images showing metastases (arrows).
Recurrent Gynecologic Malignancy
Magnetic resonance imaging has been a valuable tool for patients who have been treated for malignancy, for surveillance for recurrence and for assessing response to treatments such as chemo- and radiation therapy. In an extent of disease workup, it is important to evaluate the pelvic sidewall for invasion. Pelvic sidewall invasion has a poor prognosis. The pelvic sidewall is comprised of 3 major muscle groups: the obturator internis, the piriformis, and the levator ani muscles. Magnetic resonance has a very high, nearly 100%, negative predictive value for absence of disease in the pelvic sidewall. If there is abnormal signal in the pelvic sidewall, there may be contiguity with tumor from direct extension or gross invasion; however, there are some false-positive cases (radiation changes, infection, etc). Overall, accuracy is in the 80% to 90% and higher range. Thus, MRI is extremely useful to evaluate patients who are candidates for radical surgery for cure with pelvic exenteration. Pelvic sidewall invasion generally precludes an attempt at radical surgery in most cases and is a critically important MR finding.