What is the preferred initial imaging test, such as Computed Tomography (CT) scan, Magnetic Resonance Imaging (MRI), or Positron Emission Tomography (PET) scan, for a patient recently diagnosed with ovarian cancer, possibly associated with endometriosis, before surgery?

Preoperative Imaging for Newly Diagnosed Ovarian Cancer

CT scan of the chest, abdomen, and pelvis with intravenous contrast is the standard and preferred initial imaging modality for staging newly diagnosed ovarian cancer before surgery. 1

Primary Imaging Recommendation

Obtain CT thorax, abdomen, and pelvis with IV contrast as your first-line staging study after diagnosis. 1 This recommendation comes directly from the 2023 ESMO Clinical Practice Guidelines, which explicitly state that initial imaging should comprise pelvic ultrasound (which you've likely already done for diagnosis) and CT of the thorax, abdomen, and pelvis to complete clinical staging and aid surgical planning. 1

Why CT is the Standard of Care

• CT provides comprehensive staging of the entire disease extent, including peritoneal implants, lymph node involvement, pleural disease, and distant metastases. 1
• CT is currently the modality of choice for staging ovarian cancer according to ACR Appropriateness Criteria. 1
• CT detects peritoneal implants as small as 5 mm and accurately identifies sites that would preclude optimal cytoreduction. 2, 3
• CT and MRI have equivalent accuracy (82-84%) for staging ovarian cancer, but CT is preferred due to faster acquisition, routine use of gastrointestinal contrast, and less susceptibility to patient motion. 1, 4

When to Consider MRI Instead

MRI pelvis with IV contrast should be reserved for specific scenarios:

• Borderline tumors where minimizing radiation exposure is prioritized. 1
• Young patients requiring fertility preservation to avoid ionizing radiation. 1
• CT findings are inconclusive or indeterminate and additional tissue characterization is needed. 1
• Suspected endometriosis-associated malignancy where MRI's superior soft-tissue contrast helps differentiate endometriomas from malignant transformation. 1

MRI has 93% accuracy in separating ovarian malignancy from benign adnexal masses and provides equivalent staging accuracy to CT (sensitivity 88%, specificity 74%, accuracy 84%). 1 However, MRI's limitations include longer acquisition time, greater susceptibility to motion artifact, and lack of routine gastrointestinal contrast use. 1

PET/CT: Not for Initial Staging

Do NOT obtain PET/CT for initial staging of newly diagnosed ovarian cancer. 1

Why PET/CT is Not Recommended Initially

• PET/CT is unsupported for primary diagnosis and tissue characterization of ovarian cancer. 1
• Low specificity (as low as 54%) makes it unreliable for initial evaluation. 1
• False-negative results occur with borderline tumors, mucinous tumors, early carcinomas, and low-grade tumors. 1
• False-positive results are common with fibromas, dermoid cysts, hydrosalpinges, and endometriosis—particularly problematic in your patient with endometriosis-associated cancer. 1

Limited Role for PET/CT

PET/CT may be useful only as an adjunct when CT findings are indeterminate or for staging advanced disease, where fusion PET/CT has shown higher accuracy than CT alone for detecting small peritoneal deposits and lymph nodes. 1 However, this is not the initial test of choice.

Critical Pitfalls to Avoid

Do not skip chest imaging. CT chest is essential for detecting pleural effusions and pulmonary metastases, which upstage disease to Stage IV and fundamentally alter surgical planning. 1 Preoperative detection of moderate to large pleural effusion predicts poor post-treatment outcome. 1

Ensure IV contrast is administered unless contraindicated, as contrast is essential for detecting and characterizing tumor deposits and assessing vascular involvement. 1

In the context of endometriosis: Be aware that endometriosis itself can cause false-positive findings on imaging and elevated CA-125 levels. 1 However, endometriosis is associated with increased risk of endometrioid and clear-cell ovarian carcinomas. 1 The presence of endometriosis does not change the recommendation for CT as initial staging—it remains the standard approach.

Surgical Planning Implications

The CT findings directly impact surgical decision-making by identifying inoperable tumor sites that would preclude optimal cytoreduction (residual tumor >1 cm). 1, 3 CT has 76% sensitivity and 99% specificity for predicting suboptimal debulking, with 96% negative predictive value. 3 This information helps determine whether primary cytoreductive surgery or neoadjuvant chemotherapy followed by interval debulking is the appropriate initial approach. 1, 3