**Core Concept**
In the management of ovarian cancer, serial monitoring of CA125 levels is a useful marker to assess disease recurrence or response to treatment. Elevated CA125 levels can indicate tumor progression or relapse, necessitating further investigation and intervention.

**Why the Correct Answer is Right**
The correct next step in managing a patient with raised CA125 levels in ovarian cancer follow-up is to perform a thorough diagnostic workup to confirm disease recurrence. This may involve imaging studies such as CT or PET scans to assess for tumor growth or metastasis. The CA125 antigen is a mucin-type glycoprotein produced by ovarian cancer cells, and elevated levels are associated with tumor burden.

**Why Each Wrong Option is Incorrect**
**Option A:** Immediate initiation of chemotherapy without confirmation of disease recurrence may be unnecessary and expose the patient to potential treatment-related toxicities.
**Option B:** Routine pelvic examination may not be sufficient to detect recurrence, as the tumor may be occult or metastasized to distant sites.
**Option C:** Repeat imaging studies without clinical correlation may lead to unnecessary radiation exposure and costs.

**Clinical Pearl / High-Yield Fact**
In ovarian cancer, a 2-fold increase in CA125 levels over baseline values is often used as a threshold to investigate for disease recurrence.

**Correct Answer: B. Routine pelvic examination may not be sufficient to detect recurrence, as the tumor may be occult or metastasized to distant sites.**