Detection here can be an onerous oncological task because post-op and radiation changes so closely mimic local tumor recurrence. As Dr. Natally Horvat noted in this ARRS Quick Bytes video, true differentiation requires tracking morphological, intensity, and temporal changes across sequential scans.
- Benign Post-Treatment Findings: Typically remain stable or decrease in size over time, present a non-invasive and symmetric appearance, and demonstrate low T2 signal intensity.
- Local Recurrence Findings: Increase in size over time, present a nodular and asymmetric appearance, exhibit invasive behavior, and demonstrate intermediate T2 signal intensity.
Case in Point: A 32-year-old patient presented with colonic obstruction from an upper rectal tumor with extramural vascular invasion touching the lateral pelvic sidewall, necessitating urgent R1 resection of a high-grade tumor.
- Initial follow-up CT revealed subtle fat stranding in the left lateral pelvic sidewall.
- Months later, the patient developed new lumbar pain and hydronephrosis; enlargement of the lateral pelvic mass confirmed local recurrence.
Dr. Horvat’s 4-Step Surveillance:
- Baseline vs. Restaging: Search specifically for high-risk tumor features present prior to resection.
- Review the Notes: ID surgical margins and complications that alter expected healing patterns.
- Post-Op Points: Review all serial scans for subtle bed changes.
- Correlate Clinically: Cross-reference suspicions against labs and symptoms.
RadFYI: Knowing high-risk margin sites and meticulously tracking the surgical bed against baseline scans is essential to spot early, subtle recurrences before severe complications develop.
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