Fixing Hot Spots in Cervical Cancer Radiation

An online adaptive system that recalculates radiation plans daily can, in rare cases, deliver an excessive dose to the target.
A recent cervical‑cancer case highlighted this risk when a hot spot—a region receiving higher than intended dose—was detected mid‑treatment.

Why It Happened

• Tumor proximity to leaf limits: The tumor’s edge lay close to the linear accelerator’s multileaf collimator (MLC) boundaries.
• Beam‑shaping constraints: The MLC could not fully conform the beam to the target, causing dose irregularities.

Immediate Response

1. Real‑time detection: The adaptive plan flagged the hot spot during delivery.
2. On‑the‑fly adjustment: Clinicians manually nudged the target’s position within the plan.
3. Plan re‑optimization: The system recalculated beam weights to redistribute dose evenly.

Workflow Enhancement

• Pre‑finalization check: A new verification step now evaluates target position relative to MLC limits before plan approval.
• Automated nudging: If the target is too close to a leaf boundary, the system automatically adjusts its coordinates.
• Dose‑uniformity audit: A quick uniformity assessment ensures no hot spots before treatment begins.

Lessons for the Field

• Early detection is critical; incorporate real‑time monitoring tools.
• Position checks safeguard against geometric constraints that can skew dose distribution.
• Collaborative review: Encourage multidisciplinary oversight when adaptive plans cross hardware limits.

By documenting this incident and the corrective workflow, the report provides a practical roadmap for other teams to enhance both the safety and reliability of adaptive radiation treatments.