Pathology-Intraoperative Radiotherapy (IORT)

I. Definition and Principle:

Intraoperative radiotherapy (IORT) delivers a single, high dose of external beam radiotherapy (EBRT) directly to exposed diseased tissue during surgery. This targeted approach aims to minimize radiation exposure to healthy surrounding tissues, reducing morbidity compared to conventional radiotherapy. The radiation source can be orthovoltage X-rays or electrons.

II. Advantages & Disadvantages:

Advantages:

• Precise targeting of diseased tissue during surgery.
• Reduced radiation damage to healthy tissues.

Disadvantages:

• Requires specialized equipment in the operating room.
• Increased radiation safety protocols and staff training needed.
• Requires a radiation oncologist's presence during surgery.
• Risk of significant radiation damage to adjacent normal tissues with a single large dose.
• Limited long-term follow-up data.
• Potential for inducing secondary malignancies (e.g., sarcomas), particularly in animal studies.
• Complex treatment planning due to limited preoperative data on treatment volume.

III. Long-Term Effects and Risks:

• Animal studies suggest that IORT doses up to 30Gy carry minimal long-term risk if radiosensitive structures (nerves, blood vessels, spinal cord, bowel) are shielded.
• Nerve damage threshold: 20-25Gy, with a 6-9 month latency period.
• Secondary malignancy risk: Animal studies (dogs) show a high incidence of sarcomas compared to other modalities. Further human data is needed to ascertain human risk.

IV. Specific Tumor Applications:

The effectiveness and safety of IORT varies across different tumor types:

V. Limitations and Future Directions:

• Technical and logistical challenges limit widespread adoption.
• Advances in conformal EBRT may reduce the advantage of IORT.
• Conventional Conformal Radiotherapy (CRT) offers better reproducibility in setup, dosimetry, and fractionation.
• Further research and clinical trials are needed to fully assess IORT's efficacy and safety profile. Current use is primarily limited to specialist centres.

VI. Key Concepts to Remember:

• Targeted approach: IORT delivers radiation directly to the tumor during surgery.
• Single high dose: A significant advantage but also a significant risk factor.
• Limited long-term data: More research is needed to assess long-term effects and risks.
• Tumor-specific efficacy: The success of IORT varies greatly depending on the type of cancer.
• Technological limitations: Current technology and logistical challenges hinder widespread use.