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Intraoperative Radiotherapy (IORT)

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IORT uses a high single-fraction radiation dose (10-30 Gy) is delivered during surgery to a surgically-exposed tumour bed, immediately after a chunk of the tumour has been surgically excised. This slide includes topics like APBI, IOERT, IOHDR.

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Intraoperative Radiotherapy (IORT)

  1. 1. IORTINTRAOPERATIVE RADIOTHERAPY Victor Ekpo
  2. 2. INTRODUCTION There are 3 major methods of treating cancer: • Radiotherapy • Surgery • Chemotherapy IORT IORT uses a high single-fraction radiation dose (10-30 Gy) is delivered during surgery to a surgically-exposed tumour bed, immediately after a chunk of the tumour has been surgically excised.
  3. 3. OBJECTIVES IORT has two (2) objectives: • increase the probability of local control of the tumour. • increase the therapeutic ratio between local control of the tumour and tolerance of the adjacent healthy tissues and organs. IORT is used for tumours difficult to be controlled by surgery or external radiotherapy alone. It has been used for all types of cancers – rectal cancers, sarcomas, gynaecological cancers, breast cancers, gastroesophageal cancers, pancreatic cancers, etc.
  4. 4. OBJECTIVES (contd.) The surgery attempts to shrink the tumour. Possibly to decrease the Oxygen Enhancement Ratio, and improve the radiosensitivity of the tumour volume. Typically, when surgical resection of a tumour mass is performed, not all the tumour can be removed without significant morbidity. Therefore, a bulk of the tumour is removed surgically, and the remnant is treated with RT.
  5. 5. TECHNIQUES The radiation may be delivered either of 2 methods: • IOERT (uses megavoltage electron superficial beams) - Intraoperative Electron Radiation Therapy • IOHDR Intraoperative High Dose Rate Brachytherapy (>12Gy/hr) In the early days, orthovoltage X-ray beams were also used, but no longer in regular use, due to low tissue penetration.
  6. 6. IOERT IOHDR Machine LINAC Standard (electron) applications for all treatment HDR Brachytherapy Custom made applicators for different anatomical locations Source 3-12MeV Electrons Iridium-192 or miniature X-ray sources Homogeneity Better dose homogeneity More variation across tissue Treatment Time Faster (2-4 mins). Total procedure (30 - 45 mins) Slower (5-30 mins). Total procedure (45 - 120 mins) Cost Costlier Lower cost Sites Only superficial and accessible sites Unsuitable for pelvic locations, narrow cavities. Any site. Can treat any site, including large and convoluted surfaces.
  7. 7. TECHNIQUES Miniature X-ray sources is a new technological development, as a form of IOHDR. It is used in treatment of early stage breast cancer as a form of accelerated partial breast irradiation (APBI) with Breast Conserving Surgery (BCS). Fig: Miniature X-ray Applicator by Xoft Axxent
  8. 8. Miniature X-ray / IORT Machine Head and Neck Cancer Gastroesophageal Cancer
  9. 9. I. Determine position of tumour II. Open a small incision for surgery III Surgically, remove tumour IV. Position applicator in tumour bed V. Irradiate for about 30 mins VI. Remove applicator, Close incision Fig: IOHDR for Breast Cancer (Image Source: Zeiss) TREATMENT PLANNING
  10. 10. Fig: Patient about to undergo IORT
  11. 11. Fig: Patient undergoing IOERT using LINAC (Image Courtesy: Gregorio Maranon University Hospital HGUGM, Spain)
  12. 12. ELIGIBILITY FOR IORT (APBI) *following ASTRO guidelines for APBI FACTORS SUITABLE PATIENT GROUP CAUTIONARY PATIENT GROUP UNSUITABLE PATIENT GROUP Age ≥ 50 years 40 – 49 years < 40 years Tumour Size ≤ 2 cm 2.1 – 3.0cm > 3.0cm DCIS Status (Ductal Carcinoma in-situ) Patients with low-risk DCIS (abnormal cells in the milk ducts) – STAGE cT1cN0M0 Intermediate-risk (spreading from milk ducts to surrounding breast tissue) High-risk Lesion location Localised breast tumour suitable for breast conservation - - BRCA 1/2 Mutation (Breast Cancer Gene Carrier) Negative or Not Known Undergoing current genetic testing Present
  13. 13. TREATMENT PLANNING The IORT team consists of a surgeon, radiation oncologist, medical physicist, anaesthesiologist, nurse, pathologist and radiation therapist. The treatment plan depends on the organ/tumour treated, and is usually agreed upon between the radiation oncologist and medical physicist. IORT requires an Operating Room (OR) for the surgical procedure and a treatment room for delivery of the radiation dose.
  14. 14. TREATMENT PLANNING (contd.) The transition between the OR and RT treatment rooms must be carefully planned and all steps involved properly worked out and practised, esp. as the patient may still be under anaesthesia, and the surgical area upon. The RT treatment room must be adequately sterilized to OR standards. Where possible, the OR and RT rooms should be merged into one location.
  15. 15. IORT Applicators are important for three reasons: ● To define the target area; ● To shield tissues outside the target area from radiation; ● To keep sensitive tissues from falling into the target area during irradiation. In breast cancer treatment, it protects against irradiating the heart and the lungs. TREATMENT PLANNING (contd.)
  16. 16. TREATMENT PLANNING (contd.) AAPM TG-48 recommends that: • 90% isodose curve should cover the target volume, • Dose should be prescribed at dmax Beam energy is usually selected to place the 90% isodose line of the dose distribution of the chosen applicator at the distal depth of the target.
  17. 17. ISODOSE CURVES
  18. 18. QA/QC IN IORT Quality Assurance in IORT procedure consists of three components: • Basic quality assurance dealing with the IORT equipment. • Pre-treatment quality assurance dealing with equipment preparation and verification prior to IORT treatment. • Treatment quality assurance during the IORT procedure.
  19. 19. ADVANTAGES • Reduces the chance of residual tumour at the site of surgery (eliminates microscopic tumour foci), thus maximizing local control (LC) of tumours, and reducing probability of local recurrence (LR). • Maximizes the radiobiological effect of a single high dose of radiation. • Faster treatment time (reduces it from weeks to 1 day). • Minimal exposure of surrounding tissues (esp. OARs) to radiation, thus reducing normal tissue toxicity.
  20. 20. DISADVANTAGES • Since IORT is almost always given in a single session, it becomes more difficult to correct misadministration of dose. • Requires dedicated equipment (HDR machine). • In IOERT, transporting the patient from the OR to the LINAC is tasking. Though this is being solved by mobile LINACs like the CyberKnife.
  21. 21. DISADVANTAGES (contd.) • Higher risk of long-term deterministic effects, such as fibrosis, in late responding tissues. • The dose is usually high and close to the tolerance levels of the normal tissue. Thus, a second full-dose course of radiotherapy may not usually possible, even after months.
  22. 22. CONCLUSION IORT provides a convenient time-saving advanced radiotherapy option requiring a multi-disciplinary medical team working closely together. There are certain eligibility criteria for patients to receive IORT, which depends on patient’s age, general health, spread of tumour, stage of tumour, etc. However, when used, it has been shown to have good LC and LR results, comparable to conventional fractional radiotherapy.
  23. 23. REFERENCES E. B. Podgorsak. Radiation Oncology Physics: A Handbook For Teachers And Students. IAEA: 2005. G. Tosi, M. Ciocca. Radiation Protection in the Commissioning and in the Use of a IORT-dedicated Mobile LINAC. Italy: European Institute of Oncology. 2003. IORT: An Emerging Technology. Imaging Technology News. www.itnonline.com/article/iort-emerging-technology . Accessed: March 30, 2017. Intraoperative radiotherapy with electrons: Fundamentals, Results and Innovation. www.ecancer.org/journal/7/full/339... Accessed: April 2, 2017. G. N. Cohen, M. Zaider. AAPM Monograph No. 31, Brachytherapy Physics, (2nd Edition) Intraoperative Radiation Therapy (IORT). New York. Memorial Sloan- Kettering Cancer Center. 2005.
  24. 24. THANK YOU

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