[4] In virtually every tumor site, electron IORT improves local control, reducing the need for additional surgeries or interventions.
The following is a list of disease sites currently treated by IOERT: Since 1975, breast cancer rates have declined in the U.S., largely due to mammograms and the use of adjuvant treatments such as radiotherapy.
In one of the largest published studies so far called (ELIOT),[5] researchers found that after treating 574 patients with full-dose IOERT with 21 Gy, at a median follow-up of 20 months, there was an in-breast tumor recurrence rate of only 1.05%.
More research is needed for defining the optimal dose of IOERT, alone or in combination with EBRT, and for determining when it may be appropriate to use it as part of the treatment for higher risk patients.
Furthermore, research shows that a boost given by IOERT reduces the ability for surviving tumor cells to replicate, creating extra time for healing of the surgical wound before EBRT is administered.
[14][15] Spanish[16] and German doctors,[17] in 1905 and 1915 respectively, used intraoperative radiation therapy (IORT) in an attempt to eradicate residual tumors left behind after surgical resection.
The X-rays penetrated beyond the tumor bed to the normal tissues beneath, had poor dose distributions, and took a relatively long time to administer.
[18] In 1965, the modern era of IOERT began in Japan at Kyoto University where patients were treated with electrons generated by a betatron[19] Compared with other forms of IORT such as orthovoltage X-ray beams, electron beams improved IOERT dose distributions, limited penetration beyond the tumor, and delivered the required dose much more rapidly.
Even though this reduced the overall dose that could potentially be delivered to the tumor site, the early Japanese results were impressive, particularly for gastric cancer.
However, about 30-50% of the patients planned for IOERT were found to be unsuitable candidates for IORT at the time of surgery, mainly because the disease had spread to adjacent organs.
[23][24][25] Their approach combined maximal surgical resection and IOERT and, in most cases, did not include conventional external beam therapy as part of the treatment.
Furthermore, they introduced several technical innovations to IOERT, including the use of television for simultaneous periscopic viewing of the tumor by the surgical team.
In 1985, IOERT began in Italy and involved a specialized method to facilitate surgery followed by transport to the radiotherapy treatment room.
[27][28][29] In 1982 the Joint Center for Radiation Therapy (JCRT),[30] at Harvard Medical School, attempted to reduce the cost of performing IORT in an OR by using orthovoltage X-rays to provide the intraoperative dose, which was similar to the approach used in Germany in 1915.
[32] These factors were major obstructions to the widespread adoption of IORT because they added significant cost to treatment as well as logistical complications to surgery, including an increased risk of infection to the patient.
Because portable LINACs for IOERT produced electron beams of energy less than or equal to 12 MeV and did not use bending magnets, the secondary radiation emitted was so low that it didn’t require permanent shielding in the operating room.
[31] By using mobile units, the possibility of treating patients with IORT was no longer restricted to the availability of special shielded operating rooms, but could be done in regular unshielded ORs.
In 1998, a technique called TARGIT (targeted intraoperative radio therapy) was designed at the University College London for treating the tumor bed after wide local excision (lumpectomy) of breast cancer.