Surgical Organ Displacement for Proton Radiotherapy

Reviewer: Eric Shinohara MD, MSCI
Abramson Cancer Center of the University of Pennsylvania
Ultima Vez Modificado: 13 de octubre del 2009

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Presenter: Dr. J Jesseph
Presenter's Affiliation: Proton Radiotherapy Institute, Indiana University, Bloomington, Indiana
Type of Session: Scientific

Background

  • Compared with photon based therapy, proton therapy has the potential to greatly reduce dose to normal structures.
  • Nonetheless, there are still situations where the successful treatment of tumors will be limited by the doses that are delivered to normal adjacent structures.
  • There may be ways to combine the use of surgical displacement of organs to limit dose to normal structures with proton therapy.
  • This presentation provides the experience using surgical techniques for organ displacement in proton therapy at the Midwest Proton Radiotherapy Facility (MPRI).

Materials and Methods

  • This presentation outlines a case series in which surgical displacement was used to move critical structures.
  • IRB approval was obtained to review CT and MRI images from patients who had tumors of the abdomen and pelvis which were felt to be untreatable due to their proximity to normal critical tissues, such as the bowel.
  • Patients had unresectable or recurrent tumors of the abdomen and pelvis.
  • Patients underwent surgical organ displacement with subsequent treatment with protons.
    • All organ displacement was done with either autologous omental displacement or breast prosthesis.
    • All patients underwent open surgical procedures.

Results

  • The age range of patients included in this study was 16-81 years .
  • Patients who were a part of this study included:
    • A patients with a recurrent bladder cancer after cystectomy.
    • A patient with a desmoid tumor of the rectus sheath which had been resected three times.
    • A patient with a recurrent rectal cancer who had been treated with radiation and an APR previously.
    • A 21 year-old girl with a T3 low rectal cancer who was treated neoadjuvantly with protons.
    • A patient with recurrent cholangiocarcinoma of the liver who had received radiation previously.
    • A patient with an enlarging, unresectable cholangiocarcinoma of the liver.
    • Two patients with unresectable hepatocellular carcinoma.
    • A patient with a fourth recurrence of a chondrosarcoma
  • No surgical complications were encountered due to organ displacement.
  • All patients were treated with protons successfully after organ displacement.
  • The mean target dose was 63 CGE with a dose range of between 35-72 CGE.
  • No patient had grade 2 or greater toxicity, and there have been no deaths as of last follow up.

Author's Conclusions

  • There is great potential for collaboration between surgeons and radiation oncologists to improve on proton therapy delivery.
  • The potential benefit from organ displacement may be greater for proton therapy compared with photon based therapy.
  • By altering the patients anatomy surgically, untreatable tumors may be rendered treatable and potentially, uncurable tumors may become curable in select cases.

Clinical/Scientific Implications

  • Surgical displacement may be more tolerable in patients receiving proton therapy as there is less normal tissue irradiated, especially in patients who may need additional surgical procedures at a later time.
  • Surgical displacement may also allow greater dose escalation to be used, which could potentially improve local control and as the authors imply, may someday improve outcomes.
  • In addition to the benefit of moving critical structures, there may be the potential to create less inhomogeneiety along the proton beam path with the use of organ displacement, which could provide improvements in proton delivery and may even allow smaller margins to be used.
  • This study suggests that the improved dose distribution seen with protons may be made even more effective with organ displacement, and suggests that untreatable patients may be rendered treatable with organ displacement.  This study also suggests that the combined use of organ displacement and proton therapy appears tolerable.  This is an interesting study though further studies are needed due to the small number of patients. Other techniques and newer appliances should also be investigated.

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