Stereotactic radiotherapy

SHORT VERSION

Stereotactic radiotherapy is a radiotherapy modality in which beams originating from different angles converge on the tumor. This technique allows irradiating small tumors with high doses per session and reducing the number of sessions compared with conventional radiotherapy.

Stereotactic radiotherapy is a very high precision (millimeter level) external radiotherapy modality in which radiation beams originating from different angles converge on the tumor. This revolutionary technique for cancer treatment was developed in the last two decades. Stereotactic radiotherapy allows irradiating small tumors with very high doses per session and in fewer sessions compared with “standard” radiotherapy.. In stereotactic radiotherapy, the dose gradient between tumor and surrounding organs is very high, thus limiting the dose received by healthy tissue and the risk of toxicity. Because of the high dose per session, the treatment margins (i.e. the safety margins around the tumor to ensure complete coverage by radiation) are reduced compared with those of standard radiotherapy. Therefore all possible movements of the tumor volume to be treated must be precisely controlled and the patient’s treatment position must be perfectly maintained.

Stereotactic radiotherapy requires:

  • access to highly technical equipment
  • the use of immobilization devices to limits the patient’s movements as much as possible
  • precise delineation of the tumor volumes
  • the use of real-time imaging for patient’s repositioning
  • sometimes, live target tracking techniques (called gating or tracking techniques)

Stereotactic radiation therapy was originally developed to treat small brain tumors. Today, radiation oncologists are increasingly using this technique for tumors at other, if they are small and well-delineated (e.g. lung cancer and lung cancer metastases, liver cancer and liver cancer metastases, pancreatic cancer, localized prostate cancer recurrences, brain metastases, bone metastases, abdominal-pelvic lymph node metastases, adrenal gland and kidney metastases).

Because of the narrower treatment margins, the doses received by healthy tissue are lower and side effects are much rarer. However, the potential late side effects are more serious than in conventional radiotherapy.Therefore, this radiation therapy modality must be performed by specialized teams. As always, the potential side effects will depend on the treated area (for instance, seizures in the case of brain irradiation, rib fractures in the case of thoracic irradiation).