The incidence of second brain tumors related to cranial irradiation

Abstract

Secondary brain tumor (SBT) is a devastating complication of cranial irradiation (CI). We reviewed the literature to determine the incidence of SBT as related to specific radiation therapy (RT) treatment modalities. The relative risk of radiation-associated SBT after conventional and conformal RT is well established and ranges from 5.65 to 10.9; latent time to develop second tumor ranges from 5.8 to 22.4 years, depending on radiation dose and primary disease. Theories and dosimetric models suggest that intensity-modulated radiation therapy may result in an increased risk of SBT, but clinical evidence is limited. The incidence of stereotactic radiosurgery-related SBT is low. Initial data suggest that no increased risk from proton therapy and dosimetric models predict a lower incidence of SBT compared with photons. In conclusion, the incidence of SBT related to CI is low. Longer follow-up is needed to clarify the impact of intensity-modulated radiation therapy, proton therapy and other developing technologies.

Keywords:

• brain neoplasms
• conformal radiotherapy
• conventional radiotherapy
• intensity-modulated radiation therapy
• proton therapy
• radiotherapy
• second primary neoplasms
• stereotactic radiosurgery

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Key issues

• The risk of radiation-associated secondary brain tumor (SBT) after conventional and conformal radiotherapy is well established.

• Intensity-modulated radiation therapy might result in an increased risk of second malignancies induced by radiation.

• Associated malignant tumors after stereotactic radiosurgery appear to be very low.

• Proton beam therapy may reduce the incidence of SBT compared with photon radiotherapy.

• Ongoing studies that include long-term follow-up will need to assess the true incidence of SBT related to newer technologies.

Notes