Physical, Biological, and Clinical Merits of High Energy Boron Ions for Radiation Therapy

Abstract

The lightest ions beyond protons, principally helium, lithium, and boron ions, make highly specific molecular Bragg peak radiation therapy of malignant tumors possible with minimal adverse normal tissue reactions. The Bragg peak ionization density is mainly elevated in a few mm wide spot at the end of these ions with substantially increased local apoptosis and senescence induction. Mainly placing Bragg peaks in the gross tumor volume with increased local therapeutic effect and only low ionization density and easily repairable damage in normal tissues. The possible geometrical accuracy of the dose delivery will be ≈1 mm with these ions. Interestingly, high-resolution molecular tumor imaging will then be possible, particularly with 8Boron ions that are our lightest positron emitter allowing immediate accurate PET-CT imaging to delineate the target volume dose delivery. Compared to carbon ions the boron radiation damage to normal tissues in front of and behind the tumor is reduced at the same time as tumor apoptosis and senescence are increased. A mean tumor cure as high as 80% should be possible with Boron ion therapy using new clinical fractionation principles and even more when early tumor detection and malignancy estimation methods are brought into more regular clinical use.