Temporal lobe (TL) damage following surgery and high-dose photon and proton irradiation in 96 patients affected by chordomas and chondrosarcomas of the base of the skull

Purpose: To determine the temporal lobe (TL) damage rate in 96 patients treated with high-dose proton and photon irradiation for chordomas and chondrosarcomas of the base of the skull. Methods and Materials: The records of 96 consecutive patients treated at Massachusetts General Hospital (MGH) and Harvard Cyclotron Laboratory (HCL) between June 1984 and 1993, for chordomas and chondrosarcomas of the base of the skull were reviewed. All the patients had undergone some degree of resection of the tumor prior to radiation therapy. Seventy-five patients were classified as 'primary tumors' and 21 as recurrent or regrowing tumors after one or more surgical procedures. All the patients were randomized to receive 66.6 or 72 cobalt Gray equivalent (CGE) on a prospective dose-searching study by proton and photon irradiation (Radiation Therapy Oncology Group No.85-26) with conventional fractionation (1.8 CGE/day, 5 fractions/week). All treatments were planned using the three-dimensional (3D) planning system developed at the Massachusetts General Hospital, and the dose was delivered using opposed lateral fields for the photon component and a noncoplanar isocentric technique for the proton component. Clinical symptoms of TL damage were classified into 4 grades. Computerized tomography (CT) and magnetic resonance imaging (MRI) scans were evaluated for white matter changes. Abnormalities associated with persistent or recurrent tumor were distinguished from radiation-induced changes. TLs were delineated on the original scans of the 10 patients with damage and those of a group of 33 patients with no clinical or MRI evidence of injury. Dose distributions were calculated and dose- volume histograms were obtained for these patients. Results: Of the patients, 10 developed TL damage, with bilateral injury in 2 and unilateral injury in 8. The cumulative TL damage incidence at 2 and 5 years was 7.6 and 13.2%, respectively. The MRI areas suggestive of TL damage were always separated from the