3.2 I Cataract
Five patients developed bilateral cataracts at a median duration of 3.2 years (1.2 – 5.1 years) after completion of radiation (Table 3). All these patients received CSI for embryonal tumors (4 medulloblastoma, 1 primitive neurectodermal tumor/PNET). The incidence of cataract was 12% (5/42) in the cohort overall, and 38% (5/13) for those who received CSI. Four patients had posterior sub-capsular cataracts, with details not available for 1 patient who died due to disease, a few months after cataract detection at an outside center. Three patients underwent cataract surgery.
Of the 5 patients with cataracts after CSI, 2 each received 23.4 and 36 Gy RBE, and 1 received 25.2 Gy RBE to the whole brain and spinal cord, with a median of 29.3 Gy to the lenses. The median radiation dose to the lens for patients with cataract was significantly higher than that for patients without cataract (Table 4).
Multivariable analysis identified CSI radiation volume, infratentorial tumor location and the use of radiosensitizer chemotherapy as significant risk factors for the development of cataract (Table 5) and ocular complications overall (cataract and dry eyes) (Supplementary Table 2). All 5 patients who developed cataract after CSI, had infratentorial tumors, and 4 received radiosensitizing chemotherapy (2 Vincristine, 1 Carboplatin and Vincristine, 1 Temozolomide and Irinotecan). Of the 13 patients in the cohort who received CSI, 12 had infratentorial tumors (10 medulloblastoma, 1 mucoid spindle sarcoma, 1 primitive neurectodermal tumor in the cervical spinal cord). All 10 patients with medulloblastoma received weekly Vincristine during radiation, and 1 received additional Carboplatin.
One patient with craniopharyngioma, with a normal eye exam prior to radiation, developed left retinal scarring 2.2 years after, and cataract 3.5 years and 4.7 years in the left and right eyes, respectively, after IFRT. She received both photon and proton radiation, and hence was excluded from analysis.