Role of radiation therapy to the brain in leukemic patients with cranial nerve palsies in the absence of radiological findings

The value of brain radiotherapy for leukemic patients with cranial nerve pa lsies in the absence of radiological evidence of leukemic infiltration is n ot well defined. This retrospective study was undertaken to evaluate the ef fectiveness of brain irradiation in reversing the cranial nerve palsies in leukemic patients with no radiological evidence of intracranial leukemic in filtration. Records of leukemic patients who received brain radiotherapy be tween June 1980 and December 1993 were reviewed. Criteria for inclusion wer e 1) no evidence of intracranial leukemic infiltration by computed axial to mography (CT) or magnetic resonance imaging scan (MRI), 2) no evidence of l eukemic infiltration on ophthalmologic examination, and 3) no previous radi otherapy to the brain. Actuarial survival rates were calculated using the K aplan-Meier method. Pearson's chi-squared test was used to compare response s. Twenty-eight patients met these criteria. The median age was 38 years (r ange 3-75 years): Seventeen patients had acute lymphoblastic leukemia, nine had acute myelogenous leukemia, and two had chronic myelogenous leukemia. Four patients had initial presentation with leukemia, and 24 presented with relapse. Twenty-six patients had cerebrospinal fluid cytology that was pos itive for leukemic cells. Fifteen patients had involvement of more than one cranial nerve, and nine had bilateral involvement. The most commonly invol ved nerves were the facial (n = 18), oculomotor (n = 9), and abducens nerve s (n = 8). Twenty-six patients received whole-brain radiotherapy. Two recei ved radiation to the base of the skull only. The median radiation dose was 24 Gy (range 16-30 Gy) at 2-3 Gy per fraction. Every patient had either con comitant intrathecal (n = 6) or systemic (n = 5) chemotherapy or both (n = 17) with radiation. Fourteen patients had complete reversal of the cranial nerve deficit, eight had partial recovery, and four had no response or prog ression of the disease. The response was unknown in two patients. Factors a ssociated with complete response were unilateral versus bilateral involveme nt (72% vs. 13%, P = 0.005) and single versus multiple nerve involvement (7 5% vs. 36%, P = 0.045). In conclusion, radiation therapy to whole brain was effective in reversing cranial nerve deficits from leukemia, although the leukemic infiltration may not be visualized by CT or MRI. No dose-response relationship was observed in the range we examined.