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Optic nerve and chiasmatic tolerance to radiotherapy
S408
I. J. Radiation Oncology
● Biology ● Physics
Volume 60, Number 1, Supplement, 2004
21 patients, a gross total resection (GTR) was attained. In 24 patients, only a subtotal resection (STR) was possible. Six of the patients undergoing GTR and 9 of the patients undergoing STR had postoperative RT as part of their initial treatment. Median dose to the primary tumor was 5,500 cGy in 180- to 200-cGy fractions. Four patients received postoperative chemotherapy in conjunction with adjuvant RT (2 patients in the GTR group and 2 in the STR group). One patient received chemotherapy for recurrent disease (drop metastases). Nine patients received salvage RT for recurrence or local progression after resection (3 patients in the GTR group and 6 in the STR group). Overall follow-up for survivors ranged from 2.6 to 17.3 years (median, 7.0 years). Results: The majority of tumors were located within one or both of the lateral ventricles; however, 3 extraventricular tumors were identified in the left temporal lobe, left frontal lobe, and hypothalamus. Median patient age was 28 years (range 4 –71 years). The overall 5-year survival and local control rates were 81% and 71%, respectively. The 5-year survival rate was 74% for patients undergoing STR and 88% for those undergoing GTR (P ⫽ 0.18). The 5-year local control rate was 69% for patients undergoing STR and 73% for those undergoing GTR (P ⫽ 0.43). The 5-year local control rate was 93% in patients receiving postoperative RT as compared to 57% in the 30 patients who did not receive RT after resection (P ⫽ 0.024). This, however, did not translate into a statistically significant survival benefit. The patients that had RT had a 77% 5-year survival rate as compared to an 83% rate in the group that did not have adjuvant treatment (P ⫽ 0.90). The efficacy of postoperative RT in enhancing local control is of particular importance when GTR is not possible. The 5-year local control rate was 100% for patients who received RT after STR compared with 48% for those who did not (P ⫽ 0.013); however, there was no difference in overall survival at 5 years (78% STR ⫹ RT vs. 73% STR alone, P ⫽ 0.68). The 4 patients who received adjuvant chemotherapy in addition to RT all maintained local control. The one patient who received salvage chemotherapy for drop metastases to the spinal cord had a partial response, but further tumor growth was evident on MRI less than 13 months later. Five of the 9 patients who had salvage RT received it in the form of stereotactic radiosurgery (18 –20 Gy at the margin). The other 4 patients were salvaged with fractionated RT (4100 to 6000 cGy). One patient died 2 years after salvage RT, one was lost to follow up immediately after RT, and the remaining 7 patients were alive and free of disease 1 to 10 years after RT. Conclusions: Complete surgical removal should be the treatment goal for central neurocytomas because it results in a very high likelihood of local control and survival. When this is not possible, postoperative RT should be considered as it appears to significantly improve local control rates. However, postoperative RT does not translate into a survival benefit, most likely due to the effectiveness of salvage RT. The use of chemotherapy in the setting of STR or recurrent disease requires further study. Though central neurocytomas are typically benign, this series demonstrates that they can act in a more malignant fashion as evidenced by distant metastasis. Nevertheless, overall prognosis is quite favorable with 5-year survival rate of 81%.
2124
Optic Nerve and Chiasmatic Tolerance to Radiotherapy
W. Yi,1 D. Smith,2 L. S. Constine1 Department of Radiation Oncology, University of Rochester Medical Center, Rochester, NY, 2Department of Ophthalmology, University of Rochester Medical Center, Rochester, NY 1
Purpose/Objective: To evaluate functional integrity of the optic nerve and chiasm after radiotherapy and thus assess the radiation tolerance dose of the visual pathway. Materials/Methods: Thirty patients who received significant radiation doses (greater than 36 Gy) to the optic nerve and chiasm from 1977 to 2001 for treatment of various malignancies (13 pituitary adenoma, 4 astrocytoma, 3 medulloblastoma, 2 ependymoma, 2 cranipharyngioma, 2 rhabdomyosarcoma, 1 optic glioma, 1 mixed astrocytoma, 1 hemagioendothelioma, 1 non-Hodgkin’s lymphoma) were included in this study. Dose to the optic nerve and chiasm ranged from 36 Gy to 60 Gy (five:⬎35 G, ⬍40 Gy; three:⬎40 Gy, ⬍45 Gy; five:⬎45 Gy, ⬍50 Gy; fourteen:⬎50 Gy, ⬍55 Gy; three:⬎55 Gy, ⬍60 Gy). All patients were treated in 1.8 Gy or 2.0 Gy daily fractions. Age at RT ranged from 5 to 79 years(mean age of 30.5 years old). The function of the optic nerve and chiasm was evaluated for each patient with visual evoked response (VER) testing. The mean time from RT to VER was 4.9 years (ranged from less than one year to 17 years). VERs record electrical responses from visual stimulation. Pattern, amplitude, and latency (time from stimulation to response) were recorded and analyzed to discriminate radiation effects from other causes of abnormalities. Results: Twelve of 30 patients (40.0%) demonstrated abnormal VER results. Of patients with abnormal VER findings, three (25.0%), four (33.3%), and five (41.7%) were found to have decreased amplitude only, increased latency only, and both, respectively. Abnormal VER findings were attributed to tumor compression or infiltration in 10 of these 12 patients (83.3%). One patient’s abnormal VER could not be explained. One patient who received 45 Gy to the optic nerve and chiasm when he was 5 years old for ependymoma (15 years prior to VER) was found to have mildly increased latency bilaterally. Clinically, he was asymptomatic (visual acuity with correction: OD 20/15, OS 20/20). This was interpreted to be due to radiation. Overall, only 1 of 30 patients (3.3%) was found to have abnormal VER findings due to radiotherapy. Conclusions: Following radiotherapy to the anterior visual pathway, most patients do not demonstrate functional changes of the optic nerve and chiasm that can be attributed to radiation. Radiation doses up to 60 Gy given in conventional fractionation appears to be well tolerated by the optic nerve and chiasm in most patients. Further studies involving more patients and systematic evaluations (e.g. pre and post-RT VER) are needed to more accurately determine the radiation tolerance dose of the optic nerve and chiasm as well as pathogenesis of radiation optic neuropathy.
2125
Radiation Tolerance of the Optic Apparatus
1
B. Cook, L. A. Withrow,2 S. A. Spencer,1 R. Ove,1 J. B. Fiveash1 Radiation Oncology, University of Alabama-Birmingham, Birmingham, AL, 2University of Louisville, Louisville, KY
1
Purpose/Objective: Many clinicians limit the dose to the optic apparatus (chiasm, optic nerve, and retinas) to 45–50 Gy during treatment planning for targets in the brain and certain head and neck malignancies. Such a restriction may compromise adequate coverage of the planning target volume and lead to suboptimal tumor control, especially for malignant tumors. We sought to
I. J. Radiation Oncology
● Biology ● Physics
Volume 60, Number 1, Supplement, 2004
21 patients, a gross total resection (GTR) was attained. In 24 patients, only a subtotal resection (STR) was possible. Six of the patients undergoing GTR and 9 of the patients undergoing STR had postoperative RT as part of their initial treatment. Median dose to the primary tumor was 5,500 cGy in 180- to 200-cGy fractions. Four patients received postoperative chemotherapy in conjunction with adjuvant RT (2 patients in the GTR group and 2 in the STR group). One patient received chemotherapy for recurrent disease (drop metastases). Nine patients received salvage RT for recurrence or local progression after resection (3 patients in the GTR group and 6 in the STR group). Overall follow-up for survivors ranged from 2.6 to 17.3 years (median, 7.0 years). Results: The majority of tumors were located within one or both of the lateral ventricles; however, 3 extraventricular tumors were identified in the left temporal lobe, left frontal lobe, and hypothalamus. Median patient age was 28 years (range 4 –71 years). The overall 5-year survival and local control rates were 81% and 71%, respectively. The 5-year survival rate was 74% for patients undergoing STR and 88% for those undergoing GTR (P ⫽ 0.18). The 5-year local control rate was 69% for patients undergoing STR and 73% for those undergoing GTR (P ⫽ 0.43). The 5-year local control rate was 93% in patients receiving postoperative RT as compared to 57% in the 30 patients who did not receive RT after resection (P ⫽ 0.024). This, however, did not translate into a statistically significant survival benefit. The patients that had RT had a 77% 5-year survival rate as compared to an 83% rate in the group that did not have adjuvant treatment (P ⫽ 0.90). The efficacy of postoperative RT in enhancing local control is of particular importance when GTR is not possible. The 5-year local control rate was 100% for patients who received RT after STR compared with 48% for those who did not (P ⫽ 0.013); however, there was no difference in overall survival at 5 years (78% STR ⫹ RT vs. 73% STR alone, P ⫽ 0.68). The 4 patients who received adjuvant chemotherapy in addition to RT all maintained local control. The one patient who received salvage chemotherapy for drop metastases to the spinal cord had a partial response, but further tumor growth was evident on MRI less than 13 months later. Five of the 9 patients who had salvage RT received it in the form of stereotactic radiosurgery (18 –20 Gy at the margin). The other 4 patients were salvaged with fractionated RT (4100 to 6000 cGy). One patient died 2 years after salvage RT, one was lost to follow up immediately after RT, and the remaining 7 patients were alive and free of disease 1 to 10 years after RT. Conclusions: Complete surgical removal should be the treatment goal for central neurocytomas because it results in a very high likelihood of local control and survival. When this is not possible, postoperative RT should be considered as it appears to significantly improve local control rates. However, postoperative RT does not translate into a survival benefit, most likely due to the effectiveness of salvage RT. The use of chemotherapy in the setting of STR or recurrent disease requires further study. Though central neurocytomas are typically benign, this series demonstrates that they can act in a more malignant fashion as evidenced by distant metastasis. Nevertheless, overall prognosis is quite favorable with 5-year survival rate of 81%.
2124
Optic Nerve and Chiasmatic Tolerance to Radiotherapy
W. Yi,1 D. Smith,2 L. S. Constine1 Department of Radiation Oncology, University of Rochester Medical Center, Rochester, NY, 2Department of Ophthalmology, University of Rochester Medical Center, Rochester, NY 1
Purpose/Objective: To evaluate functional integrity of the optic nerve and chiasm after radiotherapy and thus assess the radiation tolerance dose of the visual pathway. Materials/Methods: Thirty patients who received significant radiation doses (greater than 36 Gy) to the optic nerve and chiasm from 1977 to 2001 for treatment of various malignancies (13 pituitary adenoma, 4 astrocytoma, 3 medulloblastoma, 2 ependymoma, 2 cranipharyngioma, 2 rhabdomyosarcoma, 1 optic glioma, 1 mixed astrocytoma, 1 hemagioendothelioma, 1 non-Hodgkin’s lymphoma) were included in this study. Dose to the optic nerve and chiasm ranged from 36 Gy to 60 Gy (five:⬎35 G, ⬍40 Gy; three:⬎40 Gy, ⬍45 Gy; five:⬎45 Gy, ⬍50 Gy; fourteen:⬎50 Gy, ⬍55 Gy; three:⬎55 Gy, ⬍60 Gy). All patients were treated in 1.8 Gy or 2.0 Gy daily fractions. Age at RT ranged from 5 to 79 years(mean age of 30.5 years old). The function of the optic nerve and chiasm was evaluated for each patient with visual evoked response (VER) testing. The mean time from RT to VER was 4.9 years (ranged from less than one year to 17 years). VERs record electrical responses from visual stimulation. Pattern, amplitude, and latency (time from stimulation to response) were recorded and analyzed to discriminate radiation effects from other causes of abnormalities. Results: Twelve of 30 patients (40.0%) demonstrated abnormal VER results. Of patients with abnormal VER findings, three (25.0%), four (33.3%), and five (41.7%) were found to have decreased amplitude only, increased latency only, and both, respectively. Abnormal VER findings were attributed to tumor compression or infiltration in 10 of these 12 patients (83.3%). One patient’s abnormal VER could not be explained. One patient who received 45 Gy to the optic nerve and chiasm when he was 5 years old for ependymoma (15 years prior to VER) was found to have mildly increased latency bilaterally. Clinically, he was asymptomatic (visual acuity with correction: OD 20/15, OS 20/20). This was interpreted to be due to radiation. Overall, only 1 of 30 patients (3.3%) was found to have abnormal VER findings due to radiotherapy. Conclusions: Following radiotherapy to the anterior visual pathway, most patients do not demonstrate functional changes of the optic nerve and chiasm that can be attributed to radiation. Radiation doses up to 60 Gy given in conventional fractionation appears to be well tolerated by the optic nerve and chiasm in most patients. Further studies involving more patients and systematic evaluations (e.g. pre and post-RT VER) are needed to more accurately determine the radiation tolerance dose of the optic nerve and chiasm as well as pathogenesis of radiation optic neuropathy.
2125
Radiation Tolerance of the Optic Apparatus
1
B. Cook, L. A. Withrow,2 S. A. Spencer,1 R. Ove,1 J. B. Fiveash1 Radiation Oncology, University of Alabama-Birmingham, Birmingham, AL, 2University of Louisville, Louisville, KY
1
Purpose/Objective: Many clinicians limit the dose to the optic apparatus (chiasm, optic nerve, and retinas) to 45–50 Gy during treatment planning for targets in the brain and certain head and neck malignancies. Such a restriction may compromise adequate coverage of the planning target volume and lead to suboptimal tumor control, especially for malignant tumors. We sought to