Dose Comparison of Treatment Plans Using Different Ir-192 Sources and Treatment Planning Systems for Intracavitary HDR Brachytherapy / 의학물리

For HDR intracavitary brachytherapy with ovoids and a tandem, we compared the dose discrepancy of treatment plans using two different Ir-192 sources (microSelectron, Varian) and generated on two different treatment planning systems (PLATO, BrachyVision). The treatment plans of ten patient treated from Oct. 2007 to Jan. 2008 were selected for these comparisons. For the comparison of dose calculation using different sources, the average discrepancies were -0.91+/-0.09%, 0.27+/-0.07%, 0.22+/-0.39%, and 0.88+/-0.37% in total treatment time and at B-point and ICRU bladder and rectum reference point, respectively. Comparing the two systems, the average dose discrepancies between treatment planning programs were -0.22+/-0.42%, -0.25+/-0.29%, -0.23+/-0.63%, and -0.17+/-0.76%, and the average dose discrepancies between positioning methods (PLATO with film and BrachyVision with digitial image) were -0.61+/-0.59%, -0.77+/-0.45%, -0.72+/-1.70%, and 0.35+/-2.82% at A-point, B-point, and ICRU bladder and rectum reference points, respectively. The rectal dose discrepancies between two systems were reached 5.87%. The difference in the dwell position expected by each TPS are mainly affected by the differences in the positioning method in TPSs and have an effect on dose calculations of rectal and bladder located in AP direction.

Sequential Chemoradiotherapy for Stage I/II Nasal Natural Killer/T Cell Lymphoma / 대한방사선종양학회지

PURPOSE: Authors would report the results of sequential CHOP chemotherapy (cyclophosphamide, adriamycin, vincristine, and prednisone) and involved field radiotherapy (IFRT) for early stage nasal natural killer/T-cell lymphoma (NKTCL). MATERIALS AND METHODS: Fourteen among 17 patients, who were registered at the Samsung Medical Center tumor registry with stage I and II nasal NKTCL from March 1995 to December 1999 received this treatment protocol. Three to four cycles of CHOP chemotherapy were given at 3 weeks' interval, which was followed by local IFRT including the known tumor extent and the adjacent draining lymphatics. RESULTS: Favorable responses after chemotherapy (before IFRT) were achievable only in seven patients (5 CR's+2 PR's: 50%), while seven patients showed disease progression. There were six patients with local failures, two with distant relapses, and none with regional lymphatic failure. The actuarial overall survival and progression-free survival at 3 years were 50.0% and 42.9%. All the failures and deaths occurred within 13 months of the treatment start. The factors that correlated with the improved survival were the absence of 'B' symptoms, the favorable response to chemotherapy and overall treatment, and the low risk by international prognostic index on univariate analyses. CONCLUSION: Compared with the historic treatment results by IFRT either alone or followed by chemotherapy, the current trial failed to demonstrate advantages with respect to the failure pattern and survival. Development of new treatment strategy in combining IFRT and chemotherapy is required for improving outcomes.

Stereotactic Radiosurgery and Fractionated Stereotactic Radiotherapy for Intracranial Schwannoma / 대한암학회지

PURPOSE: To assess the radiologic response and cranial nerve morbidity in intracranial schwannoma patients treated with stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT). MATERIALS AND METHODS: Twenty-six patients with intracranial schwannoma were treated with linear accelerator- based SRS or FSRT between February 1995 and October 1999. The origin of schwannoma was acoustic nerve in twenty-one patients, facial nerve in two, trigeminal nerve in two, and glossopharyngeal nerve in one. SRS were performed with the median peripheral dose of 14 Gy (range 12-16), and FSRT were done with the median peripheral dose of 25 2 Gy (range 50-60). RESULTS: With a median follow-up period of 33 months (range 12-67), the local control rate was 100%. Tumorregression was noted in eleven patients, and tumor stabilization was found in the remaining fifteen. Useful hearing preservation was achieved in two of three patients. Facial nerve neuropathy was shown in two patients and one patients developed trigeminal nerve neuropathy. CONCLUSION: Stereotactic radiotherapy including SRS and FSRT provided excellent local control in intracranial schwannoma. It shows the possibility of a high rate of hearing preservation and an acceptable neurotoxicity, although the number of patients are small and follow-up is relatively short.

Clinical Experience of LINAC-based Stereotactic Radiosurgery for Angiographically Occult Vascular Malformations / 대한방사선종양학회지

PURPOSE: To establish the role of stereotactic radiosurgery (SRS) for the treatment of patients with angiographically occult vascular malformation (AOVM). MATERIALS AND METHODS: Eleven patients (12 lesions) with AOVM were treated with linear accelerator-based SRS between February 1995 and December 1999. A magnetic resonance imaging of each patients showed well-circumscribed vascular lesion with reticulated core of heterogeneous signal intensity and peripheral rim of low signal intensity. SRS were performed with the median peripheral dose of 16 Gy (range 13~25). A single isocenter was used with median collimator size of 14 mm (range 8~20) diameter. RESULTS: With a median follow-up period of 42 months (range 12~56), rebleeding occurred in 3 AOVMs at 5, 6 and 12 months after SRS but no further bleeding did. Two patients experienced radiation-induced necrosis associated with permanent neurologic deficit and one patient showed transient edema of increased T2 signal intensity. CONCLUSION: SRS may be effective for the prevention of rebleeding in AOVM located in surgically inaccessible region of the brain. Careful consideration should be needed in the decision of case selection and dose prescription because the incidence of radiation-induced complications is too high to be accepted.