• Radiation Oncology Journal
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• v.13 no.3
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• pp.277-283
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• 1995

Purpose : This study was performed to measure dose alteration at the air-tissue interface resulting from rebuild-up to the loss of charged particle equilibrium in the tissues around the air-tissue interfaces. Materials and Methods : The 6 and 10-MV photon beam in dual energy linear accelerator were used to measure the surface dose at the air-tissue interface The polystyrene phantom sized $25{\times}25{\times}5\;cm^3$ and a water phantom sized $29{\times}29{\times}48\;cm^3$ which incorporates a parallel-plate ionization chamber in the distal side of air gap were used in this study. The treatment field sizes were $5{\times}5\;cm^2,\;10{\times}10\;cm^2\;and\;20{\times}20\;cm^2$. Air cavity thickness was variable from 10 mm to 50 mm. The observed-expected ratio (OER) was defined as the ratio of dose measured at the distal junction that is air-tissue interface to the dose measured at the same point in a homogeneous phantom. Results : In this experiment, the result of OER was close or slightly over than 1.0 for the large field size but much less (about 0.565) than 1.0 for the small field size in both photon energy. The factors to affect the dose distribution at the air-tissue interface were the field size, the thickness of air cavity. and the photon energy. Conclusion : Thus, the radiation oncologist should take into account dose reduction at the air-tissue interface when planning the head and neck cancer especially pharynx and laryngeal lesions, because the dose can be less nearly $29{\%}$ than predicted value.

• Radiation Oncology Journal
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• v.14 no.1
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• pp.9-15
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• 1996

Purpose: The traditional approach with surgery and/or radiotherapy(RT) for advanced head and neck cancer Provides anticipated cure rates of $10-65\%$ depending on stages and sites. Recently, combined modality with chemotherapy have been extensively investigated in attempts to improve survival and local control. We retrospectively analysed our experience of 31 patients with advanced head and neck cancer. Materials and Methods : November 1983 to October 1994. 31 Patients with Stage III and IV squamous cell head and neck cancer were treated with RT. Sixteen patients were treated with RT alone, and IS patients were treated with combined RT plus chemotherapy. All patients were treated with 4-MV LINAC and radiation dose ranged from 5000 cGy to 7760 cGy (median 7010 cGy). In combined group, 7 patients were treated with cisplatin plus 5-FU 2 patients were treated with methotrexate plus leucovorin plus 5-FU plus cisplatin or carboplatin, and 6 patients were treated with cisplatin as a radiosensitizer. Results : Median follow up period was 16 months (range 4-134 months). The major responses (CR+PR) were noted in 10 patient ($66.6\%$) of the RT alone group and 14 patient ($93.3\%$) of the chemoradiation group. There was no statistical difference in CR rate between the two groups The overall survival rates at 5 years were $23.4\%$ in the radiation alone group, $23.5\%$ in the chemoradiation group Disease-free survival rates at 3 years were $44.5\%$ in the radiation alone group, $40\%$ in the chemoradiation group. There was no statistical differences in overall survival rates and disease-free survival rates between the two groups. Local recurrences occurred in $71.5\%$ of the radiation alone group, $72.7\%$ of the chemoradiation group and distant metastasis occurred in $14.4\%$ of radiation alone group, $9.1\%$ of the chemoradiation group. The frequencies of complications were comparable in both groups except hematologic toxicity Conclusion : Total response rates in the combined chemotherapy and radiotherapy was relatively higher than radiotherapy alone. But our result failed to show any survival benefit of the combined chemotherapy and radiotherapy. The accrual of large number of patients and long term follow-un may be necessary to confirm the present result of combined chemotherapy and radiotherapy.