量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Purpose: High linear energy transfer (LET) particles are believed to decrease tumor radiation resistance originating from hypoxia. However, no proof of this effect has been provided by clinical trials and related clinical research. Hence, we investigated the radiation biological aspects of high LET carbon beam therapy on cervical cancer.
Experimental Design: This study involved 49 patients with stage 3B bulky and 4A cervical cancer treated with high LET carbon beams between October 1995 and June 2000. Oxygen partial pressure (pO2) was measured by using a needle-type polarographic oxygen electrode.
Results: The 4-year disease-free survival rates of patients with pO2=<20 mmHg (hypoxic tumor) and >20 mmHg (oxygenated tumor) before treatment were 37% and 21%, respectively.
The local control rates of hypoxic and oxygenated tumors before treatment were 58% and 54%, respectively. The disease-free survival rates of hypoxic and oxygenated tumors assessed by oxygen status at the 5th day of irradiation (5th Day) were 33% and 32%, respectively. The local control rates of hypoxic and oxygenated tumors at the 5th Day were 60% and 58%, respectively. There was no significant prognostic difference between the hypoxic and oxygenated tumors.
Conclusion: The similar disease-free survival and local control rates between the hypoxic and oxygenated tumors before and during treatment indicated that the role of the tumor oxygenation status was not so important in local control in carbon beam therapy. These results indicated that high LET carbon beam irradiation might reduce the radiation-resistant nature stemming from tumor hypoxia.
Carbon beam therapy overcomes the radiation resistance of uterine cervical cancer originating from hypoxia
