Nakano Takashi, Suzuki Yoshiyuki, Ohno Tatsuya, Kato Shingo, Suzuki Michiya, Morita Shinroku, Sato Shinichiro, Oka Kuniyuki, Tsujii Hirohiko
Research Center Hospital of Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
Clin Cancer Res. 2006 Apr 1;12(7 Pt 1):2185-90. doi: 10.1158/1078-0432.CCR-05-1907.
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.
This study involved 49 patients with stage IIIb bulky and stage IVa cervical cancer treated with high LET carbon beams between October 1995 and June 2000. Oxygen partial pressure (pO(2)) was measured by using a needle-type polarographic oxygen electrode.
The 4-year disease-free survival rates of patients with pO(2) </= 20 mm Hg (hypoxic tumor) and pO(2) > 20 mm Hg (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 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 hypoxic and oxygenated tumors.
The similar disease-free survival and local control rates between 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.
高传能线密度（LET）粒子被认为可降低由缺氧引起的肿瘤放射抗性。然而，临床试验及相关临床研究尚未证实这一效果。因此，我们研究了高LET碳离子束治疗宫颈癌的放射生物学特性。
本研究纳入了1995年10月至2000年6月间接受高LET碳离子束治疗的49例IIIb期巨块型和IVa期宫颈癌患者。采用针型极谱氧电极测量氧分压（pO₂）。
治疗前氧分压≤20 mmHg（缺氧肿瘤）和pO₂>20 mmHg（富氧肿瘤）患者的4年无病生存率分别为37%和21%。治疗前缺氧和富氧肿瘤的局部控制率分别为58%和54%。照射第5天时根据氧状态评估的缺氧和富氧肿瘤的无病生存率分别为33%和32%。第5天时缺氧和富氧肿瘤的局部控制率分别为60%和58%。缺氧和富氧肿瘤之间无显著的预后差异。
治疗前及治疗期间缺氧和富氧肿瘤的无病生存率及局部控制率相似，表明肿瘤氧合状态在碳离子束治疗的局部控制中作用不显著。这些结果表明，高LET碳离子束照射可能降低肿瘤缺氧导致的放射抗性。
