Carbon beam therapy overcomes the radiation resistance of uterine cervical cancer originating from hypoxia.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Nakano
Takashi
T
Research Center Hospital of Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan. tnakano@med.gunma-u.ac.jp
Suzuki
Yoshiyuki
Y
Ohno
Tatsuya
T
Kato
Shingo
S
Suzuki
Michiya
M
Morita
Shinroku
S
Sato
Shinichiro
S
Oka
Kuniyuki
K
Tsujii
Hirohiko
H
D002244:Carbon; D015687:Cell Hypoxia / Q000528:radiation effects; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D004566:Electrodes; D005260:Female; D063193:Heavy Ion Radiotherapy; D006801:Humans; D018499:Linear Energy Transfer; D008875:Middle Aged; D010100:Oxygen / Q000032:analysis / Q000378:metabolism; D010313:Partial Pressure; D010315:Particle Accelerators; D011048:Polarography / Q000379:methods; D011237:Predictive Value of Tests; D011836:Radiation Tolerance / Q000528:radiation effects*; D015996:Survival Rate; D002583:Uterine Cervical Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*
D002244:Carbon; D010100:Oxygen