Purpose: The phase I/II clinical study of carbon beam therapy was undertaken for 31 cases of advanced cervical cancer of stages IIIB and IVA from June 1995 to November 1997. The main purpose was to determine clinically useful fraction doses without severe acute reaction of normal tissues and to assess tumor control dose levels achievable without significant normal tissue toxicity.
Patients and methods: The treatment was given with four fixed fractions per week (24 fractions over 6 weeks) and was initiated with a fraction dose of 2.2 Gray equivalent (GyE), and the dose was increased as 2.4 GyE, 2.6 GyE, 2.8 GyE, and 3.0 GyE. Consequently, the total dose initiated was 52.8 GyE, to increase up to 72.0 GyE in 4.8-GyE increments in the dose-escalation fashion. Thirty patients with eligible advanced cervical cancers consisting of 27 squamous cell carcinomas and three adenocarcinomas were analyzed.
Results: Acute response of normal tissues was less than with photon treatment until fraction doses of 2.8 GyE were administered, and patients finished treatment with comfortable conditions. Severe late complications occurred in the two patients who received more than 67.2 GyE. The 2-year cumulative survival rate and the local control rate of 27 patients with squamous cell carcinoma were 61.5% and 59.3%, respectively. According to stages, the 2-year survival rates of stage IIIB and IVA patients were 54.4% and 75.0%, respectively. The 2-year local control rates of stage IIIB and IVA patients were 52.6% and 75.0%, respectively.
Discussion: These results indicated that the disease control seems to be relatively better for very advanced disease and with dose escalation treatment. Local control was not significantly correlated with total dose and tumor volume. The results of the present study, despite small numbers and short observation, suggest that an adequate fraction dose for pelvis fields is 2.8 to 3.0 GyE and that the carbon beam therapy might be advantageous for advanced cervical cancer.