40. Chromosomal Aberrations Detected by lnterphase Chromosome Painting in Lymphocytes from Cancer Patients Given X-ray or Carbon Ion Therapy

Shigeru Yamada¹, Marco Durante², Ryonfa Lee³, Takashi Nakano¹, Koichi Ando³ and Hirohiko Tsujii¹; ¹Research Center of Charged Particle Therapy ³International Space Radiation Laboratory National Institute of Radiological Sciences, Chiba, Japan, ²Department of Physics, University Federico II , Italy

Keywords: chromosome abberation, carbon ion beam, clinical research

We measured chromosomal aberrations in peripheral blood lymphocytes from cancer patients treated with X-rays or carbon ions. Blood samples from patients diagnosed for esophageal or uterus cervux cancer were obtained before, during, and at the end of the radiation treatment. Patients with similar pathologies, tumor positions, and field sizes were cornpared in the present study. The novel technique of interphase chromosome painting was used to detect aberrations in prematurely condensed chromosomes 2 and 4. Fraction of aberrant lymphocytes was measured as a function of the tumor. The results demonstrate that carbon ions induce a lower level of cytogenetic damage in lymphocytes than X-rays.

A total of 40 patients being treated for different cancers at NIRS were involved in the study. Patients were treated either with carbon ions accelerated at the HIMAC or I0M/v X-rays produced in a LINAC Tumor pathology was squamous cell carcinoma for all patients, except for one melanoma of the esopha gus inferior.

Treatment planning with IOMV X-rays consisted of daily fractions of 1.6-2.OGy. Patients treated with carbon ions were exposed at the HIMAC, 290 or 350 Me/v, 6-8cm spread out Bragg peak (SOBP) Treatment planning was designed to deliver a uniform equivalent dose (in GyE) to the target volume. GyE was calculated as the product between physical dose distribution and RBE values for cell killing in each point along the SOBP. RBE values ranged from 2 to 3 along the SOBP. Daily fractions of 2.7-3.6GyE were used.

Blood samples were obtained at different times before, during, and at the end of treatment. Pretreatment samples were exposed in vitro to X-rays (2OOkVp) in the dose range 1-4Gy at a dose rate of 1 Gy/min. PBL from 3 uterus cancer patients were also exposed in vitro to the 290 MeV carbon ion beam at a dose rate of approximately 5Gy/min at 13 and 83KeV/mm.

Lymphocytes were isolated from the whole-blood and stimulated to in vitro growth in medium supplemented with phytohaemagglutinin. PCC was induced by calyculin A. Slides were hybridized in situ with whole-chromosome human DNA probes specific for chromosomes 2 and 4. Fraction of aberrant cells was calculated at the ratio between the number of spreads containing one or more aberrations involv ing chromosomes 2 and/or 4, and the total number of PBL scored (ranging from 200 to 2000).

The in vitro experimental data for X-rays were pooled from 11 different patients, while data for carbon ion beams are pooled from three different pa tients. No significant differences in the in vitro response of PBL from the different patients were detected. Similarly, no significant difference was observed for PBL exposed in vitro to carbon ions at the HIMAC. Carbon ions were more efficient than X rays in the induction of chromosomal aberrations in vitro. The RBE (evaluated at 15% aberrant cells, corresponding to an X-ray dose of 2Gy) of carbon ions was 1.43 and 3.97 at 13 and 83 KeV/ p m, respectively.

Eleven patients treated for cancer in esophagus inferior were examined as in the in vivo study Frequency of chromosomal aberrations increased as a function of the number of fractions delivered to the target volume. The dose-response curves of the two X-ray patients had a similar shape, but one patient showed more damages than the other. The differ ences could be explained based on the X-ray field size difference, which was 140cm² for the patient displaying a higher frequency of chromosomal aberra tions, and 84cm² for the other. The three carbon ion beams patients displayed similar respose, although different field sizes were exposed (115,108 and 61 cm²). The fraction of aberrant PBL was lower for two carbon ion beams patients as compared to X-ray pattents.

For uterus cervical cancer the field size was around 200cm² for all patients. All patients treated with carbon ions presented a lower frequency of aberrant PBL than X-irradrated counterparts.

It was concluded Chat interphase chromosome painting (chemical induction of PCC combined with FISH) is a useful tool for monitoring patient response to X-rays or charged-particle cancer therapy The fraction of complex type chromosomal exchanges correlates with acute toxicity in patients treated for esophageal cancer.

Publications:
1)Yamada, S., Durante, M., Ando, K., Furusawa, Y., Kawata, T., Majima, H. and Ando, K. CANCERLETTERS150 215-221 2000.
2)Durante, M., Yamada, S., Ando K., Furusawa, Y Kawata, T., Majima, H., Nakano, T. and Tsujii, H. Int. J. Radiation Oncology Biol. Phys. 47, 793798, 2000.
3) Durante, M, Yamada, S, Ando, K ,Furusawa, Y Kawata, T., Majima, H., Nakano, T. and Tsujii, n. t't.y.. u.a. sz.z 44, 1289-1298, 1999.
4)Durante, M, Kawata, T, Nakano, T. and Yamada, s. ,xa.. sp... n.s. 22,1653-1662, 1998.