Hisao Ito

G2 chromatid damage and repair kinetics in normal human fibroblast cells exposed to low- or high-LET radiation

Radiation-induced chromosome damage can be measured in interphase using the Premature Chromosome Condensation (PCC) technique. With the introduction of a new PCC technique using the potent phosphatase inhibitor calyculin-A, chromosomes can be condensed within five minutes, and it is now possible to examine the early damage induced by radiation. Using this method, it has been shown that high-LET radiation induces a higher frequency of chromatid breaks and a much higher frequency of isochromatid breaks than low-LET radiation. The kinetics of chromatid break rejoining consists of two exponential components representing a rapid and a slow time constant, which appears to be similar for low- and high-LET radiations. However, after high-LET radiation exposures, the rejoining process for isochromatid breaks influences the repair kinetics of chromatid-type breaks, and this plays an important role in the assessment of chromatid break rejoining in the G2 phase of the cell cycle.

A case of gastric lymphoma with marked interfractional gastric movement during radiation therapy.

Radiation therapy (RT) with or without chemotherapy has been a widely accepted treatment for patients with localized gastric lymphoma. We encountered a patient with gastric diffuse large B-cell lymphoma, whose stomach volume, and the position and location of the clips that had been endoscopically placed to define the gastric lesions clearly differed considerably at three simulation times. The positions of the clips moved between 5 and 35u2009mm (mean 24u2009mm) laterally on simulation films. The mean movement of these clips along the cephalocaudal directions was 8u2009mm (range 0–15u2009mm). There have been no published articles which systemically evaluated interfractional gastric motion between each treatment session. Therefore this is an important observation in the management of patients with gastric lymphoma with RT.

Dose–volume factors predicting radiation pneumonitis in patients receiving salvage radiotherapy for postlobectomy locoregional recurrent non-small-cell lung cancer

BackgroundThe correlation between treatment-related factors and lung toxicity has not been sufficiently evaluated in salvage radiotherapy.MethodsTwenty-one patients with recurrent non-small- cell lung cancer (NSCLC) after lobectomy received salvage radiotherapy to a total dose of 46–60u2009Gy. The effects of radiotherapy parameters on the development of radiation pneumonitis (RP) were examined using dose–volume histograms.ResultsGrade 1 RP was observed in 4, grade 2 in 2, and grade 3 in 1 patient. Patients who developed RP had a significantly higher value in V dose (V13, V20) parameters and mean lung dose (MLD) than those who did not develop RP. Concerning G2 or higher RP, 3 patients who developed ≥G2 RP had a significantly higher value in V20, V13, and MLD than the remaining patients with P values of 0.01, 0.015, and 0.016, respectively. The mean V20, V13, and MLD in these 3 patients were 27%, 29.3%, and 14.8u2009Gy, respectively, whereas the mean V20, V13, and MLD in the remaining 18 patients were 15.8%, 18.3%, and 8.8u2009Gy, respectively. Three of 6 patients with a V20 ≥20% developed ≥G2 RP whereas this did not occur in the remaining patients (P = 0.015). Similarly, 3 of 6 patients with a V13 ≥23% developed ≥G2 RP whereas this did not occur in the remaining patients (P = 0.015).ConclusionsThese data suggest that a somewhat lower V dose value or MLD, as compared with the setting of definitive radiotherapy, could be a surrogate for RP in patients undergoing salvage radiotherapy for recurrent NSCLC.