Chieko Murayama

Contribution of indirect action to radiation-induced mammalian cell inactivation: dependence on photon energy and heavy-ion LET.

Abstract Ito, A., Nakano, H., Kusano, Y., Hirayama, R., Furusawa, Y., Murayama, C., Mori, T., Katsumura, Y. and Shinohara, K. Contribution of Indirect Action to Radiation-Induced Mammalian Cell Inactivation: Dependence on Photon Energy and Heavy-Ion LET. Radiat. Res. 165, 703–712 (2006). The contribution of indirect action mediated by OH radicals to cell inactivation by ionizing radiations was evaluated for photons over the energy range from 12.4 keV to 1.25 MeV and for heavy ions over the linear energy transfer (LET) range from 20 keV/μm to 440 keV/μm by applying competition kinetics analysis using the OH radical scavenger DMSO. The maximum level of protection provided by DMSO (the protectable fraction) decreased with decreasing photon energy down to 63% at 12.4 keV. For heavy ions, a protectable fraction of 65% was found for an LET of around 200 keV/μm; above that LET, the value stayed the same. The reaction rate of OH radicals with intracellular molecules responsible for cell inactivation was nearly constant for photon inactivation, while for the heavy ions, the rate increased with increasing LET, suggesting a reaction with the densely produced OH radicals by high-LET ions. Using the protectable fraction, the cell killing was separated into two components, one due to indirect action and the other due to direct action. The inactivation efficiency for indirect action was greater than that for direct action over the photon energy range and the ion LET range tested. A significant contribution of direct action was also found for the increased RBE in the low photon energy region.

Detection of tumor cells in the portal and peripheral blood of patients with colorectal carcinoma using competitive reverse transcriptase-polymerase chain reaction

In spite of many reports, it remains unclear whether the presence of tumor cells in circulating blood flow predicts a poor prognosis.

Prophylactic hepatic arterial infusion chemotherapy for the prevention of liver metastasis in patients with colon carcinoma: A randomized controlled trial

The liver is the most frequent site of recurrence after curative resection in patients with colon carcinoma. For liver metastasis, a high response rate can be achieved with hepatic arterial infusion (HAI) chemotherapy. In the current study, the authors administered 5‐fluorouracil (5‐FU) as adjuvant chemotherapy by HAI to patients with colon carcinoma without liver metastases and studied its effects on recurrence in the liver and survival.

Risk of lymph node and distant metastases in patients with early invasive colorectal cancer classified as Haggitt's level 4 invasion: Image analysis of submucosal layer invasion

PURPOSE Tumor invasion in patients with early invasive colorectal cancer has been classified into four levels proposed by Haggitt. Level 4 invasion into the submucosa has been defined as a risk factor for lymph node metastasis; however, the false-positive rate remains high. This study was designed to determine risk factors for lymph node and distant metastases in addition to Haggitt’s Level 4 invasion. METHODS Seventy-one of 142 patients with submucosa-invasive colorectal cancer underwent intestinal resection as an initial surgical treatment between 1975 and 2000. The subjects of this study were 65 of these 71 patients, all of whom were diagnosed as having Haggitt’s Level 4 invasion. The depth, width, and area of submucosal invasion were measured with an image analyzer. RESULTS Lymph node metastasis was noted in 11 (16.9 percent) of the 65 patients. There were no significant differences in the depth or area of submucosal invasion between node-positive and node-negative patients. However, the width of submucosal invasion was significantly greater in node-positive than in node-negative patients (P = 0.001). When 5-mm-wide submucosal invasion was used as an indicator for intestinal resection, 37 patients were found to have indications for bowel resection, and 11 (29.7 percent) of the 37 had lymph node metastases. Distant metastasis was noted in five patients (7.7 percent). The depth, width, and area of submucosal invasion in patients with distant metastasis did not differ significantly from those without distant metastasis. CONCLUSION Although further prospective investigation is required, the positive predictive value increases from 17 to 30 percent when the width of submucosal invasion is added to Haggitt’s Level 4 as an indicator for bowel resection.

Evaluation of d-18F-FMT, 18F-FDG, l-11C-MET, and 18F-FLT for Monitoring the Response of Tumors to Radiotherapy in Mice

O-18F-fluoromethyl-d-tyrosine (d-18F-FMT) is a promising novel agent for tumor imaging by PET. The aim of this study was to evaluate the potential of d-18F-FMT and the other conventional ligands used for tumor imaging, namely, 18F-FDG, l-11C-methionine (l-11C-MET), and 3′-deoxy-3′-18F-fluorothymidine (18F-FLT), as a PET ligand for monitoring early responses to radiotherapy in tumor-bearing mice. Methods: C3H/HeN mice inoculated with murine squamous cell carcinomas were treated with a single dose of x-ray irradiation at 2, 6, 20, or 60 Gy. Tumor uptake of each ligand was examined 1, 3, and 7 d after the irradiation. Results: Tumor uptake of d-18F-FMT was decreased on day 1 after irradiation at 6, 20, or 60 Gy, and the decrease persisted until day 7. Tumor uptake of 18F-FDG was elevated on days 1 and 3 after irradiation at 2, 6, or 20 Gy, followed by a decrease in uptake on day 7 in mice irradiated at 20 or 60 Gy. Decreased tumor uptake of l-11C-MET was observed only on day 3 after the irradiation. Decreased tumor uptake of 18F-FLT was detected on day 1 after irradiation at 2, 6, 20, or 60 Gy; thereafter, the dose-dependent decrease in uptake was no longer seen. Only for d-18F-FMT were significant positive correlations found between ligand uptake at all the time points examined and tumor volume on day 14 after various doses of irradiation. Conclusion: The findings suggest that d-18F-FMT is a promising PET ligand for early-phase detection and prediction of the effects of radiation therapy.

Risk of Lymph Node and Distant Metastases in Patients With Early Invasive Colorectal Cancer Classified as Haggitt’s Level 4 Invasion

AbstractPURPOSE: Tumor invasion in patients with early invasive colorectal cancer has been classified into four levels proposed by Haggitt. Level 4 invasion into the submucosa has been defined as a risk factor for lymph node metastasis; however, the false-positive rate remains high. This study was designed to determine risk factors for lymph node and distant metastases in addition to Haggitt’s Level 4 invasion. METHODS: Seventy-one of 142 patients with submucosa-invasive colorectal cancer underwent intestinal resection as an initial surgical treatment between 1975 and 2000. The subjects of this study were 65 of these 71 patients, all of whom were diagnosed as having Haggitt’s Level 4 invasion. The depth, width, and area of submucosal invasion were measured with an image analyzer. RESULTS: Lymph node metastasis was noted in 11 (16.9 percent) of the 65 patients. There were no significant differences in the depth or area of submucosal invasion between node-positive and node-negative patients. However, the width of submucosal invasion was significantly greater in node-positive than in node-negative patients (P = 0.001). When 5-mm-wide submucosal invasion was used as an indicator for intestinal resection, 37 patients were found to have indications for bowel resection, and 11 (29.7 percent) of the 37 had lymph node metastases. Distant metastasis was noted in five patients (7.7 percent). The depth, width, and area of submucosal invasion in patients with distant metastasis did not differ significantly from those without distant metastasis. CONCLUSION: Although further prospective investigation is required, the positive predictive value increases from 17 to 30 percent when the width of submucosal invasion is added to Haggitt’s Level 4 as an indicator for bowel resection.

Phase I/II Study of Preoperative Concurrent Chemoradiotherapy with S-1 for Locally Advanced, Resectable Rectal Adenocarcinoma

Purpose: To assess the maximum tolerability of a combination of S-1 and preoperative radiotherapy and to evaluate the feasibility and activity in patients with locally advanced rectal cancer. Methods: Patients (n = 30) with adenocarcinoma of the middle or lower rectum were enrolled in a phase I (n = 9) and/or phase II (n = 21) trial. A total dose of 45 Gy was delivered in 25 fractions over 5 weeks, and S-1 was orally administered twice a day on days 1–14 and 22–35. Surgical resection was scheduled 4–8 weeks after the completion of chemoradiation. Results: In phase I, the recommended dose (RD) of S-1 was 80 mg/m2/day, and the maximum-tolerated dose was never reached. A total of 27 cases, including the 6 RD cases in phase I, were enrolled in phase II. In phase II, a pathological complete response (pCR) was observed in 6/27 patients (22%), pathological downstaging was observed in 21/27 patients (78%), and a tumor volume reduction of 69 ± 22% was obtained. These results were similar to the previously reported pCR rates of 16–18%, pathological downstaging rates of 49–59%, and tumor volume reduction of 68% after chemoradiotherapy with capecitabine. Grade 3 adverse events consisted of one case of leukopenia (4%), 2 cases of anemia (7%) and 3 cases of diarrhea (11%). Overall, the adverse events were very mild. Hand-foot syndrome was not observed. Conclusion: The efficacy of chemoradiotherapy with S-1 seems to be equivalent to the efficacy reported for chemoradiotherapy with capecitabine, but the adverse events were much milder, although further study is warranted.

Biopsy Specimens Obtained 7 Days After Starting Chemoradiotherapy (CRT) Provide Reliable Predictors of Response to CRT for Rectal Cancer

PURPOSE Preoperative chemoradiation therapy (CRT) significantly decreases local recurrence in locally advanced rectal cancer. Various biomarkers in biopsy specimens obtained before CRT have been proposed as predictors of response. However, reliable biomarkers remain to be established. METHODS AND MATERIALS The study group comprised 101 consecutive patients with locally advanced rectal cancer who received preoperative CRT with oral uracil/tegafur (UFT) or S-1. We evaluated histologic findings on hematoxylin and eosin (H&E) staining and immunohistochemical expressions of Ki67, p53, p21, and apoptosis in biopsy specimens obtained before CRT and 7 days after starting CRT. These findings were contrasted with the histologic response and the degree of tumor shrinkage. RESULTS In biopsy specimens obtained before CRT, histologic marked regression according to the Japanese Classification of Colorectal Carcinoma (JCCC) criteria and the degree of tumor shrinkage on barium enema examination (BE) were significantly greater in patients with p21-positive tumors than in those with p21-negative tumors (P=.04 and P<.01, respectively). In biopsy specimens obtained 7 days after starting CRT, pathologic complete response, histologic marked regression according to both the tumor regression criteria and JCCC criteria, and T downstaging were significantly greater in patients with apoptosis-positive and p21-positive tumors than in those with apoptosis-negative (P<.01, P=.02, P=.01, and P<.01, respectively) or p21-negative tumors (P=.03, P<.01, P<.01, and P=.02, respectively). The degree of tumor shrinkage on both BE as well as MRI was significantly greater in patients with apoptosis-positive and with p21-positive tumors than in those with apoptosis-negative or p21-negative tumors, respectively. Histologic changes in H&E-stained biopsy specimens 7 days after starting CRT significantly correlated with pathologic complete response and marked regression on both JCCC and tumor regression criteria, as well as with tumor shrinkage on BE and MRI (P<.01, P<.01, P<.01, P<.01, and P=.03, respectively). CONCLUSIONS Immunohistochemical expressions of p21 and apoptosis together with histologic changes on H&E-stained biopsy specimens obtained 7 days after starting CRT are strong predictors of the response to CRT.

Radiosensitization by a new potent nucleoside analog: 1-(1′,3′,4′-trihydroxy-2′-butoxy)methyl-2-nitroimidazole(RP-343)

PURPOSE A new hypoxic cell sensitizer has been synthesized; this is a 2-nitroimidazole nucleoside analog having erythritol as a sugar moiety at the N-1 position of the imidazole ring (RP-343). Its possibility as a potent hypoxic cell sensitizer was compared with those of RP-170 and etanidazole. METHODS AND MATERIALS Radiosensitization was tested in two murine tumors, EMT6 using in vitro and in vivo-in vitro assays and SCCVII using growth delay and TCD50 assays. Pharmacokinetic study was performed in Balb/c mice bearing EMT6 tumors and in Beagle dogs. LD50 of each sensitizer was obtained with ICR mice. RESULTS As might be expected from the almost identical electron affinities of the three sensitizers, they were equally effective against hypoxic EMT6 cells in vitro. While having the lowest partition coefficient (0.035), RP-343 exhibited almost equally effective distribution to tumors and sensitizing radiation activity. An intravenous (i.v.) injection of 100 mg/kg of RP-343, RP-170 and etanidazole showed an almost equal sensitizer enhancement ratio (SER) of about 1.4 to solid EMT6 tumor under in vivo-in vitro assay and a virtually equal SER of 1.33-1.44 to solid SCCVII tumor under both tumor growth delay assay and TCD50 assay. A great advantage of RP-343 over RP-170 and etanidazole is its very much lower toxicity; their LD50 in mice were > 6.0, 4.3 and 4.8 g/kg, respectively, on i.v. injection. The lower toxicity of RP-343 was supported by its lower concentrations in the brain; the RP-343 AUC for brain was 0.43 times that of RP-170. Three indices were selected to compare the three nitroimidazoles. SER at 5% LD50 doses of RP-343, RP-170 and etanidazole was 1.66, 1.59 and 1.56. At the same toxicity levels, RP-343 was found to have better sensitization of solid tumors over both etanidazole and RP-170. The maximum tumor concentration/AUC for brain (Cmax,tumor/AUCbrain) ratios for RP-343 and RP-170 were 9.62 and 3.98. CONCLUSIONS This extremely high ratio of RP-343 could explain its lower toxicity than RP-170 or etanidazole. The therapeutic risk index defined as D1.5/LD50 (D1.5 is the sensitizer dose to obtain the SER of 1.5 in vivo) for RP-343, RP-170 and etanidazole were 0.022, 0.033 and 0.036, respectively. Especially, the effectively lower therapeutic risk index for RP-343 presents the possibility of clinical advantage over etanidazole.

Liposome‐Encapsulated Hemoglobin Ameliorates Tumor Hypoxia and Enhances Radiation Therapy to Suppress Tumor Growth in Mice

We hypothesize that liposome-encapsulated hemoglobin with high O₂ affinity (P₅₀0₂ = 12 mm Hg, h-LEH) may increase O₂ delivery to hypoxic tumors and enhance radiation therapy synergistically to suppress tumor growth. First, h-LEH (5, 10, and 20 mL/kg) was intravenously infused 30 min before radiation (20 Gy) of SCCVII tumor grown in C3H/HeN mice. Second, 10 mL/kg of h-LEH was administered 30, 60, 90, and 120 min prior to radiation to determine optimal timing. Tumor size was monitored thereafter to titrate tumor growth suppression. Third, additional mice with SCCVII tumor were infused with h-LEH or empty liposome (EL), and tumors were excised at various time points for immunohistochemical examination of h-LEH and hypoxia-inducible factor-1α (HIF-1α). h-LEH was most effective at 10 mL/kg in comparison to 5 or 20 mL/kg of h-LEH or EL. Tumor growth was most suppressed when the interval between h-LEH infusion and radiation was shortest, 30 min. As a result, 10 mL/kg of h-LEH infusion 30 min prior to radiation prolonged 5-fold tumor-growth time from 20.0 days (radiation and EL) to 26.5 days, P<0.01, synergy ratio 1.42. While human hemoglobin (h-LEH) was detected in tumors 0.5 to 24 h after administration, HIF-1α accumulation was sparse and became significantly reduced compared to controls 48 and 72 h after h-LEH infusion. h-LEH (10 mL/kg) was highly effective in enhancing radiation therapy synergistically under ambient respiration against tumor growth in mice. Decreased accumulation of HIF-1α in h-LEH-treated tumor may suggest targeted tumor oxygenation as a potential mechanism.