RESUMO
Objective To explore the dosimetric effect of using a split of the gross tumor volume (GTV) delineation approach during intensity-modulated radiotherapy (IMRT) treatment planning for advanced T-stage nasopharyngeal carcinoma (NPC) with prevertebral space involvement (PSI).Methods Twenty NPC patients with T3-T4 tumors with prevertebral space involvement were studied.Two kinds of plans were generated based on the same protocol.The first plan was GTV-split consisting of organ at risk (including spine cord and brain stem) overlapping and non-overlapping subsegments.The subsegments were assigned independent dose constraint.The second plan was done based on a standard treatment planning protocol.The two plans were compared with respect to target coverage and organ at risk (OAR) sparing,and target conformity index.Results Two plans both met requirement of dose coverage of target and constraints on normal tissue.Regarding the planning gross target volume (PGTV),the doses of < 93% volume of plan 1 and plan 2 were [(0.63 ± 0.21)%,and (0.68 ± 0.10)%,P =0.049];the doses of > 110% volume of plan 1 and plan 2 were [(11.59 ± 7.Ol) %,and (12.71 ± 6.03) %,P =0.041];the doses of >115% volume of plan 1 and plan 2 were [(2.05 ± 0.80)%,and (2.76 ± 1.14)%,P =0.049];about OARs,the maximal dose of spine cord for plan 1 and plan 2 were (41.00 ± 4.52) Gy and (45.00 ± 3.25) Gy (P =0.048);and the target coverage and target conformity index of plan 1 were better than those of plan 2,the p-values were 0.063,and 0.135,respectively.The difference between two plans was statistically significant (P < 0.05).Conclusions A split-GTV delineation,independent dose constraint,and multi-course IMRT for advanced T-stage nasopharyngeal carcinoma with prevertebral space involvement optimized IMRT treatment planning,improved target coverage and target conformity index,and decreased the maximal dose for the spine cord and brain stem.It is feasible and has advantage to decrease the dose to OARs.The approach deserves to be further studied.
RESUMO
Objective To investigate radio-sensitivity and expression of GRP78 protein in the survival subclones of nasopharyngeal carcinoma (NPC) C666-1 cells.Methods NPC C666-1 cells were first irradiated with X-ray at a large dose of 8Gy.Three survival subclones were selected and named as C666-1-R1, C666-1-R2, and C666-1-R3.The radio-sensitivity was analyzed for the radiated survival subclones and their parent control C666-1 cells with Methyl Thiazolyl Tetrazolium assay(MTT) and Trypan blue dye methods.The expression of GRP78 was analyzed for three survival subclones and control C666-1 with Western blot.Results After 6 Gy irradiation, the cell survival rate of three subclones was higher than that of the control cells, especially a significant difference for C666-1-R2 cells (P < 0.05), which suggested a radioresistance in C666-1-R2 cells.Moreover, GRP78 expression in each subclone was significantly higher than that of parent C666-1 cells (P < 0.05).Conclusions The irradiated-survival subclone C666-1-R2 was radio-resistant.GRP78 was overexpressed in the irradiated-survival subclones.GRP78 might be an ideal target for treatment of a nasopharyngeal carcinoma.
RESUMO
Objective To investigate the influence of intensity-modulated radiation pattern on ra-diobiological effects of nasopharyngeal carcinoma cell line CNE2.Methods Colony formation assay was used to calculate cell surviving fraction, and compare the cell survival curves and the surviving fraction with single-hit multi-target model fitting survival curves to different delivery time and dose rates.Results ⑴Nasopharyngeal carcinoma cell line CNE2 was irradiated on two models:conventional radiation ( CR) mod-el;intensity modulated radiation model ( IMRT model, which was divided into 10 min IMRT irradiated group, 15 min irradiated group, and 20 min irradiated group) .Except that the parameters of radiation biol-ogy did no significantly differ between CR model and 10 min IMRT irradiated group ( P >0.05) , the other groups among radiobiology parameters surviving fraction (SF2), quasi-threshold dose(Dq) and extrapolation number(N) were all significant differences ( P SF2 600 Mu/min ( P <0.05) when the CNE2 cells were treated with dose rates of 300 Mu /min and 600 Mu/min.Conclusions ⑴There were not significant changes in the biological effects until the delivery time prolonged to more than 10 minutes.When the delivery time extended to more than 15 minutes, the survival fraction was increasing with the radiation time risen.⑵The dose rates used in the experiment did not show any effect on the radiobiology parameters without SF2 .
RESUMO
Objective To investigate the effect of ionization to the expression of HIF-1α and p53 of nasopharyngeal carcinoma (NPC) in anoxia condition. Method Nasopharyngeal carcinoma cell line CNE-1 was divided into three groups, control group, radiation group, and hypoxia plus radiation group. The cell viability was analyzed by MTT method, Immunofluorescent technique was performed to de-termine the expression location of HIF-1α in CNE-1. And the expression of HIF-1α and P53 protein were measured with flow cytometry. Re-sults The results of MTr detection showed that the survival fraction of the control group was the highest. The minimum survival fraction was found in the radiation group (P<0.05). There was no HIF-1αprotein expression in cytoplasm except the radiation plus hypoxia group. With the flow cytometer technique, the expression of HIF-1αprotein in the radiation plus hypoxia group was higher than that in the radiation group. No statistical significance was found between the radiation group and the control group. When detecting the expression of P53 protein with the same technique, the expression of P53 was highest in the hypoxia plus radiation group and lowest in the control group (P<0.05). Conclusion The expression of HIF-1α inducted by Hypoxia can prevent NPC cell from the damages of radiation. The HIF-1α decreases the radiosensitivlty through inducing p53 expression in NPC CNE-1 cell line.