Radiotherapy For Nasopharyngeal Cancer Research Articles

External Auditory Canal Cholesteatoma after Radiation Therapy for Nasopharyngeal Cancer: Case Series and Systematic Review

The authors performed a systematic review, in accordance with the PRISMA guidelines, across multiple databases, including all original studies published until November 2022, focusing on External auditory canal cholesteatoma (EACC) after radiation therapy (RT) for nasopharyngeal cancer (NC). Inclusion criteria were original articles reporting on secondary EACC after RT for NC. Articles were critically appraised to assess level of evidence using the Oxford Center for Evidence-Based Medicine criteria. Overall, 138 papers were identified and after duplicate removal (34 papers) and excluding papers not in English, 93 papers were assessed for eligibility; finally, only five papers were included and summarized with the three cases coming from our institution. These mainly involved the anterior and the inferior part of the EAC. The mean time of diagnosis after RT was the largest series of 6.5 years (with a range from 0.5 to 15.4 years). Patients undergoing RT for NC have 18 times a higher risk of developing EACC compared to the normal population. EACC is probably one of the most underreported side effects, because patients may present variable clinical findings, which could lead to misdiagnosis. Early diagnosis of RT related EACC is advised to enable conservative treatment.

Association between single nucleotide polymorphisms in DNA repair genes and the efficacy of radiotherapy in nasopharyngeal carcinoma patients.

Single nucleotide polymorphisms (SNPs) in DNA repair genes are mainly correlated with the response to radiotherapy in nasopharyngeal cancer (NPC). In NPC patients, previous research has studied the association between X-ray repair cross-complementing group 1 and 3 (XRCC1 and XRCC3) polymorphisms and radio-therapeutic response. The objective of our study was to test the association between XRCC1 Arg399Gln and XRCC3 Thr241Met polymorphisms and the response to radiotherapy in the NPC Moroccan population. A total of 100 patients with NPC were genotyped for polymorphisms in XRCC1 and XRCC3 genes. The results revealed that the genotypes and alleles of both SNPs did not show any significant association with clinical stages (for XRCC1 Arg399Gln: p [genotype] = 0.559; p [allele] = 0.440) and (for XRCC3 Thr241Met: p [genotype] = 0.638; p [allele] = 0.567). Moreover, in the study of the association between the polymorphisms and radiotherapy, the response to radiation therapy between genotypes and alleles was not statistically significant (for XRCC1 Arg399Gln p [genotype] = 0.583; p [allele] = 0.459) and (for XRCC3 Thr241Met p [genotype] = 0.660; p [allele] = 0.590). The present study suggests that XRCC1 Arg399Gln polymorphism does not have any impact on the radio-therapeutic response in Moroccan NPC patients whereas XRCC3 Thr241Met polymorphism may act as a prognostic indicator for NPC patients treated with radiotherapy. However, studies with a larger sample are needed to confirm our results.

Feasibility and safety of neck level IB-sparing radiotherapy in nasopharyngeal cancer: a long-term single institution analysis.

Nasopharyngeal cancer (NPC) has a higher prevalence of regional nodal metastasis than other head and neck cancers; however, level IB lymph node involvement is rare. We evaluated the safety and feasibility of level IB-sparing radiotherapy (RT) for NPC patients. We retrospectively reviewed 236 patients with NPC who underwent definitive intensity-modulated RT with or without chemotherapy between 2004 and 2018. Of them, 212 received IB-sparing RT, and 24 received non-IB-sparing RT. We conducted a propensity score matching analysis to compare treatment outcomes according to IB-sparing status. In addition, dosimetric analysis of the salivary glands was performed to identify the relationship between xerostomia and the IB-sparing RT. The median follow-up duration was 78 months (range, 7 to 194 months). Local, regional, and distant recurrences were observed in 11.9%, 6.8%, and 16.1% of patients, respectively. Of the 16 patients with regional recurrence, 14 underwent IB-sparing RT. The most common site categorization of regional recurrence was level II (75%), followed by retropharyngeal lymph nodes (43.8%); however, there was no recurrence at level IB. In the matched cohorts, IB-sparing RT was not significantly related to treatment outcomes. However, IB-sparing RT patients received a significantly lower mean ipsilateral and contralateral submandibular glands doses (all, p < 0.001) and had a lower incidence of chronic xerostomia compared with non-IB-sparing RT patients (p = 0.006). Our results demonstrated that IB-sparing RT is sufficiently safe and feasible for treating NPC. To reduce the occurrence of xerostomia, IB-sparing RT should be considered without compromising target coverage.

665P Retinal vessels characteristics analysis as a predictive tool for post-radiation neurocognitive impairment in patients with nasopharyngeal cancer

Post-radiation neurocognitive decline is a debilitating late complication after (chemo-)radiotherapy for nasopharyngeal cancer (NPC). Radiation dose correlates poorly with neurocognitive outcomes. This study explored the association between retinal vessel characteristics with neurocognitive outcomes in NPC survivors using an artificial intelligence-based analytic platform.

Olfactory function, olfactory bulb volume, and quality of life after radiotherapy for nasopharyngeal cancer

Olfactory function, olfactory bulb volume, and quality of life after radiotherapy for nasopharyngeal cancer

Dynamic Changes of Post-Radiotherapy Plasma Epstein-Barr Virus DNA in a Randomized Trial of Adjuvant Chemotherapy Versus Observation in Nasopharyngeal Cancer.

To study the dynamic changes in plasma Epstein-Barr virus (pEBV) DNA after radiotherapy in nasopharyngeal cancer (NPC). We conducted a randomized controlled trial of adjuvant chemotherapy versus observation in patients with NPC who had detectable pEBV DNA at 6 weeks post-radiotherapy. Randomized patients had a second pEBV DNA checked at 6 months post-randomization. The primary endpoint was progression-free survival (PFS). We prospectively enrolled 789 patients. Baseline post-radiotherapy pEBV DNA was undetectable in 573 (72.6%) patients, and detectable in 216 (27.4%) patients, of whom 104 (13.2%) patients were eligible for randomization to adjuvant chemotherapy (n = 52) versus observation (n = 52). The first post-radiotherapy pEBV DNA had a sensitivity of 0.48, specificity of 0.81, area under receiver-operator characteristics curve (AUC) of 0.65, false positive (FP) rate of 13.8%, and false negative (FN) rate of 14.4% for disease progression. The second post-radiotherapy pEBV DNA had improved sensitivity of 0.81, specificity of 0.75, AUC of 0.78, FP rate of 14.3%, and FN rate of 8.1%. Patients with complete clearance of post-radiotherapy pEBV DNA (51%) had survival superior to that of patients without post-radiotherapy pEBV DNA clearance (5-year PFS, 85.5% vs. 23.3%; HR, 9.6; P < 0.0001), comparable with patients with initially undetectable post-radiotherapy pEBV DNA (5-year PFS, 77.1%), irrespective of adjuvant chemotherapy or observation. Patients with NPC with detectable post-radiotherapy pEBV DNA who experienced subsequent pEBV DNA clearance had superior survival comparable with patients with initially undetectable post-radiotherapy pEBV DNA. Post-radiotherapy pEBV DNA clearance may serve as an early surrogate endpoint for long-term survival in NPC.

Monte Carlo simulation of non-target organ doses and radiation-induced secondary cancer risk in Tanzania from radiotherapy of nasopharyngeal by using Co-60 source

A few studies have reported the risks of secondary cancer in patients after radiation therapy in Tanzanian hospitals. This study was designed to assess non-target organ doses from Co-60 teletherapy for patients with nasopharyngeal cancer and to estimate the risk of radiation-induced secondary cancer. Specific organ-absorbed doses were evaluated in anatomically realistic 15-year-old and adult male phantoms based on Monte Carlo simulation. The assessed organ doses were used to calculate the lifetime secondary cancer risks in non-target organs according to the BEIR VII risk models. Survival information and the baseline cancer risks were associated with statistical data for the Tanzanian population. The average absorbed doses in non-target organs depended heavily on the distance from the target isocentre and patient's age. Organs near the tumour target, such as the salivary glands, brain, thyroid glands, eye bulb and oesophagus, received very high absorbed doses. The absorbed doses decreased exponentially towards the testis and prostate which are far from the tumour target. The highest received absorbed doses in non-target organs were due to the leakage in the gantry head and scattered radiation from collimator and inside the patient body. The absorbed doses were higher for young patients than in adults because of the larger body area exposed to high-dose radiation. The lifetime attributed risks for all organs considered were relatively lower than the baseline cancer risks. Results can help provide future database about radiation-induced second primary cancer incidence after Co-60 external beam radiation therapy for nasopharyngeal cancer in Tanzania and in many other developing countries.

Clinical significance of the post-radiotherapy 18F-fludeoxyglucose positron emission tomography response in nasopharyngeal carcinoma

Objective:The aim of the present study was to evaluate the clinical significance of the post-radiotherapy 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) response for detecting residual disease and predicting survival outcome in patients with nasopharyngeal cancer.Methods:We reviewed 143 patients with nasopharyngeal cancer who underwent 18F-FDG PET within 6 months after completion of radiotherapy between 2001 and 2012. 18F-FDG PET findings at the primary tumor (T–) and regional lymph nodes (N–) were separately assessed and considered negative [PET (–)] or positive [PET (+)] depending on the remaining focal increased uptake of 18F-FDG that was greater than that of the surrounding muscle or blood vessels. The standard of reference was histopathological confirmation or clinical/imaging follow-up. Overall survival (OS), distant metastasis-free survival (DMFS), and locoregional recurrence-free survival (LRRFS) rates were estimated from the date of the start of radiotherapy.Results:The median follow-up period was 73 months (range, 9–182 months). Overall, 83 and 66% of patients achieved T–PET (-) and N–PET (-) responses, and the negative-predictive values (NPVs) for T– and N– were 100 and 99%, respectively. The sensitivity, specificity, and positive-predictive value were 100, 84, and 8% for T–, and 67, 80, and 7% for N–, respectively. The 5-year OS, DMFS, and LRRFS rates were 83, 83, and 87%, respectively, and patients with N–PET (+) with SUVmax >2.5 showed significantly inferior 5-year OS and DMFS rates than patients with N–PET (-) or N–PET (+) with SUVmax ≤2.5 (44 vs 86%, p = 0.004; 36 vs 85%, p < 0.001).Conclusion:In patients that have received definitive (chemo)radiotherapy for nasopharyngeal cancer, 18F-FDG PET within 6 months of completion of treatment has a high NPV for predicting residual disease and is prognostic for long-term treatment outcomes. Patients with remaining focal increased uptake of 18F-FDG at lymph nodes may benefit from more aggressive treatments, and further studies are needed to validate the clinical significance of post-radiotherapy 18F-FDG PET.Advances in knowledge:We found that post-radiotherapy 18F-FDG PET findings have a high NPV for detecting residual disease and are a significant prognostic factor for treatment outcomes.

Early prediction of acute xerostomia during radiation therapy for nasopharyngeal cancer based on delta radiomics from CT images.

Acute xerostomia is the most common side effect of radiation therapy (RT) for head and neck (H&N) malignancies. Investigating radiation-induced changes of computed tomography (CT) radiomics in parotid glands (PGs) and saliva amount (SA) can predict acute xerostomia during the RT for nasopharyngeal cancer (NPC). CT and SA data from 35 patients with stages I-IVB were randomly collected from an NPC clinical trial registered on the clinicaltrials.gov (ID: NCT01762514). All patients received radical treatment based on intensity-modulated RT (IMRT) with a prescription dose of 68.1 Gy in 30 fractions. The patients' ages ranged 24-72 years, and each patient had five CT sets acquired at treatment position: at the 0th, 10th, 20th, 30th fractions during the RT, and at 3-month later after the RT. The PGs for each CT set were delineated by a radiation oncologist and verified independently by another. Patients' saliva was collected every other 10 days during the RT. Acute xerostomia was evaluated based on the RTOG acute toxicity scoring and the SA. In total, 1,703 radiomics features were calculated for PGs from each CT set, including feature value at 0th fraction (FV0F), FV10F, and delta FV (ΔFV10F-0F), respectively. Extensive experiments were conducted to achieve the optimal results. RidgeCV and Recursive Feature Elimination (RFE) were used for feature selection, while linear regression was used for predicting SA30F. Four more patients were added for independent testing. Substantial changes in various radiomics metrics of PGs were observed during the RT. Eight normalized feature value (NFV), selected from NFV0F, predicted SA10F with a mean square error (MSE) of 0.9042 and a R2 score of 0.7406. Fourteen NFV, selected from ΔNFV10F-0F, NFV0F, and NFV10F to predict SA30F, showed the best predictive ability with an MSE of 0.0569. The model predicted the level of acute xerostomia with a precision of 0.9220 and a sensitivity of 100%, compared to the clinical observed SA. For the independent test, the MSE of PSA30F was 0.0233. This study demonstrated that radiation-induced acute xerostomia level could be early predicted based on the SA and radiomics changes of the PGs during IMRT delivery. SA, NFV0F, NFV10F, and especially ΔNFV10F-0F provided the best performance on acute xerostomia prediction for individual patient based on RidgeCV_RFE_LinearRegression method of delta radiomics.

Use of intensity-modulated radiation therapy for nasopharyngeal cancer in Japan: analysis using a national database.

Intensity-modulated radiation therapy (IMRT) yields better outcomes and fewer toxicities for radiation therapy (RT) of head and neck cancers (HNCs), including nasopharyngeal cancer (NPC). IMRT is the standard RT treatment and has been widely adopted in Western countries to treat HNCs. However, its uptake in clinical practice among NPC patients has never been studied. We investigated the use of IMRT for NPC using data from a nationwide cancer registry to describe the use of IMRT among NPC patients in Japan. We analyzed the data of patients with HNC, including NPC, who underwent IMRT between 2012 and 2014, as recorded in the hospital-based cancer registries linked with insurance claims. We calculated the proportion of patients with NPC who underwent IMRT at each hospital. To evaluate the use of IMRT for NPC, the IMRT use for NPC was compared with the proportion of patients with prostate cancer who underwent IMRT. Among 508 patients with NPC who underwent RT at one of 87 hospitals, 348 (69%) underwent IMRT. This proportion gradually increased between 2012 and 2014 (62%, 64% and 77%). Meanwhile, 4790 patients with prostate cancer (90%) underwent IMRT. Although some hospitals where IMRT was performed treated many patients with NPC, the proportion of patients with NPC who were treated with IMRT was low. IMRT has not been widely adopted in Japan for treating NPC. Barriers for adopting its use should be identified to close the gap between the standard and actual medical practice in Japan.

The results of nasopharyngeal cancer patients treated by simultaneous integrated boost technique and concomitant chemotherapy

Background/aim To assess the efficacy and side effects of concurrent weekly chemotherapy and radiotherapy with simultaneous integrated boost (SIB) technique for nasopharyngeal cancer (NPC). Materials and methods A total of 51 consecutive patients with diagnosis of NPC were treated between February 2010 and December 2015. The median dose for PTV70 (range: 60–82) was given in 33 fractions (range: 31–35). Forty-five of the patients received concomitant weekly chemotherapy between 3–7 cycles (median 6). Eleven patients received neoadjuvant and thirty-nine patients received adjuvant chemotherapy. ResultsAt a median follow-up 43 months (range: 2–76) the estimated 5-year overall survival and disease-free survival were 74.6% and 62.6%, respectively. ConclusionIn radiotherapy of advanced NPC, generally a considerable amount of normal head and neck tissues might have to be irradiated in addition to gross tumor volume, involved node, and elective neck irradiation. Together with chemoradiotherapy, poor oral hygiene and inadequate nutritional support result in excessive morbidity. Despite loco-regional success of concurrent chemoradiotherapy, distant metastasis is still the major pattern of treatment failure in the intensity modulated radiotherapy era. We need to improve our adjuvant chemotherapy regimens or develop new drugs.

Investigation on the status of radiation therapy for nasopharyngeal cancer in Chongqing city

Objective: The objective of the study is to investigate the regional capacity and implementation of radiotherapy for nasopharyngeal carcinoma (NPC) in Chongqing city. Materials and Methods: The questionnaires, self-designed electronic forms in a uniform format, were distributed to 37 radiotherapy institutions, which covered all the medical units equipped with radiotherapy equipment in this city. Results: Of the 37 radiotherapy units in Chongqing, 27 could deliver radiotherapy for NPC, but the remaining 10 institutions could not due to equipment limitations. From January to December 2017, a total of 2904 patients with NPC were treated with radiotherapy. Patients from the five teaching hospitals in the main districts of the city accounted for 86% of the participants. There were four representative types of radiotherapy plan based on radiation technology among these units. Of the 37 units, 18 used intensity-modulated radiotherapy, 6 adopted three-dimensional conformal radiotherapy, 2 chose volumetric modulated arc therapy, and 1 delivered two-dimensional traditional radiotherapy; only 10 units applied magnetic resonance imaging (MRI)-computed tomography registration and fusion for gross tumor volume delineation in NPC treatment, and only 3 units routinely acquired nasopharyngeal and neck MRI scans to evaluate tumor shrinkage during treatment. Conclusion: Obvious distinctions exist between various units in Chongqing city in radiotherapeutic strategy, radiotherapy plan, frequency of image-guided radiation therapy, and mid-treatment evaluation for NPC radiotherapy. We need to learn and apply NPC guideline and consensus to improve NPC radiotherapy in Chongqing and to construct a rule with regional characteristics.

Frequency of cone beam computed tomography guidance in radiotherapy for nasopharyngeal carcinoma

Objective To analyze setup errors in cone beam computed tomography (CBCT)-guided radiotherapy for nasopharyngeal cancer (NPC) and evaluate the use frequency of CBCT. Methods Twenty-six patients newly diagnosed with NPC who received CBCT scan no less than 3 times per week during the whole course (7 weeks) of intensity-modulated radiotherapy (IMRT) were enrolled as subjects. Two setup errors were recorded each week: the setup error in the first CBCT analysis (Ef) and the setup error in the subsequent CBCT analysis (Ec). Comparisons of Ef between two different weeks, Ec between two different weeks, and between Ef and Ec in the same week were made by analysis of variance. Results During the 7 weeks, there were no significant differences in Ef in the medial-lateral (ML), superior-inferior (SI), or anterior-posterior (AP) direction between any two weeks (all P>0.05); there were also no significant differences in Ec in the ML or SI direction between any two weeks (all P>0.05); there was a significant difference in Ec in the AP direction between two different weeks (P 0.05); there were also no significant differences between Ef and Ec in the AP direction in any week (P>0.05) except for the first week (P<0.05). Conclusions In IMRT for NPC, the setup errors in the ML and SI directions are stable in the whole course of radiotherapy, while the setup errors in the AP direction are different between the first week and subsequent weeks. Daily CBCT scan in the first week and weekly CBCT scan in the subsequent weeks are highly recommended for most patients to reduce the use frequency of CBCT. Key words: Tomography, X-ray computed; Use frequency; Nasopharyngeal neoplasms/radiotherapy

PO-070: Conventional vs bifractionated radiotherapy innasopharyngeal cancer 10years followup of phase3 trial

PO-070: Conventional vs bifractionated radiotherapy innasopharyngeal cancer 10years followup of phase3 trial

Radiotherapy of nasopharyngeal cancer using Rapidarc: dosimetric study of military teaching hospital Mohamed V, Morocco

BackgroundThe aim of the present study is to assess efficacy and efficiency of Volumetric-modulated arc therapy (VMAT) technique in treatment of nasopharyngeal cancer in our institution and to report toxicity related to this technique.MethodsBetween June 2013 and January 2015, thirty-two patients with non metastatic nasopharyngeal cancer were curatively treated using VMAT Rapidarc. Dose prescription was performed using two different schedules, it consisted of either simultaneous integrated boost or simultaneous modulated accelerated radiation therapy delivering 70 Gy in 35 fractions and 69.96 in 33 fractions respectively. The choice was leaved at the discretion of the treating physician. The optimization process was performed by Eclipse software version 10.0 (Varian Medical Systems), using PRO algorithm (Progressive resolutive optimisation) version 3. Data was collected from dose-volume histograms for both planning target volumes (PTV) and organs at risk (OAR). We calculated the homogeneity index and the conformity index as well as the number of monitor units MU and the treatment delivery time. We also reported acute and late toxicity related to radiation therapy.ResultsFor the PTV high risk (HR), intermediate risk (PTV IR) and low risk (LR) the D95% was 97.21 ± 1.5, 97.5 ± 3.3 and 97.10 ± 6.86 respectively. Whereas, The D5% was 104.6 ± 2.16, 103.8 ± 2.1 and 100.89 ± 7.26. The CI for PTV HR was 0.98 ± 0.02 and the HI was 0.08 ± 0.02. The mean treatment delivery time was 2.3 ± 0.2, and the mean MU number was 527.6 ± 131.4. Grade 4 toxicity was not reported in any case. Grade 3 xerostomia was observed in only 3(9.4%) patients and no patients developed grade 3 hearing loss.ConclusionOur results confirmed the abilities of VMAT to provide excellent coverage of target volumes while sparing OAR especially the nervous structures and salivary glands.

Resveratrol enhances the radiosensitivity of nasopharyngeal carcinoma cells by downregulating E2F1.

Identification of safe, effective radiosensitizing agents is urgently needed to improve the outcome of radiotherapy in nasopharyngeal cancer(NPC). In this study, we assessed the ability of the polyphenol resveratrol to act as a radiosensitizer invitro and invivo. CNE-1 cells were treated with 50µM resveratrol for 24h, then irradiated. E2F transcription factor1(E2F1) was stably knockeddown and overexpressed using lentiviruses. A xenograft model of NPC was established in nude mice using CNE-1cells. Compared to controlDMSO‑treated CNE-1 cells, resveratrol inhibited colony-forming ability and induced G1phase cell cycle arrest. Radiation survival curves confirmed resveratrol significantly sensitized CNE-1 cells, and resveratrol in combination with 2Gy irradiation synergistically increased apoptosis. Immunoblotting showed resveratrol dose-and time-dependently downregulated E2F1 and phospho-AKT(p-AKT). Knockdown of E2F1 significantly increased radiosensitivity and downregulated p-AKT; overexpression of E2F1 reversed resveratrol-induced radiosensitivity and upregulated p-AKT. Invivo, 50 mg/kg/day resveratrol and 4Gy irradiation led to significantly lower tumor volume and tumor weight compared to resveratrol or irradiation alone. Our findings show that resveratrol increases the radiosensitivity of NPC cells by downregulating E2F1 and inhibiting p-AKT, and therefore has potential as a radiosensitizer for NPC.

SU‐F‐J‐98: Improvement and Evaluation Of Deformation Image Registration On Parotid Glands During Radiation Therapy for Nasopharyngeal Cancer

Purpose:To quantitatively evaluate the strategic innovation and accuracy variation of deformation registration algorithm for parotid glands using the similarity Dice coefficient during the course of radiation therapy (RT) for nasopharyngeal cancer (NPC).Methods:Daily MVCT data for 10 patients with pathologically proven nasopharyngeal cancers were analyzed. The data were acquired using tomotherapy (TomoTherapy, Accuray) at the PLA General Hospital. The prescription dose to the primary target was 70Gy in 33 fractions. Two kinds of contours for parotid glands on daily MVCTs were obtained by populating these contours from planning CTs to the daily CTs via rigid‐body registration with or without the rotation shifts using the in‐house tools and the Adaptive plan software (Adaptive Plan, TomoTherapy), and were edited manually if necessary. The diffeomorphic Demons algorithm developed in the in‐house tool was used to propagate the parotid structures from the daily CTs to planning CTs. The differences of the mapped parotid contours in two methods were evaluated using Dice similarity index (DSI). Two‐tailed t‐test analysis was carried out to compare the DSI changes during the course of RT.Results:For 10 patient plans, the accuracy of deformation image registration (DIR) with the rotation shift was obviously better than those without the rotation shift. The Dice scores of the ipsi‐ and contra‐lateral parotids for with and without the rotation shifts were found to be correlated with each other [0.904±0.031 vs 0.919±0.030 (p&lt;0.001); 0.900±0.031 vs 0.910±0.032 (p&lt;0.001)]. The Dice scores for the parotids have shown the reduction with the changes of parotid volumes during RT. The DSI values between the first and last fraction were 0.932±0.020 vs 0.899±0.030 in 10 patient plans.Conclusion:DIR was successfully improved using the strategic innovation for ART. And the decrease of DIR accuracy has also been found during the delivery of fractionated radiotherapy.This work was supported in part by the grant from Chinese Natural Science Foundation (Grant No. 11105225).

Impact of X-linked inhibitor of apoptosis protein on survival of nasopharyngeal carcinoma patients following radiotherapy.

This study aims to investigate CNE1 and CNE2 cell proliferation and apoptosis of nasopharyngeal cancer (NPC) and X-linked inhibitor of apoptosis protein (XIAP) expression in NPC patients after radiotherapy. Quantitative real-time quantitative polymerase chain reaction (qRT-PCR) and Western Blot detected XIAP and XIAP-associated factor1 (XAF1) messenger RNA (mRNA) and protein expression of CNE1 and CNE2 in NPC cells irradiated by γ-ray; MTT and flow cytometry assays detected CNE2 cells proliferation and apoptotic rate, respectively. With a retrospective analysis of 109 NPC patients in Xinxiang Central Hospital, immunohistochemistry (IHC) method detected XIAP expression, followed by a 5-year clinical analysis of the prognosis relevance after radiotherapy. In vitro, the inhibition and apoptotic rates of cells increased with the growth of radiation dose. qRT-PCR and Western blot detection declared that XIAP mRNA and protein expression increased, whereas XAF1 mRNA and protein expression decreased with the growth of radiation dose and exposure time. And XIAP mRNA and protein expression were negatively correlated with proliferation and apoptotic rates of the cells. In vivo, positive XIAP expression rate was negatively correlated with pathological tumor-node-metastasis (p-TNM) staging and tumor differentiation. Further, high XIAP expression, high p-TNM staging, and lower degree of differentiation were significantly correlated with the decrease of NPC patients' survival rate. Additionally, XIAP expression, p-TNM staging, and degrees of differentiation were independent risk factors for the survival of the NPC patients after radiotherapy. Increased XIAP expression and decreased XAF1 expression may be one reason for the apoptosis delays of CNE1 and CNE2 cells after irradiation, and the XIAP expression or the p-TNM staging and degree of differentiation are independent risk factors for NPC patients' survival after radiotherapy, providing a molecular rationale for radiotherapy and prognosis of NPC.

EP-1095: Prognostic role of FDG PET-CT performed before and during radiotherapy for nasopharyngeal cancer

EP-1095: Prognostic role of FDG PET-CT performed before and during radiotherapy for nasopharyngeal cancer

RNF8 plays an important role in the radioresistance of human nasopharyngeal cancer cells in vitro

Tumor residue or recurrence is common after radiation therapy for nasopharyngeal cancer (NPC) since the tumor cells can repair irradiation-induced DNA damage. The ubiquitination cascade mediates the assembly of repair and signaling proteins at sites of DNA double-strand breaks (DSBs). Ring finger protein 8 (RNF8) is an E3 ubiquitin ligase that triggers ubiquitination at the site of DSBs. The present study aimed to identify whether and how RNF8 small interfering RNA (siRNA) treatment enhances the radiosensitivity of irradiated human NPC cell lines. The CNE1, CNE2, and SUNE human NPC cell lines were stably transfected with a constructed RNF8-targeting siRNA expression vector. Western blotting was used to detect the effectiveness of RNF8 downregulation by RNF8 siRNA. The siRNA-transfected (RNF8-) and non-transfected (RNF8+) cells were irradiated at different doses by a linear accelerator. The growth inhibition ratio and apoptosis rate were detected by the methyl thiazolyl tetrazolium (MTT) assay and flow cytometry, respectively. The ataxia-telangiectasia mutated (ATM), DNA-PKcs, Chk1, Chk2, Nbs1 and Ku80 protein levels in each group were determined. The growth inhibition ratio and apoptotic percentage of RNF8- cells were higher than those of the RNF8+ cells in each of the three cell lines. Lower protein expression levels of Chk1, Chk2, ATM, and Nbs1 were observed in the irradiated RNF8- cells compared to the irradiated RNF8+ cells in each of the three cell lines (P<0.01). As a result, a conclusion could be drawn that RNF8 recruits and ubiquitinates many factors to repair DNA damage, including DSBs, thereby conferring radioresistance to NPC cells.