Long-term Therapeutic Outcome and Prognostic Factors of Patients with Nasopharyngeal Carcinoma Receiving Intensity-modulated Radiotherapy: An Analysis of 608 Patients from Low-endemic Regions of China

Objective To evaluate the long-term outcome and prognostic factors of patients with nasopharyngeal carcinoma(NPC)from low-endemic regions of China who received definitive intensity-modulated radiation therapy(IMRT).Methods The clinical data from 608 patients with newly-diagnosed non-metastatic NPC who have received initial treatment at our cancer center from January,2008 to December,2013 were retrospectively reviewed.All patients received definitive IMRT,and 87.7%received platinum-based chemotherapy.Results The median follow-up duration was 51 months(follow-up rate,98.5%;range,10–106 months)for the entire cohort.The 5-year overall survival rate was 79.7%.The 5-year local relapse-free survival rate,regional relapse-free survival rate,distant metastasis-free survival rate and progression-free survival rate were 92.4%,93.3%,79.2%and 74.3%,respectively.A total of 153 patients had experienced treatment failure,with distant metastasis as the primary cause in 77.1%(118/153).Patients with T4 or N3 diseases had a significantly poorer prognosis than other subcategories.Stage T4 and N3 were closely associated with distant metastasis,with the metastatic rate of 29.3%and 45.5%,respectively.Conclusion IMRT provides patients with non-metastatic NPC with satisfactory long-term survival.Both T stage and N stage are important prognostic factors for NPC patients.Patients with T4 or N3 diseases have significantly increased distant metastatic rates and poor survival time.

Proton Irradiation Effects on the Structural and Tribological Properties of Polytetrafluoroethylene

Polytetrafluoroethylene （PTFE） was irradiated with protons in a ground-based simulation facility to study the effects of proton irradiation on the structural and tribological properties of PTFE. The structural changes were characterized by X-ray photoelectron spectroscopy （XPS） and attenuated total-reflection FTIR （ATR-FTIR）, while the tribological properties were evaluated by friction and wear tests. It was found that proton irradiation induced the degradation of PTFE molecular chains, resulting in the increase of C concentration and the decrease in F concentration on the sample surfaces, and the surface chemical structure and morphology of the samples changed, which affected the friction coefficient and decreased the wear rate of the specimens as the friction and wear tests revealed.