Abstract. An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution. In order to account for the refractory material in the aerosol, we also present estimates of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a PM2.5 Tapered Element Oscillating Microbalance (TEOM), and a PM2.5 DustTrak Aerosol Monitor) show that the AMS + BC + soil mass concentration is consistent with the total PM2.5 mass concentration during MCMA-2003 within the combined uncertainties. In Mexico City, the organic fraction of the estimated PM2.5 at CENICA represents, on average, 54.6% (standard deviation σ=10%) of the mass, with the rest consisting of inorganic compounds (mainly ammonium nitrate and sulfate/ammonium salts), BC, and soil. Inorganic compounds represent 27.5% of PM2.5 (σ=10%); BC mass concentration is about 11% (σ=4%); while soil represents about 6.9% (σ=4%). Size distributions are presented for the AMS species; they show an accumulation mode that contains mainly oxygenated organic and secondary inorganic compounds. The organic size distributions also contain a small organic particle mode that is likely indicative of fresh traffic emissions; small particle modes exist for the inorganic species as well. Evidence suggests that the organic and inorganic species are not always internally mixed, especially in the small modes. The aerosol seems to be neutralized most of the time; however, there were some periods when there was not enough ammonium to completely neutralize the nitrate, chloride and sulfate present. The diurnal cycle and size distributions of nitrate suggest local photochemical production. On the other hand, sulfate appears to be produced on a regional scale. There are indications of new particle formation and growth events when concentrations of SO2 were high. Although the sources of chloride are not clear, this species seems to condense as ammonium chloride early in the morning and to evaporate as the temperature increases and RH decreases. The total and speciated mass concentrations and diurnal cycles measured during MCMA-2003 are similar to measurements during a previous field campaign at a nearby location.

IMPORTANCEThe role of locoregional radiotherapy in patients with de novo metastatic nasopharyngeal carcinoma (mNPC) is unclear.OBJECTIVE To investigate the efficacy and safety of locoregional radiotherapy in de novo mNPC.DESIGN, SETTING, AND PARTICIPANTS Patients with biopsy-proven mNPC, who demonstrated complete or partial response (RECIST v1.1) following 3 cycles of cisplatin and fluorouracil chemotherapy, were enrolled. Eligible patients were randomly assigned (1:1) to receive either chemotherapy plus radiotherapy or chemotherapy alone. Overall, 126 of 173 patients screened were eligible to the study, and randomized to chemotherapy plus radiotherapy (n = 63) or chemotherapy alone (n = 63). Median (IQR) follow-up duration was 26.7 (17.2-33.5) months. INTERVENTIONSThe chemotherapy regimens were fluorouracil continuous intravenous infusion at 5 g/m 2 over 120 hours and 100 mg/m 2 intravenous cisplatin on day 1, administered every 3 weeks for 6 cycles. Patients assigned to the chemotherapy plus radiotherapy group received intensity-modulated radiotherapy (IMRT) after chemotherapy. MAIN OUTCOMES AND MEASURESThe primary end point of the study was overall survival (OS). The secondary end point was progression-free survival (PFS) and safety. RESULTSOverall, 126 patients were enrolled (105 men [83.3%] and 21 women [16.7%]; median [IQR] age, 46 [39-52] years). The 24-month OS was 76.4% (95% CI, 64.4%-88.4%) in the chemotherapy plus radiotherapy group, compared with 54.5% (95% CI, 41.0%-68.0%) in the chemotherapy-alone group. The study met its primary end point of improved OS (stratified hazard ratio [HR], 0.42; 95% CI, 0.23-0.77; P = .004) in favor of chemotherapy plus radiotherapy. Progression-free survival was also improved in the chemotherapy plus radiotherapy group compared with the chemotherapy-alone group (stratified HR, 0.36; 95% CI, 0.23-0.57). No significant differences in acute hematological or gastrointestinal toxic effects were observed between the treatment arms. The frequency of acute grade 3 or higher dermatitis, mucositis, and xerostomia was 8.1%, 33.9%, and 6.5%, respectively, in the chemotherapy plus radiotherapy group. The frequency of late severe grade 3 or higher hearing loss and trismus was 5.2% and 3.4%, respectively, in the chemotherapy plus radiotherapy group. CONCLUSIONS AND RELEVANCEIn this randomized clinical trial, radiotherapy added to chemotherapy significantly improved OS in chemotherapy-sensitive patients with mNPC.

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