ABSTRACT
Objective: Studies have demonstrated that tonsillectomy may alter the risk of oropharyngeal cancer (OPC). We systematically reviewed the evidence and pooled data to examine such an association. Methods: PubMed, Embase, and Scopus were searched up to 25th April 2023. Studies reporting an association between tonsillectomy and oropharyngeal cancer risk at any site were included. Results: Five studies were eligible. All examined the risk of tonsillar and base of the tongue (BOT) cancer with prior history of tonsillectomy. On meta-analysis of the data, prior history of tonsillectomy was associated with a significantly decreased risk of tonsillar cancer. The second meta-analysis showed that history of tonsillectomy did not significantly alter the risk of BOT cancer. However, after exclusion of one study, the results showed an increased risk of BOT cancer with a history of tonsillectomy. Conclusions: The scarce data available in the literature suggests that tonsillectomy may reduce the risk of tonsillar cancer but does not alter the risk of BOT cancer. Further studies are needed to explore the association between tonsillectomy and the risk of OPC.
ABSTRACT
This study investigated the performance of thermophilic-mesophilic (T-M) and mesophilic-thermophilic (M-T) two-phase sludge anaerobic digestion at different inoculation proportions after a change in digestion temperature. After temperature change, the pH, total ammonia nitrogen (TAN), free ammonia nitrogen (FAN), solubility chemical oxygen demand (SCOD), and total alkalinity (TA) levels of two-phase digesters were between thermophilic control digesters and mesophilic control digesters. However, the volatile fatty acid (VFA) levels of two-phase digesters were higher than those of thermophilic or mesophilic control digesters. The bacteria communities of M-T two-phase digesters were more diverse than those of T-M. After a change in digestion temperature, the bacterial community was dominated by Coprothermobacter. After a change of digestion temperature, the relative abundance (RA) of Methanobacterium, Methanosaeta, and Methanospirillum of M-T two-phase digesters was higher than that of T-M two-phase digesters. In comparison, the RA of Methanosarcina of T-M two-phase digesters was higher than that of M-T two-phase digesters. The ultimate methane yields of thermophilic control digesters were greater than those of mesophilic control digesters. Nevertheless, the ultimate methane yield levels of M-T two-phase digesters were greater than those of T-M two-phase digesters. The ultimate methane yields of all two-phase digesters presented an earlier increase and later decrease trend with the increasing inoculation proportion. Optimal methane production condition was achieved when 15% of sludge (T-M15) was inoculated under mesophilic-thermophilic conditions, which promoted 123.6% (based on mesophilic control) or 27.4% (based on thermophilic control). An optimal inoculation proportion (about 15%) balanced the number and activity of methanogens of high-solid sludge anaerobic digestion.
