The Optimal Duration of Treatment Many studies have confirmed that the long-term use of aspirin has clear anti-tumor effects. Rothwell PM et al. [19] investigated the anti-tumor effects of aspirin by screening out two distinct groups of patients (aspirinusers and aspirin-free) with an average treatment time of more than 4 years. From the eight eligible studies they evaluated, it was clear that aspirin had anti-tumor effects that were independent of the treatment dose (more/ less than 75 mg),

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... aspirin treatment reduced the mortality risk of many cancers when oral aspirin use was sustained for at least five years [13]. Aspirin reduces the development of esophageal cancer [8], pancreatic cancer, gastric cancer, colorectal cancer and prostate cancer [5], but their prevention seems to required sustained use of aspirin for at least 5 years, with the anti-tumors effects becoming more prominent with an increasing duration of aspirin use [13]. Aspirin did not have any apparent effect when used for less than 5 years, and required even longer for any effect on gastric, colorectal and prostate cancer. Based on these studies, the consensus of researchers is that patients need to take oral aspirin regularly for at least 5 years to experience anti-tumor effects. Abstract: Beyond the antipyretic analgesic and anti-inflammatory effects for which aspirin has historically been used, studies have shown that aspirin also plays an important role in the prevention or treatment a variety of diseases. The anti-tumor effects of aspirin have received increasing attention during the past decade. Many studies have explored the molecular mechanisms underlying these anti-tumor effects in vitro and in vivo, and abundant discoveries have been made through observational or interventional clinical studies. In terms of its molecular function, aspirin has been shown to prevent tumor cell growth through inhibiting the signal transduction of the COX, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), NFκB/IκB, and Bcl-2/Bax pathways. Under certain conditions, aspirin can also induce autophagy, which is an inhibitory mechanism for some tumors. This article provides a comprehensive overview of the anti-tumor effects of aspirin and discusses the concrete mechanisms underlying aspirin's anti-tumor effects that have been discovered in the past 30 years. 8. van Staalduinen J, Frouws M, Reimers M, Bastiaannet E, van Herk-Sukel MP, Lemmens V, de Steur WO, Hartgrink HH, van de Velde CJ, Liefers GJ. The effect of aspirin and nonsteroidal anti-inflammatory drug use after diagnosis on survival of oesophageal cancer patients. Br J Cancer 2016;114(9):1053-9. 9.