====== Overall survival ======

The length of time from either the date of diagnosis or the start of treatment for a disease, such as cancer, that patients diagnosed with the disease are still alive. In a clinical trial, measuring the overall survival is one way to see how well a new treatment works. Also called OS. 
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Although overall survival (OS) is the standard for determining [[Glioblastoma treatment]] efficacy, using OS as an endpoint when studying new therapeutic strategies can be problematic because of potential influence of therapies prior to or subsequently following the therapy being studied. For example, it is difficult to definitively conclude that [[bevacizumab]] has no efficacy in [[Glioblastoma]] when a large percentage of patients in the placebo arms in both III trials studying efficacy of bevacizumab (i.e. AVAglio and RTOG-0825) eventually crossed over and received bevacizumab (31% in [[AVAglio trial]]
((Chinot OL, Wick W, Mason W, Henriksson R, Saran F, Nishikawa R, Carpentier AF,
Hoang-Xuan K, Kavan P, Cernea D, Brandes AA, Hilton M, Abrey L, Cloughesy T.
Bevacizumab plus radiotherapy-temozolomide for newly diagnosed glioblastoma. N
Engl J Med. 2014 Feb 20;370(8):709-22. doi: 10.1056/NEJMoa1308345. PubMed PMID:
24552318.
))
and 48% in [[RTOG 0825]]
((Gilbert MR, Dignam JJ, Armstrong TS, Wefel JS, Blumenthal DT, Vogelbaum MA,
Colman H, Chakravarti A, Pugh S, Won M, Jeraj R, Brown PD, Jaeckle KA, Schiff D, 
Stieber VW, Brachman DG, Werner-Wasik M, Tremont-Lukats IW, Sulman EP, Aldape KD,
Curran WJ Jr, Mehta MP. A randomized trial of bevacizumab for newly diagnosed
glioblastoma. N Engl J Med. 2014 Feb 20;370(8):699-708. doi:
10.1056/NEJMoa1308573. PubMed PMID: 24552317; PubMed Central PMCID: PMC4201043.
)).
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Preoperatively measured [[necrosis]] volume and necrosis-tumor ratio (NTR) are the most important radiological features of [[Glioblastoma]] with a strong influence on OS. No other measuring techniques are specific enough and comparable with 3D segmentation
((Henker C, Kriesen T, Glass Ä, Schneider B, Piek J. Volumetric quantification
of glioblastoma: experiences with different measurement techniques and impact on 
survival. J Neurooncol. 2017 Jul 28. doi: 10.1007/s11060-017-2587-5. [Epub ahead 
of print] PubMed PMID: 28755324.
)).