Review Article a consequence of chemostatic, not chemotoxic mechanism of action of targeted molecular therapies. Resistance to treatment exhibited by some cell lines poses a fundamental problem and indicates the lack of possibility of full recov- ery from GIST on Imatinib [17–19] treatment. Conclusions The variety of problems that arise in diagnostics and treat- ment monitoring of GIST tumors requires a thorough knowledge of this disease on the part of the reporting radi- ologist; optimally, provided by training in centers special- izing in the treatment of GIST. References: 1. Hirota S, Isozaki K, Moriyama Y et al: Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors. Science, 1998; 279(5350): 577–80 2. van Oosterom AT, Judson I, Verweij J et al: Safety and efficacy of imatinib (STI571) in metastatic gastrointestinal stromal tumours: a phase I study. Lancet, 2001; 358(9291): 1421–23 3. Radford IR: Imatinib. Novartis. Curr Opin Investig Drugs, 2002; 3(3): 492–99 4. Stachura J, Limon J, Ruka W et al: GIST Nowotwory podścieliskowe (stromalne) przewodu pokarmowego. Wydawnictwo Via Medica, 2003 [in Polish] 5. Kim HC, Lee JM, Kim SH et al: Small gastrointestinal stromal tumours with focal areas of low attenuation on CT: pathological correlation. Clinical Radiology, 2005; 60(3): 384–88 6. Rutkowski P, Debiec-Rychter M, Ruka W: Gastrointestinal stromal tumors: key to diagnosis and choice of therapy. Mol Diagn Ther, 2008; 12(3): 131–43 7. Horton KM, Juluru K, Montogomery E et al: Computed tomography imaging of gastrointestinal stromal tumors with pathology correlation. J Comput Assist Tomogr, 2004; 28(6): 811–17 8. Hersh MR, Choi J, Garrett C et al: Imaging gastrointestinal stromal tumors. Cancer Control, 2005; 12(2): 111–15 9. Blay JY, Bonvalot S, Casali P et al: Consensus meeting for the management of gastrointestinal stromal tumors. Report of the GIST Consensus Conference of 20–21 March 2004, under the auspices of ESMO. Ann Oncol, 2005; 16(4): 566–78 10. Linton KM, Taylor MB, Radford JA: Response evaluation in gastrointestinal stromal tumours treated with imatinib: misdiagnosis of disease progression on CT due to cystic change in liver metastases. BrJ Radiol, 2006; 79(944): 40–44 © Pol J Radiol, 2011; 76(3): 38-48 Also, the importance of the flow of information between clinicians and radiologists evaluating effectiveness of che- motherapy increases. Radiologists have to possess informa- tion on the type of drug the patient receives, its mechanism of action and duration of treatment. They also must know whether there were interruptions in treatment and if so, when it was discontinued. Lack of this information may result in incorrect interpretation of changes seen in radio- logical studies and have fatal consequences for the patient. Due to the appearance of new patterns of therapeutic response in targeted molecular therapy and unique pat- terns of neoplastic progression, the criteria for radiologi- cal evaluation using CT that are based on measurements of tumor dimensions should be changed. 11. Choi H, Charnsangavej C, Faria SC et al: Correlation of computed tomography and positron emission tomography in patients with metastatic gastrointestinal stromal tumor treated at a single institution with imatinib mesylate: proposal of new computed tomography response criteria. J Clin Oncol, 2007; 25(13): 1753–59 12. Bechtold RE, Chen MY, Stanton CA et al: Cystic changes in hepatic and peritoneal metastases from gastrointestinal stromal tumors treated with Gleevec. Abdominal imaging, 2003; 28(6): 808–14 13. Choi H, Charnsangavej C, de Castro Faria S et al: CT evaluation of the response of gastrointestinal stromal tumors after imatinib mesylate treatment: a quantitative analysis correlated with FDG PET findings. AJR, 2004; 183(6): 1619–28 14. Chen MY, Bechtold RE, Savage PD: Cystic changes in hepatic metastases from gastrointestinal stromal tumors (GISTs) treated with Gleevec (imatinib mesylate). AJR, 2002; 179(4): 1059–62 15. Choi H: Critical issues in response evaluation on computed tomography: lessons from the gastrointestinal stromal tumor model. Curr Oncol Rep, 2005; 7(4): 307–11 16. Mabille M, Vanel D, Albiter M et al: Follow-up of hepatic and peritoneal metastases of gastrointestinal tumors (GIST) under Imatinib therapy requires different criteria of radiological evaluation (size is not everything!!!). Eur J Radiol, 2009; 69(2): 204–8 17. Benjamin RS, Choi H, Macapinlac HA et al: We should desist using RECIST, at least in GIST. J Clin Oncol, 2007; 25(13): 1760–64 18. Desai J, Shankar S, Heinrich MC et al: Clonal evolution of resistance to imatinib in patients with metastatic gastrointestinal stromal tumors. Clin Cancer Res, 2007; 13(18): 5398–405 19. Shankar S, vanSonnenberg E, Desai J et al: Gastrointestinal stromal tumor: new nodule-within-a-mass pattern of recurrence after partial response to imatinib mesylate. Radiology, 2005; 235(3): 892–98 48