What are the current outcomes of advanced gastrointestinal stromal tumors: who are the long-term survivors treated initially with imatinib?

Abstract

The introduction of imatinib to clinical practice revolutionized therapy of advanced gastrointestinal stromal tumors (GIST), but its long-term results have been only just collected. We have attempted to identify factors related to the long-term survival. We have analyzed the data of 430 inoperable/metastatic/recurrent GIST patients treated with imatinib in reference centers, assessed the factors influencing the long-term overall survival (OS), and compared the outcomes in three periods of initiation of imatinib therapy during one decade (2001–2003, 2004–2006, 2007–2010). During analyzed time periods, we have found decrease in median largest tumor size at the start of imatinib therapy: 90.5 mm (2001–2003) versus 74 mm (2004–2006) versus 58 mm (2007–2010) (p = 0.002). Median progression-free survival (PFS) on 1st line imatinib was 37.5 months, without differences in PFS between three groups. Median OS was 5.8 years, 8-year OS rate was 43 %, and no difference in OS was demonstrated for patients treated in analyzed time periods. Independent good prognostic factors for longer OS were as follows: surgery of residual disease, initial WHO performance status 0/1, normal baseline albumin level, and the presence of exon 11 KIT mutations. Current median OS in advanced GIST reaches 6 years. The long-term survivors were characterized by smaller maximal tumors at imatinib start, better blood tests results, better performance status, and the surgical removal of residual disease. The latter might reduce the impact of tumor size and equalize the long-term results of therapy during last decade from introduction of imatinib. After introduction of subsequent lines of therapy (as sunitinib), the effect of primary mutational status on the long-term OS is also less visible.