Masitinib in advanced gastrointestinal stromal tumor (GIST) after failure of imatinib: a randomized controlled open-label trial.

BACKGROUND: Masitinib is a highly selective tyrosine kinase inhibitor with activity against the main oncogenic drivers of gastrointestinal stromal tumor (GIST). Masitinib was evaluated in patients with advanced GIST after imatinib failure or intolerance. PATIENTS AND METHODS: Prospective, multicenter, randomized, open-label trial. Patients with inoperable, advanced imatinib-resistant GIST were randomized (1 : 1) to receive masitinib (12 mg/kg/day) or sunitinib (50 mg/day 4-weeks-on/2-weeks-off) until progression, intolerance, or refusal. Primary efficacy analysis was noncomparative, testing whether masitinib attained a median progression-free survival (PFS) (blind centrally reviewed RECIST) threshold of >3 months according to the lower bound of the 90% unilateral confidence interval (CI). Secondary analyses on overall survival (OS) and PFS were comparative with results presented according to a two-sided 95% CI. RESULTS: Forty-four patients were randomized to receive masitinib (n = 23) or sunitinib (n = 21). Median follow-up was 14 months. Patients receiving masitinib experienced less toxicity than those receiving sunitinib, with significantly lower occurrence of severe adverse events (52% versus 91%, respectively, P = 0.008). Median PFS (central RECIST) for the noncomparative primary analysis in the masitinib treatment arm was 3.71 months (90% CI 3.65). Secondary analyses showed that median OS was significantly longer for patients receiving masitinib followed by post-progression addition of sunitinib when compared against patients treated directly with sunitinib in second-line [hazard ratio (HR) = 0.27, 95% CI 0.09-0.85, P = 0.016]. This improvement was sustainable as evidenced by 26-month follow-up OS data (HR = 0.40, 95% CI 0.16-0.96, P = 0.033); an additional 12.4 months survival advantage being reported for the masitinib treatment arm. Risk of progression while under treatment with masitinib was in the same range as for sunitinib (HR = 1.1, 95% CI 0.6-2.2, P = 0.833). CONCLUSIONS: Primary efficacy analysis ensured the masitinib treatment arm could satisfy a prespecified PFS threshold. Secondary efficacy analysis showed that masitinib followed by the standard of care generated a statistically significant survival benefit over standard of care. Encouraging median OS and safety data from this well-controlled and appropriately designed randomized trial indicate a positive benefit-risk ratio. Further development of masitinib in imatinib-resistant/intolerant patients with advanced GIST is warranted.

Rationale and design of a UK database for a rare cancer type: the GEM Registry for gastrointestinal stromal tumours.

BACKGROUND: Despite advances in the management of and changes in clinical practice, little is known about the epidemiology, patterns of care and outcomes of gastrointestinal stromal tumour (GIST) patients in the UK. Patient registries are receiving increasing attention as they can provide important information on clinical practice and patient outcomes. The rationale and study design of the GIST Epidemiology and Management (GEM) Registry, which forms part of the routine clinical practice for GISTs in several UK centres, are described. METHODS: The GEM Registry is a secure web-based registry system designed around a Microsoft Access core using SQL interface. Demographic, surgical, histopathological and clinical data will be captured including treatment outcomes and survival. The registry was piloted in six centres and following further fine tuning of the data sets, ethical committee submission and approval was completed. RESULTS: The GEM National Registry is the first of its kind to be implemented in rare cancers in UK. The registry is being rolled out initially in selected centres with the aim to expand to other centres. The first publication reporting analyses of the central data set is anticipated for the summer of 2013. CONCLUSION: GEM Registry will enable us to obtain a clear picture of incidence/prevalence of GISTS in UK. Clinicians will be able to review the prognostic and predictive value of variables in a large prospective data set. The data can be used for planning the delivery and improving the quality of care. This information is likely to inform clinical practice and, in years to come, guide the development and implementation of clinical trials for novel tyrosine kinase inhibitors. The results will not only benefit the GIST community, but also serve as a basis for the study of other rare tumour types.

A review of the surgical management of metastatic gastrointestinal stromal tumours (GISTs) on imatinib mesylate (Glivec).

Gastrointestinal stromal tumours (GISTs) are defined as a group of C-KIT positive mesenchymal tumours of the gastrointestinal tract. Although they may arise throughout the gut, the commonest sites are stomach and small intestine. Over 80% of metastases are to the liver and omentum. Targeted therapy (imatinib) can inhibit C-KIT and thereby aberrant tumoural proliferation. Imatinib may induce shrinkage of lesions and cystic change. Such physical changes often correspond with reduced metabolic activity demonstrated by (18-FDG)PET scans. These changes may enable metastatectomy reducing tumour pain and the risk of haemorrhage and rupture in the short term. In the long term, resection may lessen the risk of recurrence by removing potentially resistant clones. The precise role of palliative resection for GIST metastases on imatinib remains unclear. Imatinib has changed the natural history of metastatic GISTs, with increased survival times. Surgery remains an important management strategy in the metastatic setting because complete pathological responses are rare with imatinib. Surgery is likely to provide the best palliation, greatest reduction in tumour burden and eliminate resistant clones. A multidisciplinary team approach with expertise concentrated in a few centres specialising in the management of these rare tumours is vital to the successful outcome. Future issues regarding the management of differential response of the metastases to imatinib are highlighted. With the emergence of techniques enabling identification of the precise mutational status of the C-KIT oncogene, the imatinib/surgery sequence could be tailored to the type of C-KIT mutation.