Prognostic factors after imatinib secondary resistance: survival analysis in patients with unresectable and metastatic gastrointestinal stromal tumors

English version of Japanese Clinical Practice Guidelines 2022 for gastrointestinal stromal tumor (GIST) issued by the Japan Society of Clinical Oncology

The Japan Society of Clinical Oncology Clinical Practice Guidelines 2022 for gastrointestinal stromal tumor (GIST) have been published in accordance with the Minds Manual for Guideline Development 2014 and 2017. A specialized team independent of the working group for the revision performed a systematic review. Since GIST is a rare type of tumor, clinical evidence is not sufficient to answer several clinical and background questions. Thus, in these guidelines, we considered that consensus among the experts who manage GIST, the balance between benefits and harms, patients' wishes, medical economic perspective, etc. are important considerations in addition to the evidence. Although guidelines for the treatment of GIST have also been published by the National Comprehensive Cancer Network (NCCN) and the European Society for Medical Oncology (ESMO), there are some differences between the treatments proposed in those guidelines and the treatments in the present guidelines because of the differences in health insurance systems among countries.

Surgery for metastatic gastrointestinal stromal tumor: to whom and how to?

Although imatinib is a standard treatment for metastatic or recurrent gastrointestinal stromal tumors (GISTs), acquired c-kit mutations reportedly cause secondary resistance to imatinib. Sunitinib is a tyrosine kinase inhibitor (TKI) that can be used as second-line therapy in imatinib-resistant or -intolerant GISTs. For sunitinib-resistant or -intolerant GISTs, regorafenib is a standard third-line treatment. Although TKI therapies have revolutionized the treatment of recurrent or metastatic GISTs, they cannot cure GISTs. Therefore, in the era of TKIs, role of cytoreductive surgery for recurrent or metastatic GISTs has been discussed. Retrospective studies of treatment strategies with front-line surgery prior to imatinib have shown that initial cytoreduction confers no benefit in cases of advanced or recurrent GIST, and administering imatinib is the principle treatment. Most retrospective studies report cytoreductive surgery to be feasible in patients with metastatic GIST whose disease is stable or responsive to imatinib. Cytoreductive surgery may be indicated in limited disease progression refractory to imatinib when complete resection is possible, but case selection is critical. Cytoreductive surgery for metastatic GIST treated with sunitinib seems less feasible because of high rates of incomplete resections and complications. The role of cytoreductive surgery for metastatic GISTs would be difficult to establish in a prospective study; individualized treatments need to be carefully designed based on c-kit and platelet-derived growth factor receptor alpha (PDGFRA) mutations and other factors.

Surgery and imatinib therapy for liver oligometastasis of GIST: a study of Japanese Study Group on GIST

We conducted a multicenter prospective study to clarify the efficacy and safety of surgery and imatinib for liver oligometastasis of gastrointestinal stromal tumors. Eligible gastrointestinal stromal tumor patients were enrolled in the surgery trial or the imatinib trial. Primary endpoints were recurrence-free survival and progression-free survival, respectively. The trials were prematurely terminated due to amendment of guidelines for adjuvant imatinib therapy and low patient accrual. In the surgery trial, all the six patients showed hepatic recurrence: median recurrence-free survival was 145 days (range: 62-1366 days). Of the five patients receiving salvage imatinib therapy, two showed progressive disease although no death was observed. Of the five patients enrolled in the imatinib trial, one died of pneumonia after progressive disease, and four had not shown progressive disease as of last visit. The results suggest that liver oligometastasis of gastrointestinal stromal tumor may not be controllable by surgery alone and require concomitant imatinib therapy.