Discontinuation of imatinib in patients with oligometastatic gastrointestinal stromal tumour who are in complete radiological remission: a prospective multicentre phase II study.

INTRODUCTION: Metastatic gastrointestinal stromal tumour (GIST) is considered incurable, and life-long treatment with tyrosine kinase inhibitors is recommended. We investigated whether selected patients with metastatic GIST may remain in durable remission despite imatinib discontinuation. PATIENTS: In this 1-group, prospective, multicentre phase II trial selected patients with oligometastatic (≤3 metastases) GIST discontinued imatinib treatment. Eligible patients had been treated with imatinib >5 years without progression and had no radiologically detectable metastases after metastasectomy, radiofrequency ablation (RFA) or complete response to imatinib. The primary endpoint was progression-free survival (PFS) 3-years after stopping imatinib. Overall survival (OS) and quality of life (QoL) were secondary endpoints. RESULTS: The trial closed prematurely due to slow accrual. Between January 5, 2017, and June 5, 2019, 13 patients were enrolled, of whom 12 discontinued imatinib. The median follow-up time was 55 months (range, 36 to 69) after study entry. Five (42%) of the 12 eligible patients remained progression free, and seven (58%) progressed with a median time to progression 10 months. Median PFS was 23 months and the estimated 3-year PFS 41%. Six of the seven patients who progressed restarted imatinib, and all six responded. Three-year OS was 100%, and all patients were alive at the time of the study analysis. QoL measured 5 and 11 months after discontinuation of imatinib demonstrated improvement compared to the baseline. INTERPRETATION: A substantial proportion of selected patients with oligometastatic GIST treated with imatinib and metastasis surgery/RFA may remain disease-free for ≥3 years with improved QoL after stopping of imatinib.

Integrating Anatomical, Molecular and Clinical Risk Factors in Gastrointestinal Stromal Tumor of the Stomach.

BACKGROUND: Adjuvant imatinib for 3 years is recommended to patients with high-risk gastrointestinal stromal tumor (GIST). Risk stratification is inaccurate, and risk assessments are further complicated by the increased use of neoadjuvant treatment. Anatomical criteria for prognostication have not been investigated. METHODS: Clinical, molecular, and anatomical variables were retrospectively studied in a population-based cohort of 295 patients with gastric GIST resected between 2000 and 2018. Gastric subsite was divided into the upper, middle, and lower thirds. Growth pattern was classified as luminal, exophytic, or transmural based on imaging and surgical reports. RESULTS: Of 113 tumors in the upper third of the stomach, 103 (91.2%) were KIT mutated, 7 (6.2%) were PDGFRA mutated, and 104 (92.0%) harbored genotypes sensitive to imatinib. Transmural tumors were strongly associated with a high mitotic index. Five-year recurrence-free survival (RFS) was 71% for patients with transmural tumors versus 96% with luminal or exophytic tumors (hazard ratio [HR] 8.45, 95% confidence interval [CI] 3.69-19.36; p < 0.001), and, in high-risk patients, 5-year RFS was 46% for patients with transmural tumors versus 83% with luminal or exophytic tumors (HR 4.47, 95% CI 1.71-11.66; p = 0.001). Among 134 patients with tumors > 5 cm, there were 29 recurrences. Only five patients with exophytic or luminal tumors had recurrent disease, of whom four had tumor rupture. Five-year RFS for patients with exophytic/luminal tumors >5 cm without rupture was 98%. CONCLUSIONS: In the upper third, over 90% of tumors were sensitive to imatinib. Patients with exophytic or luminal tumors without rupture, irrespective of size, had an excellent prognosis and may not benefit from adjuvant therapy.

Multimodal kreftbehandling av gastrointestinal stromal tumor.

Gastrointestinal stromal tumour (GIST) is a subtype of sarcoma that may occur in any part of the gastrointestinal system, most frequently in the stomach and small intestine. The most common symptoms are bleeding and abdominal pain. In this clinical review, we summarise the progress made with this condition and discuss the recommended diagnostics and treatment of GIST.

Metastatic mesenteric dedifferentiated leiomyosarcoma: a case report and a review of literature.

BACKGROUND: Abdominal leiomyosarcoma arising from the mesentery is a rare malignancy. It is an aggressive entity with an overall 5 year survival rate between 20 and 30 %. Surgical resection is the cornerstone of primary treatment and may be curative for localized disease. However, patients often develop intra-abdominal relapse and/or metastatic disease. If surgical resection is not feasible, palliative chemotherapy is the treatment of choice. However, there are no clear guidelines regarding chemotherapy; neither in the adjuvant nor advanced setting. CASE PRESENTATION: We present a 40 year-old woman, with a mesenteric leiomyosarcoma, who underwent radical tumor resection and did not receive adjuvant oncological therapy. Three months postoperatively, she developed metastatic disease to the lungs and liver. After multidisciplinary assessment she received an unconventional histological-subtype-tailored chemotherapy comprising 3-4 regimens. Initially, there was a decrease both in number and size of metastases. Ultimately, an almost complete radiological response was seen. Subsequent surgical resection and radiofrequency ablation of residual metastatic foci in the liver and lung brought her into complete clinical remission. She is presently tumor free, 36 months following diagnosis of metastatic disease. CONCLUSIONS: To our knowledge, this is the first report of a patient with metastatic mesenteric leiomyosarcoma who is in complete clinical and radiological long-term remission following very aggressive multimodal treatment; including intense poly-drug chemotherapy and without any demonstrable long-term side effects. Given the rarity of mesenteric leiomyosarcoma and lack of guidelines regarding oncological therapy, we suggest that multimodal therapy including aggressive chemotherapy, guided by a multidisciplinary team, is essential to achieve an optimal outcome.