Citations

617 Background: Currently, there is no published data on the efficacy of SSAs for well-differentiated G3 NETs. Randomized trials have demonstrated a progression-free survival (PFS) benefit and limited tumor response for lower grade 1-2 NETs, but the optimal systemic therapy for metastatic/unresectable G3 NETs is unknown. We sought to evaluate the efficacy of SSAs in G3 NETs. Methods: We performed a retrospective analysis of Mayo Clinic patients treated with SSAs for metastatic/unresectable G3 NETs, querying data from 1992 - present. Inclusion criteria were: centrally reviewed pathology confirming well-differentiated morphology, G3 based on WHO classification, SSA monotherapy, and radiological data available to assess response. Patients who had prior lines of treatment were included as long they subsequently were treated with single-agent SSA. Poorly-differentiated tumors were excluded. The primary endpoint was PFS. Best overall response was determined by radiographic regression, stabilization, or progression of tumor size. Results: Ninety patient records were reviewed, with 14 meeting inclusion criteria (diagnosed 2014 – 2018). Median Ki-67 proliferative index was 25%. Two patients (14%) had a partial response to SSA therapy, five (36%) had stable disease, and seven (50%) had progressive disease. The estimated median PFS was 4.4 months (95% CI 2.9 – 24). Of the 7 patients with stable disease or partial response, the median time to progression was 8.7 months. Three patients had stable disease for greater than 9 months (24, 29 and 42 months, respectively). Overall survival was not estimable. There was no association of Ki-67 index with PFS based on a proportional hazards model. Conclusions: This is the first report on the efficacy of SSAs for G3 NETs. Although half of the patients in our series had at least stable disease, the PFS was modest at only 4.4 months. Given their favorable side-effect profile compared to cytotoxic chemotherapy, SSAs may present an attractive option to be further explored in a prospective fashion. We are presently updating this data by reassessing response using RECIST criteria.

321 Background: G3 NENs are aggressive, and optimal systemic treatment is unclear. Temozolomide (TEM)-based regimens have been used to treat grade 1-2 NETs, but their efficacy in G3 NENs (Ki-67 > 20%) remains undetermined. Aims: To assess the clinical efficacy of TEM-containing regimens in advanced grade III gastroenteropancreatic NENs (GEPNENs). Methods: A multicentre retrospective review (2008-2017) of patients with metastatic/unresectable G3 GEPNENs who received a TEM-containing regimen. The primary endpoint was time to treatment failure (TTF). Radiologic response was extracted from local reports without formal RECIST criteria. Results: 118 patients in six centers were included (median age 55, 65% male, 15% functional, 75% pancreatic NEN). 57% were well-differentiated, 35% poorly-differentiated, and 18% unknown based on local pathology reports. The regimen used was CAPTEM in 93% and TEM in 7%. Best radiological responses were: complete response (1%), partial response (39%), stable disease (22%), progressive disease (31%), unknown (7%) not by RECIST. Median TTF was 150 days and median overall survival (OS) 18.0 months. Fifteen patients (14%) required dose reductions/discontinuation due to adverse events. TTF was shorter for patients on TEM alone (p = 0.02, Table 1). Well-differentiated NENs had better response rate (52% vs 26%, p = 0.02) and overall survival (30.1 vs 12.0 mo, p = 0.008) compared to poorly-differentiated NEN. Conclusions: This is the largest TEM treatment series in G3 NEN, involving collaboration of several major North American NET centers. 40% of patients showed some degree of response, and treatment was generally well-tolerated. TEM-based regimens should be considered a viable treatment option in this setting. Prospective confirmatory trials (such as EA2142) may face difficulties in accrual due to disease rarity. [Table: see text]