SEQTOR Phase III Trial Shows Equivalent Survival for Streptozotocin/5-FU and Everolimus Sequencing in Pancreatic NETs
Key Insights
The international SEQTOR phase III trial found no significant difference in 12-month progression-free survival between everolimus-first (71.4%) and streptozotocin/5-FU-first (61.8%) treatment sequences in advanced pancreatic neuroendocrine tumors (search).
Streptozotocin plus 5-fluorouracil demonstrated significantly higher objective response rates (30.3% vs 11.6%, P=.012) and more durable responses with median duration exceeding two years compared to everolimus first-line.
Both treatment sequences provided comparable overall survival outcomes, with median survival of 61.7 months for everolimus-first versus 50.6 months for streptozotocin/5-FU-first approaches.
The first randomized phase III trial to directly compare treatment sequencing strategies in advanced pancreatic neuroendocrine tumors (search) (panNETs (search)) has demonstrated that both everolimus-first and streptozotocin plus 5-fluorouracil (STZ/5-FU)-first approaches provide equivalent long-term disease control and overall survival. The international SEQTOR-GETNE study, published in ESMO Open in December 2025, offers critical evidence to guide personalized treatment decisions in this biologically heterogeneous disease.
Study Design and Patient Population
The SEQTOR trial was an international, open-label, randomized, crossover phase III study conducted across eight European countries. The study enrolled 141 patients with unresectable or metastatic, well-differentiated (WHO grade 1-2) panNETs (search) who had radiologic progression within 12 months or were treatment-naive. Patients were randomized 1:1 to receive either everolimus 10 mg daily followed by STZ/5-FU at progression, or the reverse sequence.
The study's primary endpoint was modified during the trial from combined progression-free survival (PFS) across both treatment lines to 12-month PFS after first-line therapy (12-month PFS1) due to slow accrual and longer-than-expected survival outcomes. Key secondary endpoints included PFS to first and second treatments, overall response rate (ORR), duration of response, overall survival, and safety.
Primary Efficacy Results
The trial failed to demonstrate a statistically significant difference in its primary endpoint of 12-month PFS1 between treatment sequences. The 12-month PFS1 rate was 71.4% (95% CI, 59.4%-81.6%) with upfront everolimus compared to 61.8% (95% CI, 49.2%-73.3%) with upfront STZ/5-FU (OR, 0.65; 95% CI, 0.32-1.32; P = .229). Median first-line PFS was similarly prolonged at 19.4 months (95% CI, 16.8-27.6) and 22.7 months (95% CI, 13.3-28.6), respectively (HR, 1.16; 95% CI, 0.77-1.75; P = .474).
Across both treatment lines, median PFS2 was approximately 9-10 months with either sequence, showing no meaningful difference between arms. Combined PFS1+2 exceeded 30 months in both treatment arms, demonstrating the substantial disease control achievable with sequential therapy.
Response Rates Favor STZ/5-FU
A clear difference emerged in tumor response rates, with STZ/5-FU achieving significantly higher response rates than everolimus regardless of treatment sequence. The first-line ORR was 30.3% with STZ/5-FU versus 11.6% with everolimus (P = .012). Per blinded independent review committee assessment, the ORR was 30.2% (95% CI, 19.2%-43.0%) versus 10.3% (95% CI, 4.2%-20.1%) in the respective arms (P = .004).
Responses to STZ/5-FU were highly durable, with median duration of response exceeding two years in the first-line setting at 25.2 months (95% CI, 22.3-35.1) compared to 4.5 months (95% CI, 0-35.2) for everolimus. This trend continued in the second-line setting, where STZ/5-FU maintained a 30.6% ORR versus 9.1% for everolimus.
Survival Outcomes and Subgroup Analyses
Overall survival was comparable between treatment sequences, with median OS of 61.7 months for everolimus-first and 50.6 months for STZ/5-FU-first approaches (HR, 1.43; 95% CI, 0.86-2.37). Exploratory subgroup analyses suggested that younger patients, those with ECOG performance status 0, and patients with grade 2 tumors derived particularly high response benefit from STZ/5-FU. Conversely, signals of better survival with upfront everolimus were observed in older patients, those with ECOG 1-2, and grade 1 tumors, although these findings were hypothesis-generating.
Safety and Tolerability Profile
Toxicity profiles reflected known class effects for both agents. Everolimus was associated with higher rates of mucositis, skin toxicity, hyperglycemia, edema, and pneumonitis, requiring significantly more dose reductions and treatment interruptions. Among patients treated with everolimus first, the incidence of grade 3 or greater toxicities was 55.1% versus 43.9% with STZ/5-FU first. STZ/5-FU was linked primarily to gastrointestinal symptoms and mild renal impairment, most often low grade. No toxic deaths occurred in either treatment arm.
Pneumonitis was reported in 7% versus 21% of patients treated with everolimus as first- or second-line therapy. Quality-of-life scores declined gradually over time in both arms with no major overall differences between sequences, although the everolimus-first group showed a more pronounced decline in physical functioning over time.
Clinical Implications for Treatment Selection
According to lead author Jaume Capdevila, MD, PhD, senior medical oncologist at Vall d'Hebron University Hospital, "Although the assessment of sequentiality was not feasible, both strategies provide comparable 12-month PFS1 rates, disease control, and OS, indicating that neither is superior as an initial option. [Streptozotocin plus 5-fluorouracil] achieves higher response rates regardless of treatment sequence, suggesting its selection as the preferred therapy when cytoreduction is necessary."
The SEQTOR trial provides the first prospective randomized evidence to guide treatment sequencing in advanced panNETs (search). While neither sequence demonstrated superior long-term outcomes, the significantly higher and more durable response rates with STZ/5-FU make it the preferred choice when rapid tumor shrinkage is clinically necessary. The study firmly supports a personalized treatment strategy where tumor grade, growth kinetics, patient fitness, comorbidities, and the clinical need for cytoreduction should guide first-line selection rather than a fixed sequencing algorithm.