Randomized phase II multicenter trial | EXTEND Investigators | n = 41 randomized | Oligometastatic PDAC | Journal of Clinical Oncology 2024 **Ludmir et al.** Ethan B. Ludmir, Alexander D. Sherry, Chad Tang Published in Journal of Clinical Oncology, 2024 Enrollment: 2019–2023 [PubMed Link](https://pubmed.ncbi.nlm.nih.gov/39102622/) --- ### Essential Takeaway EXTEND showed that adding comprehensive metastasis-directed therapy to systemic therapy improved progression-free survival compared with systemic therapy alone in patients with oligometastatic pancreatic ductal adenocarcinoma. This is important because it provides randomized evidence supporting the existence of an oligometastatic disease state in PDAC and suggests that carefully selected patients may benefit from treatment of all visible disease sites. --- ### Clinical Question Does adding metastasis-directed therapy to systemic therapy improve progression-free survival compared with systemic therapy alone in oligometastatic pancreatic ductal adenocarcinoma? --- ### Population - Oligometastatic PDAC - ≤5 metastatic lesions - Metastases amenable to metastasis-directed therapy - ECOG performance status 0–2 - ≤4 prior lines of systemic therapy for metastatic disease - Patients could have synchronous or metachronous oligometastatic disease Most patients had 1–2 metastatic lesions. - 41 patients randomized - 40 patients included in the per-protocol PFS analysis - 19 patients in MDT arm - 21 patients in control arm --- ### Study Design #### Arm 1 — MDT + Systemic Therapy - Metastasis-directed therapy (MDT) to all active radiologic disease: definitive local treatment of all visible metastatic disease sites, most commonly with stereotactic ablative radiotherapy. - Primary tumor treated as applicable - Systemic therapy continued at treating oncologist discretion MDT was usually radiotherapy: - Most metastases treated with stereotactic ablative radiotherapy - Some lesions treated with radiofrequency ablation #### Arm 2 — Systemic Therapy Alone - Standard systemic therapy chosen by treating oncologist - Crossover to MDT permitted at progression --- ### Endpoints #### Primary Endpoint Progression-free survival in the per-protocol population Progression included: - RECIST 1.1 radiographic progression - clinical progression - death #### Secondary Endpoints - Overall survival - Time to next-line systemic therapy - Time to local failure - Time to new lesion formation - Toxicity - Quality of life #### Exploratory Endpoints - Systemic immune response measures --- ### Key Results #### Progression-Free Survival MDT significantly improved PFS: - 10.3 vs 2.5 months - HR 0.43 - p = 0.030 At 1 year, PFS was: - 42% with MDT + systemic therapy - 9% with systemic therapy alone --- #### Overall Survival No statistically significant OS improvement was shown: - 12 vs 10 months - HR 0.58 - p = 0.20 The trial was not powered for OS, and crossover was permitted. --- #### Time to Next-Line Systemic Therapy Numerically longer with MDT: - 19 vs 8 months - HR 0.53 - p = 0.24 This suggests MDT may help delay treatment escalation or transition to next-line therapy in selected patients. --- ### Toxicity No grade 3 or higher adverse events related to MDT were observed. No grade 4 or 5 treatment-emergent adverse events occurred, regardless of attribution. Quality-of-life comparisons were limited by sample size and did not show clear differences. --- ### Additional Findings #### Supports an Oligometastatic PDAC State EXTEND provides the strongest randomized evidence to date that a clinically meaningful oligometastatic state may exist in pancreatic cancer. #### Comprehensive MDT Was the Strategy The intervention was not treatment of a single lesion. The MDT arm treated **all active radiologic disease**, including metastases and the primary tumor when applicable. This matters because the trial tests a comprehensive disease-control strategy rather than isolated palliation. #### Possible Immune Mechanism Exploratory translational analyses suggested systemic immune activation after MDT. Findings included: - increased activated CD8+ T-cell populations - increased IL-15 signaling - T-cell receptor clonal expansion - associations between immune activation markers and improved PFS/OS These findings are hypothesis-generating. --- ### Interpretation EXTEND is a small but important randomized trial suggesting that selected patients with oligometastatic PDAC may benefit from comprehensive local therapy to all visible disease sites. The trial does not establish MDT as a universal standard for metastatic PDAC, but it supports MDT as a reasonable consideration in carefully selected patients with limited metastatic burden, controlled disease biology, and technically treatable lesions. The main signal is PFS benefit, not proven OS benefit. --- ### Important Limitations #### Small Phase II Trial Only 41 patients were randomized, and 40 were included in the primary PFS analysis. #### Not Powered for Overall Survival The OS analysis was limited by small numbers, crossover, and non-cancer deaths. #### Broad Eligibility Patients could have variable metastatic timing, prior therapy exposure, and disease sites. #### Selection Bias Remains Important Even though randomized, the population was highly selected by definition: - limited number of lesions - MDT-feasible disease - good performance status - no history of polymetastatic disease #### Hypothesis-Generating Immune Data The immune correlates are interesting but exploratory and should not be overinterpreted. --- ### Practice Impact EXTEND supports considering metastasis-directed therapy in highly selected patients with oligometastatic PDAC, especially when all active disease sites can be treated safely. For HPB surgeons, the trial is relevant because it strengthens the rationale for multidisciplinary discussion of oligometastatic PDAC rather than automatically treating all metastatic recurrence as uniformly systemic and non-local. Potential practice implications: - supports tumor board discussion of oligometastatic PDAC - reinforces importance of disease biology and treatment response - may justify MDT/SBRT/ablation in selected patients - should not be generalized to polymetastatic or rapidly progressive PDAC