One-Year (Yr) Recurrence-Free Survival (Rfs) From A Randomized, Open Label Phase Ii Study Of Neoadjuvant (Neo) Talimogene Laherparepvec (T-Vec) Plus Surgery (Surgx) Versus Surgx For Resectable Stage Iiib-Ivm1a Melanoma (Mel).

9520 Background: We previously reported that neo T-VEC + surgx resulted in a pathologic CR rate of 21% and an OR rate of 14.7% in a randomized trial of neo T-VEC + surgx vs upfront surgx in pts with resectable stage IIIB/C/IVM1a MEL (Andtbacka et al, ASCO 2018; NCT02211131). Here, we present results from an interim 1-yr analysis of RFS. Methods: Patients (pts) with resectable stage IIIB/C/IVM1a MEL, ≥ 1 injectable cutaneous, subcutaneous, or nodal lesions ≥ 10 mm, and no systemic tx 3 mos prior were randomized 1:1 to 6 doses/12 wks of T-VEC followed by surgx during wks 13-18 (Arm 1) vs upfront surgx during wks 1-6 (Arm 2). T-VEC was given at standard dosing until surgx, no injectable tumors, or intolerance. This analysis conducted on the ITT set estimated a between-group difference in 1-yr RFS per protocol. An RFS event was defined as the first of local, regional or distant recurrence or death due to any cause after surgx. Pts without a R0 surgical outcome or withdrew prior to surgx were considered an event at randomization for RFS. In a sensitivity analysis, RFS was calculated from randomization to the date of the first post-surgx event regardless of surgical outcome. Results: 150 pts were randomized (76 Arm 1, 74 Arm 2). Median (range) follow-up time was 20.6 (0.1, 38.5) mos in Arm 1 and 20.0 (0.1, 35.3) mos in Arm 2. 75% in Arm 1 and 93% in Arm 2 had surgx as planned. R0, R1, and R2 rates, respectively, for Arm 1 were 42.1%, 31.6%, and 1.3% and for Arm 2 were 37.8%, 51.4%, and 4.1%. At 1 yr, 33.5% of pts in Arm 1 and 21.9% of pts in Arm 2 remained recurrence free (HR 0.73, P= 0.048). From the sensitivity analysis, 55.8% of pts in Arm 1 and 39.3 % in Arm 2 remain recurrence free at 1 yr (HR 0.63, P= 0.024). OS rates at 1 yr were 95.9% in Arm 1 and 85.8% in Arm 2 (HR 0.47, P= 0.076). Pts receiving subsequent adjuvant tx was 8 (11%) in Arm 1 and 20 (29%) in Arm 2- most common was immunotherapy 6 (8.2%) and 8 (11.6%), respectively. Conclusions: In the largest randomized neo trial to date in resectable stage IIIB-IVM1a MEL, the following outcomes were improved with neo T-VEC monotherapy vs surgx: R0 surgical resections, 1-yr RFS, and OS. Primary analysis of RFS at 2 yrs is expected. Clinical trial information: NCT02211131.