Differential benefit from fractionated dose-dense first-line chemotherapy for epithelial ovarian cancer (EOC) according to KELIM-evaluated tumor primary chemosensitivity: Exploratory analyses of ICON-8 trial

Abstract

Background: ICON8 phase III trial did not show improvement in PFS or OS with first-line weekly dose-dense chemotherapy in EOC. This analysis evaluated the impact of tumor intrinsic primary chemosensitivity (assessed with modeled CA-125 ELIMination rate constant K (KELIM) based on the CA-125 kinetics during the first 100 days of chemo), on survival by treatment arms. Methods: Retrospective analysis of ICON8 where EOC patients were treated with chemo (Arm 1, standard (std) carboplatin AUC5-6 & paclitaxel 175mg/m2 q3weeks; Arm 2, carboplatin AUC 5-6 q3weeks and weekly paclitaxel 80 mg/m2; or Arm 3, weekly carboplatin AUC 2 & paclitaxel 80 mg/m2; ratio1:1:1) and debulking primary surgery (immediate (IPS), or delayed (DPS)). The association between standardized KELIM (dichotomized as favorable ≥ 1, or unfavorable < 1) and efficacy of treatment arms and surgery completeness was assessed univariate & multivariate analyses. Results: Of 1,566 enrolled patients, KELIM was calculated in 1,004 with ≥ 3 CA-125 available values. KELIM did not differ by treatment arm. Irrespective of surgical strategy, both KELIM and surgery completeness were significant prognostic factors, but treatment arms were not. In 354 IPS patients, 225 had unfavorable KELIM (63%). Weekly dose-dense carboplatin-paclitaxel (Arm 3) (compared to std chemo-Arm 1) was associated with improved survival in unfavorable KELIM patients (PFS:19.6 vs 11.0 months, HR 0.80 [0.54-1.17]; OS : 53.7 vs 40.1 months, HR 0.75 [0.50-1.14]), and worse survival in those with favorable KELIM (PFS: 26.7 vs 48.2 months, HR 1.27 [0.72-2.22]; OS: NR vs 69.2 months, HR 1.05 [0.53-2.06]). Maximum benefit was seen in highest-risk diseases (unfavorable KELIM + incomplete IPS; n = 116; PFS: 17.0 vs 7.4 months, HR 0.49 [0.29-0.82]; OS: 42.6 vs 27.0 months, HR 0.56 [0.33-0.96]). In 611 patients treated with neo-adjuvant chemo +/- DPS (279 unfavorable KELIM, 46%), the same trend for higher survival benefit from dose-dense carboplatin-paclitaxel was found in those with unfavorable KELIM (PFS: 10.8 vs 7.4 months, HR 0.84 [0.63-1.13]; OS: 26.4 vs 23.5 months, HR 0.80 [0.60-1.08]), and reversely. The higher KELIM, the higher the likelihood of complete surgery (OR 4.82 [3.21-7.37]). The prognostic impact of the surgery completeness was greater in unfavorable KELIM patients. Conclusions: In ICON8 trial, both the tumor primary chemosensitivity (by KELIM) and completeness of debulking surgery were major drivers of the prognosis & survival. Dose-dense fractionated chemotherapy in 1st-line setting may be beneficial for patients with lower tumor chemosensitivity, whilst it might be detrimental in those with highly chemosensitive disease. The greatest OS benefit (HR 0.56) from dose-dense chemotherapy was seen in highest-risk diseases (unfavorable KELIM and incomplete IPS).