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International audience; BACKGROUND: Recent studies suggest improvements in response to salvage chemotherapy (CT) after immune checkpoint inhibitors (ICIs) in several types of cancer. Our objective was to assess the efficacy of chemotherapy re-challenge after ICI, compared with second-line chemotherapy without previous ICI in patients with locally advanced or metastatic urothelial carcinoma (la/mUC). METHODS: In this multicentre retrospective study, we included all patients with la/mUC initiating second or third-line chemotherapy from January 2015 to June 2020. We compared patients treated with second-line chemotherapy without previous ICI (CT2) and patients treated with third-line chemotherapy after ICI (CT3). The primary end-point was objective response rate (ORR) in CT3 compared with CT2. Secondary end-points included progression-free survival (PFS) and toxicities. RESULTS: Overall, 553 patients were included. ORRs were 31.0% (95% CI, 26.5 to 35.5) and 29.2% (95% CI, 21.9 to 36.6), respectively, in CT2 and CT3, with no statistically significant differences (P = 0.62). In subgroup analyses, no differences in ORR were observed by Bellmunt risk group, type of chemotherapy (platinum or taxanes), duration of response to first-platinum-based chemotherapy (< or ≥ 12 months) or FGFR-status. Median PFS was 4.6 months (95% CI, 3.9 to 5.1) and 4.9 months (95% CI, 4.1 to 5.5) in CT2 and CT3, respectively, and grade 3-4 hematologic toxicity occurred in 35.0% and 22.4% of patients. CONCLUSION: This large multicentre retrospective study provides clinically relevant real-world data. Chemotherapy re-challenge after ICI in la/mUC achieves ORR and PFS comparable with those obtained in CT2 with an acceptable safety profile. These updated results offer more promising outcomes than historically reported with second-line chemotherapy data.

International audience; BACKGROUND: Early detection of ESR1 mutations is a key element for better personalization of the management of patients with HR+/HER2- Metastatic Breast Cancer (MBC). Analysis of circulating tumor DNA from liquid biopsies is a particularly well-suited strategy for longitudinal monitoring of such patients. MATERIALS AND METHODS: Using the naica® three-color digital PCR platform, we developed a screening assay allowing the detection of 11 ESR1 mutations and designed a sequential strategy for precise mutation identification. We then applied this strategy in the analysis of plasma circulating cell-free DNA from 109 HR+/HER2- MBC patients and performed a double-blind comparison study on a subset of patients with the multiplex assay used at the Institut Curie (IC) for the PADA-1 study. RESULTS: Thirty-one patients (28.4%) harboured at least one ESR1 mutation, with the following frequencies: D538G (41.03%), Y537S (25.64%), E380Q (10.26%), Y537N (10.26%), "(536-540)" (7.69%), Y537C (2.56%), and L536R (2.56%). The presence of ESR1 mutation(s) was significantly associated with liver metastases (p = 0.0091). A very good agreement (91%) was observed with the IC assay. CONCLUSION: Our assays have proven to be robust and highly sensitive and are very well-suited for monitoring ESR1 mutations in the plasma of MBC patients.

430 Background: Primary urethral cancer (PUC) is a rare and heterogeneous malignancy. Due to its scarcity, little data are available on the optimal treatment sequence and survival, especially in metastatic patients. Methods: Data from patients diagnosed with a PUC between 01/01/2000 and 12/31/2018 were retrospectively collected from nine French referral centers. Survival rate were estimated with the Kaplan-Meier method and prognostic factors were analyzed using the Cox proportional hazards model and the log-rank test. In order to increase the statistical power of survival analysis in the metastatic stage, patients with synchronous and metachronous metastatic disease were pooled. Results: We identified 44 (62%) males and 27 (38%) females with a PUC. The most frequent histological types were urothelial carcinomas (40.0%), squamous cell carcinomas (34.3%) and adenocarcinomas (14.3%). Twenty-five (35.2%) patients were diagnosed at a localized stage (≤ T2, N0, M0); 35 (49.3%) at a locally advanced stage (≥ T3 or ≥ N1, M0) and 11 (15.5%) at a distant stage (M1). Twenty-seven patients had a metachronous metastatic cancer. Multimodality therapy was used in 24.0% and 57.1% of the patients with a localized and locally advanced disease, respectively. In the entire cohort, median overall survival (OS) was 52.5 months (IC95% 32.2 – 64.1) and stage at diagnosis was a predictor of OS (p < 0.0001). For the 60 patients with a non-metastatic disease, 39 (65%) had a recurrence or were dead and the median disease-free survival (DFS) was 21.2 months (IC95% 16.8 – 34.5). Nodal involvement was the only factor associated with DFS (HR: 2.03, p = 0.0390). Multimodal treatment compared with unimodal treatment was not significantly associated with DFS (HR: 1.22, p = 0.5419). Regarding survival of the 38 metastatic patients, the median OS was 15.2 months (IC95% 8.2 – 23.5) and the median progression-free survival was 6.4 months (IC95% 4.4 – 9.8). Conclusions: This retrospective study showed an important heterogeneity in terms of histology, stage at diagnosis, and treatment of PUC. In this cohort, the multimodal approach did not show any improvement in survival of non-metastatic patients. This study is one of the few to describe the survival in metastatic patients.

492 Background: Immune checkpoints inhibitors (ICIs) have recently changed therapeutic landscape of la/mUC. Recent studies suggested an improvement of response to salvage chemotherapy (CT) after ICIs in several cancer types including urothelial carcinoma. We assumed that efficacy of CT rechallenge after ICIs may be improved compared to second-line CT without previous ICIs in patients (pts) with la/mUC. Methods: CIMUC is a French multicentric retrospective study including all pts with la/mUC initiating second or third-line CT from January 1st 2015 to June 30th 2020. Two groups of pts were defined: pts in group 1 (G1) were treated with a second-line CT without previous ICIs; pts in group 2 (G2) were treated with third line CT after ICIs. Primary endpoint was objective response rate (ORR: proportion of patients with complete or partial response, according to RECIST 1.1 criteria) in G2 versus G1. Secondary endpoints were progression-free survival (PFS), defined as time from initiation of second or third-line CT to disease progression or death from any cause, and toxicities. This study is supported by the French Genito Urinary Group (GETUG). Results: 553 pts were included. Baseline characteristics of the 2 groups are summarized in the Table. ORRs were 31% (95%CI [26.5-35.5]) and 29.2% (95%CI [21.9-36.6]) respectively in G1 and G2, without statistically significant difference (p=0.617), even after adjustment for Bellmunt risk factors (p=0.3214). In subgroups analysis, no difference in ORR was observed by type of CT (platinum or taxanes), duration of response (DOR) to first-platinum-based CT (< 12 months or ≥ 12 months) and FGFR-status. We did not identify any predictive factor of OR in G2 in multivariate analysis. Median PFS were 4.6 months (95%CI [3.88; 5.06]) and 4.86 months (95%CI [4.11; 5.45]), respectively in G1 and G2. Grade 3/4 hematologic toxicity occurred in 35% and 22.4%, respectively in G1 and G2. Conclusions: While ORR was not superior in G2 versus G1, pts derive comparable benefit in a further line of treatment (G2) in terms of ORR and PFS. Despite limits inherent to any retrospective study, CIMUC represents one of the largest retrospective studies in this setting.[Table: see text]