BackgroundProstate cancer is one of the most common cancers in men and the fourth leading cause of cancer mortality worldwide. Although major progress has been achieved in the last years for patients with metastatic castrate-resistant prostate cancer (mCRPC), thanks to next-generation androgen receptor axis targeted drugs, taxanes, and bone-targeted agents, immunotherapy has not been widely approved and used for the treatment of prostate cancer. Two large studies with ipilimumab, an anti-CTLA-4 (cytotoxic T-lymphocyte antigen 4) antibody reported improved progression-free survival, but not statistically improved overall survival at the primary analysis (CA184 043 and CA184 095).Case presentationHere, we report on two patients who received ipilimumab in these trials and are still in long-term complete remission with a follow-up of 64 and 52 months respectively after the initiation of ipilimumab. Immunohistochemical staining for hMLH1, hMSH2, hMSH6 and PMS2 was performed on archival prostate biopsy samples from one of the two patients; they exhibited normal protein expression. Interestingly for this patient, a high CD3+ and CD8+ T cell infiltration was observed on archival prostate biopsies as well as Treg FoxP3+ T cells.ConclusionIpilimumab produces clinical activity in patients with CRPC, including very long responders with no detectable residual disease.

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e16527 Background: Gastric cancer (GC) occurs in 50% of case after 70 years old (y/o). Radical surgery or perioperative treatments have to be balanced with safety management in those potential frail patients. Methods: We perfomed a retrospective review of our single institution database to address the outcome of patient (pts) > 70y/o who underwent radical surgery for GC with or without neoadjuvant and adjuvant treatment. Results: From 2005 to 2019, 60 eligible patients (pts) have undergone radical surgery for resectable GC. Median age at diagnosis was 74.2y/o [70.3-92.8] and 82% were male. Initial echoendoscopy staged 12% of T1/T2 tumor versus 70% of T3/T4, whereas 60% were found with lymph node spreading (N+). 80% of pts were given neoadjuvant treatment: chemoradiation (58%), chemotherapy (45%) or radiation alone (1%). 1/4 pt received perioperative chemotherapy. Only one patient had post-operative radiation with FOLFOX and none had adjuvant radiation alone. Surgery procedure was total (27%) or sub-total (5%) gastrectomy, polar-oesogastrectomy with thoracotomy (18%) or without thoracotomy (50%). Post-operative mortality within 3 months was 5% (n = 3) including 2 pts in the first 30 days. For the global cohort, median overall survival (mOS) was 44.75 months and median progression free survival (mPFS) was 21.2 months. Patients who frontly underwent radical surgery (n = 15, 25%) had small disease with 13% pT0 and 60% of pT1 on final pathology. Only 27% had pT2/T3 but all had vascular and/or peri-nervous emboli. Two of them (13%) were pN+. The mOS was 60 months and mPFS 60 months in this cohort and 33% of pts end/was lost of follow up. Only one metastatic relapse was identifies and no local relapse. Six pts died (40%): 2 in the 30-days post surgery (13%), 3 (30%) from other cause than GC and 1 (7.5%) because of GC distant relapse. The cohort treated with neoadjuvant chemotherapy (n = 45, 75%) was given platinum and anthracycline-based regimen in 73% and 16% of cases, respectively. 1% received fluoropyrimidine +/- irinotecan. 53% associated radiation to neoadjuvant chemotherapy. After neoadjuvant treatment completion, 47% of downstaging (including 18% of pCR), 33% of stable stage and 15.5% of upstaging was observed and 40% of initial usN+ was pN0. After perioperative treatment, mOS was 31 months and mPFS was 18.9 months. Overall 44% experienced local and/or distant relapse. Conclusions: Age above 70y/o should not systematically exclude patient from neoadjuvant or perioperative treatment and radical surgery, which is feasible in selected population displaying long term result in focal and distant disease control.

e16737 Background: Brain metastases (BM) occur extremely rare in pancreatic adenocarcinoma (PDAC) and few data are available regarding those patients‘ care and outcomes. Methods: We performed a retrospective monocentric analysis of our database to identify patients (pts) diagnosed with PDAC and BM from July 1997 to December 2019. Results: 16 pts were eligible among 4900 pts diagnosed with PDAC in our institution (0.3%). Median age was 64 years (38.2-74.6) with 50% female. At diagnosis, 68.8% were metastatic including 27.3% with synchronous BM. About 1/3 pts had ≥ 2 lines of chemotherapy before BM. BM were discovered from neurological symptoms in 62% of cases and either with systematic brain CT/MRI or unknown in 19% for both. BM treatment was: surgery (25%), whole brain radiation therapy (RT) (43.8%), stereotactic RT (6.3%), radiosurgery (6.3%), best supportive care (BSC) or unknown (6.3%). At follow-up cutoff date (01/01/2020), most of pts were dead (75%), 2 were alive and 2 lost of follow-up. Mean interval between initial diagnosis and BM was 9.9 months (mths) (0-73). Median time to develop BM was different between pts with non-metastatic or metastatic disease at diagnosis: 16.3 mths (6.5-44) and 4.2 mths (0-36.1), respectively (HR = 0.43 (CI95: 0.14-1.09; p = 0.09)). Median overall survival (mOS) was 14.5 mths (1.6-80.2). Definitely, the non-metastatic group at diagnosis had better survival with mOS of 40.2 mths (24.7-80.2) compared to 6.5 mths (1.7-49.8) for the metastatic group (HR = 0.24 (CI95: 0,06-0,63; p = 0.012)). The median survival period after diagnosis of BM was only 3.4 mths (0.5-13.7). Pts who underwent BM surgery had better survival with a median survival from surgery of 5.5 months (4-13.7) compared to RT (0.8 mths (0.4-2)) or BSC (0.6 mths (0.5-5.9)). HR for surgery versus RT was 0.12 (CI95: 0.02-0.31; p = 0.003). After BM diagnosis, 43.8% of patients had a systemic chemotherapy, without objective response on BM. One interesting metastatic pt with BRCA1 mutation achieved a complete response (CR) after FOLFIRINOX. One BM occurred 2 years after diagnosis, was treated with surgery + RT but relapsed 4.5 mths later with new BM. Extra-cranial CR was persistent. This pt, still alive, had the longest survival period after diagnosis of BM (13.7 mths) and OS (49.8 months). Conclusions: To our knowledge, this is one of the largest cohort reported of BM in PDAC. Very few cases exist to guide therapy. Surgery appears to be the best treatment for BM, when feasible. Further investigations are still needed to understand the pathogenicity of BM in pancreatic cancer.