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Louis de Mestier, Jean-Baptiste Danset, Cindy Neuzillet, Vinciane Rebours, Jérôme Cros, Nadem Soufir, and Pascal Hammel

Germline BRCA2 mutations are the first known cause of inherited (familial) pancreatic ductal adenocarcinoma (PDAC). This tumor is the third most frequent cancer in carriers of germline BRCA2 mutations, as it occurs in around 10% of BRCA2 families. PDAC is known as one of the most highly lethal cancers, mainly because of its chemoresistance and frequently late diagnosis. Based on recent developments in molecular biology, a subgroup of BRCA2-associated PDAC has been created, allowing screening, early surgical treatment and personalized systemic treatment. BRCA2 germline mutation carriers who have ≥1 first-degree relative, or ≥2 blood relatives with PDAC, should undergo screening and regular follow-up based on magnetic resonance imaging and endoscopic ultrasound. The goal of screening is to detect early invasive PDAC and advanced precancerous lesions suitable for a stepwise surgical complete (R0) resection. Increasing evidence on the molecular role of the BRCA2 protein in the homologous recombination of DNA damages suggest that BRCA2-related PDAC are sensitive to agents causing DNA cross-linking damage, such as platinum salts, and treatments targeting rescue DNA repair pathways, such as poly(ADP-ribose) polymerase inhibitors that are currently under investigation.

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Louis de Mestier, Clarisse Dromain, Gaspard d'Assignies, Jean-Yves Scoazec, Nathalie Lassau, Rachida Lebtahi, Hedia Brixi, Emmanuel Mitry, Rosine Guimbaud, Frédéric Courbon, Michèle d'Herbomez, and Guillaume Cadiot

Well-differentiated neuroendocrine tumors (NETs) are a group of heterogeneous rare tumors. They are often slow-growing and patients can have very long survival, even at the metastatic stage. The evaluation of tumor progression and therapeutic responses is currently based on Response Evaluation Criteria In Solid Tumors v1.1 (RECIST) criteria. As for other malignancies, RECIST criteria are being reexamined for NETs in the era of targeted therapies because tumor response to targeted therapies is rarely associated with shrinkage, as opposed to prolonged progression-free survival. Therefore, size-based criteria no longer seem to be suitable to the assessment of NET progression and therapeutic responses, especially considering targeted therapies. New imaging criteria, combining morphological and functional techniques, have proven relevant for other malignancies treated with targeted therapies. To date, such studies have rarely been conducted on NETs. Moreover, optimizing the management of NET patients also requires considering clinical, biological, and pathological aspects of tumor evolution. Our objectives herein were to comprehensively review current knowledge on the assessment of tumor progression and early prediction of therapeutic responses and to broaden the outlook on well-differentiated NETs, in the era of targeted therapies.

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Louis de Mestier, Anne Couvelard, Anela Blazevic, Olivia Hentic, Wouter W de Herder, Vinciane Rebours, Valérie Paradis, Philippe Ruszniewski, Leo J Hofland, and Jérôme Cros

The efficacy of alkylating agents (temozolomide, dacarbazine, streptozotocin) in patients with advanced neuroendocrine tumors (NETs) has been well documented, especially in pancreatic NETs. Alkylating agents transfer methyl adducts on DNA bases. Among them, O6-methylguanine accounts for many of their cytotoxic effects and can be repaired by the O6-methylguanine-methyltransferase (MGMT). However, whether the tumor MGMT status could be a reliable biomarker of efficacy of alkylating agents in NETs is still a matter of debate. Herein, we sought to provide a critical appraisal of the role of the MGMT status in NETs. After reviewing the molecular mechanisms of repair of DNA damage induced by alkylating agents, we aimed to comprehensively review the methods of determination of the MGMT status and its impact on prognosis, prediction of objective response and progression-free survival in patients with advanced digestive NETs treated by alkylating agents. About half of pancreatic NETs are MGMT-deficient, as determined by impaired tumor MGMT expression or by MGMT promoter methylation. Overall, while published studies are heterogeneous and mostly limited in size, they advocate that MGMT deficiency may be a relevant biomarker for increased objective response rate, prolonged progression-fee survival and overall survival in patients with advanced NETs treated by alkylating agents. While these data require confirmation in prospective controlled studies, future research should focus on the standardization of MGMT status assessment. Additional mechanisms of repair of DNA damages induced by alkylating agents should be explored in order to identify biomarkers complementary to MGMT and targets for potential antitumor synergy, such as PARP.

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Ophélie De Rycke, Thomas Walter, Marine Perrier, Olivia Hentic, Catherine Lombard-Bohas, Romain Coriat, Guillaume Cadiot, Anne Couvelard, Philippe Ruszniewski, Jérôme Cros, and Louis de Mestier

A rechallenge is common after the initial efficacy of alkylating-based chemotherapy (ALK) in pancreatic neuroendocrine tumors (PanNET). High MGMT expression seems associated with a lower response to ALK. We aimed to evaluate the efficacy and toxicity of ALK rechallenge in PanNET, and to assess the evolution of MGMT expression under ALK. All consecutive patients with advanced PanNETs who received initial ALK (achieving tumor control) followed by a pause of > 3 months, then an ALK rechallenge (ALK2) upon progression were retrospectively studied (cohort A). The primary endpoint was progression-free survival under ALK2 (PFS2). The MGMT expression was retrospectively assessed by immunohistochemistry (H-score) in consecutive PanNET surgically resected following ALK (cohort B). We found that Cohort A included 62 patients (median Ki67 8%), for whom ALK1 followed by a pause achieved an objective response rate of 55% and a PFS1 of 23.7 months (95% IC, 19.8–27.6). ALK2 achieved no objective response and stability in 62% of patients. The median PFS2 was 9.2 months (IC 95% 7.1–11.3). At multivariable analysis, a hormonal syndrome (P = 0.032) and a pause longer than 12 months (P = 0.041) were associated with a longer PFS2. In cohort B (17 patients), the median MGMT H-score increased from 45 (IQR 18–105) before ALK to 100 (IQR 56–180) after ALK (P = 0.003). We conclude that after the initial efficacy of ALK treatment, a pause followed by ALK rechallenge might be appropriate to prolong tumor control, improve quality of life and limit long-term adverse events. Increased MGMT expression under ALK might explain the low efficacy of ALK rechallenge.

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Louis de Mestier, Angela Lamarca, Jorge Hernando, Wouter Zandee, Teresa Alonso-Gordoa, Marine Perrier, Annemieke M E Walenkamp, Bipasha Chakrabarty, Stefania Landolfi, Marie-Louise F. Van Velthuysen, Gursah Kats-Ugurlu, Alejandra Carminoa, Maxime Ronot, Prakash Manoharan, Alejandro Garcia-Alvarez, Tessa Brabander, María Isabel García Gómez-Muriel, Guillaume Cadiot, Anne Couvelard, Jaume Capdevilla, Marianne E Pavel, and Jerome Cros

There is no standardized treatment for grade 3 neuroendocrine tumors (G3 NETs). We aimed to describe the treatments received in patients with advanced G3 NETs and compare their efficacy. Patients with advanced digestive G3 NETs treated between 2010 and 2018 in seven expert centers were retrospectively studied. Pathological samples were centrally reviewed, and radiological data were locally reviewed. We analyzed RECIST-defined objective response (OR), tumor growth rate (TGR) and progression-free survival (PFS) obtained with first- (L1) or second-line (L2) treatments. We included 74 patients with advanced G3 NETs, mostly from duodenal or pancreatic origin (71.6%), with median Ki-67 of 30%. The 126 treatments (L1=74; L2=52) included alkylating-based (n=32), etoposide-platinum (n=22) or adenocarcinoma-like chemotherapy (n=20), somatostatin analogs (n=21), targeted therapies (n=22) and liver-directed therapies (n=7). Alkylating-based chemotherapy achieved the highest OR rate (37.9%) compared to other treatments (multivariable OR 4.22, 95% CI [1.5-12.2]; p=0.008). Adenocarcinoma-like and alkylating-based chemotherapies showed the highest reductions in 3-month TGR (p<0.001 and p=0.008, respectively). The longest median PFS were obtained with adenocarcinoma-like chemotherapy (16.5 months [9.0-24.0]) and targeted therapies (12.0 months [8.2-15.8]), while the shortest PFS were observed with somatostatin analogues (6.2 months [3.8-8.5]) and etoposide-platinum chemotherapy (7.2 months [5.2-9.1]). Etoposide-platinum CT achieved shorter PFS than adenocarcinoma-like (multivariable HR 3.69 [1.61-8.44], p=0.002) and alkylating-based chemotherapies (multivariable HR 1.95 [1.01-3.78], p=0.049). Overall, adenocarcinoma-like and alkylating-based chemotherapies may be the most effective treatments for patients with advanced G3 NETs regarding OR and PFS. Etoposide-platinum chemotherapy has poor efficacy in this setting.