The peritoneum is a common site of metastasis in advanced gastric cancer (GC). Diagnostic laparoscopy is now routinely performed as part of disease staging, leading to an earlier diagnosis of synchronous peritoneal metastasis (PM). The biology of GCPM is unique and aggressive, leading to a dismal prognosis. These tumors tend to be resistant to traditional systemic therapy, and yet, this remains the current standard-of-care recommended by most international clinical guidelines. As this is an area of unmet clinical need, several translational studies and clinical trials have focused on addressing this specific disease state. Advances in genomic sequencing and molecular profiling have revealed several promising therapeutic targets and elucidated novel biology, particularly on the role of the surrounding tumor microenvironment in GCPM. Peritoneal-specific clinical trials are being designed with a combination of locoregional therapeutic strategies with systemic therapy. In this review, we summarize the new knowledge of cancer biology, advances in surgical techniques, and emergence of novel therapies as an integrated strategy emerges to address GCPM as a distinct clinical entity.
PTR was found to increase OS while stoma creation had no impact on OS. The benefits and safety of undergoing PTR may be a result of selection bias. Further prospective studies are required to confirm the observations of this study.
Immune checkpoint inhibition (ICI) is an established therapeutic option for patients with deficient mismatch repair or high levels of microsatellite instability tumors. Yet, response to ICI among this group is varied, with nearly one-third of patients exhibiting primary resistance. Initial efforts in studying mechanisms of resistance to ICI have focused on intrinsic tumor factors. Host factors such as metastatic niches have unique biological properties that may mediate resistance to ICI but have been less studied date. Patients with metastatic d-MMR/MSI-H gastrointestinal cancers and peritoneal metastases (PM) who had concurrent ascites have been recently shown to have worse outcomes with ICI therapy compared with patients with PM without ascites and patients with non-PM metastases. The juxtaposition of tumors with an intrinsic sensitivity to ICI failing to respond by virtue of the presence of ascites within the peritoneum, brings to the forefront the critical role of the metastatic niche. In this commentary, we discuss mechanisms for ICI resistance that may arise from the immunoprivileged state of the peritoneal cavity, paracrine factors within malignant ascites or tumor-peritoneum interactions. An improved understanding of the peritoneal microenvironment and the use of peritoneal-directed therapies may ameliorate the modest benefit of ICIs in this unique clinical entity.
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