Regression vs. Controls identified 43 significantly up-regulated mRNAs, linked to interferon-α response, and down-regulation of 99 mRNAs, linked to TNF-α signaling via NF-kB, inflammatory response, epithelial-mesenchymal transition, KRAS signaling, and hypoxia (FDR≤0.05).<h4>Conclusions</h4>In regressive fibrosis of PM-PC after systemic chemotherapy and PIPAC (Regression), downregulation of mRNAs related to key tumor biological pathways was identified. This evidence concerns the gene NFKB1 and neoplasm.