Nerves enable cancer progression, as cancers have been shown to extend along nerves through the process of perineural invasion, which carries a poor prognosis. Furthermore, the innervation of some cancers promotes growth and metastases. It remains unclear, however, how nerves mechanistically contribute to cancer progression. Here, we demonstrated that Schwann cells promote cancer invasion through direct cancer cell contact. Histological evaluation of murine and human cancer specimens with perineural invasion uncovered a subpopulation of Schwann cells that associates with cancer cells. Coculture of cancer cells with dorsal root ganglion extracts revealed that Schwann cells direct cancer cells to migrate toward nerves and promote invasion in a contact-dependent manner. Upon contact, Schwann cells induced the formation of cancer cell protrusions in their direction and intercalated between the cancer cells, leading to cancer cell dispersion. The formation of these processes was dependent on Schwann cell expression of neural cell adhesion molecule 1 (NCAM1) and ultimately promoted perineural invasion. Moreover, NCAM1-deficient mice showed decreased neural invasion and less paralysis. Such Schwann cell behavior reflects normal Schwann cell programs that are typically activated in nerve repair but are instead exploited by cancer cells to promote perineural invasion and cancer progression.

Background: Thermal ablation is a definitive local treatment for selected colorectal liver metastases (CLM) that can be ablated with adequate margins. A critical limitation has been local tumor progression (LTP). Methods: This prospective, single-group, phase 2 study enrolled patients with CLM < 5 cm in maximum diameter, at a tertiary cancer center between November 2009 and February 2019. Biopsy of the ablation zone center and margin was performed immediately after ablation. Viable tumor in tissue biopsy and ablation margins < 5 mm were assessed as predictors of 12-month LTP. Results: We enrolled 107 patients with 182 CLMs. Mean tumor size was 2.0 (range, 0.6–4.6) cm. Microwave ablation was used in 51% and radiofrequency ablation in 49% of tumors. The 12- and 24-month cumulative incidence of LTP was 22% (95% confidence interval [CI]: 17, 29) and 29% (95% CI: 23, 36), respectively. LTP at 12 months was 7% (95% CI: 3, 14) for the biopsy tumor-negative ablation zone with margins ≥ 5 mm vs. 63% (95% CI: 35, 85) for the biopsy-positive ablation zone with margins < 5 mm (p < 0.001). Conclusions: Biopsy-proven complete tumor ablation with margins of at least 5 mm achieves optimal local tumor control for CLM, regardless of the ablation modality used.

63 Background: Trastuzumab-based therapy is the standard therapeutic approach for patients with metastatic HER2+ esophagogastric (EG) tumors. While trastuzumab prolongs survival in this population, responses are rarely complete and resistance invariably develops. Loss of HER2 and presence of co-occurring molecular alterations may impact the efficacy of HER2 targeted agents in second line setting. Methods: We reviewed clinical and pathologic data of patients (pts) with metastatic HER2+ (IHC 3+ or FISH >2.0) EG adenocarcinoma undergoing trastuzumab/chemotherapy treatment at MSKCC. Samples with ample tissue were analyzed using an on-site 341 cancer-associated gene bait capture, next generation sequencing (NGS) assay. When available, biopsy at the time of disease progression on trastuzumab was tested for HER2 by IHC and FISH. Results: Eighty four pts with Stage IV HER2+ EG adenocarcinoma (57 IHC 3+, 27 IHC2+/FISH+) treated with trastuzumab with chemotherapy. Median progression free survival on 1^stline trastuzumab therapy 9.4 months (mos) [95%CI: 6.9-13.3 mos]. Median overall survival 20.3 mos [95%CI: 14.7-22.4 mos]. Post-trastuzumab biopsy available in 23 of 84 (27%) pts, of those 35% (8 of 23) lost HER2 positivity (4-IHC 0, 4 FISH negative). NGS performed on 24 of 84 (28%) samples. Alterations were observed in EGFR (13%), TP53 mut (92%), cell cycle mediators such as cyclin dependent kinases (42%) and the phosphoinositide 3-kinase/AKT/mTOR axis (21%). Conclusions: Loss of HER2 expression occurs in patients with HER2+ EG cancer treated with trastuzumab and presents a possible mechanism for trastuzumab resistance. Our data suggest the need for repeat biopsies to accurately determine appropriate use of second-line HER2 directed therapy.

Tumor evolution and intratumor heterogeneity in colorectal carcinoma: insights from comparative genomic profiling of primary tumors and matched metastases

Local recurrences at the anastomotic area are clonally related to the primary tumor in sporadic colorectal carcinoma