Maithao N. Le

Gene polymorphisms predict toxicity to neoadjuvant therapy in patients with rectal cancer.

Toxicity from neoadjuvant chemoradiation therapy (NT) increases morbidity and limits therapeutic efficacy in patients with rectal cancer. The objective of this study was to determine whether specific polymorphisms in genes associated with rectal cancer response to NT were correlated with NT‐related toxicity.

Gene Expression Variations in Microsatellite Stable and Unstable Colon Cancer Cells

BACKGROUND Microsatellite instability (MSI) is a marker of chemoresistance, but it is associated with improved survival compared with microsatellite-stable (MSS) colon cancers. We hypothesized that MSI tumors overexpress chemoresistance-associated genes and underexpress DNA damage/repair genes. We used ultra high-throughput sequencing (UHTS) to assess the expression of representative genes in MSI and MSS colon cancer cell lines. METHODS Solexa UHTS was used to examine gene expression in HCT116 (MSI) and HT29 (MSS) cells, and normal colonic mucosa (NCM). We compared expression of 40 genes involved in chemoresistance, DNA repair, DNA damage, and drug metabolism pathways. RESULTS We observed gene expression differences between MSI and MSS cell lines in 8 out of 40 genes involved in mismatch repair (MMR), DNA repair, drug metabolism, and chemoresistance. MMR gene expression was lower in MSI cells, which is consistent with the MSI phenotype, whereas DNA repair genes were highly expressed in these cells. Genes associated with chemoresistance and drug metabolism also had increased expression in MSI cells. No difference in expression of DNA damage genes was observed between MSI and MSS cell lines. CONCLUSION Using UHTS gene expression analysis, we identified differential expression of genes between MSI and MSS cell lines which may account for resistance to chemotherapy in MSI tumors. UHTS expression analysis has the potential to identify genome-wide predictors of response or resistance to chemotherapy.

The extent of lymphadenectomy and overall survival depend on the timing of radiotherapy for rectal cancer.

540 Background: Accurate staging and local disease control depend on the extent of lymphadenectomy (LAD) in rectal cancer. Previous studies suggest that lymph node (LN) number varies with neoadjuvant therapies. Our objectives were to measure the impact of timing of radiotherapy on extent of LAD and to determine the prognostic role of LN number in rectal cancer. METHODS Patients undergoing curative-intent surgery for rectal adenocarcinoma (1988-2006) in Los Angeles County were identified from the Cancer Surveillance Program. Patients were grouped according to radiotherapy timing (neoadjuvant, adjuvant, or none). To measure prognostic significance, an optimal cutoff was assessed for patients with N0 disease by dichotomizing LN numbers from 3-7. RESULTS Query of the registry identified 6,358 patients. Of these, 20% (n = 1,280), 25% (n = 1,573), and 55% (n = 3,545) received neoadjuvant, adjuvant, and no radiotherapy, respectively. There was no difference in LN number in patients with and without radiotherapy (7 vs. 8 LNs, p = NS). However, within the radiotherapy cohort, there was significantly lower LNs in the neoadjuvant group (5 vs. 9 LNs, respectively; p < 0.001). Survival differences favored the groups with higher LN number. The optimal LN cutoff with no survival difference was 7 in the adjuvant radiotherapy group; there was no optimal cutoff for neoadjuvant therapy patients. CONCLUSIONS From our population-based cohort, we observed that patients receiving neoadjuvant radiotherapy had decreased LN retrieval and that LN number was non-prognostic. In contrast, the extent of LAD is a prognostic factor for overall survival in patients receiving adjuvant radiotherapy. [Table: see text] No significant financial relationships to disclose.

Minimally Invasive Gastrectomy for Gastric Cancer: A Single Institution Experience

third portion (D3) underwent segmental resection, while 1 patient with tumor at the second portion (D2) underwent standard Whipple resection and 1 patient with tumor at D2/D3 junction underwent standard Whipple with en bloc resection. On follow up, 5 patients are alive today (follow-up range 15-48 months) including 2 of the patients presenting with recurrent disease. Of these 5 patients, 2 had positive nodes and 3 had negative nodes. Since rescue surgery, all have no evidence of recurrent disease. Conclusion: Long-term survival can be achieved in select patients with initially unresectable duodenal adenocarcinoma. From our experience, neoadjuvant chemotherapy may improve resectability of previously unresectable duodenal adenocarcinoma.