Sites of gastric cancer recurrence after adjuvant chemoradiotherapy

68

Background: Since the Intergroup 0116 study in 2000, adjuvant post-operative chemoradiotherapy (CRT) has been offered routinely to similar patients with resected gastric cancer at Princess Margaret Hospital (PMH) using CT-planned and 3D conformal/intensity modulated radiotherapy (RT). The objective of this study was to analyze patterns of recurrence with respect to RT treatment volumes.

Methods: Date and site (local, locoregional or distant) of first recurrence data was obtained from chart review for all patients treated at PMH with adjuvant CRT for resected gastric adenocarcinoma (Jan. 1, 2000-Nov. 30, 2009). Patients whose recurrences were limited to local (gastric remnant, duodenal margin, gastric bed recurrence) and/or regional sites (regional lymph node recurrence) were selected for analysis. When available, diagnostic imaging of recurrence site was registered to the original planning RT dataset. The center of mass for each recurrence was identified as a point and its location categorized according to the isodose encompassing it; in-field (≥ 90%), marginal (50%-89%), and out-of-field (< 50%).

Results: Three-year OS, and RFS were 66% (95% CI: 58-73) and 58% (50-60), respectively. Of 203 patients treated, 75 recurrences were identified (Table). Of the 13 local/locoregional recurrences, 4 were in-field, 1 marginal, 1 could not be registered due to change in body habitus, and 7 did not have an available original dataset.

Conclusions: Rates of isolated local and/or regional recurrence in this study were low. This represents a change in the pattern seen with surgery alone suggesting the addition of CRT results in decreased isolated local and/or regional recurrence. Of the small number of local and/or regional recurrences available for analysis, all were in-field or marginal. Further studies involving a larger cohort of patients might allow for more meaningful analysis of trends in recurrence site with evolving RT techniques.

[Table: see text]

No significant financial relationships to disclose.

Bacterial genetic loci implicated in the Pseudomonas putida GR12-2R3--canola mutualism: identification of an exudate-inducible sugar transporter

Pseudomonas putida GR12-2R3 promotes the emergence and growth of diverse plant species. Analyses of TnphoA insertion mutations are revealing bacterial characteristics pertinent to the plant-microbe interaction. Pseudomonas putida PG269 is a TnphoA insertion derivative of GR12-2R3 that expresses canola seed exudate-inducible alkaline phosphatase (PhoA) activity. It promoted the growth of canola roots, as well as strain GR12-2R3, and outgrew its parent when they were cocultured in the presence of canola roots or in liquid seed exudate medium. (In contrast, mutant PG126 failed to promote canola root growth and was outgrown by its parent strain.) The PhoA activity of strain PG269 was induced by glucosamine and other sugars; glucosamine inhibited the growth of strain GR12-2R3 and stimulated the growth of strain PG269. Strain PG269 contained two TnphoA insertions: seiA1::TnphoA and seiB1::TnphoA. Strain PG312, which contained only insertion seiA1::TnphoA, shared all aspects of the PG269 phenotype, except the ability to outcompete strain GR12-2R3 during coculture. Insertion seiA1::TnphoA interrupted an open reading frame related in sequence to members of the MalF family of sugar transporter subunits. The PhoA-inducing fraction of canola seed exudate was hydrophilic, low in molecular weight, and heat stable. It cochromatographed with basic amino acids and amino sugars, and was inactivated by strains GR12-2R3 and PG269. Gene seiA may encode a subunit of an ABC transporter with broad specificity for glucose and related sugars whose expression can be induced by exudate sugars.