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- Simán, Henrik, et al.
(författare)
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Helicobacter pylori and CagA seropositivity and its association with gastric and oesophageal carcinoma.
- 2007
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 1502-7708 .- 0036-5521. ; 42:8, s. 933-940
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Helicobacter pylori infection is an established risk factor for non-cardia gastric adenocarcinoma. Infection with H. pylori strains harbouring the cagA pathology island may augment this association. H. pylori infection may at the same time reduce the risk for oesophageal carcinoma. However, prospective data on the association between CagA seropositivity and gastric or oesophageal carcinomas are limited. The purpose of this study was to investigate whether CagA seropositivity among H. pylori seropositive subjects is associated with gastric or oesophageal carcinomas. Material and methods. A nested case-control study was performed in the Malmo Preventive Medicine cohort consisting of 32,906 middle-aged subjects. Tumour cases were identified by the Swedish National Cancer Registry. The Western blot method Helicoblot 2.1 was used to detect H. pylori and CagA seropositivity. Results. Non-cardia gastric adenocarcinoma was associated with H. pylori seropositivity, odds ratio 17.8 (95% CI: 4.2 - 74.8; 67 cases). The odds ratio for CagA seropositivity among H. pylori seropositive subjects was 9.7 ( 95% CI: 1.5 - infinity). No significant associations were found between cardia gastric adenocarcinoma and H. pylori or CagA seropositivity among H. pylori seropositive subjects; odds ratios were 1.5 ( 95% CI: 0.51 - 4.8) and 2.7 ( 95% CI: 0.38 - infinity), respectively ( 24 cases). Oesophageal adenocarcinoma and oesophageal squamous cell carcinoma were not significantly associated with H. pylori seropositivity or with CagA seropositivity among H. pylori seropositive subjects; the odds ratios associated with oesophageal adenocarcinoma were 0.46 ( 95% CI: 0.07 - 2.6) and 0.38 ( 95% CI: 0.02 - 24), respectively. Corresponding odds ratios for oesophageal squamous cell carcinoma were 0.44 ( 95% CI: 0.15 - 1.2; 37 cases) and 2.0 ( 95% CI: 0.24 - infinity), respectively. Conclusions. CagA seropositivity among H. pylori seropositive subjects is a risk factor for non-cardia gastric adenocarcinoma.
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- Carlsson, Fredrik, et al.
(författare)
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Using eigenstructure of the Hessian to reduce the dimension of the intensity modulated radiation therapy optimization problem
- 2006
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Ingår i: Annals of Operations Research. - : Springer Science and Business Media LLC. - 0254-5330 .- 1572-9338. ; 148:1, s. 81-94
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Tidskriftsartikel (refereegranskat)abstract
- Optimization is of vital importance when performing intensity modulated radiation therapy to treat cancer tumors. The optimization problem is typically large-scale with a nonlinear objective function and bounds on the variables, and we solve it using a quasi-Newton sequential quadratic programming method. This study investigates the effect on the optimal solution, and hence treatment outcome, when solving an approximate optimization problem of lower dimension. Through a spectral decompostion, eigenvectors and eigenvalues of an approximation to the Hessian are computed. An approximate optimization problem of reduced dimension is formulated by introducing eigenvector weights as optimization parameters, where only eigenvectors corresponding to large eigenvalues are included. The approach is evaluated on a clinical prostate case. Compared to bixel weight optimization, eigenvector weight optimization with few parameters results in faster initial decline in the objective function, but with inferior final solution. Another approach, which combines eigenvector weights and bixel weights as variables, gives lower final objective values than what bixel weight optimization does. However, this advantage comes at the expense of the pre-computational time for the spectral decomposition.
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