| 1. |
- El Ouali, Mourad, et al.
(författare)
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An approximation algorithm for the partial vertex cover problem in hypergraphs
- 2016
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Ingår i: Journal of combinatorial optimization. - : SPRINGER. - 1382-6905 .- 1573-2886. ; 31:2, s. 846-864
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Tidskriftsartikel (refereegranskat)abstract
- Let be a hypergraph with set of vertices and set of (hyper-)edges . Let be the maximum size of an edge, be the maximum vertex degree and be the maximum edge degree. The -partial vertex cover problem in hypergraphs is the problem of finding a minimum cardinality subset of vertices in which at least hyperedges are incident. For the case of and constant it known that an approximation ratio better than cannot be achieved in polynomial time under the unique games conjecture (UGC) (Khot and Ragev J Comput Syst Sci, 74(3):335-349, 2008), but an -approximation ratio can be proved for arbitrary (Gandhi et al. J Algorithms, 53(1):55-84, 2004). The open problem in this context has been to give an -ratio approximation with , as small as possible, for interesting classes of hypergraphs. In this paper we present a randomized polynomial-time approximation algorithm which not only achieves this goal, but whose analysis exhibits approximation phenomena for hypergraphs with not visible in graphs: if and are constant, and , we prove for -uniform hypergraphs a ratio of , which tends to the optimal ratio 1 as tends to . For the larger class of hypergraphs where , is not constant, but is a constant, we show a ratio of . Finally for hypergraphs with non-constant , but constant , we get a ratio of for , leaving open the problem of finding such an approximation for k < m/4(.)
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| 2. |
- Fohlin, Helena, 1979-
(författare)
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Long-term prognostic and predictive factors in hormone receptor positive breast cancer
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The breast cancer survival in Sweden is good (almost 90 % 5-year relative survival) and has increased over time. For women with hormone receptor negative tumors, most relapses occur within the first 5 years after diagnosis. Thereafter the recurrence risk decreases rapidly. For women with estrogen receptor positive (ER+) tumors the annual risk for late recurrences is 1 – 2 %, even after 5 years of endocrine therapy. This risk accumulates so that approximately 25 % of the patients that are recurrence-free after five years from diagnosis may experience a relapse within further 15 years of follow-up. The relatively high long-term risk calls for identification of prognostic and predictive markers with long-term effect. Though, the number of such markers with proven significance is limited. Of the clinical characteristics, only nodal status and to some extent tumor size and tumor grade have been shown to have long-term prognostic value. In this thesis, we propose long-term prognostic and predictive markers for breast cancer.In paper I, we suggest the protein v-akt murine thymoma viral oncogene homologue 2 (AKT2) as a long-term prognostic marker among patients with ER+ tumors. In our study, besides nodal status, AKT2 was the only factor with long-term prognostic value. This is in accordance with some other studies, though we also showed that the significance of AKT2 was limited to ER+ tumors and that the impact increased with higher ER expression.Approximately 75 – 85 % of the ER+ tumors are also progesterone receptor positive (PR+). ER+/progesterone receptor negative (PR-) tumors are considered to be more aggressive and patients with such tumors are often treated with chemotherapy. In this group, more specific subgroups for targeted therapy are needed.Whereas ER has long been established as a predictive factor regarding tamoxifen benefit, the role of PR has not been clarified to date. In paper II, we showed that PR status adds predictive value to ER considering the long-term benefit from tamoxifen.In paper III, we aimed to identify new prognostic markers among patients with ER+ tumors. Systemically untreated patients with ER+/PR- tumors and high expression of the Ras-related protein RAB6C (RAB6C) had reduced distant recurrence rate. Therefore, we suggest RAB6C as a candidate marker for subgroup division among patients with ER+/PR- tumors.According to the results from paper II, there might be subgroups of patients with ER+/PRtumors that do benefit from tamoxifen. The aim of paper IV was to identify such subgroups. Here, we suggest that patients with ER+/PR- tumors and low RAB6C expression do benefit from tamoxifen.The results from this thesis may encourage further studies for more specific subgroup divisions. Such studies may lead to changes in the management program, where some patients with ER+ tumors should receive prolonged or more intense treatment and others reduced treatment based on the pathological markers AKT2, PR and RAB6C.
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| 3. |
- Johansson, Henrik J, et al.
(författare)
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Proteomics profiling identify CAPS as a potential predictive marker of tamoxifen resistance in estrogen receptor positive breast cancer
- 2015
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Ingår i: Clinical Proteomics. - : Springer Science and Business Media LLC. - 1542-6416 .- 1559-0275. ; 12:1, s. 8-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Despite the success of tamoxifen since its introduction, about one-third of patients with estrogen (ER) and/or progesterone receptor (PgR) - positive breast cancer (BC) do not benefit from therapy. Here, we aim to identify molecular mechanisms and protein biomarkers involved in tamoxifen resistance.RESULTS: Using iTRAQ and Immobilized pH gradient-isoelectric focusing (IPG-IEF) mass spectrometry based proteomics we compared tumors from 12 patients with early relapses (<2 years) and 12 responsive to therapy (relapse-free > 7 years). A panel of 13 proteins (TCEAL4, AZGP1, S100A10, ALDH6A1, AHNAK, FBP1, S100A4, HSP90AB1, PDXK, GFPT1, RAB21, MX1, CAPS) from the 3101 identified proteins, potentially separate relapse from non-relapse BC patients. The proteins in the panel are involved in processes such as calcium (Ca(2+)) signaling, metabolism, epithelial mesenchymal transition (EMT), metastasis and invasion. Validation of the highest expressed proteins in the relapse group identify high tumor levels of CAPS as predictive of tamoxifen response in a patient cohort receiving tamoxifen as only adjuvant therapy.CONCLUSIONS: This data implicate CAPS in tamoxifen resistance and as a potential predictive marker.
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| 4. |
- Nordenskjöld, Anna, 1969, et al.
(författare)
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Breast cancer survival trends in different stages and age groups - a population-based study 1989-2013
- 2019
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Ingår i: Acta Oncologica. - : TAYLOR & FRANCIS LTD. - 0284-186X .- 1651-226X. ; 58:1, s. 45-51
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Tidskriftsartikel (refereegranskat)abstract
- Background: During the recent decades, breast cancer survival has gradually improved but there is limited knowledge on the improvement in population-based studies of patients diagnosed with different stages of the disease and in different age groups.Patients and methods: In two Swedish health care regions a total of 42,220 female breast cancer patients below 90years of age were diagnosed between 1989 and 2013. They were treated and followed according to national and regional guidelines and formed a population-based cohort.Results: Using patients diagnosed in 1989-1993 as a reference to the relative risk, 5-year mortality decreased with 49% for patients diagnosed at the end of the observation period (CI 95% 45-58). The mortality tended to decrease for patients with all stages of breast cancer and test for trend resulted in a statistically significant improvement over time in 5-year relative survival in stage III and IV and in 10-year survival in stage I and III. For each operable stage of disease, patients aged below 40years or more than 70years when diagnosed tended to have less favorable survival than patients diagnosed between 40-69years of age. Test for trend resulted in statistically significant improvements over time for patients diagnosed at ages below 40, 40-54 and 54-69, but less marked improvements for patients older than 70 when diagnosed.Conclusions: During the period 1989-2013 the relative risk of 5-year mortality decreased with 49%. Improvements were seen in all age groups but were unevenly distributed between stages and age groups pointing to the need for further improvements for younger and elderly patients.
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| 5. |
- Nordenskjöld, Anna, 1969, et al.
(författare)
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No clear effect of postoperative radiotherapy on survival of breast cancer patients with one to three positive nodes: a population-based study
- 2015
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Ingår i: Annals of Oncology. - : Oxford University Press (OUP): Policy B - Oxford Open Option F. - 0923-7534 .- 1569-8041. ; 26:6, s. 1149-1154
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Tidskriftsartikel (refereegranskat)abstract
- Background: In published radiotherapy trials, the failure rate in the control arm among patients with one to three positive nodes is high compared with that seen with modern adjuvant treatments. Therefore, the generalizability of the results has been questioned. The aim of the present study was to compare relative survival in breast cancer patients between two Swedish regions with screening mammography programs and adjuvant treatment guidelines similar with the exception of the indication of radiotherapy for patients with one to three positive nodes. Patients and methods: Between 1989 and 2006, breast cancer patients were managed very similarly in the west and southeast regions, except for indication for postoperative radiotherapy. In patients with one to three positive nodes, post-mastectomy radiotherapy was generally given in the southeast region (89% of all cases) and generally not given in the west region (15% of all cases). For patients with one to three positive nodes who underwent breast-conserving surgery, patients in the west region had breast radiotherapy only, while patients in the southeast region had both breast and lymph nodes irradiated. Results: The 10-year relative survival for patients with one to three positive lymph nodes was 78% in the west region and 77% in the southeast region (P = 0.12). Separate analyses depending on type of surgery, as well as number of examined nodes, also revealed similar relative survival. Conclusion: Locoregional postoperative radiotherapy has well-known side-effects, but in this population-based study, there was little or no influence of this type of radiotherapy on survival when one to three lymph nodes were involved.
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| 6. |
- Nordenskjöld, Anna, 1969, et al.
(författare)
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Progesterone receptor positivity is a predictor of long-term benefit from adjuvant tamoxifen treatment of estrogen receptor positive breast cancer
- 2016
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Ingår i: Breast Cancer Research and Treatment. - : Springer Science and Business Media LLC. - 0167-6806 .- 1573-7217. ; 160:2, s. 313-322
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The independent predictive information from progesterone receptor (PgR) positivity for breast cancer treated with tamoxifen has been questioned after an overview by the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). However, the studies in the overview were to a large content performed before modern PgR immunohistochemistry (IHC) was developed. We therefore investigated the predictive value of PgR determined with IHC in estrogen receptor (ER)-positive tumors from patients participating in the Stockholm trial of adjuvant tamoxifen therapy. Methods: The Stockholm Breast Cancer Study Group conducted a randomized trial during 1976 through 1990 comparing adjuvant tamoxifen versus control. The patients were stratified according to tumor size and lymph node status in high-risk and low-risk groups. In this study, we evaluated 618 patients with ER-positive “low-risk” breast cancer (size≤30mm, lymph node-negative) for whom PgR was determined by IHC at one pathology laboratory. The median time of follow-up was 21years. Results: Patients with ER-positive tumors that were also PgR-positive by IHC did benefit from tamoxifen, while we could not show any long-term benefit for those with tumors positive for ER only (recurrence rate ratio 0.43, 95% CI 0.29–0.62 and 0.87, 95% CI 0.52–1.46, respectively). We further investigated the influence of different levels of PgR positivity on recurrence risk. The results show that at all receptor levels with≥10% stained PgR-positive cells, the patients did benefit from tamoxifen. There was no clear linear trend in benefit with increasing proportion of stained cells. Conclusions: PgR positivity determined by IHC is a marker indicating long-term benefit from adjuvant tamoxifen in patients with ER-positive tumors. © 2016, The Author(s).
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