Diagnostic accuracy of tests for lymph node status in primary cervical cancer: a systematic review and meta-analysis

Background

Lymph node status is the key to determining the prognosis and treatment of cervical cancer. However, it cannot be assessed clinically, and testing for nodal metastasis is controversial. We sought to systematically review the diagnostic accuracy literature on sentinel node biopsy, positron emission tomography, magnetic resonance imaging and computed tomography to evaluate the accuracy of each index test in determining lymph node status in patients with cervical cancer.

Methods

We searched MEDLINE (1966–2006), EMBASE (1980–2006), Medion (1980–2006) and the Cochrane library (Issue 2, 2006) for relevant articles. We also manually searched the reference lists from primary articles and reviews, and we contacted experts in the field for conference abstracts and unpublished studies. We performed random-effects meta-analysis of accuracy indices, and we performed meta-regression analysis to test the effect of study quality on diagnostic accuracy and to identify other sources of heterogeneity.

Results

We included 72 relevant primary studies, involving a total of 5042 women, in our analysis. We found that, in determining lymph node status, sentinel node biopsy had a pooled positive likelihood ratio of 40.8 (95% confidence interval [CI] 24.6–67.6) and a pooled negative likelihood ratio of 0.18 (95% CI 0.14–0.24). The pooled positive likelihood ratios (and 95% CI) were 15.3 (7.9–29.6) for positron emission tomography, 6.4 (4.9–8.3) for magnetic resonance imaging and 4.3 (3.0–6.2) for computed tomography. The pooled negative likelihood ratios (and 95% CIs) were 0.27 (0.11–0.66) for positron emission tomography, 0.50 (0.39–0.64) for magnetic resonance imaging and 0.58 (0.48–0.70) for computed tomography. Using a 27% pretest probability of lymph node metastasis among all cases (regardless of stage), we found that a positive sentinel node biopsy result increased post-test probability to 94% (95% CI 90%–96%), whereas a positive finding on positron emission tomography increased it to 85% (75%–92%).

Interpretation

Sentinel node biopsy has greater accuracy in determining lymph node status among women with primary cervical cancer than current commonly used imaging methods.In the United States and European Union it is estimated that cervical cancer is diagnosed in about 42 000 women each year.^1,2 The International Federation of Gynecology and Obstetrics criteria currently used to stage cervical cancer do not account for lymph node involvement, but the lymphatic spread of the disease is key to determining prognosis and appropriate treatment.The primary treatment options for early cervical cancer (stage 1B1 or less advanced) are surgery and chemoradiotherapy, which have similar survival rates.³ Surgical treatment offers some degree of fertility preservation and may not have the long-term complications associated with chemoradiotherapy. However, because it is not possible to clinically detect pelvic and para-aortic lymph node metastasis, surgery typically includes lymphadenectomy, which may reveal metastatic spread. In such cases, chemoradiotherapy is required, which would make the initial surgical procedure unnecessary in retrospect. There has been considerable interest in using a preoperative, noninvasive test to determine lymph node status in order to select the most appropriate treatment option. Such a test could avoid unnecessary surgical intervention, reduce morbidity and correctly direct choice of treatment.In recent years, the use of magnetic resonance imaging and computed tomography to determine lymph node status has increased; however, neither method has been formally included as part of International Federation of Gynecology and Obstetrics staging of cervical cancer. Sentinel node biopsy and positron emission tomography have emerged as competitors to magnetic resonance imaging and computed tomography. The accuracy of magnetic resonance imaging, computed tomography and positron emission tomography has been assessed previously in reviews,^4–6 but updates are required because recent studies have reported on their diagnostic accuracy⁷ and on quality assessment in diagnostic reviews.⁸ Given this background, we performed a systematic review of the literature to compare the accuracy of these 4 methods in determining lymph node status in patients with cervical cancer.     

Persistent epithelial dysfunction and bacterial translocation after resolution of intestinal inflammation

Epithelial secretion may play an important role in reducing bacterial colonization and translocation in intestine. If so, secretory dysfunction could result in increased susceptibility to infection and inflammation. We investigated whether long-term colonic secretory dysfunction occurs after a bout of colitis and if this is accompanied by an increase in bacterial colonization and translocation. Rats were studied 6 wk after induction of colitis with trinitrobenzene sulfonic acid when inflammation had completely resolved, and epithelial permeability was normal. Intestinal loops were stimulated with either Clostridium difficile toxin A or a phosphodiesterase inhibitor. In vitro, colonic tissue from previously sensitized rats was exposed to antigen (ovalbumin). Secretory responses to all three stimuli were suppressed in rats that had previously had colitis. These rats exhibited increased (16-fold) numbers of colonic aerobic bacteria and increased (>3-fold) bacterial translocation, similar to results in rats studied after resolution of enteritis. Postcolitis bacterial translocation was prevented by daily treatment with an inhibitor of inducible nitric oxide synthase. This study demonstrates that intestinal inflammation results in prolonged impairment of colonic epithelial secretion, which may contribute to increases in bacterial load and bacterial translocation. Epithelial dysfunction of this type could underlie an increased propensity for further bouts of inflammation, a hallmark of diseases such as inflammatory bowel disease.     

Evolutionary optimization of classifiers and features for single-trial EEG Discrimination

Background  

State-of-the-art signal processing methods are known to detect information in single-trial event-related EEG data, a crucial aspect in development of real-time applications such as brain computer interfaces. This paper investigates one such novel approach, evaluating how individual classifier and feature subset tailoring affects classification of single-trial EEG finger movements. The discrete wavelet transform was used to extract signal features that were classified using linear regression and non-linear neural network models, which were trained and architecturally optimized with evolutionary algorithms. The input feature subsets were also allowed to evolve, thus performing feature selection in a wrapper fashion. Filter approaches were implemented as well by limiting the degree of optimization.     

Agonist-dependent desensitization of the kappa opioid receptor by G protein receptor kinase and beta-arrestin.

We used the Xenopus oocyte expression system to examine the regulation of rat kappa opioid receptor (rKOR) function by G protein receptor kinases (GRKs). kappa agonists increased the conductance of G protein-activated inwardly rectifying potassium channels in oocytes co-expressing KOR with Kir3.1 and Kir3.4. In the absence of added GRK and beta-arrestin 2, desensitization of the kappa agonist-induced potassium current was modest. Co-expression of either GRK3 or GRK5 along with beta-arrestin 2 significantly increased the rate of desensitization, whereas addition of either beta-arrestin 2, GRK3, or GRK5 alone had no effect on the KOR desensitization rate. The desensitization was homologous as co-expressed delta opioid receptor-evoked responses were not affected by KOR desensitization. The rate of GRK3/beta-arrestin 2-dependent desensitization was reduced by truncation of the C-terminal 26 amino acids, KOR(Q355Delta). In contrast, substitution of Ala for Ser within the third intracellular loop [KOR(S255A,S260A, S262A)] did not reduce the desensitization rate. Within the C-terminal region, KOR(S369A) substitution significantly attenuated desensitization, whereas the KOR(T363A) and KOR(S356A,T357A) point mutations did not. These results suggest that co-expression of GRK3 or GRK5 and beta-arrestin 2 produced homologous, agonist-induced desensitization of the kappa opioid receptor by a mechanism requiring the phosphorylation of the serine 369 of rKOR.     

CDC28 phosphorylates Cac1p and regulates the association of chromatin assembly factor i with chromatin

Chromatin Assembly Factor I (CAF-I) plays a key role in the replication-coupled assembly of nucleosomes. It is expected that its function is linked to the regulation of the cell cycle, but little detail is available. Current models suggest that CAF-I is recruited to replication forks and to chromatin via an interaction between its Cac1p subunit and the replication sliding clamp, PCNA, and that this interaction is stimulated by the kinase CDC7. Here we show that another kinase, CDC28, phosphorylates Cac1p on serines 94 and 515 in early S phase and regulates its association with chromatin, but not its association with PCNA. Mutations in the Cac1p-phosphorylation sites of CDC28 but not of CDC7 substantially reduce the in vivo phosphorylation of Cac1p. However, mutations in the putative CDC7 target sites on Cac1p reduce its stability. The association of CAF-I with chromatin is impaired in a cdc28–1 mutant and to a lesser extent in a cdc7–1 mutant. In addition, mutations in the Cac1p-phosphorylation sites by both CDC28 and CDC7 reduce gene silencing at the telomeres. We propose that this phosphorylation represents a regulatory step in the recruitment of CAF-I to chromatin in early S phase that is distinct from the association of CAF-I with PCNA. Hence, we implicate CDC28 in the regulation of chromatin reassembly during DNA replication. These findings provide novel mechanistic insights on the links between cell-cycle regulation, DNA replication and chromatin reassembly.