On approximate pseudo-maximum likelihood estimation for LARCH-processes

Linear ARCH (LARCH) processes were introduced by Robinson [J. Econometrics 47 (1991) 67--84] to model long-range dependence in volatility and leverage. Basic theoretical properties of LARCH processes have been investigated in the recent literature. However, there is a lack of estimation methods and corresponding asymptotic theory. In this paper, we consider estimation of the dependence parameters for LARCH processes with non-summable hyperbolically decaying coefficients. Asymptotic limit theorems are derived. A central limit theorem with $\sqrt{n}$-rate of convergence holds for an approximate conditional pseudo-maximum likelihood estimator. To obtain a computable version that includes observed values only, a further approximation is required. The computable estimator is again asymptotically normal, however with a rate of convergence that is slower than $\sqrt{n}.$Comment: Published in at http://dx.doi.org/10.3150/09-BEJ189 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Cultivation of circulating tumor cells in esophageal cancer

The presence of circulating tumor cells (CTCs) in patients with metastatic carcinoma is generally associated with poor clinical outcome. There have been many investigations showing a possible use of CTCs as minimally invasive predictive and prognostic biomarker in cancer medicine. In this report a size-based method (MetaCell®) for quick and easy enrichment and cultivation of CTCs is presented to enable possible CTCs use in esophageal cancer (EC) management. In total, 43 patients with diagnosed EC, 20 with adenocarcinoma (AdenoCa) and 23 with squamous cell carcinoma (SCC), were enrolled into the adaptive prospective-like study .All the patients were candidates for surgery. The CTCs were detected in 27 patients (62.8%), with a higher rate in adenocarcinoma (75%) than SCC (52%). Finally, there were 26 patients with resectable tumors exhibiting CTCs-positivity in 69.2% and 17 patients with non-resectable tumors with 41.7% CTCs-positivity. Interestingly, in the patients undergoing neoadjuvant therapy, the CTCs were detected at time of surgery in 55.5% (10/18). The overall size-based filtration approach enabled to isolate viable CTCs and evaluate to their cytomorphological features by means of vital fluorescent staining. The CTCs were cultured in vitro for further downstream applications including immunohistochemical analysis. This is the first report of the successful culturing of esophageal cancer CTCs. The detection of CTCs presence could help in the future to guide timing of surgical treatment in EC patients

Tumours of the thymus: a cohort study of prognostic factors from the European Society of Thoracic Surgeons database

OBJECTIVES A retrospective database was developed by the European Society of Thoracic Surgeons, collecting patients submitted to surgery for thymic tumours to analyse clinico-pathological prognostic predictors. METHODS A total of 2151 incident cases from 35 institutions were collected from 1990 to 2010. Clinical-pathological characteristics were analysed, including age, gender, associated myasthenia gravis stage (Masaoka), World Health Organization histology, type of thymic tumour [thymoma, thymic carcinoma (TC), neuroendocrine thymic tumour (NETT)], type of resection (complete/incomplete), tumour size, adjuvant therapy and recurrence. Primary outcome was overall survival (OS); secondary outcomes were the proportion of incomplete resections, disease-free survival and the cumulative incidence of recurrence (CIR). RESULTS A total of 2030 patients were analysed for OS (1798 thymomas, 191 TCs and 41 NETTs). Ten-year OS was 0.73 (95% confidence interval 0.69-0.75). Complete resection (R0) was achieved in 88% of the patients. Ten-year CIR was 0.12 (0.10-0.15). Predictors of shorter OS were increased age (P < 0-001), stage [III vs I HR 2.66, 1.80-3.92; IV vs I hazard ratio (HR) 4.41, 2.67-7.26], TC (HR 2.39, 1.68-3.40) and NETT (HR 2.59, 1.35-4.99) vs thymomas and incomplete resection (HR 1.74, 1.18-2.57). Risk of recurrence increased with tumour size (P = 0.003), stage (III vs I HR 5.67, 2.80-11.45; IV vs I HR 13.08, 5.70-30.03) and NETT (HR 7.18, 3.48-14.82). Analysis using a propensity score indicates that the administration of adjuvant therapy was beneficial in increasing OS (HR 0.69, 0.49-0.97) in R0 resections. CONCLUSIONS Masaoka stages III-IV, incomplete resection and non-thymoma histology showed a significant impact in increasing recurrence and in worsening survival. The administration of adjuvant therapy after complete resection is associated with improved surviva

From short to long memory: Aggregation and estimation

Contemporaneous aggregation of asymptotically stationary AR(1) processes is considered where the squared random coefficients are beta-distributed. Based on the sample correlation coefficients for the individual AR(1) processes, an estimator for the parameters of the underlying beta distribution, and thus for the long memory parameter of the aggregated process, is introduced. Consistency and asymptotic normality are derived and the new estimator is shown to be asymptotically equivalent to the maximum likelihood estimator of the beta distribution.

Tumours of the thymus: a cohort study of prognostic factors from the European Society of Thoracic Surgeons database.

OBJECTIVES: A retrospective database was developed by the European Society of Thoracic Surgeons, collecting patients submitted to surgery for thymic tumours to analyse clinico-pathological prognostic predictors. METHODS: A total of 2151 incident cases from 35 institutions were collected from 1990 to 2010. Clinical-pathological characteristics were analysed, including age, gender, associated myasthenia gravis stage (Masaoka), World Health Organization histology, type of thymic tumour [thymoma, thymic carcinoma (TC), neuroendocrine thymic tumour (NETT)], type of resection (complete/incomplete), tumour size, adjuvant therapy and recurrence. Primary outcome was overall survival (OS); secondary outcomes were the proportion of incomplete resections, disease-free survival and the cumulative incidence of recurrence (CIR). RESULTS: A total of 2030 patients were analysed for OS (1798 thymomas, 191 TCs and 41 NETTs). Ten-year OS was 0.73 (95% confidence interval 0.69–0.75). Complete resection (R0) was achieved in 88% of the patients. Ten-year CIR was 0.12 (0.10–0.15). Predictors of shorter OS were increased age (P < 0–001), stage [III vs I HR 2.66, 1.80–3.92; IV vs I hazard ratio (HR) 4.41, 2.67–7.26], TC (HR 2.39, 1.68–3.40) and NETT (HR 2.59, 1.35–4.99) vs thymomas and incomplete resection (HR 1.74, 1.18–2.57). Risk of recurrence increased with tumour size (P = 0.003), stage (III vs I HR 5.67, 2.80–11.45; IV vs I HR 13.08, 5.70–30.03) and NETT (HR 7.18, 3.48–14.82). Analysis using a propensity score indicates that the administration of adjuvant therapy was beneficial in increasing OS (HR 0.69, 0.49–0.97) in R0 resections. CONCLUSIONS: Masaoka stages III–IV, incomplete resection and non-thymoma histology showed a significant impact in increasing recurrence and in worsening survival. The administration of adjuvant therapy after complete resection is associated with improved survival