P.M. van de Ven

Instability of MaxWeight Scheduling Algorithms

MaxWeight scheduling algorithms provide an effective mechanism for achieving queue stability and guaranteeing maximum throughput in a wide variety of scenarios. The maximum-stability guarantees however rely on the fundamental premise that the system consists of a fixed set of sessions with stationary ergodic traffic processes. In the present paper we examine a scenario where the population of active sessions varies over time, as sessions eventually end while new sessions occasionally start. We identify a simple necessary and sufficient condition for stability, and show that MaxWeight policies may fail to provide maximum stability. The intuitive explanation is that these policies tend to give preferential treatment to flows with large backlogs, so that the rate variations of flows with smaller backlogs are not fully exploited. In the usual framework with a fixed collection of flows, the latter phenomenon cannot persist since the flows with smaller backlogs will build larger queues and gradually start receiving more service. With a dynamic population of flows, however, MaxWeight policies may constantly get diverted to arriving flows, while neglecting the rate variations of a persistently growing number of flows in progress with relatively small remaining backlogs. We also perform extensive simulation experiments to corroborate the analytical findings.

Outcomes of concurrent chemoradiotherapy in patients with stage III non-small-cell lung cancer and significant comorbidity

BACKGROUND published trials of concurrent chemoradiotherapy (CCRT) in stage III non-small-cell lung cancer (NSCLC) generally excluded patients with significant comorbidity. We evaluated outcomes in patients who were selected by using radiation planning parameters and were considered, despite comorbidity, fit enough to receive cisplatin-based chemotherapy. PATIENTS AND METHODS from 2003 to 2008, 89 patients with stage III NSCLC fit to receive cisplatin-based chemotherapy and a V(20) <42% underwent CCRT at one center outside clinical trials. Most received one cycle of cisplatin-gemcitabine, followed by two to three cycles of cisplatin-etoposide concurrent with involved-field thoracic radiotherapy between 46 and 66 Gy. RESULTS median age was 64 years; performance status (PS) of zero, one or two in 20/64/5 patients; one or more comorbidities in 41.6%; 14% were treated previously for NSCLC. Median V(20) was 26.6% (range 4%-39.4%). Grade III esophagitis and pneumonitis occurred in 28.1% and 7.9% of patients, respectively, while 4.5% died during treatment. Median overall survival was 18.2 months [95% confidence interval (CI) 13.1-23.3 months]. Independent prognostic factors for overall survival were PS (0 versus ≥ 1, P = 0.041) and planning target volume (P = 0.022). CONCLUSIONS patients with significant comorbidity who are fit to undergo cisplatin-based CCRT achieve median survivals similar to that reported in phase III trials and with relatively few late toxic effects.

Abandonment of childhood cancer treatment in Western Kenya

Background The most important reason for childhood cancer treatment failure in low-income countries is treatment abandonment. Objective The aim of this study was to explore reasons for childhood cancer treatment abandonment and assess the clinical condition of these children. Design This was a descriptive study using semistructured questionnaires. Home visits were conducted to interview families of childhood cancer patients, diagnosed between January 2007 and January 2009, who had abandoned treatment at the Moi Teaching and Referral Hospital (MTRH). Results Between January 2007 and January 2009, 222 children were newly diagnosed with a malignancy at MTRH. Treatment outcome was documented in 180 patients. Of these 180 patients, 98 (54%) children abandoned treatment. From December 2011 until August 2012, 53 (54%) of the 98 families were contacted. Due to lack of contact information, 45 families were untraceable. From 53 contacted families, 46 (87%) families agreed to be interviewed. Reasons for abandonment were reported by 26 families, and they were diverse. Most common reasons were financial difficulties (46%), inadequate access to health insurance (27%) and transportation difficulties (23%). Most patients (72%) abandoned treatment after the first 3 months had been completed. Of the 46 children who abandoned treatment, 9 (20%) were still alive: 6 (67%) of these children looked healthy and 3 (33%) ill. The remaining 37 (80%) children had passed away. Conclusions Prevention of childhood cancer treatment abandonment requires improved access to health insurance, financial or transportation support, proper parental education, psychosocial guidance and ameliorated communication skills of healthcare providers.

Two overlooked contributors to abandonment of childhood cancer treatment in Kenya: parents' social network and experiences with hospital retention policies.

The principal reason for childhood cancer treatment failure in low‐income countries is treatment abandonment, the most severe form of nonadherence. Two often neglected factors that may contribute to treatment abandonment are as follows: (a) lack of information and guidance by doctors, along with the negative beliefs of family and friends advising parents, which contributes to misconceptions regarding cancer and its treatment, and (b) a widespread policy in public hospitals by which children are retained after doctors discharge until medical bills are settled.

Socio-economic Status Plays Important Roles in Childhood Cancer Treatment Outcome in Indonesia

BACKGROUND The influence of parental socio-economic status on childhood cancer treatment outcome in low-income countries has not been sufficiently investigated. Our study examined this influence and explored parental experiences during cancer treatment of their children in an Indonesian academic hospital. MATERIALS AND METHODS Medical charts of 145 children diagnosed with cancer between 1999 and 2009 were reviewed retrospectively. From October 2011 until January 2012, 40 caretakers were interviewed using semi-structured questionnaires. RESULTS Of all patients, 48% abandoned treatment, 34% experienced death, 9% had progressive/ relapsed disease, and 9% overall event-free survival. Prosperous patients had better treatment outcome than poor patients (P<0.0001). Odds-ratio for treatment abandonment was 3.3 (95%CI: 1.4-8.1, p=0.006) for poor versus prosperous patients. Parents often believed that their childs health was beyond doctor control and determined by luck, fate or God (55%). Causes of cancer were thought to be destiny (35%) or Gods punishment (23%). Alternative treatment could (18%) or might (50%) cure cancer. Most parents (95%) would like more information about cancer and treatment. More contact with doctors was desired (98%). Income decreased during treatment (55%). Parents lost employment (48% fathers, 10% mothers), most of whom stated this loss was caused by their childs cancer (84% fathers, 100% mothers). Loss of income led to financial difficulties (63%) and debts (55%). CONCLUSIONS Treatment abandonment was most important reason for treatment failure. Treatment outcome was determined by parental socio-economic status. Childhood cancer survival could improve if financial constraints and provision of information and guidance are better addressed.

Achieving target throughputs in random-access networks

Random-access algorithms such as CSMA provide a popular mechanism for distributed medium access control in large-scale wireless networks. In recent years, tractable stochastic models have been shown to yield accurate throughput estimates for CSMA networks. We consider a saturated random-access network on a general conflict graph, and prove that for every feasible combination of throughputs, there exists a unique vector of back-off rates that achieves this throughput vector. This result entails proving global invertibility of the non-linear function that describes the throughputs of all nodes in the network. We present several numerical procedures for calculating this inverse, based on fixed-point iteration and Newtons method. Finally, we provide closed-form results for several special conflict graphs using the theory of Markov random fields.

Influence of health-insurance access and hospital retention policies on childhood cancer treatment in Kenya

Kenyan national policies for public hospitals dictate that patients are retained on hospital wards until their hospital bills are paid, but this payment process differs for patients with or without access to National Hospital Insurance Fund (NHIF) at diagnosis. Whether these differences impact treatment outcomes has not been described. Our study explores whether childhood cancer treatment outcomes in Kenya are influenced by health‐insurance status and hospital retention policies.

Salvage surgery for locoregional recurrence or persistent tumor after high dose chemoradiotherapy for locally advanced non-small cell lung cancer.

OBJECTIVES Curative intent treatment options for locoregional recurrence or persistent tumor after radical chemoradiotherapy for locally-advanced non-small cell lung cancer (NSCLC) are limited. In selected patients, surgery can be technically feasible, although it is widely believed to be hazardous. As data regarding the outcome of this approach is sparse, we evaluated our institutional experience with salvage surgery. MATERIALS AND METHODS Patients with a pulmonary resection for in-field locoregional recurrence or persistent tumor after high dose chemoradiotherapy (≥60 Gy) for the treatment of non-small cell lung cancer, were identified and retrospectively analyzed. RESULTS A total of 15 patients treated between January 2007 and August 2015 were eligible for evaluation. In 13 patients (87%), the indication for surgery was a locoregional recurrence, while 2 patients had persistent tumor. The prior median radiotherapy dose was 66 Gy (range 60-70). All patients underwent an anatomical resection, with 8 patients having a pneumonectomy, and all pathological specimens revealed the presence of viable tumor. The in-hospital morbidity rate was 40% (6 patients), and the 90-day mortality rate was 6.7% (1 patient). Median follow-up was 12.1 months. The estimated median overall and event-free survivals were 46 months and 43.6 months, respectively. CONCLUSION Salvage surgery for locoregional recurrence or persistent tumor after high dose chemoradiotherapy, resulted in acceptable morbidity, mortality and promising outcome. It should be considered as a treatment option for selected patients.

Equalizing throughputs in random-access networks

Random-access algorithms such as CSMA provide a popular mechanism for distributed medium access control in largescale wireless networks. In recent years, tractable models have been shown to yield accurate throughput estimates for CSMA networks. We consider the saturated model on a general conflict graph, and prove that for each graph, there exists a vector of activation rates (or mean back-off times) that leads to equal throughputs for all users. We describe an algorithm for computing such activation rates, and discuss a few specific conflict graphs that allow for explicit characterization of these fair activation rates.

Substitution of Usual Perioperative Care by eHealth to Enhance Postoperative Recovery in Patients Undergoing General Surgical or Gynecological Procedures: Study Protocol of a Randomized Controlled Trial

Background Due to the strong reduction in the length of hospital stays in the last decade, the period of in-hospital postoperative care is limited. After discharge from the hospital, guidance and monitoring on recovery and resumption of (work) activities are usually not provided. As a consequence, return to normal activities and work after surgery is hampered, leading to a lower quality of life and higher costs due to productivity loss and increased health care consumption. Objective With this study we aim to evaluate whether an eHealth care program can improve perioperative health care in patients undergoing commonly applied abdominal surgical procedures, leading to accelerated recovery and to a reduction in costs in comparison to usual care. Methods This is a multicenter randomized, single-blinded, controlled trial. At least 308 patients between 18 and 75 years old who are on the waiting list for a laparoscopic cholecystectomy, inguinal hernia surgery, or laparoscopic adnexal surgery for a benign indication will be included. Patients will be randomized to an intervention or control group. The intervention group will have access to an innovative, perioperative eHealth care program. This intervention program consists of a website, mobile phone app, and activity tracker. It aims to improve patient self-management and empowerment by providing guidance to patients in the weeks before and after surgery. The control group will receive usual care and will have access to a nonintervention (standard) website consisting of the digital information brochure about the surgical procedure being performed. Patients are asked to complete questionnaires at 5 moments during the first 6 months after surgery. The primary outcome measure is time to return to normal activities based on a patient-specific set of 8 activities selected from the Patient-Reported Outcomes Measurement Information System (PROMIS) physical functioning item bank version 1.2. Secondary outcomes include social participation, self-rated health, duration of return to work, physical activity, length of recovery, pain intensity, and patient satisfaction. In addition, an economic evaluation alongside this randomized controlled trial will be performed from the societal and health care perspective. All statistical analyses will be conducted according to the intention-to-treat principle. Results The enrollment of patients started in September 2015. The follow-up period will be completed in February 2017. Data cleaning and analyses have not begun as of the time this article was submitted. Conclusions We hypothesize that patients receiving the intervention program will resume their normal activities sooner than patients in the control group and costs will be lower. ClinicalTrial Netherlands Trial Registry NTC4699; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=4699 (Archived by WebCite at http://www.webcitation.org/6mcCBZmwy)