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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Article
  • Peer Reviewed
UC Irvine Previously Published Works (2016)
We consider a situation in which a home improvement project contractor has a team of regular crew members who receive compensation even when they are idle. Because both projects arrivals and the completion time of each project are uncertain, the contractor needs to manage the utilization of his crews carefully. One common approach adopted by many home improvement contractors is to accept multiple projects to keep his crew members busy working on projects to generate positive cash flows. However, this approach has a major drawback because it causes "intentional" (or foreseeable) project delays. Intentional project delays can inflict explicit and implicit costs on the contractor when frustrating customers abandon their projects and/or file complaints or lawsuits. In this paper, we present a queueing model to capture uncertain customer (or project) arrivals and departures, along with the possibility of customer abandonment. Also, associated with each admission policy (i.e., the maximum number of projects that the contractor will accept), we model the underlying tradeoff between accepting too many projects (that can increase customer dissatisfaction) and accepting too few projects (that can reduce crew utilization). We examine this tradeoff analytically so as to determine the optimal admission policy and the optimal number of crew members. We further apply our model to analyze other issues including worker productivity and project pricing. Finally, our model can be extended to allow for multiple classes of projects with different types of crew members.
    Cover page: A queueing model for managing small projects under uncertainties
    • Thesis
    • Peer Reviewed
    UC Irvine Electronic Theses and Dissertations (2017)

    This dissertation consists of three essays on applications of interdisciplinary research in operations management. The first essay addresses issues in healthcare. Our goal is to evaluate the cost-effectiveness of bevacizumab compared to the baseline treatment with only chemotherapy in recurrent/persistent and metastatic cervical cancer using recently reported updated survival and toxicology data. We developed a Markov model with 5 patient health states for both treatments. With data based on the Gynecologic Oncology Group 240 randomized trials and the 2013 MediCare Services Drug Payment Table and Physician Fee Schedule, we present monthly transition probabilities and cost data. Our results show that chemotherapy plus bevacizumab can delay progression, but incur more complications.

    The second essay lies at the interface between operations management and marketing. We aim to understand the tradeoffs in offering outlet stores. In particular, we study how much differentiation should be kept between the main and outlet stores from three perspectives: price, product and location. We find that an outlet store is more likely to be opened when travel sensitivity is lower or costs associated with it are lower. Moreover, offering an outlet store encourages the rm to improve the quality of the product sold in the main store as to reduce the cannibalization effect. We also observe that location differentiation has a substitution effect on quality and price differentiation.

    In the third essay, we study several operational challenges for the on-demand service platforms. We consider a situation when an on-demand service platform uses earning sensitive independent providers with heterogeneous reservation prices to serve its time and price sensitive customers with heterogeneous valuation of the service. We present a queueing model with endogenous supply and endogenous demand to model this on-demand service platform. Based on our analysis, we find that it is optimal for the platform to charge a higher price, pay a higher wage, and offer a higher payout ratio when the potential customer demand increases. We use a set of actual data from a large on-demand ride-hailing platform in numerical experiments to illustrate some of our main insights.

      Cover page: Interdisciplinary Research in Operations Management: Applications in Healthcare, Retailing and On-demand Service Platforms
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2020)
      BACKGROUND:Olaparib was approved on December 19, 2014 by the US FDA as 4th-line therapy (and beyond) for patients with germline BRCA1/2 mutations; rucaparib was approved on December 19, 2016 as 3rd-line therapy (and beyond) for germline or somatic BRCA1/2-mutated recurrent disease. On October 23, 2019, niraparib was approved for treatment of women with damaging mutations in BRCA1/2 or other homologous recombination repair genes who had been treated with three or more prior regimens. We compared the cost-effectiveness of PARPi(s) with intravenous regimens for platinum-resistant disease. METHODS:Median progression-free survival (PFS) and toxicity data from regulatory trials were incorporated in a model which transitioned patients through response, hematologic complications, non-hematologic complications, progression, and death. Using TreeAge Pro 2017, each PARPi(s) was compared separately to non‑platinum-based and bevacizumab-containing regimens. Costs of IV drugs, managing toxicities, infusions, and supportive care were estimated using 2017 Medicare data. Incremental cost-effectiveness ratios (ICERs) were calculated and PFS was reported in quality adjusted life months for platinum-resistant populations. RESULTS:Non‑platinum-based intravenous chemotherapy was most cost effective ($6,412/PFS-month) compared with bevacizumab-containing regimens ($12,187/PFS-month), niraparib ($18,970/PFS-month), olaparib ($16,327/PFS-month), and rucaparib ($16,637/PFS-month). ICERs for PARPi(s) were 3-3.5× times greater than intravenous non‑platinum-based regimens. CONCLUSION:High costs of orally administered PARPi(s) were not mitigated or balanced by costs of infusion and managing toxicities of intravenous regimens typically associated with lower response and shorter median PFS. Balancing modest clinical benefit with costs of novel therapies remains problematic and could widen disparities among those with limited access to care.
        Cover page: Cost-effectiveness of niraparib, rucaparib, and olaparib for treatment of platinum-resistant, recurrent ovarian carcinomaCreative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2020)
        BACKGROUND: Olaparib was approved on December 19, 2014 by the US FDA as 4th-line therapy (and beyond) for patients with germline BRCA1/2 mutations; rucaparib was approved on December 19, 2016 as 3rd-line therapy (and beyond) for germline or somatic BRCA1/2-mutated recurrent disease. On October 23, 2019, niraparib was approved for treatment of women with damaging mutations in BRCA1/2 or other homologous recombination repair genes who had been treated with three or more prior regimens. We compared the cost-effectiveness of PARPi(s) with intravenous regimens for platinum-resistant disease. METHODS: Median progression-free survival (PFS) and toxicity data from regulatory trials were incorporated in a model which transitioned patients through response, hematologic complications, non-hematologic complications, progression, and death. Using TreeAge Pro 2017, each PARPi(s) was compared separately to non‑platinum-based and bevacizumab-containing regimens. Costs of IV drugs, managing toxicities, infusions, and supportive care were estimated using 2017 Medicare data. Incremental cost-effectiveness ratios (ICERs) were calculated and PFS was reported in quality adjusted life months for platinum-resistant populations. RESULTS: Non‑platinum-based intravenous chemotherapy was most cost effective ($6,412/PFS-month) compared with bevacizumab-containing regimens ($12,187/PFS-month), niraparib ($18,970/PFS-month), olaparib ($16,327/PFS-month), and rucaparib ($16,637/PFS-month). ICERs for PARPi(s) were 3-3.5× times greater than intravenous non‑platinum-based regimens. CONCLUSION: High costs of orally administered PARPi(s) were not mitigated or balanced by costs of infusion and managing toxicities of intravenous regimens typically associated with lower response and shorter median PFS. Balancing modest clinical benefit with costs of novel therapies remains problematic and could widen disparities among those with limited access to care.
          Cover page: Cost-effectiveness of niraparib, rucaparib, and olaparib for treatment of platinum-resistant, recurrent ovarian carcinoma.
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2019)
          We consider an on-demand service platform using earning-sensitive independent providers with heterogeneous reservation price (for work participation) to serve its time and price-sensitive customers with heterogeneous valuation of the service. As such, the supply and demand are “endogenously” dependent on the price the platform charges its customers and the wage the platform pays its independent providers. We present an analytical model with endogenous supply (number of participating agents) and endogenous demand (customer request rate) to study this on-demand service platform. To coordinate endogenous demand with endogenous supply, we include the steady-state waiting time performance based on a queueing model in the customer utility function to characterize the optimal price and wage rates that maximize the profit of the platform. We first analyze a base model that uses a fixed payout ratio (i.e., the ratio of wage over price), and then extend our model to allow the platform to adopt a time-based payout ratio. We find that it is optimal for the platform to charge a higher price when demand increases; however, the optimal price is not necessarily monotonic when the provider capacity or the waiting cost increases. Furthermore, the platform should offer a higher payout ratio as demand increases, capacity decreases or customers become more sensitive to waiting time. We also find that the platform should lower its payout ratio as it grows with the number of providers and customer demand increasing at about the same rate. We use a set of actual data from a large on-demand ride-hailing platform to calibrate our model parameters in numerical experiments to illustrate some of our main insights.
            Cover page: Coordinating Supply and Demand on an On-Demand Service Platform with Impatient Customers
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2015)

            Objective

            To evaluate the cost-effectiveness of bevacizumab in recurrent/persistent and metastatic cervical cancer using recently reported updated survival and toxicology data.

            Methods

            A Markov decision tree based on the Gynecologic Oncology Group 240 randomized trial was created. The 2013 MediCare Services Drug Payment Table and Physician Fee Schedule provided costs. In the 5-year model subjects transitioned through the following states: response, progression, minor complications, severe complications, and death. Patients experiencing a health utility per month according to treatment effectiveness were calculated. Because cervical cancer survival is measured in months rather than years, results were reported in both quality adjusted cervical cancer life months and years (QALmonth, QALY), adjusted from a baseline of having advanced cervical cancer during a month.

            Results

            The estimated total cost of therapy with bevacizumab is approximately 13.2 times that for chemotherapy alone, adding $73,791 per 3.5months (0.29year) of life gained, resulting in an incremental cost-effectiveness ratio (ICER) of $21.083 per month of added life. The ICER increased to $5775 per month of added life and $24,597/QALmonth ($295,164/QALY) due to the smaller difference in QALmonths. With 75% bevacizumab cost reduction, the ICER is $6737/QALmonth ($80,844/QALY), which translates to $23,580 for the 3.5month (0.29year) gain in OS.

            Conclusions

            Increased costs are primarily related to the cost of drug and not the management of bevacizumab-induced complications. Cost reductions in bevacizumab result in dramatic declines in the ICER, suggesting that cost reconciliation in advanced cervical cancer may be possible through the availability of biosimilars, and/or less expensive, equally efficacious anti-angiogenesis agents.
              Cover page: A Markov model to evaluate cost-effectiveness of antiangiogenesis therapy using bevacizumab in advanced cervical cancer.Creative Commons 'BY' version 4.0 license
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