Publications by authors named "Gregory Gan"

Background: Bladder cancer patients unable to receive cystectomy or who choose to pursue organ-sparing approach are managed with definitive (chemo)radiotherapy. However, this standard of care has not evolved in decades and disease recurrence and survival outcomes remain poor. Identifying novel therapies to combine with radiotherapy (RT) is therefore paramount to improve overall patient outcomes and survival.

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Objective: Proton spot-scanning arc therapy (ARC) is an emerging modality that can improve the high-dose conformity to targets compared with standard intensity-modulated proton therapy (IMPT). However, the efficient treatment delivery of ARC is challenging due to the required frequent energy changes during the continuous gantry rotation. This work proposes a novel method that delivers a multiple IMPT (multi-IMPT) plan that is equivalent to ARC in terms of biologically effective dose (BED).

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Background: The clinical translation of proton minibeam radiation therapy (pMBRT) presents significant challenges, particularly in developing an optimal treatment planning technique. A uniform target dose is crucial for maximizing anti-tumor efficacy and facilitating the clinical acceptance of pMBRT. However, achieving a high peak-to-valley dose ratio (PVDR) in organs-at-risk (OAR) is essential for sparing normal tissue.

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Background: Immunotherapy in combination with chemotherapy is first-line treatment for patients with extensive-stage small-cell lung cancer (ES-SCLC). Growing evidence suggests that radiation, specifically stereotactic body radiation therapy (SBRT), may enhance the immunogenic response as well as cytoreduce tumor burden. The primary objective of the study is to determine the progression free survival for patients with newly diagnosed ES-SCLC treated with combination multisite SBRT and chemo-immunotherapy (carboplatin, etoposide, and durvalumab).

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Background: Proton minibeam radiation therapy (pMBRT) can deliver spatially fractionated dose distributions with submillimeter resolution. These dose distributions exhibit significant heterogeneity in both depth and lateral directions. Accurate characterization of pMBRT doses requires dosimetry devices with high spatial resolution and a wide dynamic range.

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Article Synopsis
  • FLASH radiotherapy (FLASH) enhances organ protection but poses a challenge in balancing physical and biological dose coverage, necessitating a new metric called FLASH effective dose (FED) for improvement assessment compared to conventional methods.
  • The study introduces a novel treatment planning technique, SDDRO-DMF, which optimizes FED through models that quantify the FLASH effect and radiobiological mechanisms.
  • Validation shows SDDRO-DMF significantly reduces high doses to organs-at-risk (OAR) in proton FLASH, achieving specific dose constraints in cases like SBRT lung treatment, where it was the only method to meet dose limitations effectively.
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Background: Minibeam represents a preclinical spatially fractionated radiotherapy modality with great translational potential. The advantage lies in its high therapeutic index (compared to GRID and LATTICE) and ability to treat at greater depth (compared to microbeam). Proton minibeam radiotherapy (pMBRT) is a synergy of proton and minibeam.

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Head and neck cancer (HNC) is a challenging disease that lacks effective treatment, particularly in the cases that spread locoregionally and metastasize distantly, dramatically reducing patient survival rates. Expanding the understanding of the mechanisms of the metastatic cascade is critical for creating more effective therapeutics that improve outcomes for HNC patients. A true grasp of cancer metastasis requires the consideration of all cell types that contribute to the inflammatory HNC microenvironment as drivers of this process.

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Objective: To determine differences in post-treatment QoL across treatment settings in patients receiving adjuvant radiation therapy for head and neck squamous cell carcinoma (HNSCC).

Methods: This was a prospective observational cohort study of patients with HNSCC initially evaluated in a head and neck surgical oncologic and reconstructive clinic at an academic medical center (AMC). Participants were enrolled prior to treatment in a prospective registry collecting demographic, social, and clinical data.

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Introduction: The transmission dynamics of the recent mpox outbreak highlights the lack of infrastructure available to rapidly respond to novel STI outbreaks, of which Asia and Oceania remains particularly susceptible. Here, we simulate outbreaks in this setting and propose the use of pre-emptive vaccination within the men who have sex with men (MSM) community before the arrival and establishment of the virus.

Materials And Methods: Using data driven heterogeneous sexual contact networks, we simulated outbreaks of mpox in Singapore, Hong Kong, and Sydney.

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Background: Transmission intensity for mosquito-borne diseases are highly heterogenous and multi-factorial. Understanding risk factors associated to disease transmission allow the optimization of vector control. This study sets out to understand and compare the combined anthropogenic and environmental risk factors of four major mosquito-borne diseases, dengue, malaria, chikungunya and Japanese encephalitis in Thailand.

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Objectives: Understand the prognostic impact of perineural invasion (PNI) in early-stage oral cavity squamous cell carcinoma (OCSCC). Assess the influence of adjuvant radiotherapy on outcomes of patients with PNI-positive early-stage OCSCC.

Materials And Methods: Retrospective seven-institution cohort study including patients with pathologic T1-2 N0-1 OCSCC who underwent primary surgery with negative margins.

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Importance: Timely initiation of postoperative radiation therapy (PORT) is associated with reduced recurrence rates and improved overall survival in patients with head and neck squamous cell carcinoma (HNSCC). Measurement of the association of social-ecological variables with PORT delays is lacking.

Objective: To assess individual and community-level factors associated with PORT delay among patients with HNSCC.

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Objective: In patients with head and neck squamous cell carcinoma (HNSCC), initiating postoperative radiotherapy (PORT) greater than 42 days after surgery is associated with a higher risk of poor survival outcomes. Social support has been shown to modulate behaviors related to care-seeking and treatment adherence. In this study, we sought to determine the relationship between social support metrics and PORT delays.

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Purpose: To provide evidence-based recommendations for practicing physicians and other health care providers on immunotherapy and biomarker testing for head and neck cancers.

Methods: ASCO convened an Expert Panel of medical oncology, surgical oncology, radiation oncology, radiology, pathology, and patient advocacy experts to conduct a literature search, including systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 2000 through 2022. Outcomes of interest included survival, overall response, and locoregional control.

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We report a microfluidic assay to select active severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral particles (VPs), which were defined as intact particles with an accessible angiotensin-converting enzyme 2 receptor binding domain (RBD) on the spike (S) protein, from clinical samples. Affinity selection of SARS-CoV-2 particles was carried out using injection molded microfluidic chips, which allow for high-scale production to accommodate large-scale screening. The microfluidic contained a surface-bound aptamer directed against the virus's S protein RBD to affinity select SARS-CoV-2 VPs.

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Objective: To evaluate the effect of histopathologic skin invasion on 2- and 5-year disease-free survival (DFS) and overall survival (OS) in patients treated with primary surgery for locally advanced oral cavity squamous cell carcinoma (OCSCC).

Study Design: A retrospective case-control study was performed comparing previously untreated patients with pT4a OCSCC with and without skin invasion.

Setting: Academic medical center.

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Introduction: Standard of care for radiosensitization in head and neck squamous cell carcinoma (HNSCC) is concurrent chemoradiotherapy (CCRT) with high-dose cisplatin. The optimal chemoradiation regimen for patients medically unfit for cisplatin is unclear. We compared our experience with concurrent cetuximab (CTX) versus other cytotoxic non-cisplatin agents.

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This study was performed to identify treatment related toxicities in older adults undergoing concurrent chemoradiotherapy for head and neck cancer and nutritional and skeletal muscle measures that might identify frailty. Imaging analysis was done with the following skeletal muscle measurements: skeletal muscle index (SMI), skeletal muscle density (SMD), and skeletal muscle gauge (SMG). Patients were dichotomized by age into younger (<70 years old, 221 patients) and older age groups (≥70 years old, 51 patients).

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Purpose: Compared to CONV-RT (with conventional dose rate), FLASH-RT (with ultra-high dose rate) can provide biological dose sparing for organs-at-risk (OARs) via the so-called FLASH effect, in addition to physical dose sparing. However, the FLASH effect only occurs, when both dose and dose rate meet certain minimum thresholds. This work will develop a simultaneous dose and dose rate optimization (SDDRO) method accounting for both FLASH dose and dose rate constraints during treatment planning for pencil-beam-scanning proton therapy.

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Cancer and the immune system share an intimate relationship. Chronic inflammation increases the risk of cancer occurrence and can also drive inflammatory mediators into the tumor microenvironment enhancing tumor growth and survival. The p38 MAPK pathway is activated both acutely and chronically by stress, inflammatory chemokines, chronic inflammatory conditions, and cancer.

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Background: Lung is the most common site of distant metastasis for patients with head and neck squamous cell carcinoma (HNSCC). However, differentiating second primary lung cancers from metastasis may be difficult for p16 negative HNSCC.

Case: We describe a case of oral cavity squamous cell carcinoma (SCC) who was found to have lung nodule and hilar lymphadenopathy (LAD) after surgery and radiation therapy.

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Importance: Stereotactic body radiotherapy (SBRT) for oligometastases is hypothesized to improve survival and is increasingly used. Little evidence supports its safe use to treat patients with multiple metastases.

Objective: To establish safety of SBRT dose schedules in patients with 3 to 4 metastases or 2 metastases in close proximity to each other.

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Intracellular pathogens have evolved to utilize normal cellular processes to complete their replicative cycles. Pathogens that interface with proliferative cell signaling pathways risk infections that can lead to cancers, but the factors that influence malignant outcomes are incompletely understood. Human papillomaviruses (HPVs) predominantly cause benign hyperplasia in stratifying epithelial tissues.

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