Quantitative Total-Body Imaging of Blood Flow with High Temporal Resolution Early Dynamic 18F-Fluorodeoxyglucose PET Kinetic Modeling.

Quantitative total-body PET imaging of blood flow can be performed with freely diffusible flow radiotracers such as 15O-water and 11C-butanol, but their short half-lives necessitate close access to a cyclotron. Past efforts to measure blood flow with the widely available radiotracer 18F-fluorodeoxyglucose (FDG) were limited to tissues with high 18F-FDG extraction fraction. In this study, we developed an early-dynamic 18F-FDG PET method with high temporal resolution kinetic modeling to assess total-body blood flow based on deriving the vascular transit time of 18F-FDG and conducted a pilot comparison study against a 11C-butanol reference. Methods: The first two minutes of dynamic PET scans were reconstructed at high temporal resolution (60×1 s, 30×2 s) to resolve the rapid passage of the radiotracer through blood vessels. In contrast to existing methods that use blood-to-tissue transport rate ( K 1 ) as a surrogate of blood flow, our method directly estimates blood flow using a distributed kinetic model (adiabatic approximation to the tissue homogeneity model; AATH). To validate our 18F-FDG measurements of blood flow against a flow radiotracer, we analyzed total-body dynamic PET images of six human participants scanned with both 18F-FDG and 11C-butanol. An additional thirty-four total-body dynamic 18F-FDG PET scans of healthy participants were analyzed for comparison against literature blood flow ranges. Regional blood flow was estimated across the body and total-body parametric imaging of blood flow was conducted for visual assessment. AATH and standard compartment model fitting was compared by the Akaike Information Criterion at different temporal resolutions. Results: 18F-FDG blood flow was in quantitative agreement with flow measured from 11C-butanol across same-subject regional measurements (Pearson R=0.955, p<0.001; linear regression y=0.973x-0.012), which was visually corroborated by total-body blood flow parametric imaging. Our method resolved a wide range of blood flow values across the body in broad agreement with literature ranges (e.g., healthy cohort average: 0.51±0.12 ml/min/cm3 in the cerebral cortex and 2.03±0.64 ml/min/cm3 in the lungs, respectively). High temporal resolution (1 to 2 s) was critical to enabling AATH modeling over standard compartment modeling. Conclusions: Total-body blood flow imaging was feasible using early-dynamic 18F-FDG PET with high-temporal resolution kinetic modeling. Combined with standard 18F-FDG PET methods, this method may enable efficient single-tracer flow-metabolism imaging, with numerous research and clinical applications in oncology, cardiovascular disease, pain medicine, and neuroscience.

Quantitative PET imaging and modeling of molecular blood-brain barrier permeability.

Blood-brain barrier (BBB) disruption is involved in the pathogenesis and progression of many neurological and systemic diseases. Non-invasive assessment of BBB permeability in humans has mainly been performed with dynamic contrast-enhanced magnetic resonance imaging, evaluating the BBB as a structural barrier. Here, we developed a novel non-invasive positron emission tomography (PET) method in humans to measure the BBB permeability of molecular radiotracers that cross the BBB through different transport mechanisms. Our method uses high-temporal resolution dynamic imaging and kinetic modeling to jointly estimate cerebral blood flow and tracer-specific BBB transport rate from a single dynamic PET scan and measure the molecular permeability-surface area (PS) product of the radiotracer. We show our method can resolve BBB PS across three PET radiotracers with greatly differing permeabilities, measure reductions in BBB PS of 18F-fluorodeoxyglucose (FDG) in healthy aging, and demonstrate a possible brain-body association between decreased FDG BBB PS in patients with metabolic dysfunction-associated steatotic liver inflammation. Our method opens new directions to efficiently study the molecular permeability of the human BBB in vivo using the large catalogue of available molecular PET tracers.

Changes in alcohol consumption and binge drinking during the COVID-19 pandemic among American Indians residing in California and Oklahoma.

Background: This study explored the increased quantity and frequency of alcohol use in the American Indian (AI) population during the COVID-19 pandemic.Objectives: The aims of this study were to explore possible associations between covariables and both binge drinking and alcohol consumption during COVID-19.Methods: This cross-sectional survey study analyzed data from a sample of AI individuals (63% female) residing in California (n = 411) and Oklahoma (n = 657) between October 2020-January 2021. Analysis included summary statistics and multivariable logistic regression, including a variety of socio-economic, COVID-19 concern, and tobacco and marijuana use variables.Results: One or more alcohol binge episodes were reported between October 2020-January 2021 in 19.3% of participants and elevated overall alcohol consumption was reported by 21.6% of participants. Higher odds of elevated alcohol consumption occurred in women and those following more social distancing measures. The odds of binge drinking or elevated alcohol consumption in those using both marijuana and tobacco (aOR/ adjusted odds ratio:18.9, 95% CI = 8.5, 42.2, and aOR:3.9, 95% CI = 1.7, 8.6, respectively) were higher compared to those using neither. Similarly, the odds of binge drinking or elevated alcohol consumption in those using tobacco only (aOR:4.7, 95% CI = 2.9, 7.7 and aOR: 2.0, 95% CI = 1.1, 3.5, respectively) were higher compared to those using neither.Conclusions: This study found high rates of alcohol use and bingeing during the COVID-19 pandemic. Offering collaborative, culturally sensitive, and affordable support services are important components of intervention and preparation for future stressful events on local, as well as global levels.

Association Between COVID-19 and Planned and Postponed Cancer Screenings Among American Indian Adults Residing in California and Oklahoma, March-December 2020.

OBJECTIVE: Little is known about how the COVID-19 pandemic affected cancer screenings among American Indian people residing in California and Oklahoma, 2 states with the largest American Indian populations. We assessed rates and factors associated with cancer screenings among American Indian adults during the pandemic. METHODS: From October 2020 through January 2021, we surveyed 767 American Indian adults residing in California and Oklahoma. We asked participants whether they had planned to obtain screenings for breast cancer, cervical cancer, and colorectal cancer (CRC) from March through December 2020 and whether screening was postponed because of COVID-19. We calculated adjusted odds ratios (AORs) for factors associated with reasons for planned and postponed cancer screening. RESULTS: Among 395 participants eligible for breast cancer screening, 234 (59.2%) planned to obtain the screening, 127 (54.3%) of whom postponed it. Among 517 participants eligible for cervical cancer screening, 357 (69.1%) planned to obtain the screening, 115 (32.2%) of whom postponed it. Among 454 participants eligible for CRC screening, 282 (62.1%) planned to obtain CRC screening, 80 of whom (28.4%) postponed it. In multivariate analyses, women who lived with a child (vs did not) had lower odds of planning to obtain a breast cancer screening (AOR = 0.6; 95% CI, 0.3-1.0). Adherence to social distancing recommendations was associated with planning to have and postponement of cervical cancer screening (AOR = 7.3; 95% CI, 0.9-58.9). Participants who received (vs did not receive) social or financial support had higher odds of planning to have CRC screening (AOR = 2.0; 95% CI, 1.1-3.9). CONCLUSION: The COVID-19 pandemic impeded completion of cancer screenings among American Indian adults. Interventions are needed to increase the intent to receive evidence-based cancer screenings among eligible American Indian adults.

"You Don't Know If It's the Truth or a Lie": Exploring Human Papillomavirus (HPV) Vaccine Hesitancy among Communities with Low HPV Vaccine Uptake in Northern California.

BACKGROUND: Vaccine hesitancy, delaying or refusing to vaccinate despite the availability of vaccines, impedes the progress of achieving optimal HPV vaccine coverage. Little is known about the sources of human papillomavirus (HPV) vaccine hesitancy among racially/ethnically and geographically diverse communities. The purpose of this paper is to explore HPV vaccine hesitancy among rural, Slavic, and Latino communities that reside in counties with low HPV vaccine uptake rates. METHODS: Key informant interviews and focus groups were conducted with rural, Slavic, and Latino communities that reside within counties in California that have low HPV vaccine up to date rates (16-25%). Qualitative data were transcribed verbatim and analyzed using inductive and deductive thematic analysis. RESULTS: A total of seven focus groups and 14 key informant interviews were conducted with 39 individuals from seven California counties. Salient themes that contributed to HPV vaccine hesitancy included the following: social media and the anti-vaccination movement; a strong belief in acquiring immunity naturally; prior vaccine experiences; and vaccine timing concerns. Participants suggested the provision of culturally appropriate, in-language, in-person easy to understand HPV vaccine education to mitigate HPV vaccine hesitancy. CONCLUSIONS: Our findings can inform future interventions to increase HPV vaccine uptake among hesitant communities.

Tobacco and marijuana use during the COVID-19 pandemic lockdown among American Indians residing in California and Oklahoma.

INTRODUCTION: American Indian (AI) people experience a disproportionate tobacco and marijuana burden which may have been exacerbated by the COVID-19 pandemic. Little is known about the tobacco and marijuana habits of American Indian individuals during the COVID-19 pandemic. The objective of this study is to examine tobacco and marijuana use as well as change in use during the COVID-19 pandemic among the American Indian community. METHODS: This cross-sectional study analyzes survey data from a convenience sample of American Indian individuals residing in California and Oklahoma and included adults with and without cancer that resided in both rural and urban areas (n=1068). RESULTS: During October 2020 - January 2021, 36.0% of participants reported current use of tobacco products, 9.9% reported current use of marijuana products, and 23.7% reported increased use of tobacco and/or marijuana in the past 30 days, with no difference between those with cancer and those without cancer. Tobacco use was associated with marital status, age, employment status, COVID-19 exposure, COVID-19 beliefs, and alcohol consumption. Marijuana use was associated with COVID-19 beliefs, alcohol consumption, and income level. Increased tobacco and/or marijuana use was associated with baseline use of those products. Nearly a quarter of participants reported increased use of tobacco and/or marijuana products during the COVID-19 pandemic. CONCLUSIONS: We observed high rates of tobacco use during the COVID-19 pandemic, consistent with other studies. Research is needed to examine whether tobacco and marijuana use will decrease to pre-pandemic levels post-pandemic or if these behaviors will persist post-pandemic. Given these findings, there is a pressing need to increase access to evidence-based tobacco and marijuana treatment services in the AI population post COVID-19 pandemic.

Avoidance of medical care among American Indians with a history of cancer during the coronavirus pandemic.

Objectives: Assess the percentage of cancer-related appointment delays, cancelations, and the unavailability of medications experienced by American Indian participants during the COVID-19 pandemic. Methods: This cross-sectional survey study was completed between October 2020 and July 2021 by 360 individuals with cancer who lived in California and Oklahoma. Binary and multivariate logistic regression analysis was completed in SAS 9.4. Results: During the initial Covid-19 pandemic, almost one-third (30%) of respondents delayed cancer-related appointments, 42% canceled cancer-related appointments, and one-quarter (24%) were unable to access prescription medications or over-the-counter medications (27%) due to COVID-19. People who underwent testing for COVID-19 were five times more likely to delay a medical appointment [adjusted odds ratio (aOR) = 5.3, 95% CI:2.4, 11.7] and people who followed three or more social distancing measures were more than six times more likely to cancel medical appointments (aOR:6.3, 95% CI:2.9, 13.9). Conclusion: This study identifies delays, cancelations, and medication inaccessibility people identifying as American Indian faced during the coronavirus pandemic. Disparities in healthcare delivery could contribute to increased morbidity and mortality rates of cancer.

A pharmacist-led community-based survey study: Determining the impact of the Covid-19 pandemic on actionable factors associated with worse cancer outcomes and cancer health disparities.

Purpose: The goals of this cross-sectional community-based survey study were to assess the impact of the Covid-19 pandemic on actionable factors which are known to contribute to worse cancer outcomes, and to determine whether race and ethnicity-based differences exist. Methods: A survey study which captured demographic information and changes in cancer outcomes-related factors since the start of the Covid-19 pandemic, was conducted at a public Covid-19 vaccination clinic over a period of 10 days during March 2021. Surveys were administered in multiple languages. Chi-square tests and ANOVA followed by post-hoc Dunnett testing assessed for race and ethnicity-based differences. Results: A total of 949 people participated (61.6% participation rate). Ninety-three surveys were removed based on inclusion criteria giving a final participant number of 856. Many participants reported postponing cancer screenings (17.8%) and cancellation of medical appointments (22.8% and 25.8% reported cancelled appointments by providers or themselves, respectively) due to the pandemic. Participants also reported decreased physical activity (44.7%) and increased tobacco and/or marijuana usage (7.0%). Conversely, participants reported consuming more fruits and vegetables (21.4%) and decreasing alcohol consumption (21.4%). Several race-related differences but no ethnicity-related differences were observed. Conclusion: Our data can be used to help guide pharmacist-led targeted outreach in our community which will help mitigate Covid-19 pandemic-driven changes in behaviors associated with worse cancer outcomes and exacerbation of cancer health disparities. To our knowledge, this is the first cancer outcomes-related study to be conducted at a public Covid-19 vaccination site and is the first pharmacist-led study in this area.

18F-FDG gallbladder uptake: observation from a total-body PET/CT scanner.

BACKGROUND: Total-body positron emission tomography/computed tomography (PET/CT) scanners are characterized by higher signal collection efficiency and greater spatial resolution compared to conventional scanners, allowing for delayed imaging and improved image quality. These advantages may also lead to better detection of physiological processes that diagnostic imaging professionals should be aware of. The gallbladder (GB) is not usually visualized as an 18F-2-fluorodeoxyglucose (18F-FDG)-avid structure in routine clinical PET/CT studies; however, with the total-body PET/CT, we have been increasingly visualizing GB activity without it being involved in an inflammatory or neoplastic process. The aim of this study was to report visualization rates and characteristics of GB 18F-FDG uptake observed in both healthy and oncological subjects scanned on a total-body PET/CT system. MATERIALS AND METHODS: Scans from 73 participants (48 healthy and 25 with newly diagnosed lymphoma) who underwent 18F-FDG total-body PET/CT were retrospectively reviewed. Subjects were scanned at multiple timepoints up to 3 h post-injection. Gallbladder 18F-FDG activity was graded using liver uptake as a reference, and the pattern was qualified as present in the wall, lumen, or both. Participants' characteristics, such as age, sex, body-mass index, blood glucose, and other clinical parameters, were collected to assess for any significant correlation with GB 18F-FDG uptake. RESULTS: All 73 subjects showed GB uptake at one or more imaging timepoints. An increase in uptake intensity overtime was observed up until the 180-min scan, and the visualization rate of GB 18F-FDG uptake was 100% in the 120- and 180-min post-injection scans. GB wall uptake was detected in a significant number of patients (44/73, 60%), especially at early timepoint scans, whereas luminal activity was detected in 71/73 (97%) subjects, especially at later timepoint scans. No significant correlation was found between GB uptake intensity/pattern and subjects' characteristics. CONCLUSION: The consistent observation of GB 18F-FDG uptake recorded in this study in healthy participants and subjects with a new oncological diagnosis indicates that this is a normal physiologic finding rather than representing an exception.

Implementation and evaluation of a multilevel intervention to increase uptake of the human papillomavirus vaccine among rural adolescents.

PURPOSE: Geographic disparities exist in uptake of the human papillomavirus vaccine (HPV). In 2020, the National Immunization Survey-Teen reported that adolescents living in nonmetropolitan statistical areas (MSAs) had lower HPV vaccination coverage (≥ 1 dose) compared to adolescents living in MSA principal cities. This paper describes the implementation and evaluation of a multilevel pilot intervention study to increase uptake of the HPV vaccine among adolescent patients ages 11-17 of a rural health clinic. METHODS: This parent, primary care team, and clinic multilevel pilot intervention was guided by evidence-based approaches to increase HPV vaccinations, formative research, and input from the community. HPV vaccination initiation and completion rates were analyzed at baseline and 23 months follow-up. FINDINGS: The proportion of adolescent patients ages 11-17 who had initiated the HPV vaccine series was significantly greater at follow-up compared to baseline, (82.7% compared to 52.4%), χ2 (1, n = 498) = 49.2, P < .0001. The proportion of adolescent patients ages 11-17 who had completed the HPV vaccine series was also significantly greater at follow-up compared to baseline, (58.0% compared to 27.0%), χ2 (1, n = 498) = 50.8, P < .0001. CONCLUSIONS: The multilevel intervention significantly increased HPV initiation and completion rates among adolescent patients ages 11-17 at this rural health clinic. This study demonstrates the feasibility of utilizing a multilevel intervention to address low HPV vaccination rates among rural adolescents and the potential of employing this strategy for a large-scale randomizing-controlled trial.

A Cancer Health Needs Assessment Reveals Important Differences Between US-Born and Foreign-Born Latinos in California.

Background: Cancer is the leading cause of death among Latinos, the largest minority population in the United States (US). To address cancer challenges experienced by Latinos, we conducted a catchment area population assessment (CAPA) using validated questions from the National Cancer Institute (NCI) population health assessment supplement at our NCI-designated cancer center in California. Methods: A mixed-methods CAPA was administered by bilingual-bicultural staff, with a focus on understanding the differences between foreign-born and US-born Latinos. Results: 255 Latinos responded to the survey conducted between August 2019 and May 2020. Most respondents were foreign-born (63.9%), female (78.2%), and monolingual Spanish speakers (63.2%). Results showed that compared to US-born Latinos, foreign-born individuals were older, had lower educational attainment, were most likely to be monolingual Spanish speakers, were low-income, and were more likely to be uninsured. Foreign-born Latinos had lower levels of alcohol consumption and higher consumption of fruits and vegetables. The rate of preventive cancer screenings for breast, cervical and colorectal cancer did not differ by birthplace, although a low fraction (35.3%) of foreign-born Latinas who were up-to-date compared to US-born Latinas (83.3%) with colorectal cancer screening was observed. Time since the last routine check-up for all preventable cancers (cervical p=0.0002, breast p=0.0039, and colorectal p=0.0196) is significantly associated with being up to date with cancer screening. Individuals who had a check-up of two or more years ago are 84% less likely to be up to date with pap smears than those who had a check-up within the year (p=0.0060). Individuals without health insurance are 94% less likely to be up to date with mammograms and colonoscopy/FIT tests (p=0.0016 and p=0.0133, respectively) than those who are insured. There is no significant association between screening and nativity. Conclusions: Considerable differences in socio-economic and environmental determinants of health and colorectal cancer screening rates were observed between US-born and foreign-born Latinos. The present study represents the foundation for future targeted intervention among immigrant populations at our cancer center's catchment area.

A Framework for Equitable Partnerships to Promote Cancer Prevention and Control in Rural Settings.

Rural populations continue to experience persistent cancer disparities compared with urban populations particularly in cancers that can be prevented or detected early through screening and vaccination. Although the National Cancer Institute and the larger cancer research community have identified rural community partnerships as the foundation for reducing the disparities, we have identified limited application of community-based participatory research in cancer prevention and control research. Guided by the Community-Based Participatory Research Conceptual Model and our collective experience, we provide a framework for a community-cancer center partnership that focuses on promoting health equity. In this commentary, we articulate that the partnership process must foster capacity for communities and cancer centers, strive for rural representation in clinical trials and biobanking, build a pipeline for dissemination and implementation research, and create a bidirectional flow of knowledge between communities and academic institutions. Authentic partnerships with rural communities should be the ultimate goal of cancer centers, and the process described in this commentary can serve as an initial platform to build capacity and continue to strive toward that goal.

Charting a Path Towards Asian American Cancer Health Equity: A Way Forward.

On July 29, 2021, the US Food and Drug Administration's Oncology Center of Excellence convened Conversations on Cancer. This Conversation, the first ever by the US Food and Drug Administration, focused on Asian Americans and served as the platform for this Commentary. Panelists elaborated on topics ranging from heterogeneity in Asian American demographics to racism through a path to health equity and supplemented this Commentary with literature citations. Asian Americans are the fastest-growing US race group, yet data aggregation obscures distinctions and cancer disparities within the more than 24 million Asians living in the United States with harmful impacts on communities and patients, as illustrated by breast cancer survivor Susan Shinagawa's patient-to-advocate journey. Bigotry against Asian Americans has been pervasive since the 19th century, but especially during the COVID-19 pandemic. Asian Americans are unique as the first US population to experience cancer as the leading cause of death. Asian Americans are disproportionately affected by cancers because of infectious origins and have the highest rates of lung cancer among never-smoking women. The infinitesimal proportion of the National Institutes of Health's budget compared with experiencing the highest percentage increases of any US racial population more than 3 decades highlights the dearth of focused research among Asian Americans. Recognizing the heterogeneity of Asian Americans and that disaggregated data are critical for accurately characterizing distinct ethnic groups, focusing on the impact of racism and COVID-19 on cancer disparities, and focusing and prioritizing funding resources are necessary steps forward for achieving health equity for Asian Americans.

PDXNet portal: patient-derived Xenograft model, data, workflow and tool discovery.

We created the PDX Network (PDXNet) portal (https://portal.pdxnetwork.org/) to centralize access to the National Cancer Institute-funded PDXNet consortium resources, to facilitate collaboration among researchers and to make these data easily available for research. The portal includes sections for resources, analysis results, metrics for PDXNet activities, data processing protocols and training materials for processing PDX data. Currently, the portal contains PDXNet model information and data resources from 334 new models across 33 cancer types. Tissue samples of these models were deposited in the NCI's Patient-Derived Model Repository (PDMR) for public access. These models have 2134 associated sequencing files from 873 samples across 308 patients, which are hosted on the Cancer Genomics Cloud powered by Seven Bridges and the NCI Cancer Data Service for long-term storage and access with dbGaP permissions. The portal includes results from freely available, robust, validated and standardized analysis workflows on PDXNet sequencing files and PDMR data (3857 samples from 629 patients across 85 disease types). The PDXNet portal is continuously updated with new data and is of significant utility to the cancer research community as it provides a centralized location for PDXNet resources, which support multi-agent treatment studies, determination of sensitivity and resistance mechanisms, and preclinical trials.

Effect of a media intervention on hepatitis B screening among Vietnamese Americans.

Objective: There is a lack of controlled studies of community-wide interventions to increase screening for hepatitis B (HBV) among Asian Americans, particularly Vietnamese Americans, who disproportionately suffer from HBV-related illnesses. The objective of our study was to develop, implement, and evaluate the effectiveness of a media campaign to promote HBV screening among Vietnamese Americans.Design: We designed and implemented a three-year media campaign promoting HBV screening among Vietnamese Americans. Evaluation consisted of cross-sectional pre- and post-intervention population-based telephone surveys of Vietnamese Americans adults age 18-64 who spoke English or Vietnamese and lived in the Northern California (intervention) or Greater Washington, D.C. (comparison) communities in 2007 or 2011. Statistical analysis was completed in 2012. The main outcome was self-report of HBV testing, defined as participants answering 'Yes' to the question: 'Have you ever had a blood test to check for hepatitis B?'Results: The sample sizes at pre- and post-intervention were 1,704 and 1,666, respectively. Both communities reported increased exposure to HBV-related booklets, radio and television advertisements, and websites. Only the intervention community reported increased exposure to newspaper elements. HBV screening increased in both communities (intervention: 65.3% to 73.1%, p < 0.01, comparison: 57.7% to 66.0%, p < 0.01). In multivariable analyses, there was no intervention effect. In both communities, exposure to media elements (Odds Ratio 1.26 [95% Confidence Interval: 1.21, 1.31] for each additional element) was significantly associated with screening.Conclusions: Among Vietnamese Americans in 2 large communities, HBV screening rates were sub-optimal. Screening increased in both the intensive media intervention and comparison communities, and exposure to HBV-related media messages was associated with increased screening. Efforts to address HBV screening among Vietnamese Americans should include mass media messaging.

Patient and clinician factors associated with uptake of the human papillomavirus (HPV) vaccine among adolescent patients of a primary care network.

BACKGROUND: Human papillomavirus (HPV) vaccination rates for adolescents remain relatively low. The purpose of this study is to examine patient and clinician factors associated with HPV vaccination among patients, ages 11-17, of a large community-based primary care network. METHODS: Electronic health records and administrative data from a large primary care network from January 2017 - June 2018 for patients ages 11-17 (n = 10,682) and the 198 primary care clinicians that saw them were analyzed. Mixed effects logistic regression models examined the association of patient and clinician factors with HPV vaccine uptake. RESULTS: Most patients (63.0%) had at least one dose of the HPV vaccine, and 37.7% were up to date. In adjusted analyses, patients who received the tetanus, diphtheria, and pertussis (Tdap) vaccine (OR = 2.8, 95% CI: 2.1-3.9) compared to those who did not receive the vaccine and patients with five or more medical visits (OR = 1.9, 95% CI: 1.6-2.2) had the greatest odds of being up to date with the HPV vaccine series. Compared to White patients, African American/Black (OR = 0.8, 95% CI: 0.6 - 1.0) and Alaskan Native/American Indian (OR = 0.5, 95% CI: 0.3-0.9) patients were less likely to be up to date. Boys were also less likely to be up to date with the HPV vaccine series compared to girls (OR = 0.7, 95% CI: 0.7-0.8). Additionally, patients with family/general practice primary care clinicians were less likely to have their patients up to date than those with pediatricians (OR = 0.8, 95% CI: 0.6 - 1.0). CONCLUSION: HPV vaccine uptake varied by patient characteristics, heath care utilization and primary care clinician specialty. These findings may inform future evidence-based interventions aimed at increasing HPV vaccine uptake among adolescents by targeting patient sub-groups and reducing missed opportunities for vaccination.