Advancements and future directions in positron emission tomography-guided radiotherapy: a narrative review.

BACKGROUND AND OBJECTIVE: Positron emission tomography (PET) imaging has been useful in delineating tumor volumes and allowing for improved radiation treatment. The field of PET-guided radiotherapy is rapidly growing and will have significant impact on radiotherapy delivery in the future. This narrative review provides an overview of the current state of PET-guided radiotherapy as well as the future directions of the field. METHODS: For this narrative review, PubMed was searched for articles from 2010-2023. A total of 18 keywords or phrases were searched to provide an overview of PET-guided radiotherapy, radiotracers, the role of PET-guided radiotherapy in oligometastatic disease, and biology-guided radiotherapy (BgRT). The first 300 results for each keyword were searched and relevant articles were extracted. The references of these articles were also reviewed for relevant articles. KEY CONTENT AND FINDINGS: In radiotherapy, 18F-2-fluoro-2-deoxy-D-glucose (F-FDG or FDG) is the major radiotracer for PET and when combined with computed tomography (CT) scan allows for anatomic visualization of metabolically active malignancy. Novel radiotracers are being explored to delineate certain cell types and numerous tumor metrics including metabolism, hypoxia, vascularity, and cellular proliferation. This molecular and functional imaging will provide improved tumor characterization. Through these radiotracers, radiation plans can employ dose painting by creating different dose levels based upon specific risk factors of the target volume. Additionally, biologic imaging during radiotherapy can allow for adaptation of the radiation plan based on response to treatment. Dose painting and adaptive radiotherapy should improve the therapeutic ratio through more selective dose delivery. The novel PET-linear accelerator hopes to combine these techniques and more by using radiotracers to deliver BgRT. The areas of radiotracer uptake will serve as fiducials to guide radiotherapy to themselves. This technique may prove promising in the growing area of oligometastatic radiation treatment. CONCLUSIONS: Significant challenges exist for the future of PET-guided radiotherapy. However, with the advancements being made, PET imaging is set to change the delivery of radiotherapy.

Contrast-Enhanced Liver Magnetic Resonance Image Synthesis Using Gradient Regularized Multi-Modal Multi-Discrimination Sparse Attention Fusion GAN.

PURPOSES: To provide abdominal contrast-enhanced MR image synthesis, we developed an gradient regularized multi-modal multi-discrimination sparse attention fusion generative adversarial network (GRMM-GAN) to avoid repeated contrast injections to patients and facilitate adaptive monitoring. METHODS: With IRB approval, 165 abdominal MR studies from 61 liver cancer patients were retrospectively solicited from our institutional database. Each study included T2, T1 pre-contrast (T1pre), and T1 contrast-enhanced (T1ce) images. The GRMM-GAN synthesis pipeline consists of a sparse attention fusion network, an image gradient regularizer (GR), and a generative adversarial network with multi-discrimination. The studies were randomly divided into 115 for training, 20 for validation, and 30 for testing. The two pre-contrast MR modalities, T2 and T1pre images, were adopted as inputs in the training phase. The T1ce image at the portal venous phase was used as an output. The synthesized T1ce images were compared with the ground truth T1ce images. The evaluation metrics include peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and mean squared error (MSE). A Turing test and experts' contours evaluated the image synthesis quality. RESULTS: The proposed GRMM-GAN model achieved a PSNR of 28.56, an SSIM of 0.869, and an MSE of 83.27. The proposed model showed statistically significant improvements in all metrics tested with p-values < 0.05 over the state-of-the-art model comparisons. The average Turing test score was 52.33%, which is close to random guessing, supporting the model's effectiveness for clinical application. In the tumor-specific region analysis, the average tumor contrast-to-noise ratio (CNR) of the synthesized MR images was not statistically significant from the real MR images. The average DICE from real vs. synthetic images was 0.90 compared to the inter-operator DICE of 0.91. CONCLUSION: We demonstrated the function of a novel multi-modal MR image synthesis neural network GRMM-GAN for T1ce MR synthesis based on pre-contrast T1 and T2 MR images. GRMM-GAN shows promise for avoiding repeated contrast injections during radiation therapy treatment.

Knowledge and Understanding of Radiation Therapy Among Patients With Breast Cancer From Culturally Diverse Backgrounds at a Safety-Net Hospital.

INTRODUCTION: Comprehensive understanding of oncologic treatment is essential for shared decision-making. However, comprehension of information in radiation oncology consults is poorly understood, particularly among Spanish-speaking patients at safetynet hospitals. The purpose of this pilot study was to examine post-consultation radiation oncology knowledge and health literacy among breast cancer patients from culturally diverse backgrounds. METHODS: After consultation for curative post-operative breast radiotherapy (cT1-4N1-3M0), the Radiation Oncology Knowledge Assessment Survey (ROKAS) was administered to Spanish- and English-speaking patients ≥ 18 years old, from January 2021 to January 2022 at a safety-net hospital. Radiation knowledge was assessed using the ROKAS which included eight radiation-specific multiple-choice questions and two separate questions regarding short- and long-term side effects. Additional independent variables included validated questionnaires related to health literacy, health numeracy, acculturation, primary language, and sociodemographic factors. Bivariate Pearson correlations and T-test analyses were conducted to examine the relationship between the independent variables and post-consultation radiation knowledge. RESULTS: Fifty ROKAS were obtained from 25 English- and 25 Spanish-speaking breast cancer patients (median age 57 [IQR 49.75-62.25]). When compared to Englishspeaking patients, Spanish-speaking patients had lower health literacy, health numeracy, and acculturation. There was no difference in the multiple-choice ROKAS score between English- and Spanish-speakers, or correlation with the other independent factors. Higher health numeracy correlated with a higher accuracy for identifying short-term side effects. Lower accuracy of identifying long-term side effects was seen in patients with lower education levels, health literacy, health numeracy, and acculturation, with the most missed long-term side effects being arm swelling, skin toxicity, and heart toxicity. CONCLUSIONS: Patients with low health literacy, health numeracy, acculturation, and education levels as well as Spanish-speaking patients were associated with poor understanding of radiotherapy long-term side effects. Determining barriers to radiation knowledge is crucial to improve shared decision-making between patients and providers in a culturally diverse population.

Incorporation of vaginal brachytherapy to external beam radiotherapy in adjuvant therapy for high-risk early-stage cervical cancer: A comparative study.

PURPOSE: To examine trends, characteristics, and outcomes related to addition of vaginal brachytherapy (VBT) to external beam radiotherapy (EBRT) for adjuvant radiotherapy in high-risk early-stage cervical cancer. METHODS AND MATERIALS: This comparative study is a retrospective observational analysis of the National Cancer Institutes' Surveillance, Epidemiology, and End Results Program. Surgically treated women with stage T1-2 cervical cancer who had high-risk factors (nodal metastasis and/or parametrial invasion) and received adjuvant radiotherapy from 2000 to 2018 were examined. Propensity score inverse probability of treatment weighting was used to assess the survival estimates for addition of VBT use. RESULTS: Among 2470 women with high-risk factors receiving EBRT, 760 (30.8%) had additional VBT. During the study period, there was an increasing trend of VBT use from 27.4% to 36.1% (p< 0.001). In a multivariable analysis, year of diagnosis and high-risk tumor factors: parametrial involvement, large tumor size, and use of chemotherapy remained independent characteristics associated with VBT use (all, p< 0.05). In propensity score-weighted models, VBT use with EBRT and EBRT alone had comparable overall survival (5-year rates 73.8% vs. 77.4%, hazard ratio [HR] 1.07, 95% confidence interval [CI] 0.92-1.25). Nonsignificant association was also observed in squamous or nonsquamous tumors, young or old age, low or high nodal ratio, chemotherapy use, and simple or radical hysterectomy (all, p> 0.05). Lastly, the addition of VBT was not associated with cervical cancer-specific survival (subdistribution-HR 1.15, 95% CI 0.94-1.41). CONCLUSIONS: Utilization of VBT with EBRT for adjuvant radiotherapy in high-risk early-stage cervical cancer is increasing in the United States. Addition of VBT was associated with neither overall survival nor cancer-specific survival.

Racial disparities and standard treatment in locally advanced rectal cancer: a National Cancer Database study.

Background: Mortality rates in colorectal cancer (CRC) continue to be higher in Black compared to White patients. While standard treatment modalities for locally advanced rectal cancer have been shown to improve outcomes, there are limited studies assessing the receipt of standard treatment in rectal cancer based on race. Therefore, we sought to evaluate the use of standard treatment across racial groups in locally advanced rectal cancer and its effect on survival. Methods: The National Cancer Database (NCDB) was queried for patients ≥18 years old with clinical and pathologic stage II-III rectal adenocarcinoma who received treatment from 2004 to 2014. Standard treatment was defined as complete surgical excision with either neoadjuvant or adjuvant concurrent chemoradiation. Multivariable logistic regressions were used to identify racial differences in receiving standard treatment. Cox proportional hazards were used to estimate the effects of standard vs. nonstandard treatment on survival differences based on race. Results: A total of 70,677 patients with stage II (n=35,079) or stage III (n=35,598) rectal adenocarcinoma met the inclusion criteria. On multivariate analysis, Black [odds ratio (OR): 0.75; 95% confidence interval (CI): 0.71-0.79; P<0.001] and Hispanic White (OR: 0.86; 95% CI: 0.80-0.92; P>0.001) patients were less likely to receive standard treatment compared to non-Hispanic White patients. On multivariable Cox regression, nonstandard treatment was significantly associated with worse survival [hazard ratio (HR): 1.69; 95% CI: 1.65-1.73; P<0.001] compared to standard treatment. Even after adjusting for patient, demographic, and facility characteristics, Black patients had higher mortality rates compared to White patients in the whole population (HR: 1.15; 95% CI: 1.09-1.20; P<0.0001). This survival difference between Black and non-Hispanic White patients persisted in both the standard (HR: 1.10; 95% CI: 1.03-1.19; P=0.008) and nonstandard (HR: 1.17; 95% CI: 1.10-1.25; P<0.0001) treatment subgroups. Decreased survival outcomes in Black patients were more pronounced for those who underwent nonstandard treatment, particularly when treating stage III disease (HR: 1.30; 95% CI: 1.19-1.42; P<0.0001). Conclusions: Nonstandard treatment in stage II and III rectal cancer is associated with worse survival compared to standard treatment regimens. Black patients are more likely to receive nonstandard treatment and have worse survival outcomes compared to White patients.

Surviving Over a Decade With Glioblastoma: A Clinical Course Characterized by Multiple Recurrences, Numerous Salvage Treatments, and Novel Use of Cesium-131 Tiles.

The prognosis for patients diagnosed with recurrent glioblastoma (GBM) remains poor, with no clear standard of care regarding salvage therapy. Common approaches include chemotherapy, re-resection, tumor treating fields, and reirradiation. However, most studies have shown these to have limited benefits. Reirradiation is particularly difficult due to concern for increased risk of toxicity to surrounding normal brain tissue. A novel intracranial brachytherapy system called GammaTile® (GT Medical Technologies, Tempe, Arizona) involves the placement of Cesium-131 radioactive tiles in the tumor cavity following maximal safe resection. This allows for a highly conformal dose distribution with rapid fall-off to minimize overlap with prior radiation fields and for the application of radiation directly to the high-risk tumor bed. This case report highlights a patient with GBM who survived 11.5 years through multiple recurrences and discusses the many salvage treatments he received, including bevacizumab, irinotecan, and stereotactic radiosurgery (SRS). This case exemplifies that aggressive systemic and local therapies can work well in select patients allowing for long-term survival with a good quality of life. Further efforts should be made to identify which patients may benefit from these therapies. The case study additionally reports on the use of GammaTile therapy. Due to prior external beam radiation therapy and SRS to the treatment site, further external beam radiation options were limited, and the patient was offered GammaTile as local therapy. Although it did not provide a survival benefit in this case due to progressive disease outside of the field of treatment, GammaTile serves as a valuable option in providing local therapy to patients who can no longer receive further radiation. It should be used with careful consideration in lesions characterized by aggressive local invasion.

The Role of Radiotherapy Among Patients With Prostate Ductal Adenocarcinoma.

INTRODUCTION: The aim of this study was to perform a Surveillance, Epidemiology, and End Results (SEER) analysis on the effect of radiotherapy (RT) on survival among patients with prostate ductal adenocarcinoma (DA), a rare variant of prostate cancer. PATIENTS AND METHODS: Cases of T1 to 4 N0 M0 prostate DA diagnosed between 2004 and 2013 were extracted from SEER. The association between categorical variables and radiation therapy was assessed for statistical significance using the χ2 test or Fisher exact test. Difference in continuous variables across the RT groups was assessed for statistical significance using the 2-sample t test or non-parametric test. The distribution of overall survival (OS) and disease-specific survival (DSS) between the RT groups was assessed using the Kaplan-Meier method and the log rank test and after propensity matching. The association between hazards of death (HR) and covariates was examined using Cox proportional hazards model. A 2-sided P-value of .05 was used to determine statistical significance. RESULTS: A total of 205 patients met inclusion criteria. On univariate analysis, RT was associated with significant improvement in OS and DSS. On multivariate Cox regression, RT significantly decreased risk of death for both OS and DSS (HR, 0.516; 95% confidence interval [CI], 0.273-0.978 and HR, 0.232; 95% CI, 0.082-0.658, respectively). After propensity score matching, RT demonstrated a persistent improvement in both OS and DSS. CONCLUSIONS: RT decreased risk of death for both OS and DSS in patients with node-negative, nonmetastatic prostate DA on multivariable analysis. RT was also associated with improved OS and DSS after propensity matching.

Smoking Cessation at a Safety-Net Hospital: A Radiation Oncology Resident-Led Quality Improvement Initiative.

PURPOSE: Continued smoking among patients with cancer has been associated with increased toxicities, resistance to treatment, and recurrence. This resident-led quality improvement study attempted to increase smoking cessation by providing free smoking cessation medications in the radiation oncology clinic. METHODS AND MATERIALS: Twenty currently smoking patients with nonmetastatic cancer were prospectively enrolled. First line treatment was protocol-standardized combined nicotine replacement therapy (patches and lozenges). Therapy was initiated before radiation therapy and given for 12 weeks. Patient self-reported tobacco use was assessed at midtreatment, end of 12-week treatment, 3-month follow-up, 6-month follow-up, and 12-month follow-up. RESULTS: Within the initial cohort of 20 patients, average years smoked was 36.3 years (median = 37.5). In addition, 85% had attempted to quit previously. Among patients initially enrolled, 3 did not initiate radiation therapy, and 4 were removed from the study by midtreatment due to noncompliance. Midway through treatment, patients had cut self-reported cigarette use to 31% of baseline. However, 75% or more of patients had smoked within the last week at all timepoints assessed. With further follow-up, the number of cigarettes smoked daily continued to rise, reaching 61% of baseline by the 12-month follow-up. CONCLUSIONS: Patients reduced cigarette consumption, but all patients eventually resumed smoking during the 12-month follow-up. Although it is unfortunate that this study did not result in long-term smoking cessation, the results demonstrate the difficulties faced in helping patients with cancer quit, particularly patients seen at a safety-net hospital. Future efforts could be directed at intensified smoking cessation programs, likely incorporating a more standardized counseling component.

Impact of radiotherapy duration on overall survival in squamous cell carcinoma of the anus.

BACKGROUND: Prolongation of radiotherapy (RT) in the treatment of numerous types of cancer has been shown to reduce overall survival (OS). Treatment delays are common in squamous cell carcinoma of the anus (SCCA) due to the toxicity of definitive chemoradiation (CRT). The effect of these delays on outcomes has not been well evaluated. This study investigated the effects of RT prolongation on OS in patients receiving CRT for SCCA. METHODS: The National Cancer Database was queried for adult patients diagnosed with SCCA and treated with CRT from 2004-2014. Cox proportional hazard regression models examined the effect of duration of RT, measured as fractions delivered per week, on OS. Negative binomial regression assessed the effects of demographic and prognostic factors on the duration of RT. RESULTS: A total of 8,948 patients were included in the analysis of factors impacting treatment duration, and 6,429 patients in the OS analysis. Multivariable analysis (MVA) showed female gender, non-private insurance, treatment at a low or intermediate volume facility, Charlson/Deyo score ≥2, and advanced disease were associated with longer RT duration. Treatment with IMRT, with single agent chemotherapy, at an academic center, and in later years were associated with shorter RT duration. A decrease in fractions delivered per week was independently associated with reduced OS with a cutoff of 4.72 fractions per week (about 2 missed fractions over a 30 fraction treatment) delineating the largest differences in OS. CONCLUSIONS: Efforts should be made to avoid RT interruptions of any length in SCCA patients and to compensate for treatment breaks to reduce the total duration of RT.

Artifact from myomectomy/C-Section on MRI images - what does this mean for MR-guided focused ultrasound candidacy for uterine fibroids?

Background: Magnetic resonance-guided focused ultrasound (MRgFUS) is used for non-surgical treatment of uterine fibroids, often in patients who have had prior myomectomy or Cesarean section. The presence of post-surgical MRI artifacts along the beam path are a common contraindication to MRgFUS treatment. While potential problems arising from superficial cutaneous scars can be circumvented through scar patching and other techniques, deeper artifacts are difficult to bypass. Consequently, many patients with deeper artifacts are often excluded from treatment because of the assumption that these artifacts could deflect the ultrasound beam resulting in off target heating or perturb accurate MR thermometry. We sought to determine if these deep artifacts affect MRgFUS treatment efficacy or safety.Materials and Methods: A search of a MRgFUS center patient database yielded 19 patients with prior uterine surgery who had artifacts along the FUS beam path visible on MRI. Charts, operative reports (when available), screening MRI scans, and MRgFUS treatment scans were reviewed by an experienced MRgFUS treatment physician and artifacts were graded as mild, moderate, or severe.Results: One-way ANOVA showed no significant correlation between artifact severity and percent non-perfused volume (%NPV) (p = .41) or between fibroid size and % NPV (p = .49). There were no adverse events in this patient population except for one case of endometritis that occurred months after the operation, unlikely to be related to the MRgFUS treatments.Conclusion: Patients with uterine fibroids with post-operative susceptibility artifacts in the near-field can be successfully treated with MRgFUS.

Dosimetric effects of the Smit sleeve on high-dose-rate brachytherapy tandem and ovoids plans for patients with locally advanced cervical cancer.

PURPOSE: Smit sleeves are used to facilitate insertion of the intrauterine tandem during brachytherapy for cervical cancer. When a tandem and ovoids system is used the base of the Smit sleeve displaces the ovoids distally. The dosimetric impact of this displacement is not known. Herein we performed a dosimetric analysis to quantify this impact on the integral dose and dose delivered to the organs at risk (OARs). MATERIAL AND METHODS: Eleven high-dose-rate brachytherapy plans in which a Smit sleeve was used with a tandem and ovoids were reviewed. A second set of plans was generated modifying the position of the ovoids to simulate absence of the Smit sleeve. The high-risk clinical tumor volume (HR-CTV) dose coverage was maintained the same for both sets of plans by appropriately rescaling the dwell times of the simulated plan. The mean integral dose, D2cc to the OARs (bladder, bowel, sigmoid and rectum) and the ICRU rectum point dose were compared between the original and modified plans using a paired two-sample t-test. RESULTS: Simulating removal of the Smit sleeve was associated with an average reduction in the mean integral dose of 6.1% (p < 0.001) and an average reduction of 10.9% (p = 0.004) to the rectal D2cc. Doses to the remaining OARs decreased to a lesser magnitude with only that of the sigmoid being statistically significant. CONCLUSIONS: The use of a Smit sleeve with a tandem and ovoids system could lead to the delivery of a higher mean integral dose to achieve similar HR-CTV coverage. In addition, it could increase the dose to surrounding OARs, primarily the rectum. The clinical significance of these findings is unknown, but the potential dosimetric impact of using a Smit sleeve should be taken into consideration during the planning when this device is used.

Meaningful and Accurate Disclosure of Conflict of Interest at the ASTRO National Meeting: A Need for Reassessment of Current Policies.

PURPOSE:: Conflict of interest (COI) disclosure is essential to research integrity. The average reading comprehension in English is 3.8 words per second (wps). This study examines presenters at the American Society for Radiation Oncology (ASTRO) national meeting over a recent 3-year period to determine whether disclosure is presented accurately and in a manner that allows the audience to comprehend the content. METHODS:: We examined videos of presentations as well as slides from 2014 to 2016 from the ASTRO virtual meeting, noting whether a COI slide was presented, the duration the slide was visible, and the number of disclosures. Disclosures were cross-referenced for discrepancies with the publicly reported Centers for Medicare and Medicaid Services Open Payments database. Using a cutoff of 4 wps, we noted how many presentations were presented at speeds of ≤ 4 wps and > 4 wps. RESULTS:: The final data set consisted of 401 presentations delivered by 364 presenters. Using a threshold of 4 wps, 34.0% of presenters had COI slides shown too fast for the average audience to comprehend. Moreover, 16.3% of US physicians incorrectly underreported industry funding received. Of these presentations with discrepancies, 32.6% did not have a COI slide, 39.5% failed to disclose any COI, 27.9% partially disclosed COIs, and 11.6% contained multiple discrepancies. The number of wps were correlated with having a discrepancy on multivariable regression ( P = .046; odds ratio, 1.08; 95% CI, 1.01 to 1.19). CONCLUSION:: A substantial minority of presentations at ASTRO lack meaningful disclosure, and a surprising number incorrectly reported COIs. Additional guidance may be needed to promote more meaningful and accurate disclosure of COIs at major national meetings in oncology.

Magnetic Resonance-guided External Beam Radiation and Brachytherapy for a Patient with Intact Cervical Cancer.

Radiation treatment verification has improved significantly over the past decades. The field has moved from film X-rays and skin marks to fiducial tracking and daily cone beam computed tomography (CBCT) for tumor localization. We now have the ability to perform daily on-board magnetic resonance imaging (MRI), which provides superior soft tissue contrast compared to computed tomography (CT). In the management of cervical cancer, the brachytherapy literature has demonstrated that MRI allows for better delineation of the high-risk clinical target volume (HR-CTV) and the use of MRI-guided brachytherapy has translated into improved treatment outcomes. Consensus contouring guidelines for intensity modulated radiation therapy (IMRT) for cervical cancer advise including the whole uterus in the target volume and adding large planning target volume (PTV) margins to account for inter-fractional uterine motion and target motion resulting from variable rectal and bladder filling. MRI-guided radiation therapy (MRgRT) systems enable the possibility to precisely delineate the target volume on a daily basis and to perform truly adaptive delivery. This advancement in technology provides the opportunity to explore how external beam treatment volumes could be safely reduced for better sparing of pelvic organs for the benefit of our patients with cervical cancer. We describe the MR-guided definitive external beam radiation therapy and brachytherapy for a 32-year-old woman with intact cervical cancer. We contoured the uterus, bladder, rectum, and gross tumor volume (GTV) on each of her 25 set-up MRIs. We demonstrate a steady reduction in the GTV and increased displacement of the uterus and GTV as the GTV decreased in size. The findings presented suggest that cervical cancer could greatly benefit from an adaptive MRgRT approach.

Daily Tracking of Glioblastoma Resection Cavity, Cerebral Edema, and Tumor Volume with MRI-Guided Radiation Therapy.

Radiation therapy (RT) plays a critical role in the treatment of glioblastoma. Studies of brain imaging during RT for glioblastoma have demonstrated changes in the brain during RT. However, frequent or daily utilization of standalone magnetic resonance imaging (MRI) scans during RT have limited feasibility. The recent release of the tri-cobalt-60 MRI-guided RT (MR-IGRT) device (ViewRay MRIdian, Cleveland, OH) allows for daily brain MRI for the RT setup. Daily MRI of three postoperative patients undergoing RT and temozolomide for glioblastoma over a six-week course allowed for the identification of changes to the cavity, edema, and visible tumor on a daily basis. The volumes and dimensions of the resection cavities, edema, and T2-hyperintense tumor were measured. A general trend of daily decreases in cavity measurements was observed in all patients. For the one patient with edema, a trend of daily increases followed by a trend of daily decreases were observed. These results suggest that daily MRI could be used for onboard resimulation and adaptive RT for future fluctuations in the sizes of brain tumors, cavities, or cystic components. This could improve tumor targeting and reduce RT of healthy brain tissue.

Antibacterial effects of zinc oxide nanorod surfaces.

Antibacterial coating approaches are being investigated to modify implants to reduce bacterial adhesion and viability in order to reduce implant-associated infection. Nanostructured materials possess unique surface properties, and nanotopographic surfaces have been reported to modulate bacterial adhesion. Zinc oxide (ZnO) films presenting well-controlled nanorod surface structures have recently been developed. To assess the efficacy of ZnO nanorod surfaces as an anti-bacterial coating, we evaluated bacterial adhesion and viability, compared to sputtered ZnO substrates (a relatively flat control) and glass substrates (as a reference). Common implant-associated pathogens, Pseudomonas aeruginosa and Staphylococcus epidermidis were investigated. The number of adherent P. aeruginosa on ZnO nanorod surfaces was found to be reduced compared to glass and sputtered ZnO, while the adherent number of S. epidermidis on the ZnO nanorods was equivalent to glass. Regarding bacteria viability, the ZnO nanorod and sputtered ZnO surfaces demonstrated a modest, but significant bactericidal effect on adherent P. aeruginosa, killing 2.5-fold and 1.7-fold more over the number of dead P. aeruginosa on glass, respectively. A greater bactericidal effect of ZnO substrates on S. epidermidis was found, with sputtered ZnO and ZnO nanorod substrates killing -20-fold and 30-fold more over the number of dead S. epidermidis on glass, respectively. These data support the further investigation and optimization of ZnO nanorod coatings with potential for bacterial adhesion resistance and bactericidal properties.