ACR-ARS Practice Parameter for Communication: Radiation Oncology.

BACKGROUND: This practice parameter was revised collaboratively by the American College of Radiology (ACR), and the American Radium Society (ARS). Timely, accurate, and effective communications are critical to quality and safety in contemporary medical practices. Radiation oncology incorporates the science and technology of complex, integrated treatment delivery and the art of providing care to individual patients. Through written physical and/or electronic reports and direct communication, radiation oncologists convey their knowledge and evaluation regarding patient care, clinical workup, and treatment provided to others in the management of the patient. Applicable practice parameters need to be revised periodically regarding medical record documentation for professional and technical components of services delivered. METHODS: This practice parameter was developed and revised according to the process described under the heading "The Process for Developing ACR Practice Parameters and Technical Standards" on the ACR website ( https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards ) by the Committee on Practice Parameters-Radiation Oncology of the ACR Commission on Radiation Oncology in collaboration with the ARS. Both societies have reviewed and approved the document. RESULTS: This practice parameter addresses radiation oncology communications in general, including (a) medical record, (b) electronic, and (c) doctor-patient communications, as well as specific documentation for radiation oncology reports such as (a) consultation, (b) clinical treatment management notes (including inpatient communication), (c) treatment (completion) summary, and (d) follow-up visits. CONCLUSIONS: The radiation oncologist's participation in the multidisciplinary management of patients is reflected in timely, medically appropriate, and informative communication with patients, caregivers, referring physician, and other members of the health care team. The ACR-ARS Practice Parameter for Communication: Radiation Oncology is an educational tool designed to assist practitioners in providing appropriate communication regarding radiation oncology care for patients.

Performance characteristics of a prototype dialysate turbidity monitoring system to detect peritonitis in patients receiving peritoneal dialysis.

BACKGROUND: The risk of peritonitis has limited wider adoption of peritoneal dialysis (PD) in the United States. We developed a prototype bedside dialysate turbidity monitoring system, aiming to improve diagnostic accuracy relative to conventional approaches which depend on visual inspection and reporting of insensitive and non-specific symptoms. METHODS: The prototype system was tested in a single-centre, proof-of-principle clinical study in patients receiving intermittent PD. We obtained multiple effluent dialysate samples from each consenting participant. We compared turbidity measurements with diagnostic criteria endorsed by the International Society of Peritoneal Dialysis (ISPD). RESULTS: Overall, we analysed 983 specimens from 65 patients, including 105 samples from patients with peritonitis and 878 samples from patients without peritonitis. An operating point derived from a previous in vitro study yielded an unadjusted sensitivity and specificity of 95.2% and 91.5%, respectively. The majority of samples that did not meet ISPD diagnostic criteria were either cases detected before criteria were met or were related to active peritonitis treatment and resolution. CONCLUSION: This proof-of-principle study demonstrates the feasibility and diagnostic accuracy of a prototype dialysate turbidity monitoring system for peritonitis surveillance.

Vidutolimod in Combination With Atezolizumab With and Without Radiation Therapy in Patients With Programmed Cell Death Protein 1 or Programmed Death-Ligand 1 Blockade-Resistant Advanced NSCLC.

Introduction: Vidutolimod, a CpG-A TLR9 agonist, was investigated in a phase 1b study (CMP-001-003; ClinicalTrials.gov, NCT03438318) in combination with atezolizumab with and without radiation therapy (RT) in patients with advanced NSCLC. Methods: Patients with progressive disease after anti-programmed cell death protein 1 or programmed death-ligand 1 therapy received either vidutolimod and atezolizumab (part A) or vidutolimod, atezolizumab, and RT (part B). The primary objective was to evaluate the safety of vidutolimod and atezolizumab with and without RT. Key secondary end point was best objective response rate per Response Evaluation Criteria in Solid Tumors, version 1.1. Results: Between March 28, 2018, and July 25, 2019, a total of 29 patients were enrolled and received at least one dose of vidutolimod (part A, n = 13; part B, n = 16). Intratumoral injections of vidutolimod were administered successfully, including injection of visceral lesions. The most common treatment-related adverse events (≥30%) were flu-like symptoms and hypotension. No objective responses were observed; 23.1% and 50.0% of the patients in parts A and B, respectively, had stable disease as best response. In parts A and B, 15.4% and 25.0% of the patients, respectively, had tumor shrinkage (<30% decrease in tumor size, nonirradiated). Enrollment was stopped owing to lack of objective responses. In the two patients with initial tumor shrinkage in part A, a strong serum induction of C-X-C motif chemokine ligand 10 was observed. Conclusions: Vidutolimod and atezolizumab with and without RT had a manageable safety profile, with minimal clinical activity in heavily pretreated patients with programmed cell death protein 1 or programmed death-ligand 1 blockade-resistant NSCLC.

Rate of Formation of Industrial Lubricant Additive Precursors from Maleic Anhydride and Polyisobutylene.

The Alder-ene reaction of neat polyisobutylene (PIB) and maleic anhydride (MAA) to produce the industrially important lubricant additive precursor polyisobutylene succinic anhydride (PIBSA) is studied at 150-180 °C. Under anaerobic conditions with [PIB] ∼ 1.24 M (550 g mol-1 grade, >80% exo alkene) and [MAA] ∼ 1.75 M, conversion of exo-PIB and MAA follows second-order near-equal rate laws with k obs up to 5 × 10-5 M-1 s-1 for both components. The exo-alkene-derived primary product PIBSA-I is formed at an equivalent rate. The less reactive olefinic protons of exo-PIB also react with MAA to form isomeric PIBSA-II (k obs up to 6 × 10-5 M-1 s-1). Some exo-PIB is converted to endo-PIB (containing trisubstituted alkene) in a first-order process (k obs ∼ 1 × 10-5 s-1), while PIBSA-I is difunctionalized by MAA to bis-PIBSAs very slowly. The MAA- and PIB-derived activation parameter ΔG ‡(150 °C) 34.3 ± 0.3 kcal mol-1 supports a concerted process, with that of PIBSA-I suggesting a late (product-like) transition state.

Factors Associated With Image-Guided Radiation Therapy Image Rejection in a Multisite Institution.

PURPOSE: Nonclinical factors and cognitive biases have been shown to significantly affect clinical decision making. In this study, we aimed to identify clinical and environmental factors that might influence the decision to approve or reject image-guided radiation therapy (IGRT) images in a large multisite institution. METHODS: We identified all IGRT image approval and rejection decisions recorded within an electronic imaging system from July 1, 2016, to June 30, 2018. For each decision, we tabulated the following parameters: the attending physician of the patient, the physician reviewing the image, total images reviewed by the physician that day, time of day, day of week, treatment site, and imaging modality (kilovoltage or cone beam computed tomography [CBCT]). We created a binary multivariable logistic regression model to identify factors associated with IGRT image rejection. RESULTS: Overall, of 51,797 total image records evaluated, 881 (1.70%) were rejected and 50,916 (98.30%) were approved. Univariable analysis revealed that images reviewed by physicians with high rejection rates (odds ratio [OR], 3.16; P < .001) and by physicians reviewing fewer IGRT images (OR, 0.99; P = .024), images from various anatomic sites (particularly skin, breast, and head and neck), and CBCT imaging compared with kilovoltage imaging (OR, 1.49; P < .001) were associated with the increased rate of rejection. On multivariable analysis, images reviewed by physicians with high rejection rates (OR, 3.28; P < .001), images from specific anatomic sites including breast (P < .001), and CBCT imaging (P < .001) persisted as independent predictors of image rejection. CONCLUSION: These data provide important insight into the clinical, cognitive, and environmental factors that might influence the routine clinical decision of IGRT image approval. Recognition of these factors may not only improve the quality of individual decisions but also identify opportunities for systems-based quality improvement in IGRT.

Consensus Quality Measures and Dose Constraints for Head and Neck Cancer with an emphasis on Oropharyngeal and Laryngeal Cancer from the Veterans Affairs Radiation Oncology Quality Surveillance Program and American Society for Radiation Oncology Expert Panel.

PURPOSE: Safeguarding high-quality care using evidence-based radiation therapy for patients with head and neck cancer is crucial to improving oncologic outcomes, including survival and quality of life. METHODS AND MATERIALS: The Veterans Administration (VA) National Radiation Oncology Program established the VA Radiation Oncology Quality Surveillance Program (VAROQS) to develop clinical quality measures (QM) in head and neck cancer. As part of the development of QM, the VA commissioned, along with the American Society for Radiation Oncology, a blue-ribbon panel comprising experts in head and neck cancer, to develop QM. RESULTS: We describe the methods used to develop QM and the final consensus QM, as well as aspirational and surveillance QM, which capture all aspects of the continuum of patient care from initial patient work-up, radiation treatment planning and delivery, and follow-up care, as well as dose volume constraints. CONCLUSION: These QM are intended for use as part of ongoing quality surveillance for veterans receiving radiation therapy throughout the VA as well as outside the VA. They may also be used by the non-VA community as a basic measure of quality care for head and neck cancer patients receiving radiation.

The economic impact of circulating tumor-tissue modified HPV DNA for the post-treatment surveillance of HPV-driven oropharyngeal cancer: A simulation.

PURPOSE: Following treatment of HPV-driven oropharynx cancer, surveillance nasopharyngoscopy and imaging are often performed but are expensive and frequently ineffective. A novel plasma circulating tumor-tissue modified viral HPV DNA (TTMV-HPV-DNA) assay accurately detects recurrences. We modeled the cost of the new assay. METHODS: We designed and validated a partitioned survival model which replicated the results of the RTOG 1016 study and calculated cumulative surveillance costs from the payer's perspective. Two strategies were considered: a standard of routine endoscopy with imaging as needed and an alternative strategy which omitted scopes and imaging but obtained serial TTMV-HPV-DNA samples. No difference in effectiveness (QALY or LY) was assumed in the base case. A 5-year horizon was used, costs were reported in 2020 U.S. dollars discounted by 3%. Seven scenarios tested model assumptions and practice variation. Deterministic and probabilistic sensitivity analyses assessed parameter uncertainty. RESULTS: In the base case, at the list TTMV-HPV-DNA price, the cumulative cost of surveillance was $11,674 for the standard strategy and $20,756 for the TTMV-HPV-DNA strategy (+$9082 over 5 years). Probabilistic sensitivity analysis demonstrated the cost difference ranged from $4917-$12,047. The TTMV-HPV-DNA strategy was most likely to be either cost saving or cost-effective if future data demonstrate small improvements in quality or quantity of life (approximately 33 quality-adjusted life-days), if the assay reduces utilization of imaging, and if the periodicity of TTMV-HPV-DNA draws could be reduced from that on clinical trials. CONCLUSIONS: This data informs providers seeking to design more accurate, accessible, and economical post-treatment surveillance strategies.

PSA: Declining utilization of prostate brachytherapy.

PURPOSE: To analyze rates of brachytherapy use for prostate cancer over time and evaluate patient characteristics, demographics and factors predictive for its utilization. METHODS: Data was retrospectively analyzed from the National Cancer Database (NCDB) for patients with localized prostate cancer treated between 2010 and 2015. Patients were included if they had biopsy confirmed localized adenocarcinoma of the prostate, were treated with radiation as definitive local therapy, and were at least 18 years old. Utilization rates of external beam radiation (EBRT), brachytherapy (BT) and combination (EBRT + BT) were evaluated over time. Univariable (UVA) and backwards elimination multivariable (MVA) analysis were performed to determine characteristics predictive for brachytherapy use. RESULTS: We analyzed 178,837 patients with localized adenocarcinoma of the prostate treated between 2010 and 2015 with radiation therapy. During this period, the use of EBRT increased from 67% to 78%, BT (both monotherapy and combination with EBRT) decreased from 33% to 22%, BT monotherapy decreased from 25% to 16% and EBRT + BT decreased from 8% to 6%. Age >70, government funded insurance or lack of insurance, intermediate or high-risk disease and treatment at an academic center were associated with significantly lower utilization of brachytherapy (all p <0.001), while higher median zip code income was associated with increased use (p = 0.02). On multivariable analysis patients who were younger, had private insurance, were lower NCCN risk category and treated in non-academic cancer centers, had a higher rate of brachytherapy utilization. Notably, on both UVA and MVA brachytherapy practice decreased with increasing year of diagnosis (OR 0.881, 95% CI 0.853-0.910, p <0.001). CONCLUSION: Rates of brachytherapy utilization for the treatment of prostate cancer continue to decrease over time. Treatment at an academic center was associated with reduced likelihood of brachytherapy use. This has significant implications for the training of future radiation oncology residents/fellows and direct consequences for both our patients and healthcare expenditure.

Racial and Ethnic Disparities Among Participants in US-Based Phase 3 Randomized Cancer Clinical Trials.

Although improving representation of racial and ethnic groups in United States clinical trials has been a focus of federal initiatives for nearly 3 decades, the status of racial and ethnic minority enrollment on cancer trials is largely unknown. We used a broad collection of phase 3 cancer trials derived from ClinicalTrials.gov to evaluate racial and ethnic enrollment among US cancer trials. The difference in incidence by race and ethnicity was the median absolute difference between trial and corresponding Surveillance, Epidemiology, and End Results data. All statistical tests were 2-sided. Using a cohort of 168 eligible trials, median difference in incidence by race and ethnicity was +6.8% for Whites (interquartile range [IQR] = +1.8% to +10.1%; P < .001 by Wilcoxon signed-rank test comparing median difference in incidence by race and ethnicity to a value of 0), -2.6% for Blacks (IQR = -5.1% to +1.2%; P = .004), -4.7% for Hispanics (IQR = -7.5% to -0.3%; P < .001), and -4.7% for Asians (IQR = -5.7% to -3.3%; P < .001). These data demonstrate overrepresentation of Whites, with continued underrepresentation of racial and ethnic minority subgroups.

Development of a Natural Language Processing Tool to Extract Radiation Treatment Sites.

Currently, radiation oncology-specific electronic medical records (EMRs) allow providers to input the radiation treatment site using free text. The purpose of this study is to develop a natural language processing (NLP) tool to extract encoded data from radiation treatment sites in an EMR. Treatment sites were extracted from all patients who completed treatment in our department from April 1, 2011, to April 30, 2013. A system was designed to extract the Unified Medical Language System (UMLS) concept codes using a sample of 11,018 unique site names from 31118 radiation therapy (RT) sites. Among those, 5500 unique site name strings that constitute approximately half of the sample were spared as a test set to evaluate the final system. A dictionary and calculated n-gram statistics using UMLS concepts from related semantic types were combined with manually encoded data. There was an average of 2.2 sites per patient. Prior to extraction, the 20 most common unique treatment sites were used 4215 times (38.3%). The most common treatment site was whole brain RT, which was entered using 27 distinct terms for a total of 1063 times. The customized NLP solution displayed great gains as compared to other systems, with a recall of 0.99 and a precision of 0.99. A customized NLP tool was extracting encoded data from radiation treatment sites in an EMR with great accuracy. This can be integrated into a repository of demographic, genomic, treatment, and outcome data to advance personalized oncologic care.

Building a medical workforce in Tasmania: A profile of medical student intake.

OBJECTIVE: To identify under-represented groups in a medical school intake. DESIGN: Descriptive analysis of student demographic characteristics. SETTING: One state-wide medical school. PARTICIPANTS: All students enrolled between 2010 and 2016. MAIN OUTCOME MEASURE(S): Proportion of students from regional and rural areas, state versus independent schools, highest parental qualification, Aboriginal or Torres Strait Islander students. RESULTS: Of 819 students, 472 (57.6%) were from Tasmania, five (1.1%) identified as Aboriginal or Torres Strait Islanders, 335 (71.0%) completed their secondary education at independent schools and 137 (29.0%) at government schools. The overall median Modified Monash Model was 2 (range 1-6) and median Australia Statistical Geography Standard Remoteness Area was 2 (inner regional: range 1-4), reflecting that a majority came from one of the two main cities. Over two-thirds (69.5%) had a parent with a Bachelor degree or higher qualification, regardless of the school attended. Just under half (225, 47.7%) of all Tasmanian students attended a secondary school with a parental contribution of ≥$5000 per annum. These students attended a small number of independent schools, with the proportion relatively stable over the period from 2010 to 2016. CONCLUSION: Widening participation and widening access initiatives to graduate doctors who understand and want to work in communities in need might not be working as well in Tasmania as elsewhere in Australia. Social accountability might be improved by adapting a rural classification that reflects the demographic profile of Tasmania.

An in-silico quality assurance study of contouring target volumes in thoracic tumors within a cooperative group setting.

INTRODUCTION: Target delineation variability is a significant technical impediment in multi-institutional trials which employ intensity modulated radiotherapy (IMRT), as there is a real potential for clinically meaningful variances that can impact the outcomes in clinical trials. The goal of this study is to determine the variability of target delineation among participants from different institutions as part of Southwest Oncology Group (SWOG) Radiotherapy Committee's multi-institutional in-silico quality assurance study in patients with Pancoast tumors as a "dry run" for trial implementation. METHODS: CT simulation scans were acquired from four patients with Pancoast tumor. Two patients had simulation 4D-CT and FDG-FDG PET-CT while two patients had 3D-CT and FDG-FDG PET-CT. Seventeen SWOG-affiliated physicians independently delineated target volumes defined as gross primary and nodal tumor volumes (GTV_P & GTV_N), clinical target volume (CTV), and planning target volume (PTV).Six board-certified thoracic radiation oncologists were designated as the 'Experts' for this study. Their delineations were used to create a simultaneous truth and performance level estimation (STAPLE) contours using ADMIRE software (Elekta AB, Sweden 2017). Individual participants' contours were then compared with Experts' STAPLE contours. RESULTS: When compared to the Experts' STAPLE, GTV_P had the best agreement among all participants, while GTV_N showed the lowest agreement among all participants. There were no statistically significant differences in all studied parameters for all TVs for cases with 4D-CT versus cases with 3D-CT simulation scans. CONCLUSIONS: High degree of inter-observer variation was noted for all target volume except for GTV_P, unveiling potentials for protocol modification for subsequent clinically meaningful improvement in target definition. Various similarity indices exist that can be used to guide multi-institutional radiotherapy delineation QA credentialing.

Palliation or Prolongation? The Impact of a Peer-Review Intervention on Shortening Radiotherapy Schedules for Bone Metastases.

PURPOSE: Shorter fractionation radiation regimens for palliation of bone metastases result in lower financial and social costs for patients and their caregivers and have similar efficacy as longer fractionation schedules, although practice patterns in the United States show poor adoption. We investigated whether prospective peer review can increase use of shorter fractionation schedules. METHODS: In June 2016, our practice mandated peer review of total dose and fractionation for all patients receiving palliative treatment during our weekly chart rounds. We used descriptive statistics and Fisher's exact test to compare lengths of treatment of uncomplicated bone metastases before and after implementation of the peer review process. RESULTS: Between July 2015 and December 2016, a total of 242 palliative treatment courses were delivered, including 105 courses before the peer review intervention and 137 after the intervention. We observed greater adoption of shorter fractionation regimens after the intervention. The use of 8 Gy in one fraction increased from 2.8% to 13.9% of cases postadoption. Likewise, the use of 20 Gy in five fractions increased from 25.7% to 32.8%. The use of 30 Gy in 10 fractions decreased from 55.2% to 47.4% ( P = .002), and the use of ≥ 11 fractions decreased from 16.2% before the intervention to 5.8% after ( P = .006). CONCLUSION: Prospective peer review of palliative regimens for bone metastases can lead to greater adoption of shorter palliative fractionation schedules in daily practice, in accordance with national guidelines. This simple intervention may therefore benefit patients and their caregivers as well as provide value to the health care system.

Provider variability in intensity modulated radiation therapy utilization among Medicare beneficiaries in the United States.

BACKGROUND: In this study, we sought to examine the variation in intensity modulated radiation therapy (IMRT) use among radiation oncology providers. METHODS AND MATERIALS: The Medicare Physician and Other Supplier Public Use File was queried for radiation oncologists practicing during 2014. Healthcare Common Procedural Coding System code 77301 was designated as IMRT planning with metrics including number of total IMRT plans, rate of IMRT utilization, and number of IMRT plans per distinct beneficiary. RESULTS: Of 2759 radiation oncologists, the median number of total IMRT plans was 26 (mean, 33.4; standard deviation, 26.2; range, 11-321) with a median IMRT utilization rate of 36% (mean, 43%; standard deviation, 25%; range, 4% to 100%) and a median number of IMRT plans per beneficiary of 1.02 (mean, 1.07; range, 1.00-3.73). On multivariable analysis, increased IMRT utilization was associated with male sex, academic practice, technical fee billing, freestanding practice, practice in a county with 21 or more radiation oncologists, and practice in the southern United States (P < .05). The top 1% of users (28 providers) billed a mean 181 IMRT plans with an IMRT utilization rate of 66% and 1.52 IMRT plans per beneficiary. Of these 28 providers, 24 had billed technical fees, 25 practiced in freestanding clinics, and 20 practiced in the South. CONCLUSIONS: Technical fee billing, freestanding practice, male sex, and location in the South were associated with increased IMRT use. A small group of outliers shared several common demographic and practice-based characteristics.

Building a local medical workforce in Tasmania: where are international fee-paying medical graduates likely to work?

INTRODUCTION: Much of regional Australia continues to face challenges in recruitment and retention of medical practitioners, despite the apparently successful rural medical education initiatives funded by the Commonwealth Government. International fee-paying (IFP) medical students are a significant component of Australian medical education, contributing additional income and more diverse learning environments for universities. Their contribution to the Australian medical workforce is harder to determine. After obtaining registration, IFP graduates may apply to remain in Australia as skilled migrants. Since 1999 there has been a 325% increase in the number of international medical students in Australia, with approximately 73% of IFP graduates remaining in Australia for at least some postgraduate training. Recognising the potential contribution of IFP students to the Tasmanian medical workforce, the authors sought better understanding of the career intentions and work locations of IFP graduates from the medical program in Tasmania, Australia, through two studies. Firstly, a quantitative study was conducted of the locations of all IFP graduates from the Tasmanian medical program, and then a qualitative study exploring graduating students' intentions and factors that contribute to their decisions about work location choices. METHODS: This was a cohort study of IFP students who graduated from the University of Tasmania School of Medicine over the period 2000-2015. Work locations for 2016 were mapped to a Modified Monash rurality classification. Semi-structured interviews were held with 15 final year IFP medical students, exploring career intentions and location preferences. RESULTS: There were 261 IFP graduates, 54.4% male. The most common country of origin was Malaysia (55.2%). In 2016, 189 (72.4 %) were working in Australia, 42 (16.1%) in Tasmania and 126 (66.7%) in areas categorised as Modified Monash 1. Recent graduates in postgraduate year 1/2 (71.3%) were more likely to be working in Tasmania but most left for specialty training. All 15 interview participants intended to remain in Australia for at least their intern year, although at enrolment only six had planned to remain. Factors influencing workplace location decisions were (1) 'professional': greater appeal of Australian medical workplaces, intention to pursue a speciality, and to complete this at an Australian metropolitan hospital; (2) 'social': proximity to family/partner or opportunity to meet a prospective partner, family obligations, positive rural experiences; and (3) 'location': direct travel access to family. CONCLUSIONS: IFP graduates from the Tasmanian medical program make an important contribution to the Australian mainland metropolitan medical workforce, but play only a small role in workforce development for both Tasmania and the broader Australian rural and remote context. Most IFPs do not choose to work rurally. Rurally focused medical programs need to consider how they place IFP students to meet both the learning and career needs of IFP students and the goal of the rural medical programs in developing a rural workforce.

Ontogeny of myosin isoform expression and prehensile function in the tail of the gray short-tailed opossum (Monodelphis domestica).

Terrestrial opossums use their semiprehensile tail for grasping nesting materials as opposed to arboreal maneuvering. We relate the development of this adaptive behavior with ontogenetic changes in myosin heavy chain (MHC) isoform expression from 21 days to adulthood. Monodelphis domestica is expected to demonstrate a progressive ability to flex the distal tail up to age 7 mo, when it should exhibit routine nest construction. We hypothesize that juvenile stages (3-7 mo) will be characterized by retention of the neonatal isoform (MHC-Neo), along with predominant expression of fast MHC-2X and -2B, which will transition into greater MHC-1ß and -2A isoform content as development progresses. This hypothesis was tested using Q-PCR to quantify and compare gene expression of each isoform with its protein content determined by gel electrophoresis and densitometry. These data were correlated with nesting activity in an age-matched sample of each age group studied. Shifts in regulation of MHC gene transcripts matched well with isoform expression. Notably, mRNA for MHC-Neo and -2B decrease, resulting in little-to-no isoform translation after age 7 mo, whereas mRNA for MHC-1ß and -2A increase, and this corresponds with subtle increases in content for these isoforms into late adulthood. Despite the tail remaining intrinsically fast-contracting, a critical growth period for isoform transition is observed between 7 and 13 mo, correlating primarily with use of the tail during nesting activities. Functional transitions in MHC isoforms and fiber type properties may be associated with muscle "tuning" repetitive nest remodeling tasks requiring sustained contractions of the caudal flexors.NEW & NOTEWORTHY Little is understood about skeletal muscle development as it pertains to tail prehensility in mammals. This study uses an integrative approach of relating both MHC gene and protein expression with behavioral and morphometric changes to reveal a predominant fast MHC expression with subtle isoform transitions in caudal muscle across ontogeny. The functional shifts observed are most notably correlated with increased tail grasping for nesting activities.