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Results for “dose reduction”

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At least 19 recordsLinked to original sources

PubMed1979

Leaded shields for thyroid dose reduction in intraoral dental radiography.

This study evaluated the radiation dose reduction, operator acceptance, and patient acceptance of two types of leaded thyroid shields designed for use during intraoral dental radiography. Exposure levels were measured with thermoluminescent dosimeters on three groups of 20 patients undergoing complete mouth (20-film) surveys. Skin entrance dose to the thyroid was 20 mR per complete mouth survey without a shield in place, 12 mR per complete mouth survey with the experimental shield in place, and 9 mR with the commercial shield. Patients and radiologic technologist were surveyed to determine patient comfort and operator acceptability. Patient and operator acceptability were higher for the experimental shield than for the commercial shield.

Adolescent↗

PubMed1978

[Dose reduction during radiological examination using high intensity rare earth screens or increased kV (author's transl)].

Using a procedure which resembles actual practice, it has been shown that an increase in kV. results in a reduction of radiation dose similar to that obtained by using the new high intensity rare earth screens while maintaining similar detail. In practical terms this means that there is only limited usefulness for the new rare earth screens. An exception to this is the screen which reduces dose while producing similar, or better, detail than a standard screen. We could demonstrate this for the film-screen combination Trimax alpha4XD.

Humans↗

PubMed2026

De-escalation of radiotherapy in HPV-negative non-nasopharyngeal head and neck squamous cell carcinoma: a systematic review.

BACKGROUND: Definitive and postoperative radiotherapy are central components of treatment for head and neck squamous cell carcinoma (HNSCC) but are associated with significant toxicities that can impair long-term function and quality of life. De-escalation strategies, aiming to reduce treatment-related morbidity while maintaining tumor control, have attracted increasing interest. However, most research has focused on HPV-positive oropharyngeal carcinoma. Systematic evidence for HPV-negative disease remains limited. METHODS: PubMed and EMBASE were searched for prospective studies investigating radio(chemo)therapy de-escalation in HPV-negative, HPV-unspecified, or mixed non-nasopharyngeal HNSCC populations. CLINICALTRIALS: gov was searched for ongoing prospective trials. Data extraction and verification were performed independently by three investigators. RESULTS: Screening of 3156 records identified 14 published prospective studies, 10 in the definitive and four in the postoperative setting. Strategies included reduction or omission of elective nodal volumes, dose reduction, and combined approaches. Additionally, 23 ongoing prospective trials were identified. Across studies, elective nodal failure rates were consistently low (0-4.6%), with most recurrences occurring within high-dose volumes rather than de-escalated elective regions. Randomized evidence for elective nodal dose reduction is mixed: two trials maintained regional control and reduced acute toxicity, whereas another was stopped for futility. CONCLUSION: Available evidence on de-escalation in HPV-negative HNSCC is limited, derived primarily from small, heterogeneous phase II studies with mixed HPV populations. Although data are promising in selected settings, notably for elective nodal control, the randomized evidence for elective nodal dose reduction is conflicting, and further adequately designed prospective randomized trials are required.

Humans↗

PubMed1976

Volume and time factors in interstitial gamma-ray therapy.

The two suppositions which have dictated time-dose and volume relationships in interstitial gamma ray implantation have been examined in the light of recent publications. The first of these assumptions, that total dose reduction is required when the dose rate exceeds 6,000-7,000 rads in seven days, does not appear to be substantiated by clinical experiences. It appears that total dose is the critical treatment parameter and that dose rate may be increased by a factor of two or three without requiring alteration of the total dose. Although the second classical assumption, "volume increase requires dose decrease," has been shown throughout radiation therapy experience to be generally correct, it should not be applied rigidly to interstitial gamma-ray therapy. In fact, recent experiences seem to indicate that compensation with respect to volume is not an absolute necessity. Larger lesions require, if anything, higher doses than small ones. To obtain a high percentage of controlled, lesions there must be no dose reduction, regardless of increased volume treated.

Animals↗

PubMed2026

Shielding performance and clinical applicability of lead-free materials in computed tomography.

Owing to the high radiation exposure associated with computed tomography (CT) examinations and the image quality degradation caused by conventional radiation shielding materials, this study evaluated the dose reduction performance and image quality maintenance potential of a newly developed lead-free composite shielding material. This material was composed of bismuth, tungsten, tungsten carbide, aluminium, and polyurethane. Phantom-based dose measurements demonstrated that the shielding material achieved dose reduction rates ranging from 17.6% to 37.6%, depending on tube voltage. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and changes in tube current-time product (mAs) under a scout-based automatic exposure control (AEC) protocol were analysed according to the presence or absence of the shielding material across regions. For the clinical evaluation, CT scans were performed on four patients. Furthermore, the images were reviewed to evaluate whether this material affected image quality. The shielding material exhibited radiation reduction levels comparable to those reported in previous studies. SNR and CNR analyses showed minor statistical variations in certain regions; however, most differences were not statistically significant, and even significant differences remained within a range that did not compromise diagnostic image quality. Under the scout-based AEC protocol, the use of the shielding material resulted in less than 1% variation in mAs values. No visually perceptible artefacts or clinically significant image quality degradation were observed. The proposed composite shielding material demonstrated the potential to mitigate some limitations of conventional shielding materials and showed preliminary clinical feasibility as an adjunctive strategy for radiation dose reduction in CT examinations.

Radiation Protection↗

PubMed2026

Timing matters: Impact of covalent BTK inhibitor dose modifications on outcomes in chronic lymphocytic leukemia/small lymphocytic leukemia-A 7-year real-world study.

BACKGROUND: Covalent BTK inhibitors (cBTKis) are the cornerstone of chronic lymphocytic leukemia (CLL)/small lymphocytic leukemia (SLL) therapy, yet real-world data on dose modifications and their differential impact on long-term outcomes remain incompletely defined. This study investigated the incidence, timing, and the effectiveness of drug switching in a real-world CLL cohort. METHODS: In this 7-year retrospective real-world study, 324 CLL/SLL patients treated at a specialized Shanghai outpatient clinic (April 2018-April 2025; median follow-up, 42 months) were analyzed. Dose modifications were classified as dose interruption (DI) or dose reduction (DR). Their prognostic impact on progression-free (PFS) and overall survival (OS) was assessed by Kaplan-Meier analysis and multivariate Cox regression. RESULTS: The 42-month PFS rate was 70.2%. Of 324 patients, 229 (70.7%) experienced dose reductions or interruptions; infections were the predominant cause (61.9%). The full-dose (FD) group (n = 90) demonstrated superior 4-year PFS (93% vs. 58%, p < .001) and OS (98% vs. 76%, p = .007). Early modifications (0-3 months) were independent predictors of inferior PFS (hazard ratio [HR], 3.93, p = .008) and OS (HR, 3.29, p = .014). Prolonged DI (>14 days) was associated with inferior PFS (HR, 2.64) and OS (HR, 2.15), whereas DR and short DI (≤14 days) had negligible impact. Early (0-3 months) prolonged DI was devastating (3-year PFS, 41.2%; HR, 3.84, p < .001). cBTKi switching (n = 82; 100% nonprogression-driven) shortened DI (median, 6 vs. 14 days) and was independently associated with superior OS (HR, 0.34, p = .018) and PFS (HR, 0.36, p = .022). CONCLUSIONS: Early prolonged DI is the dominant adverse prognostic factor in cBTKi-treated CLL/SLL. Proactive switching minimizes treatment gaps and improves survival, supporting a timing-aware, DI- versus DR-informed approach to dose management.

Humans↗

PubMed2026

Optimizing Initial Dosing for Tacrolimus and Mycophenolate in Living Donor Liver Transplantation: A Systematic Critical Review.

BACKGROUND: The pharmacokinetics (PK) of immunosuppressive agents in living donor liver transplantation (LDLT) recipients are expected to differ from those in deceased donor liver transplantation (DDLT) recipients because of the smaller initial liver volume transplanted and pathophysiological changes during liver regeneration. Consequently, the hepatic metabolism, CYP enzyme activity, and glucuronidation may be reduced. The PK of tacrolimus (metabolized by CYP3A5) and mycophenolate (metabolized through glucuronidation) are expected to be affected early post-LDLT. However, the initial dosing recommendations for post-LDLT remain unclear. PURPOSE: This study aimed to recommend initial dosing approaches for tacrolimus and mycophenolate in LDLT recipients based on available PK data in humans. METHODS: A PubMed search was conducted in March 2025 to identify studies investigating the PK data of immediate-release tacrolimus and mycophenolate in pediatric or adult LDLT recipients. RESULTS: After screening, 8 and 8 articles on tacrolimus and mycophenolates, respectively, met the review criteria. The current literature suggests that LDLT recipients require lower tacrolimus doses than DDLT recipients, particularly in the early post-transplant period. In addition, CYP3A5 polymorphisms in both donors and recipients contribute to interindividual variability in tacrolimus exposure, further complicating tacrolimus management. Studies on mycophenolate use in LDLT recipients are limited, with insufficient evidence to support dose reduction. CONCLUSIONS: Reducing the initial tacrolimus dose in LDLT recipients by 30%-50% compared with that in DDLT recipients would be reasonable while maintaining the same initial dose of mycophenolate between LDLT and DDLT recipients.

Humans↗

PubMed1979

National Cooperative Crohn's Disease Study: adverse reactions to study drugs.

Adverse reactions to the drugs employed in the National Cooperative Crohn's Disease Study were sought prospectively at each patient visit and by retrospective review of all patient charts. Prednisone caused evident side effects in over 50% of patients on high-dose suppressive therapy and in approximately one-third of patients on prophylactic dose. Thirty-two percent of patients on high-dose, and 26% on prophylactic-dose prednisone required dose reduction or withdrawal because of side effects. Comparable figures for sulfasalazine were 14% and 12%, and for azathioprine 32% and 20%. The incidence of nausea, vomiting, or anorexia among patients taking sulfasalazine was 46% and 34%, on high and low dose respectively; however, this incidence was no different than that observed among patients taking placebo. These symptoms occasioned withdrawal from the study of only 4% and 3% of patients on high and low doses of sulfasalazine, respectively. Azathioprine produced leukopenia at a dose of 2.5 mg/kg body weight in 15% of patients and the mean white cell count, lymphocyte count, granulocyte count, and hematocrit all fell significantly in patients on this dose. Pancreatitis occurred in 5% of patients taking azathioprine but in no other patients. Sulfasalazine proved to be the safest effective suppressive drug for Crohn's disease. Prednisone toxicity, though substantial, is acceptable in view of its demonstrated suppressive efficacy. Azathioprine was approximately as toxic as prednisone but no more effective than placebo in suppressing active disease. None of the drugs was effective prophylactically, and all showed appreciable long-term toxicity.

Adult↗

PubMed1979

[General characteristics and comparative evaluation of the radioprotective properties of aryl alkyl amine adrenomimetics in experiments on mice].

The radioprotective effect (RPE) of some arylalkylamines (AAAs) was studied in experiments on mice. Mesaton and its close analogues were injected subcutaneously 15 minutes prior to irradiation at a dose of 800 rad. The protective effect is exerted by AAAs in low doses (25--50 mumole/kg), the compounds show stable and high RPE (80--80% survival, dose reduction factor being 1.3--1.4) and low toxicity (LD50 = 4--8 mumole/kg). AAAs studied are not less effective than aminothiols. Their pharmacological spectrum--K = LD50/ED50 (200--500) is superior to that of known aminothiols and indolylalkylamines.

Animals↗

PubMed1978

Pharmacokinetic and therapeutic studies of pivmecillinam in patients with normal and impaired renal function.

Pivmecillinam which is the oral form of mecillinam was evaluated by treatment of 26 patients presenting various types of urinary tract infections and by prophylactic treatment of 12 patients. Pivmecillinam given in a daily dosage of 1.2 g for periods of 1 to 56 weeks was well tolerated in all of the patients including those with impaired renal function without any dose reduction. The original bacterial strain in the urine was eradicated in 100% of the cases. Two patients had a superinfection and 4 had a recurrence during a 3-month follow-up period. The oral absorption of pivmecillinam was investigated in 15 patients with normal or slightly reduced renal function and in 5 patients on maintenance hemodialysis. High serum levels were achieved within 1 to 2 h after administration. Patients with reduced renal function showed retarded elimination rates, suggesting that the dose should be adjusted in this category of patients.

Acute Kidney Injury↗

PubMed2026

Long-Term Outcomes in Patients With Recurrent Ovarian Cancer and Exceptional Response to PARP Inhibitors.

IMPORTANCE: A subset of patients with platinum-sensitive recurrent ovarian cancer (PS-ROC) treated with maintenance poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors have exceptional response. Although licensing recommends continuing PARP inhibitors until progression or unacceptable toxic effects, the optimal duration of PARP inhibitors, and the risks of late progression, myelodysplastic syndrome (MDS), or acute myeloid leukemia (AML) in patients with exceptional response are unknown. OBJECTIVE: To determine the long-term outcomes of patients with PS-ROC who have exceptional response to PARP inhibitors, and to explore genotype-phenotype associations. DESIGN, SETTING, AND PARTICIPANTS: This was an international, multicenter, retrospective cohort study of patients with exceptional response to PARP inhibitors, defined as patients with PS-ROC and progression-free survival (PFS) of 5 years or longer from PARP inhibitor commencement. The study was conducted across 41 sites in 14 countries from January 11, 2023, to November 10, 2025. EXPOSURES: Treatment with PARP inhibitors. MAIN OUTCOMES AND MEASURES: The primary end point was PFS, and secondary end points included overall survival, toxic effects, and dose reductions. RESULTS: A total of 320 patients with exceptional response (mean [SD] age, 56.4 [9.4] years) were included, with a median follow-up of 6.8 years (95% CI, 6.6-7.0 years). The median (IQR) PARP inhibitor duration was 75.0 (64.0-91.0) months. Of patients with exceptional response, 211 (65.9%) received continuous PARP inhibitors, but 109 (34.1%) discontinued: 34 (10.6%) due to physician recommendation, 2 (7.5%) had disease progression beyond 5 years, 22 (6.9%) had toxic effects, 17 (5.3%) for patient preference, and 12 (3.8%) for another reason. The 7.5-year and 10-year PFS rates were 88.8% (95% CI, 84.5%-93.3%) and 78.7% (95% CI, 70.5%-87.9%), respectively. Among the patients, 85 (26.6%) discontinued PARP inhibitors for reasons other than disease progression, with a 10-year PFS of 90.1% (95% CI, 80.6%-100%) vs 72.5% (95% CI, 60.3%-87.2%) for those who continued taking PARP inhibitors. Five patients (1.6%) were diagnosed with late-onset MDS/AML. Patients with exceptional response were enriched for variants in the BRCA1 RING domain and the BRCA2 DNA-binding domain. CONCLUSIONS AND RELEVANCE: In this cohort study, most patients with exceptional response to PARP inhibitors remained progression free, including those who discontinued PARP inhibitors without progression. The risk of late-onset MDS/AML was low. These results can guide counseling on the duration of maintenance PARP inhibitors in patients with exceptional response and suggest that functional cure may be possible in patients with PS-ROC and exceptional response to PARP inhibitors.

Humans↗

PubMed1978

Calcitriol in dialysis patients.

We conducted a 7-month randomized, single, double, single-blind comparison of calcitriol (1,25(OH)2D3) with vitamin D3 in 22 hemodialysis patients to study the effects on the biochemical abnormalities associated with osteodystrophy. Calcitriol was given for 3 mo. All patients had initial prestudy calcium values less than or equal to 9.5 mg/100 ml, and phosphate values less than or equal to 4.5 mg/100 ml. Data were analyzed using the Normalized Trend Index (NTI). Calcitriol induced a rise in calcium (8.7 to 10.25 mg/100 ml) (p less than 0.001) and a fall in alkaline phosphatase (p less than 0.005), while D3 had no appreciable effect. The mean dose of calcitriol during treatment was 0.579 microgram/day while that for D3 was 706 IU/day. The effect on serum phosphate concentration was variable. Hypercalcemia as high as 13.2 mg/100 ml occurred in 2 of 13 patients on 1,25(OH)2D3, but in every instance promptly returned to normal with dose reduction. No other adverse effects were noted with therapy. We conclude that calcitriol reverses the biochemical abnormalities of osteodystrophy. Since its effects are rapidly reversed with discontinuation, the drug is probably safe as well as effective.

Adult↗

PubMedDate not supplied

The abrupt discontinuation of antihypertensive treatment.

Although deleterious events following abrupt withdrawal of antihypertensive treatment are relatively uncommon, considerable attention has recently been focused on this problem. A withdrawal syndrome may occur after termination of almost all types of antihypertensive drugs, but most experience has been with the centrally acting agents and with beta-adrenoreceptor blockers. Abrupt discontinuation of high doses of centrally acting drugs such as alpha-methyldopa, clonidine, and guanabenz can produce a syndrome of sympathetic overactivity that includes agitation, headache, sweating, and nausea and less commonly can provoke rapid upswings in blood pressure. If beta blockers are suddenly stopped, a similar pattern can occur that may be related to excessive activity of thyroid hormones as well as sympathetic factors. Additionally, patients with ischemic heart disease may be susceptible to an acute exacerbation of their cardiac disease when beta-blocker treatment is stopped. It seems likely that discontinuation events can be particularly severe when combinations of different types of antihypertensive medications are sud-disease when betablocker treatment is denly stopped. This problem can be dealt with by educating patients to avoid sudden drug cessation and when elective discontinuation is planned, by gradual dose reduction.

Adrenergic beta-Antagonists↗

PubMed2026

Older adults with resectable gastric cancer undergoing perioperative chemotherapy or preoperative chemoradiotherapy plus perioperative chemotherapy: A secondary analysis of the AGITG TOPGEAR phase III trial.

PURPOSE: To evaluate treatment adherence, adverse events, and survival in older (≥70 years) adults undergoing perioperative treatment for gastric cancer. METHODS: Patients with resectable gastric/gastro-esophageal junction adenocarcinoma (ECOG 0-1) enrolled in the phase III TOPGEAR trial were randomized to perioperative chemotherapy (ECF/ECX or FLOT) alone or perioperative chemotherapy plus preoperative chemoradiotherapy (45 Gy in 25 fractions with concurrent fluoropyrimidine). In this exploratory analysis, treatment completion, grade ≥ 3 adverse events (CTCAE v3.0), surgical outcomes, overall survival (OS) and progression-free survival (PFS) were compared between older and younger adults. RESULTS: Of the 574 patients enrolled, 135 (24%) were ≥ 70 years. Older adults more frequently required preoperative chemotherapy dose reductions, omissions, or delays (chemoradiotherapy: 55% vs 35%, p = 0.004; chemotherapy: 60% vs 48%, p = 0.087). Rates of grade ≥ 3 adverse events were comparable between older and younger patients (chemoradiotherapy: 66% vs 67%, p = 0.874; chemotherapy: 68% vs 59%, p = 0.220), but older adults more often had hematologic toxicity and grade ≥ 3 diarrhea in the chemotherapy group (56% vs 37%, p = 0.006; 21% vs 6%, p < 0.001). Resection rates, grade 3/4 surgical complications, number of removed lymph nodes, and 30-/90-day mortality were similar by age. OS and PFS were comparable across age groups, with numerically favorable outcomes for older adults (OS: HR 0.86, 95% CI 0.58-1.26 [chemoradiotherapy]; HR 0.75, 95% CI 0.51-1.11 [chemotherapy]; PFS: HR 0.78, 95% CI 0.53-1.15 [chemoradiotherapy]; HR 0.70, 95% CI 0.47-1.03 [chemotherapy]). CONCLUSIONS: Older adults with gastric cancer achieved comparable oncologic outcomes to younger patients, despite more frequent treatment modifications and higher hematologic toxicity.

Humans↗

PubMed2026

Identifying biomarkers of accelerated ageing in cancer patients from routine clinical data.

INTRODUCTION: Cancer and ageing have a bidirectional relationship: age is the strongest risk factor for cancer, and cancer and treatments can accelerate ageing. Therefore, biological age can differ from chronological age; biomarkers are needed to stratify interventions to minimise accelerated ageing. METHODS: PhenoAge was calculated from routine blood test results of patients attending a Geriatric Oncology clinic. PhenoAgeAccel was the residual from a regression of PhenoAge against age. RESULTS: Data were available for 173 patients (62% male). Mean PhenoAge was higher than age (84.3 (12.6) vs 76.2 (7.24), p < 0.001), though the two were correlated (r = 0.579, p < 0.001). Unlike age, PhenoAge and PhenoAgeAccel were associated with one-year mortality (PhenoAge OR=1.083, 95% CI: 1.038-1.136; PhenoAgeAccel OR=1.096, 95% CI: 1.047-1.155). PhenoAge correlated with Clinical Frailty Score and Timed Up and Go (CFS: Rs=0.31, p < 0.001; TUG: Rs=0.25, p < 0.005); there were no correlations with age. PhenoAgeAccel correlated with the number of CGA interventions made (Rs=0.17, p < 0.05), unlike age and PhenoAge. Patients with diabetes mellitus had a higher PhenoAgeAccel compared to those without (3.40 vs -1.71, p = 0.002). In patients receiving systemic anti-cancer treatment, patients with PhenoAgeAccel calculated pre-treatment had less age acceleration than those with PhenoAgeAccel calculated post-treatment, both overall (2.18 vs -2.87; p = 0.048) and in matched samples (n = 21, 7.76 vs -2.87, p < 0.001). CONCLUSIONS: PhenoAgeAccel is a greater predictor of risk than chronological age in older people with cancer. This makes it a promising biomarker to stratify patients for holistic geriatric assessment, dose reductions, or future geroprotective measures which could be integrated within electronic healthcare record systems.

Humans↗

PubMed2019

CYP2D6 genotype and adverse events to risperidone in children and adolescents.

BACKGROUND: There are few and conflicting data on the role of cytochrome P450 2D6 (CYP2D6) polymorphisms in relation to risperidone adverse events (AEs) in children. This study assessed the association between CYP2D6 metabolizer status and risk for risperidone AEs in children. METHODS: Children ≤18 years with at least 4 weeks of risperidone exposure were identified using BioVU, a de-identified DNA biobank linked to electronic health record data. The primary outcome of this study was AEs. After DNA sequencing, individuals were classified as CYP2D6 poor, intermediate, normal, or ultrarapid CYP2D6 metabolizers. RESULTS: For analysis, the 257 individuals were grouped as poor/intermediate metabolizers (n = 33, 13%) and normal/ultrarapid metabolizers (n = 224, 87%). AEs were more common in poor/intermediate vs. normal/ultrarapid metabolizers (15/33, 46% vs. 61/224, 27%, P = 0.04). In multivariate analysis adjusting for age, sex, race, and initial dose, poor/intermediate metabolizers had increased AE risk (adjusted odds ratio 2.4, 95% confidence interval 1.1-5.1, P = 0.03). CONCLUSION: Children with CYP2D6 poor or intermediate metabolizer phenotypes are at greater risk for risperidone AEs. Pre-prescription genotyping could identify this high-risk subset for an alternate therapy, risperidone dose reduction, and/or increased monitoring for AEs.

Adolescent↗

PubMed1977

[Mammography with minimal radiation dosage. Comparative studies on various imaging systems].

Using an MR-film-screen combination for mammography, only 8% of the usual radiation dose was found to be necessary. This corresponds with an average skin dose of 0.55 R per exposure. The new technique resulted in visible improvement of contrast. Some loss of detail affected in particular the recognition of macrocalcification. As the sole method for the early diagnosis of occult carcinomas of the breast, it will therefore be necessary to improve image quality. The system is suitable for control examinations and investigation of special problems. The use of the MR system with non-screen film in two planes is discussed in relation to dose reduction.

Breast Neoplasms↗

PubMed1976

The effect of metoprolol --a new selective adrenergic beta1-receptor blocking agent-- in mild hypertension.

Metoprolol, a new selective adrenergic beta1-receptor blocking drug, has been compared to placebo in a series of 24 women who previously had taken alprenolol and propranolol during a cross-over study. Blood pressure (BP) and heart rate (HR) were significantly reduced during metoprolol treatment compared to placebo. The occurrence of side-effects was similar during treatment with metoprolol and placebo. After the cross-over study the patients continued on metoprolol for more than two years, except for short periods on placebo or propranolol. During this follow-up period BP remained at a similar level when the metoprolol dose was unchanged. Dose reduction (from 50 or 100 mg t.i.d. to 50 or 100 mg b.i.d.) caused no, or only a very slight, increase in BP. No side-effects were reported during long-term treatment.

Adrenergic beta-Antagonists↗