Single vs. multiple fraction non-inferiority trial of stereotactic ablative radiotherapy for the comprehensive treatment of oligo-metastases/progression: SIMPLIFY-SABR-COMET

BACKGROUND

Radiotherapy delivery regimens can vary between a single fraction (SF) and multiple fractions (MF) given daily for up to several weeks depending on the location of the cancer or metastases. With limited evidence comparing fractionation regimens for oligometastases, there is support to explore toxicity levels to nearby organs at risk as a primary outcome while using SF and MF stereotactic ablative radiotherapy (SABR) as well as explore differences in patient-reported quality of life and experience.

METHODS

This study will randomize 598 patients in a 1:1 ratio between the standard arm (MF SABR) and the experimental arm (SF SABR). This trial is designed as two randomized controlled trials within one patient population for resource efficiency. The primary objective of the first randomization is to determine if SF SABR is non-inferior to MF SABR, with respect to healthcare provider (HCP)-reported grade 3-5 adverse events (AEs) that are related to SABR. Primary endpoint is toxicity while secondary endpoints include lesional control rate (LCR), and progression-free survival (PFS). The second randomization (BC Cancer sites only) will allocate participants to either complete quality of life (QoL) questionnaires only; or QoL questionnaires and a symptom-specific survey with symptom-guided HCP intervention. The primary objective of the second randomization is to determine if radiation-related symptom questionnaire-guided HCP intervention results in improved reported QoL as measured by the EuroQoL-5-dimensions-5levels (EQ-5D-5L) instrument. The primary endpoint is patient-reported QoL and secondary endpoints include: persistence/resolution of symptom reporting, QoL, intervention cost effectiveness, resource utilization, and overall survival.

DISCUSSION

This study will compare SF and MF SABR in the treatment of oligometastases and oligoprogression to determine if there is non-inferior toxicity for SF SABR in selected participants with 1-5 oligometastatic lesions. This study will also compare patient-reported QoL between participants who receive radiation-related symptom-guided HCP intervention and those who complete questionnaires alone.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT05784428. Date of Registration: 23 March 2023.

The renin-angiotensin aldosterone system and osteoporosis: findings from the Women's Health Initiative

New users of RAAS inhibitors, including ACE inhibitors and ARBs, have a small increased risk for fracture in the first 3 years of use, with a reduced risk of fracture with longer duration of use.

INTRODUCTION

Pharmacological inhibitors of the renin-angiotensin aldosterone system (RAAS) are used to treat hypertension. However, the relationship of these medications to osteoporosis is inconsistent, and no study has included simultaneous measurements of both incident fractures and bone mineral density (BMD).

METHODS

The association of RAAS inhibitor use (n = 131,793) with incident fractures in new users of these medications in women in the Women's Health Initiative over a minimum median follow-up of 6.5 years was assessed by Cox proportional hazard models. The association of incident fractures by a cumulative duration of use of these medications (< 3 years.) and (> 3 years.) was also estimated. Subgroup analysis of fracture risk by RAAS inhibitor use confined to women with hypertension was also performed (n = 33,820). The association of RAAS inhibitor use with changes in BMD of the hip was estimated by linear regression in 8940 women with dual energy X-ray absorptiometry measurements.

RESULTS

There was no significant association between RAAS inhibitor use and all fractures in the final adjusted multivariable models including hip BMD (HR 0.86 (0.59, 1.24)). However, among users of RAAS inhibitors, including ACE inhibitors and angiotensin receptor blockers (ARBs), hazard ratios for all incident fracture sites in final multivariable models including hip BMD showed dramatic differences by duration of use, with short duration of use (3 years or less) associated with a marked increased risk for fracture (HR 3.28 (1.66, 6.48)) to (HR 6.23 (3.11, 12.46)) and use for more than 3 years associated with a reduced fracture risk (HR 0.40 (0.24, 0.68) to (HR 0.44 (0.20, 0.97)) . Findings were similar in the subgroup of women with a history of hypertension. There was no significant change in BMD of the hip by RAAS inhibitor use.

CONCLUSIONS

In postmenopausal women, use of RAAS inhibitors, including ACE inhibitors and ARBs, is associated with an increased risk for fracture among new users of these medications in the first 3 years of use. However, long-term use (> 3 years) is associated with a reduced risk. Consideration for fracture risk may be part of the decision-making process for initiation of these medications for other disease states.

Abstract PD7-03: Cost-effectiveness analysis of intraoperative radiotherapy for ductal carcinoma in situ

Background

Whole breast radiation therapy (WBRT) following lumpectomy for ductal carcinoma in situ (DCIS) is standard of care, however, the risk of local recurrence with and without radiation ranges as low as 0.9% vs. 6.7% over 7 years. Intraoperative radiotherapy (IORT) is a potential alternative with advantages of decreased toxicity to adjacent organs, convenience, and improved quality of life. While prospective trials of IORT for DCIS are ongoing, the objective of this study was to estimate the cost-effectiveness of IORT vs. WBRT vs. no radiation for DCIS.

Methods

We developed a Markov model using TreeAge Pro 2016 to evaluate the cost-effectiveness of WBRT, IORT, and no radiation in patients with DCIS following lumpectomy. Health states included disease free, local recurrence (ipsilateral DCIS or invasive cancer), distant recurrence or death due to breast cancer, and death due to non-breast cancer causes. A 10-year time horizon and societal perspective were used. Model input parameters were derived from the literature. Costs reflected 2016 Medicare rates. The primary endpoint was incremental cost-effectiveness ratio (ICER), defined as the difference in cost, divided by the difference in quality-adjusted life years (QALYs) of two interventions. We performed analyses of subgroups defined according to DCIS risk (histologic grade, Oncotype Dx® DCIS recurrence score, low risk per RTOG 9804 criteria) and endocrine therapy use (none, tamoxifen, aromatase inhibitor). Sensitivity analyses explored uncertainty in the model.

Results

IORT was the most cost-effective strategy, with an increase of 0.18 QALYs at an incremental cost of $4,728, corresponding to an ICER of $26,943/QALY when compared with no radiation therapy. WBRT resulted in an increase in 0.18 QALYs at an incremental cost of $6859, corresponding to an ICER of $39,085/QALY. For both strategies, the ICERs did not exceed the willingness to pay (WTP) threshold of $100,000.

IORT remained the most cost-effective strategy across DCIS risk groups, but was more cost-effective in higher risk patients, as demonstrated by lower ICERs. In low risk DCIS defined by RTOG 9804 criteria, no radiation was most cost-effective. The ICERs for IORT and WBRT, $152,753 and $208,204/QALY, respectively, exceeded the WTP threshold. IORT remained cost-effective in the setting of endocrine therapy use.

Incremental Cost-Effectiveness Ratios (ICER) for each radiation strategy for the base case and scenario analyses ICER ($/QALY) No RTIORTWBRTBase Case Analysis 26,94339,085    Scenario Analysis by DCIS Risk GroupHistologic Grade   - Low 36,81152,219- High 25,64337,137    Oncotype Dx DCIS Score   - Low 92,892126,398- High 32,00345,690    Low Risk DCIS 152,753208,204    Scenario Analysis by Endocrine TherapyNo Tamoxifen 23,38734,373Tamoxifen 47,81166,616    Tamoxifen 31,96146,272Aromatase Inhibitor 41,31658,674

Conclusion

IORT was the most cost-effective radiation strategy for DCIS compared to WBRT and no radiation. This applied to all subgroups with the exception of low-risk DCIS defined by RTOG 9804 criteria for whom no radiation was the most cost-effective strategy. These findings provide support for ongoing studies examining the role of IORT for DCIS with high-risk features, as well as alternative treatment strategies for low-risk DCIS.

Citation Format: Onishi M, Connolly EP, Wright JD, Vasan S, Gross T, Tsai W-Y, Chen L, Neugut AI, Accordino MK, Kalinsky K, Crew KD, Hershman DL. Cost-effectiveness analysis of intraoperative radiotherapy for ductal carcinoma in situ [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD7-03.

Abstract P5-08-03: Predictors of aggressive end-of-life care in women metastatic breast cancer

Background: Despite recommendations against aggressive end-of-life (EOL) care, a high percentage of patients with metastatic breast cancer (MBC) receive aggressive EOL care. MBC is a heterogeneous disease with a wide variation in survival. EOL care may differ by the patients' long-term course of care. We performed a population-based analysis to evaluate patterns and predictors of aggressive EOL care and associated costs among women with MBC.

Methods: The Surveillance, Epidemiology, and End Results-Medicare database was used to identify female patients with MBC diagnosed between 2002 and 2011. Aggressive EOL care in the last month of life was identified using claims data. Specifically: ≥2 emergency department (ED) visits, ≥2 hospital admissions, &gt;14 days hospitalized, admission to the intensive care unit (ICU), admission to hospice within 3 days or less before death, and receipt of intravenous (IV) chemotherapy in the last 14 days of life were evaluated. Direct healthcare costs in the last month of life were calculated from Medicare claims. Patients were categorized into prognosis quartiles based on survival time from diagnosis. Multivariable analysis was performed to identify patient characteristics associated with aggressive EOL care and characteristics associated with high direct healthcare expenditures in last month of life in women with hormone-receptor (HR)+ and HR- MBC. High expenditures were defined as median costs &gt;75th percentile. Factors associated with high expenditures were evaluated using linear regression.

Results: We identified 5,064 eligible patients. Of these, 2,156 (42.6%) received at least one measure of aggressive EOL care in the last month of life. The most frequent aggressive EOL care received in the last month of life were ICU admissions (17.3%) and &gt;1 ED visits (14.1%). Median cost of care in the last month of life was $7,973. Predictors of aggressive EOL care included year of diagnosis (OR 1.04, 95% CI 1.02-1.06), black race as compared to whites (OR 1.50, 95% CI 1.25-1.79), being married compared to single (OR 1.15, 95% CI 1.01-1.32), and a Charlson comorbidity score of ≥2 compared to no comorbidities (OR 1.52, 95%CI 1.32-1.75). Predictors of not receiving aggressive EOL care included age &gt;74 compared to ages 70-74, receiving care in the Midwest compared to the East (OR 0.82, 95% CI 0.70-0.96), and best prognosis compared to worst prognosis (OR 0.46, 95% CI 0.39-0.55). Predictors of high last month of life expenditures were similar in both the HR+ and HR- subsets; receipt of more aggressive EOL care was also associated with higher expenditures in both HR subsets (OR 5.02, 95% CI 3.88-6.49; OR 5.43, 95% CI 3.41-8.65, respectively). Median last month of life expenditures were unchanged from 2002-2012 for the whole population ($7,658 to $5,910, p=0.93), but rose significantly in patients in the worst prognosis quartile ($9,236 to $16,926, p&lt;0.0001)

Conclusion: Patients with MBC frequently received aggressive EOL care. Women with poor prognosis were more likely to receive aggressive EOL care and have higher expenditures in the last month of life. Given the rising costs of cancer care, efforts should be made to identify patients early for EOL interventions to reduce costs, particularly in women with a poor prognosis.

Citation Format: Accordino MK, Wright JD, Vasan S, Neugut AI, Hillyer GC, Hershman DL. Predictors of aggressive end-of-life care in women metastatic breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-03.

Abstract P1-07-21: Use of serum tumor markers and high cost imaging in women with metastatic breast cancer

Background: Despite data on the sensitivity and specificity of serum tumor marker (STM) tests, there is no evidence to suggest that early changes in therapy related to rising tumor markers have an effect on survival. In fact, the limited data suggests no benefit to early change in therapy. The National Comprehensive Cancer Network recommends monitoring cancer burden in women with metastatic breast cancer (MBC) undergoing therapy; however, they do not provide specific recommendations regarding optimal frequency of STMs or of tumor imaging. We performed a population based analysis to evaluate serum tumor marker usage in patients with hormone sensitive MBC.

Methods: The Surveillance, Epidemiology, and End Results-Medicare database was used to identify female patients with hormone receptor positive MBC diagnosed between 2002 and 2011. For each patient, the dates of STMs (CEA and/or CA 15-3/CA 27.29) were recorded; if either or both CEA and CA 15-3/CA 27.29 were ordered on the same day they were counted as one test. We categorized regular STM use as the percentage of patients who had &gt;4 tests in any year, amounting to tests less than 3 months apart; and very frequent STM use as the percentage of patients who had &gt;12 tests in a year, amounting to tests less than 4 weeks apart. Multivariable analysis was performed to further examine patient characteristics associated with frequent STM use. Odds ratios were calculated comparing positron emission tomography (PET) scan use versus computed tomography (CT) use in women with frequent STM testing.

Results: We identified 3,251 eligible patients. Of these, 2,034 (62.6%) had ≥1 STM test in a given year. On average, patients who underwent STM testing were tested 4 times per year (SD 2.9) for an average of 3 years (SD 2.0). Over half of patients with STM testing had regular testing; 1,065 (52.2%) had STM less than every 3 months, 498 (24.5%) less than every 6 weeks, and 146 (7.2%) less than every 4 weeks apart in any given year. Regular STM evaluation was associated with younger age (65-74 vs 75-84) (OR 1.51, 95% CI 1.25-1.83), later year of diagnosis (OR 1.3, 95% CI 1.04-1.69), and high socioeconomic status compared to low socioeconomic status (OR 1.37, 95% CI 1.08-1.73). Similar factors were associated with very frequent STM use (&gt;12 tests/year). Use of PET scan for tumor imaging compared to CT scan use was higher in women with regular STM evaluation (OR=1.97, 95% CI 1.65-2.35) and in women with very frequent STM evaluation (OR=3.77, 95% CI 2.51-5.66).

Conclusion: Regular use of STMs is common in women with hormone receptor positive MBC. Women who had very frequent STMs were almost 4 times more likely to have expensive tumor imaging. Given the rising costs of cancer care, and the increasing survival time in women with metastatic breast cancer, efforts should be made to determine the optimal timing and modality for evaluating response to treatment.

Citation Format: Accordino MK, Wright JD, Vasan S, Neugut AI, Hu JC, Hershman DL. Use of serum tumor markers and high cost imaging in women with metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-07-21.

An evaluation of the accuracy of small-area demographic estimates of population at risk and its effect on prevalence statistics

Demographic estimates of population at risk often underpin epidemiologic research and public health surveillance efforts. In spite of their central importance to epidemiology and public-health practice, little previous attention has been paid to evaluating the magnitude of errors associated with such estimates or the sensitivity of epidemiologic statistics to these effects. In spite of the well-known observation that accuracy in demographic estimates declines as the size of the population to be estimated decreases, demographers continue to face pressure to produce estimates for increasingly fine-grained population characteristics at ever-smaller geographic scales. Unfortunately, little guidance on the magnitude of errors that can be expected in such estimates is currently available in the literature and available for consideration in small-area epidemiology. This paper attempts to fill this current gap by producing a Vintage 2010 set of single-year-of-age estimates for census tracts, then evaluating their accuracy and precision in light of the results of the 2010 Census. These estimates are produced and evaluated for 499 census tracts in New Mexico for single-years of age from 0 to 21 and for each sex individually. The error distributions associated with these estimates are characterized statistically using non-parametric statistics including the median and 2.5th and 97.5th percentiles. The impact of these errors are considered through simulations in which observed and estimated 2010 population counts are used as alternative denominators and simulated event counts are used to compute a realistic range fo prevalence values. The implications of the results of this study for small-area epidemiologic research in cancer and environmental health are considered.

Unsuspected pulmonary emboli adversely impact survival in patients with cancer undergoing routine staging multi-row detector computed tomography scanning

BACKGROUND

While symptomatic venous thromboembolism adversely impacts survival among cancer patients, the outcome of cancer patients with unsuspected pulmonary embolism (UPE) found on routine cancer staging multi-row detector computed tomography (MDCT) scans is unknown.

OBJECTIVE

To determine whether UPE detected on routine staging MDCT scans impacts overall survival among cancer patients.

PATIENTS AND METHODS

We performed a matched cohort study of cancer patients diagnosed with UPE on routine staging scans between May 2003 and August 2006. Two controls (n = 137) were individually matched by age (± 5 years), cancer type and stage for each UPE patient (n = 70). We used Cox's proportional hazard models to compare the mortality between UPE patients and their matched controls.

RESULTS

The hazard ratio (HR) for death among UPE patients was 1.51 (95% CI 1.01-2.27, P = 0.048). Compared with their matched controls, patients with UPE more proximal than the subsegmental arterial branches had a HR for death at 6 months of 2.28 (95% CI 1.20-4.33, P = 0.011) and an overall HR of 1.70 (95% CI 1.06-2.74, P = 0.027). Survival among UPE patients with isolated subsegmental PE (ISSPE) was not significantly different than that of matched controls (HR 1.04 95% CI 0.44-2.39, P = 0.92).

CONCLUSIONS

UPE identified more proximal than the subsegmental arterial branches has a significant negative impact on survival among cancer patients.

Therapeutic potential of AGE inhibitors and breakers of AGE protein cross-links

Glucose and other reducing sugars react non-enzymatically with proteins leading to the formation of advanced glycosylation end products (AGEs) and AGE-derived protein cross-linking. Formation of AGEs is a normal physiological process, which is accelerated under the hyperglycaemic condition in diabetes. Under normal conditions, AGEs build up slowly and accumulate as one ages. Numerous studies have indicated that AGEs contribute to the pathological events leading to diabetic complications, such as age-related diseases, including nephropathy, retinopathy, vasculopathy and neuropathy. Potential therapeutic approaches to prevent these complications include pharmacological inhibition of AGE formation and disruption of pre-formed AGE-protein cross-links. Studies using animal models and preliminary clinical trials have shown the ability of the AGE-inhibitor, pimagedine and the cross-link breaker, ALT-711, to reduce the severity of pathologies of advanced glycosylation. These agents offer potential treatments for glucose-derived complications of diabetes and ageing.

A cross-link breaker has sustained effects on arterial and ventricular properties in older rhesus monkeys

Nonenzymatic glycosylation and cross-linking of proteins by glucose contributes to an age-associated increase in vascular and myocardial stiffness. Some recently sythesized thiazolium compounds selectively break these protein cross-links, reducing collagen stiffness. We investigated the effects of 3-phenacyl-4,5-dimethylthiazolium chloride (ALT-711) on arterial and left ventricular (LV) properties and their coupling in old, healthy, nondiabetic Macaca mulatta primates (age 21 +/- 3.6 years). Serial measurements of arterial stiffness indices [i.e., aortic pulse wave velocity (PWV) and augmentation (AGI) of carotid arterial pressure waveform] as well as echocardiographic determinations of LV structure and function were made before and for 39 weeks after 11 intramuscular injections of ALT-711 at 1.0 mg/kg body weight every other day. Heart rate, brachial blood pressure, and body weight were unchanged by the drug. PWV and AGI decreased to a nadir at 6 weeks [PWV to 74.2 +/- 4.4% of baseline (B), P = 0.007; AGI to 41 +/- 7.3% of B, P = 0.046], and thereafter gradually returned to baseline. Concomitant increases in LV end diastolic diameter to 116.7 +/- 2.7% of B, P = 0.02; stroke volume index (SV(index)) to 173.1 +/- 40.1% of B, P = 0.01; and systolic fractional shortening to 180 +/- 29.7% of B, P = 0.01 occurred after drug treatment. The LV end systolic pressure/SV(index), an estimate of total LV vascular load, decreased to 60 +/- 12.1% of B (P = 0.02). The LV end systolic diameter/SV(index), an estimate of arterio-ventricular coupling, was improved (decreased to 54.3 +/- 11% of B, P < 0.002). Thus, in healthy older primates without diabetes, ALT-711 improved both arterial and ventricular function and optimized ventriculo-vascular coupling. This previously unidentified cross-link breaker may be an effective pharmacological therapy to improve impaired cardiovascular function that occurs in the context of heart failure associated with aging, diabetes, or hypertension, conditions in which arterial and ventricular stiffness are increased.

Renoprotective effects of a novel inhibitor of advanced glycation

AIMS/HYPOTHESIS

ALT-946, an inhibitor of advanced glycation with a minimal inhibitory effect on nitric oxide synthase, was compared with aminoguanidine in experimental diabetic nephropathy.

METHODS

In vitro and in vivo assays were used to assess the ability of ALT-946 to inhibit AGE-protein cross-link formation. Diabetic animals were randomly allocated into groups receiving aminoguanidine for 32 weeks, ALT-946 or vehicle (untreated). As a delayed intervention protocol, an additional diabetic group was treated with ALT-946 from week 16 to week 32 of the study. Non-diabetic rats were studied concurrently. Systolic blood pressure, body weight, plasma glucose, glycated haemoglobin and urinary albumin excretion were measured serially. Accumulation of advanced-glycation end products in the kidney was assessed by immunohistochemistry.

RESULTS

The ALT-946 inhibitor was more potent than aminoguanidine in inhibiting AGE-protein cross-linking both in vitro and in vivo. Increased albuminuria observed in diabetic rats was attenuated in all three treatment groups. We found no difference in body weight, blood pressure or glycaemic control with any of the treatments. The untreated diabetic group had a twofold increase in glomerular staining for advanced-glycation end products compared with the diabetic groups which received treatment.

CONCLUSION/INTERPRETATION

ALT-946 is a potent inhibitor of advanced renal glycation end-product accumulation and reproduces the renoprotective effects of aminoguanidine. Therefore, ALT-946 should be considered as a treatment for preventing or retarding diabetic nephropathy.

An advanced glycation endproduct cross-link breaker can reverse age-related increases in myocardial stiffness

Decreased elasticity of the cardiovascular system is one of the hallmarks of the normal aging process of mammals. A potential explanation for this decreased elasticity is that glucose can react nonenzymatically with long-lived proteins, such as collagen and lens crystallin, and link them together, producing advanced glycation endproducts (AGEs). Previous studies have shown that aminoguanidine, an AGE inhibitor, can prevent glucose cross-linking of proteins and the loss of elasticity associated with aging and diabetes. Recently, an AGE cross-link breaker (ALT-711) has been described, which we have evaluated in aged dogs. After 1 month of administration of ALT-711, a significant reduction ( approximately 40%) in age-related left ventricular stiffness was observed [(57.1 +/- 6.8 mmHg x m(2)/ml pretreatment and 33.1 +/- 4.6 mmHg x m(2)/ml posttreatment (1 mmHg = 133 Pa)]. This decrease was accompanied by improvement in cardiac function.

Breakers of advanced glycation end products restore large artery properties in experimental diabetes

Glucose and other reducing sugars react with proteins by a nonenzymatic, posttranslational modification process called nonenzymatic glycation. The formation of advanced glycation end products (AGEs) on connective tissue and matrix components accounts largely for the increase in collagen crosslinking that accompanies normal aging and which occurs at an accelerated rate in diabetes, leading to an increase in arterial stiffness. A new class of AGE crosslink "breakers" reacts with and cleaves these covalent, AGE-derived protein crosslinks. Treatment of rats with streptozotocin-induced diabetes with the AGE-breaker ALT-711 for 1-3 weeks reversed the diabetes-induced increase of large artery stiffness as measured by systemic arterial compliance, aortic impedance, and carotid artery compliance and distensibility. These findings will have considerable implications for the treatment of patients with diabetes-related complications and aging.

An agent cleaving glucose-derived protein crosslinks in vitro and in vivo

Glucose and other reducing sugars react with proteins by a nonenzymatic, post-translational modification process called nonenzymatic glycosylation or glycation. The sugar-derived carbonyl group adds to a free amine, forming a reversible adduct which over time rearranges to produce a class of products termed advanced-glycation end-products (AGEs). These remain irreversibly bound to macromolecules and can covalently crosslink proximate amino groups. The formation of AGEs on long-lived connective tissue and matrix components accounts largely for the increase in collagen crosslinking that accompanies normal ageing and which occurs at an accelerated rate in diabetes. AGEs can activate cellular receptors and initiate a variety of pathophysiological responses. They modify an appreciable fraction of circulating low-density lipoproteins preventing uptake of these particles by their high-affinity tissue receptors. Advanced glycation has also been implicated in the pathology of Alzheimer's disease. Because AGEs may form by a pathway involving reactive alpha-dicarbonyl intermediates, we investigated a potential pharmacological strategy for selectively cleaving the resultant glucose-derived protein crosslinks. We now describe a prototypic AGE crosslink 'breaker', N-phenacylthiazolium bromide (PTB), which reacts with and cleaves covalent, AGE-derived protein crosslinks. The ability of PTB to break AGE crosslinks in vivo points to the importance of an alpha-dicarbonyl intermediate in the advanced glycation pathway and offers a potential therapeutic approach for the removal of established AGE crosslinks.

Selective accumulation of strontium-89 in metastatic deposits in bone: radio-histological correlation

The systemic administration of 89Sr has proven effective in the palliation of painful osseous metastases. Biodistribution studies with the gamma-emitter 85Sr suggest that both its uptake and retention are increased in bone metastases, where increased mineral turnover takes place. To study the pattern and nature of this process further, bones containing metastatic deposits were obtained from three patients who had previously been treated with 148 MBq of 89Sr. The bones were cut into 0.5-1.0 cm sections. The cut surfaces which faced together were marked with India ink, and adjacent sections were submitted for histology and autoradiography. Strontium deposition and retention were observed in regions which exhibited significant osteoblastic activity, mostly in areas adjacent to metastatic deposits, but also in subchondral and endosteal locations, as well as in an area corresponding to a pathological fracture with callus formation. With these exceptions, strontium deposition was not observed in histologically normal bone or within the marrow. Our findings demonstrate directly the selective nature of accumulation and retention of 89Sr and confirm previous clinical impressions.

A direct measurement of strontium-89 activity in bone metastases

The total absorbed dose after systemic administration of 89Sr has been determined by measuring directly its activity in bone metastases. Autoradiography was performed on sections of bones obtained from patients treated with 89Sr to study the pattern of deposition. Discs of 5 and 8 mm diameter were cut from metastatic sites and normal bone. The beta-ray activity was determined with a scintillation counter, which was calibrated using similar bovine cancellous bone discs, onto which a known activity of 89Sr was transferred by pipette. From the activity measured, the initial activity (at the time of 89Sr administration) was calculated. The absorbed dose was estimated using the methodology described in NCRP Report No. 58. The estimated initial activity of 89Sr in the bone metastases varied from 2.3 to 240 MBq kg-1, with a mean value of 31 +/- 27 MBq kg-1. The total absorbed dose ranged from 1.3 to 64 Gy, with a mean of 18 +/- 16 Gy. The average total dose to normal bone sites was 1.1 +/- 0.4 Gy. The metastases to normal bone dose ratio in individual samples varied from 8 +/- 4 to 40 +/- 25. These estimates are in agreement with those obtained previously by indirect methods.