Examining interactions of illness perceptions, avoidance behavior and patient status in predicting quality of life among people with irritable bowel syndrome

Background: Illness perceptions (IPs) and avoidance behavior both predict quality of life (QoL) in people with irritable bowel syndrome (IBS). This study examined whether the effects of IPs on QoL are mediated by avoidance behaviors, and whether this mediation is moderated by participant treatment-seeking status. Methods: People with self-reported IBS (n = 253) answered a survey assessing QoL, IPs, avoidance behaviors, and treatment-seeking status. Moderated-mediation analyses investigated the paths from IPs through avoidance behaviors to QoL, with treatment-seeking status entered as a moderator. Results: The final moderated mediation model included the IPs consequences, timeline and emotional representations as independent variables and avoidance behavior and depressive reactions as mediators. This model explained 68.6% of the variance in QoL. Among treatment-seeking participants five significant mediation effects were found, whereas only one significant mediation effect was found among participants who did not report seeking treatment. Conclusions: IPs seem to drive avoidant behavioral responses to IBS symptoms, which in turn predict reductions in QoL. These relationships seem more pronounced among people who seek treatment for their symptoms. In practice, health care practitioners might help improve the QoL of people with IBS by preventing or remedying the development of negative IPs and avoidance behaviors.

The Impact of the Renin-Angiotensin-Aldosterone System on Inflammation, Coagulation, and Atherothrombotic Complications, and to Aggravated COVID-19

Atherosclerosis is considered a disease caused by a chronic inflammation, associated with endothelial dysfunction, and several mediators of inflammation are up-regulated in subjects with atherosclerotic disease. Healthy, intact endothelium exhibits an antithrombotic, protective surface between the vascular lumen and vascular smooth muscle cells in the vessel wall. Oxidative stress is an imbalance between anti- and prooxidants, with a subsequent increase of reactive oxygen species, leading to tissue damage. The renin-angiotensin-aldosterone system is of vital importance in the pathobiology of vascular disease. Convincing data indicate that angiotensin II accelerates hypertension and augments the production of reactive oxygen species. This leads to the generation of a proinflammatory phenotype in human endothelial and vascular smooth muscle cells by the up-regulation of adhesion molecules, chemokines and cytokines. In addition, angiotensin II also seems to increase thrombin generation, possibly via a direct impact on tissue factor. However, the mechanism of cross-talk between inflammation and haemostasis can also contribute to prothrombotic states in inflammatory environments. Thus, blocking of the renin-angiotensin-aldosterone system might be an approach to reduce both inflammatory and thrombotic complications in high-risk patients. During COVID-19, the renin-angiotensin-aldosterone system may be activated. The levels of angiotensin II could contribute to the ongoing inflammation, which might result in a cytokine storm, a complication that significantly impairs prognosis. At the outbreak of COVID-19 concerns were raised about the use of angiotensin converting enzyme inhibitors and angiotensin receptor blocker drugs in patients with COVID-19 and hypertension or other cardiovascular comorbidities. However, the present evidence is in favor of continuing to use of these drugs. Based on experimental evidence, blocking the renin-angiotensin-aldosterone system might even exert a potentially protective influence in the setting of COVID-19.

The role of magnetic order in VOCl

VOCl and other transition metal oxychlorides are candidate materials for next-generation rechargeable batteries. We have investigated the influence of the underlying magnetic order on the crystallographic and electronic structure by means of density functional theory. Our study shows that antiferromagnetic ordering explains the observed low-temperature monoclinic distortion of the lattice, which leads to a decreased distance between antiferromagnetically coupled V-V nearest neighbors. We also show that the existence of a local magnetic moment removes the previously suggested degeneracy of the occupied levels, in agreement with experiments. To describe the electronic structure, it turns out crucial to take the correct magnetic ordering into account, especially at elevated temperature.

Abstract P1-16-09: Low-dose chemotherapy (CT) + bevacizumab (Bev) combined with unchanged endocrine treatment (ET) in patients with recurrent luminal breast cancer progressing during ET – Effect determined by standard imaging and changes in ctDNA and CTC during treatment

Background: Several mechanisms are involved in the development of endocrine resistance, such as mutations in the ESR1, PIK3CA, and TP53 genes and/or up-regulation of tyrosine kinase receptors such as the endothelial growth factor (VEGF) receptor. Preclinical data have revealed that sensitivity to endocrine therapy may be restored if these pathways are blocked.

Aims: To investigate the progression-free survival (PFS), overall response rate (ORR), and the toxicity of the study treatment. To use circulating tumor cells (CTC) and circulating tumor DNA (ct-DNA) at base-line and during treatment for next generation sequencing (NGS) to investigate whether changes in tumor mutations or in levels of CTC/ct-DNA correlate to treatment efficacy.

Patients and methods: Thirty-two patients aged 46-77 years with confirmed advanced breast cancer (ABC) progressing during ET were included. Treatment consisted of unchanged ET with the addition of cyclophosphamide 50mg x 1 and capecitabine 500mg x 3 daily + bevacizumab 15mg/kg iv. every third week (q21). Blood samples for analysis of CTC and ctDNA were collected at base-line, after the 1st and 2nd course, and at progression. CTC were isolated by use of an immune-magnetic selection (ADNA-test) and sequenced by NGS. ctDNA were analysed by the SiMSen-Seq (Simple Multiplexed PCR-based barcoding of DNA for Sensitive mutation detection using Sequencing) that allows mutant frequencies < 0.1% to be detected.

Results: One patient did not start treatment and 2 were not evaluable. Palliative chemotherapy (1-2 lines) had been delivered before inclusion to 28% and > 1 line of palliative ET to 58% of the patients. A total of 72% (n=21) of the patients had visceral disease (of whom 7 had liver metastases), and 28% (n=8) patients bone-only disease. Median PFS was 9.1 months (range 2.1-59.3 months). Best responses were: 1 patient (3%) received complete remission; 7 patients (24%) partial response; 16 patients (55%) SD (of whom 12 had CB, defined as SD > 24 weeks), and 5 (17%) had progressive disease. The ORR (defined as CR, PR, or CB) was 69%. The most common toxicity was hypertension (62%), that resulted in termination in 2 patients, and 1 patient stopped treatment due to thrombocytopenia. Other side-effects were proteinuria grade 1-3 (24%); hand-foot-syndrome grade 1-2 (45%); mucositis grade 1 (14%); nausea grade 1 (14%) and diarrhea grade 1-3 (10%). CTC was isolated in 12 patients (37%). Three out of the 5 patients with PD at 12 weeks had detectable CTCs at base-line. Base-line ESR1, PIK3CA and TP53 mutations were found in CTC from 2 patients (17%), 7 patients (58%), and 5 patients (42%), respectively, but did not correlate to response.

Conclusion: The treatment was well tolerated with an ORR of 69%, which is considered very good in this setting. CTCs were only isolated in 37% of the patients which is comparable to previously reported results in metastatic luminal breast cancer and thus not a feasible method for monitoring treatment effect. Results on levels of consecutive ctDNA, as well as mutation pattern in relation treatment effect will be presented.

Citation Format: Linderholm BK, Ekholm M, Wännstig A-K, Lundstedt D, Carlsson L, Tzikas A-K, Svensson J, Kristiansson H, Filges S, Ståhlberg A. Low-dose chemotherapy (CT) + bevacizumab (Bev) combined with unchanged endocrine treatment (ET) in patients with recurrent luminal breast cancer progressing during ET – Effect determined by standard imaging and changes in ctDNA and CTC during treatment [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-16-09.

Abstract P4-14-10: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Ekholm M, Bendahl P-O, Fernö M, Nordenskjöld B, Stål O, Rydén L. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-14-10.

Abstract OT3-06-03: ABC-SE, Advanced Breast Cancer – Statins and Endocrine treatment

Full Title: A randomized, open-label, multi-center, phase II study to compare the efficacy and tolerability of atorvastatin 40 mg in addition to endocrine treatment in patients with estrogen receptor (ER) positive advanced breast cancer with focus on mechanisms of resistance.

Background: The majority of metastatic breast cancer patients progress during endocrine therapy and eventually become resistant to treatment. Understanding how metastatic cancer cells adapt to different therapies is key for the development of improved treatment regimens. The effectiveness of endocrine therapy in ER+ tumors may be influenced by cholesterol through the cholesterol metabolite oxysterol 27-hydroxycholesterol, which acts as an ER ligand, harboring the ability to regulate ER-dependent tumor growth. Statin-mediated inhibition of the cholesterol pathway has been demonstrated to induce anti-neoplastic effects in both breast cancer cells and human breast cancer. Hence the goal of this study is to both understand the mechanisms of resistance to endocrine treatment and test the hypothesis that addition of statins will enhance the efficacy of endocrine treatment.

Trial Design: A multi-center randomized, open-labelled, phase II trial in the first and second line metastatic treatment setting, comparing standard endocrine treatment (letrozole) with letrozole +/- atorvastatin (1:1). Upon progression in the first line setting, and as part of the translational studies of mechanisms of resistance to endocrine therapy, the patients receive second line endocrine treatment using fulvestrant.

Eligibility criteria: 1) Patients diagnosed with ER positive/HER2 negative metastatic breast cancer, including locally advanced stage IV disease, requiring systemic endocrine treatment. 2) No Previous treatment for metastatic breast cancer, unless being considered for direct entry to the second part of the study with fulvestrant.

Specific aims: To test the clinical efficacy of adding statins to endocrine treatment in advanced breast cancer. Primary endpoint: Clinical benefit rate, defined as the proportion of all randomly assigned patients who have the best overall response; complete response, partial response, or stable disease for at least 24 weeks following first-line letrozole treatment alone or in combination with atorvastatin. Translational endpoint: To elucidate mechanisms of resistance to endocrine treatment alone or in combination with statins in ER+ metastatic breast cancer.

Statistical Methods:The primary endpoint of clinical benefit rate will be compared in the two groups using a logistic regression model where the odds ratios and associated 95% CIs and p-values will be reported. The secondary endpoint, progression-free-survival, will be analyzed in crude analysis using the Kaplan-Meier and Log-Rank test as well as the Cox regression hazards analysis with the latter allowing for confounder-controlled multivariate analysis.

Present accrual and target accrual: The trial started recruiting as of October 10, 2016. The target accrual is 126 patients, whereof 17 are presently included in the trial.

Contact information for people with a specific interest in the trial:

Signe.Borgquist@med.lu.se

Citation Format: Borgquist S, Ekholm M, Feldt M, Schyman T, Zackrisson S, Bosch A. ABC-SE, Advanced Breast Cancer – Statins and Endocrine treatment [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 OT3-06-03.

Abstract P2-11-15: Immunohistochemical assessment of Ki67 with the antibodies SP6 and MIB1 - A comparison of prognostic information and reproducibility

Background

Proliferation is a key feature in breast cancer and also a clinical important factor for prognosis and treatment prediction. In the St Gallen Consensus of 2011, immunohistochemically analysed Ki67 was adopted as a surrogate marker to distinguish the “luminal A” from the “luminal B” subtype, in order to select patients with estrogen receptor positive disease expected to benefit from adjuvant chemotherapy. The mouse monoclonal antibody MIB1 is the generally accepted antibody for assessment of Ki67. However, other antibodies have been developed, e.g. the rabbit monoclonal antibody SP6. The assessment of Ki67 with MIB1 is unfortunately associated with a considerable lack of reproducibility. Rabbit monoclonal antibodies generally tend to have higher specificity without loss of sensitivity, compared to corresponding mouse monoclonal antibodies. SP6 has also been found to have reduced background staining compared to MIB1. According to these advantages, SP6 may be an alternative to MIB1 for routine staining of Ki67. Any methodological modification should, according to international recommendations, be compared against a clinically validated assay and demonstrate acceptable concordance before being introduced in clinical routine. The analysis of Ki67 with SP6 therefore needs to be evaluated and compared to MIB1 in a cohort of breast cancer patients with clinical follow-up.

Aims

To compare the antibodies SP6 and MIB1 for immunohistochemical assessment of Ki67 in primary breast cancer regarding prognostic strength and reproducibility of the evaluation.

Methods

Tissue microarray from a cohort of 237 premenopausal women with node-negative breast cancer was used for assessment of Ki67, with both SP6 and MIB1, by three different investigators. The 7th decile was applied for defining cut-off. Distant disease-free survival (DDFS) was used as endpoint and the follow-up was restricted to 5 years.

Results

Ninety per cent of the samples were classified into the same group, either high or low Ki67, irrespective of antibody used. Ki67 (high vs. low), analysed with both antibodies was associated to DDFS (34 events) in the univariable analyses (SP6: HR 2.6, 95% CI 1.3-5.2, p = 0.01 and MIB1: HR 2.8, 95% CI 1.4-5.7 p = 0.004) and showed borderline significance for DDFS in the multivariable analyses, also including HER2, age, and tumour size (SP6: HR 2.0, 95% CI 0.93-4.5, p = 0.074 and MIB1: HR 2.2, 95% CI 0.97-4.8, p = 0.058). The agreement between different assessors was somewhat higher for MIB1 than for SP6 (kappa-values 0.83-0.88 vs. 0.72-0.77).

Conclusions

SP6 was not superior to MIB1 and the two antibodies were comparable in the assessment of Ki67 for prognostic considerations in primary breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-11-15.

Hyperfine splitting and room-temperature ferromagnetism of Ni at multimegabar pressure

Magnetic and elastic properties of Ni metal have been studied up to 260 GPa by nuclear forward scattering of synchrotron radiation with the 67.4 keV Mössbauer transition of 61Ni. The observed magnetic hyperfine splitting confirms the ferromagnetic state of Ni up to 260 GPa, the highest pressure where magnetism in any material has been observed so far. Ab initio calculations reveal that the pressure evolution of the hyperfine field, which features a maximum in the range of 100 to 225 GPa, is a relativistic effect. The Debye energy obtained from the Lamb-Mössbauer factor increases from 33 meV at ambient pressure to 60 meV at 100 GPa. The change of this energy over volume compression is well described by a Grüneisen parameter of 2.09.

Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations

The elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys with additions of up to 8 at.% X were studied by combinatorial thin film growth and characterization and by ab initio calculations using the disordered local moments (DLM) approach. The lattice parameter and Young's modulus values change only marginally with X. The calculations and experiments are in good agreement. We demonstrate that the elastic properties of transition metal alloyed Fe-Mn can be predicted by the DLM model.

Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition

We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.

Effect of varying displays and room illuminance on caries diagnostic accuracy in digital dental radiographs

In clinical practice, digital radiographs taken for caries diagnostics are viewed on varying types of displays and usually in relatively high ambient lighting (room illuminance) conditions. Our purpose was to assess the effect of room illuminance and varying display types on caries diagnostic accuracy in digital dental radiographs. Previous studies have shown that the diagnostic accuracy of caries detection is significantly better in reduced lighting conditions. Our hypothesis was that higher display luminance could compensate for this in higher ambient lighting conditions. Extracted human teeth with approximal surfaces clinically ranging from sound to demineralized were radiographed and evaluated by 3 observers who detected carious lesions on 3 different types of displays in 3 different room illuminance settings ranging from low illumination, i.e. what is recommended for diagnostic viewing, to higher illumination levels corresponding to those found in an average dental office. Sectioning and microscopy of the teeth validated the presence or absence of a carious lesion. Sensitivity, specificity and accuracy were calculated for each modality and observer. Differences were estimated by analyzing the binary data assuming the added effects of observer and modality in a generalized linear model. The observers obtained higher sensitivities in lower illuminance settings than in higher illuminance settings. However, this was related to a reduction in specificity, which meant that there was no significant difference in overall accuracy. Contrary to our hypothesis, there were no significant differences between the accuracy of different display types. Therefore, different displays and room illuminance levels did not affect the overall accuracy of radiographic caries detection.

The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys

We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Néel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

Influence of the magnetic state on the chemical order-disorder transition temperature in Fe-Ni permalloy

In magnetic alloys, the effect of finite temperature magnetic excitations on phase stability below the Curie temperature is poorly investigated, although many systems undergo phase transitions in this temperature range. We consider random Ni-rich Fe-Ni alloys, which undergo chemical order-disorder transition approximately 100 K below their Curie temperature, to demonstrate from ab initio calculations that deviations of the global magnetic state from ideal ferromagnetic order due to temperature induced magnetization reduction have a crucial effect on the chemical transition temperature. We propose a scheme where the magnetic state is described by partially disordered local magnetic moments, which in combination with Heisenberg Monte Carlo simulations of the magnetization allows us to reproduce the transition temperature in good agreement with experimental data.

Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Néel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Néel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

A histological and immunohistochemical study of tissue reactions to solid poly(ortho ester) in rabbits

In many cases only the temporary presence of a biomaterial is needed in tissue support, augmentation or replacement. In such cases biodegradable materials are better alternatives than biostable ones. At present, biodegradable polymers are widely used in the field of maxillofacial surgery as sutures, fracture fixation devices and as absorbable membranes. The most often used polymers are aliphatic polyesters, such as polyglycolic acid (PGA) and polylactic acid (PLA). Poly(ortho ester) is a surface eroding polymer, which has been under development since 1970, but is used mostly in drug delivery systems in semisolid form. The aim of this study was to evaluate the tissue reactions of solid poly(ortho ester) (POE), histologically and immunohistochemically. Resorption times and the effect of 2 different sterilization methods (gamma radiation and ethylene oxide) upon resorption were also evaluated. Material was implanted into the tibia and subcutaneously into the mandibular ramus area of 24 rabbits. Follow-up times were 1-10, 14 and 24 weeks. Histological studies showed that POE induces a moderate inflammation in soft tissue and in bone. At 24 week follow-up, inflammation was mild in soft tissue and moderate in bone. In immunohistochemical studies, no highly fluorescent layer of tenascin or fibronectin was found adjacent to the implant. Resorption of gamma-sterilized rods was faster than ethylene oxide-sterilized rods. The total resorption time was more than 24 weeks in both groups. Clinically the healing was uneventful and the implants the well tolerated by the living tissue. This encourages these authors to continue studies with this interesting new material to search for the ideal material for bone filling and fracture fixation.

The copolymer of epsilon-caprolactone-lactide and tricalcium phosphate does not enhance bone growth in mandibular defect of sheep

In the field of craniomaxillofacial and orthopaedic surgery there is a constant need for bone or bone substitute. At the present, the most effective way to enhance bone healing clinically is to use autogenous bone grafts. The problems associated with the use of these autografts are donor site morbidity, limited supply and need for a second operative site. Currently there are several different synthetic products commercially available in the market; nevertheless, none of them is ideal for filling bone defects. Therefore, search for new synthetic materials for bone replacement is necessary. A mixture of tricalcium phosphate (TCP) and epsilon-caprolactone-lactide copolymer P(epsilon -CL/DL-LA) was prepared and implanted in critical size mandibular bone defects in twelve sheep. Contralateral side was used as a control. Follow-up times for histological and radiological studies were 9, 14, 24 and 52 weeks. We found that the implanted material did not enhance bone formation compared to control site. We also confirmed that defect size was of critical size, since there was no complete healing of the control site either. The results do not encourage us to continue our studies with the mixture of TCP and P(epsilon-CL/DL-LA) as a filling material for bone defects. Therefore the search for the ideal material is still ongoing.

Histological study of tissue reactions to epsilon-caprolactone-lactide copolymer in paste form

In previous studies, epsilon-caprolactone-lactide copolymer in solid form has been used in experimental animals as suture material, and as a biodegradable nerve guide. The aim of the study reported here was to assess tissue reactions to epsilon-caprolactone-lactide copolymer in paste form, histologically, and to compare bone healing at the sites of implantation versus that at control sites. The other purpose of the study was to evaluate the properties of the implanted material as a filling material for bone defects. Resorption time and intensity of inflammatory reaction were also evaluated. Material was implanted into the abdominal walls and femurs of 34 rats. Follow-up times were from 2 weeks to 1 year. The results showed that epsilon-caprolactone-lactide copolymer in paste form induces a severe inflammatory reaction when placed in muscle, and moderate inflammation when implanted into bone. The resorption time was more than 1 year. Bone healing at sites of implantation was slower than at control sites.

Mixture of epsilon-caprolactone-lactide copolymer and tricalcium phosphate: a histological and immunohistochemical study of tissue reactions

In cranio-maxillofacial surgery, bone transplantation is needed for treatment of bony defects. An autograft, allograft or biomaterial can be used. Autogenous bone grafts are considered to be the best materials available, but there are some disadvantages in their use including donorsite morbidity, need for a second operative site and limited graft supply. A search for new bone-graft materials therefore remains necessary. We prepared a mixture of tricalcium phosphate (TCP), which is a resorbable, non-toxic, osteoconductive ceramic material and epsilon-caprolactone-lactide copolymer P(epsilon-CL/DL-LA), a resorbable polymer, and placed it in the dermis and in mandibular bone defects in 13 rabbits. Follow-up times were two, three, seven, eight, 12, 15 and 18 weeks, tissue reactions were assessed, histologically and immunohistochemically. Times of resorption of the material from tissues were reported. We found that the mixture caused a mild inflammatory reaction when placed in bone and severe inflammation when placed in dermis. No highly fluorescent layer of tenascin or fibronectin was found surrounding the implant area. The mixture was excellent to handle and very easy to place into bone defects. The results are promising and have led us to continue development of the mixture.

Biocompatibility of solid poly (ortho ester)

In previous studies poly (ortho ester) (POE) has shown promise as a resorbable device, a hemostatic sealant and as a carrier for drugs in bone surgery. The aim of this study was to evaluate the tissue reactions of solid poly (ortho ester) implanted into both tibiae of 17 rabbits. One half of the rods were sterilized by gamma radiation and the other half by ethylene oxide. The follow-up times were from 1 week to 21 weeks, after which the animals were killed and the bony specimens examined histologically. The connective tissue samples were examined immunohistochemically in order to study the occurrences of two extracellular matrix glycoproteins, tenascin and fibronectin. The results showed that solid poly (ortho ester)s induce a moderate inflammatory reaction for 9 weeks. Tenascin and fibronectin were present in samples from 1 week up to 4 weeks. It was also found that gamma sterilized POE was resorbed at week 7 and ethylene oxide sterilized POE at week 13.