Pack Years of Tobacco Cigarette Smoking as a Predictor of Bony Fusion After Anterior Cervical Discectomy and Fusion

OBJECTIVE

Smoking tobacco cigarettes negatively impacts bone healing after spinal fusion. Smoking history is often assessed based on current smoker and nonsmoker status. However, in current research, smoking history has not been quantified in terms of pack years to estimate lifetime exposure and assess its effects. Our goal was to investigate the influence of smoking history, quantified in pack years, on bony fusion after anterior cervical discectomy and fusion (ACDF).

METHODS

A retrospective chart review of consecutive patients who underwent ACDF for cervical disc degeneration between September 21, 2017 and October 17, 2018 was conducted. Patient demographics, procedural variables, and postoperative outcomes were analyzed. Multivariate logistic regression analysis was performed to identify predictive factors for bony fusion following ACDF. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal discrimination threshold for smoking history pack years in association with nonfusion.

RESULTS

Among 97 patients identified, 90 (93%) demonstrated bony fusion on postoperative imaging. Mean number of smoking history pack years was 6.1±13 for the fusion group and 16 ±21 for the nonfusion group. Multivariate logistic regression analysis suggested that increased pack years of tobacco cigarette smoking was a significant predictor of nonfusion (95% confidence interval, [1.0,1.1], p=0.045). The ROC curve analysis revealed that 6.1 pack years best stratified the risk for nonfusion (area under the curve, 0.8).

CONCLUSION

Patients with a history of tobacco cigarette smoking >6.1 pack years may have an increased risk of nonfusion after ACDF.

An online calculator using machine learning for predicting survival in pediatric patients with medulloblastoma

OBJECTIVE

Medulloblastoma is the most common malignant intracranial tumor affecting the pediatric population. Despite advancements in multimodal treatment over the past 2 decades yielding a 5-year survival rate > 75%, children who survive often have substantial neurological and cognitive sequelae. The authors aimed to identify risk factors and develop a clinically friendly online calculator for prognostic estimation in pediatric patients with medulloblastoma.

METHODS

Pediatric patients with a histopathologically confirmed medulloblastoma were extracted from the Surveillance, Epidemiology, and End Results database (2000-2018) and split into training and validation cohorts in an 80:20 ratio. The Cox proportional hazards model was used to identify the univariate and multivariate survival predictors. Subsequently, a calculator with those factors was developed to predict 2-, 5-, and 10-year overall survival as well as median survival months for pediatric patients with medulloblastoma. The performance of the calculator was determined by discrimination and calibration.

RESULTS

One thousand seven hundred fifty-nine pediatric patients with medulloblastoma met the prespecified inclusion criteria. Age, sex, race, ethnicity, median household income, county attribute, laterality, anatomical location, tumor grade, tumor size, surgery status, radiotherapy, and chemotherapy were variables included in the calculator (https://spine.shinyapps.io/Peds_medullo/). The concordance index was 0.769 in the training cohort and 0.755 in the validation cohort, denoting clinically useful predictive accuracy. Good agreement between the predicted and observed outcomes was demonstrated by the calibration plots.

CONCLUSIONS

An easy-to-use prognostic calculator for a large cohort of pediatric patients with medulloblastoma was established. Future efforts should focus on improving granularity of population-based registries and externally validating the proposed calculator.

Expected motor function change following decompressive surgery for spinal metastatic disease

Background

Motor function in patients with spinal metastatic disease (SMD) directly impacts a patient's ability to receive systemic therapy and overall survival. Spine surgeons may be in the challenging position to advise a patient on expected motor function outcomes and determine a patient's suitability as a surgical candidate. We present this study to provide this critical information on anticipated motor function change to spine surgeons.

Methods

Consecutive patients undergoing spinal surgery for SMD at a National Cancer Institute-designated cancer institute were prospectively enrolled. Patient motor function status before and after surgery was assessed using the standard 0 to 5 five-point muscle strength grading scale. The difference in presurgical and postsurgical motor function (proximal and distal) was used to assess motor function changes following surgery.

Results

A total of 171 patients were included. The mean age was 62.7±10.46 years and 40.9% (70) were female. Common primary malignancy types were lung (49), kidney (28), breast (25), and prostate (23). The average proximal and distal motor function difference was 0.38 (standard deviation=1.02, p<.0001) and 0.32 (standard deviation=0.91, p<.0001) respectively showing an improvement following surgery. Patients with proximal presurgical motor function of 2, 3, and 4 had an improved motor function in 73%, 77%, and 73% of the patients. Patients with distal presurgical motor function of 2, 3, and 4 had an improved motor function in 80%, 89%, and 70% of the patients.

Conclusions

Most patients undergoing surgery for SMD have a modest improvement in motor function following surgery. The degree of improvement in most instances is less than 1 point on a 0 to 5 motor function scale. This is critical knowledge for a spinal surgeon when evaluating SMD patients with significant preoperative motor function deficits. These results aid spinal surgeons in setting expectations and evaluating the need for rapid spinal decompression.

A Novel Cervical Vertebral Bone Quality Score Independently Predicts Cage Subsidence After Anterior Cervical Diskectomy and Fusion

BACKGROUND

Surgeons can preoperatively assess bone quality using dual-energy X-ray absorptiometry or computed tomography; however, this is not feasible for all patients. Recently, a MRI-based scoring system was used to evaluate the lumbar spine's vertebral bone quality.

OBJECTIVE

To create a similar MRI-based scoring system for the cervical spine (C-VBQ), correlate C-VBQ scores with computed tomography-Hounsfield units (HU), and evaluate the utility of this scoring system to independently predict cage subsidence after single-level anterior cervical diskectomy and fusion (ACDF).

METHODS

Demographic, procedure-related, and radiographic data were collected for patients. Pearson correlation test was used to determine the correlation between C-VBQ and HU. Cage subsidence was defined as ≥3 mm loss of fusion segmental height. A multivariate logistic regression model was built to determine the correlation between potential risk factors for subsidence.

RESULTS

Of 59 patients who underwent single-level ACDF, subsidence was found in 17 (28.8%). Mean C-VBQ scores were 2.22 ± 0.36 for no subsidence levels and 2.83 ± 0.38 ( P < .001) for subsidence levels. On multivariate analysis, a higher C-VBQ score was significantly associated with subsidence (odds ratio = 1.85, 95% CI = 1.39-2.46, P < .001) and was the only significant independent predictor of subsidence after ACDF. There was a significant negative correlation between HU and C-VBQ (r 2 = -0.49, P < .001).

CONCLUSION

We found that a higher C-VBQ score was significantly associated with cage subsidence after ACDF. Furthermore, there was a significant negative correlation between C-VBQ and HU. The C-VBQ score may be a valuable tool for assessing preoperative bone quality and independently predicting cage subsidence after ACDF.

Complications associated with subaxial placement of pedicle screws versus lateral mass screws in the cervical spine (C2-T1): systematic review and meta-analysis comprising 4,165 patients and 16,669 screws

Lateral mass screw (LMS) and cervical pedicle screw (CPS) fixation are among the most popular techniques for posterior fusion of the cervical spine. Early research prioritized the LMS approach as the trajectory resulted in fewer neurovascular complications; however, with the incorporation of navigation assistance, the CPS approach should be re-evaluated. Our objective was to report the findings of a meta-analysis focused on comparing the LMS and CPS techniques in terms of rate of various complications with inclusion of all levels from C2 to T1. We conducted a systematic review of PubMed and EMBASE databases with final inclusion criteria focused on identifying studies that reported outcomes and complications for either the CPS or LMS technique. These studies were then pooled, and statistical analyses were performed from the cumulative data. A total of 60 studies comprising 4165 participants and 16,669 screws placed within the C2-T1 levels were identified. Within these studies, the LMS group had a significantly increased odds for lateral mass fractures (odds ratio [OR] = 43.2, 95% confidence interval [CI] = 2.62-711.42), additional cervical surgeries (OR = 5.56, 95%CI = 2.95-10.48), and surgical site infections (SSI) (OR = 5.47, 95%CI = 1.65-18.16). No other significant differences between groups in terms of complications were identified. Within the subgroup analysis of navigation versus non-navigation-guided CPS placement, no significant differences were identified for individual complications, although collectively significantly fewer complications occurred with navigation (OR = 5.29, 95%CI = 2.03-13.78). The CPS group had significantly fewer lateral mass fractures, cervical revision surgeries, and SSIs. Furthermore, navigation-assisted CPS placement was associated with a significant reduction in complications overall.

Vertebral Bone Quality Score Independently Predicts Proximal Junctional Kyphosis and/or Failure After Adult Spinal Deformity Surgery

BACKGROUND

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) can be catastrophic complications associated with adult spinal deformity (ASD) surgery. These complications are markedly influenced by osteoporosis, leading to additional vertebral fracture and pedicle screw loosening. The MRI-based vertebral bone quality score (VBQ) is a newly developed tool that can be used to assess bone quality.

OBJECTIVE

To investigate the utility of the VBQ score in predicting PJK and/or PJF (PJF/PJK) after ASD correction.

METHODS

We conducted a retrospective chart review to identify patients age ≥50 years who had received ASD surgery of 5 or more thoracolumbar levels. Demographic, spinopelvic parameters, and procedure-related variables were collected. Each patient's VBQ score was calculated using preoperative T1-weighted MRI. Univariate analysis and multivariate logistic regression were performed to determine potential risk factors of PJK/PJF. Receiver operating characteristic analysis and area-under-the-curve values were generated for prediction of PJK/PJF.

RESULTS

A total of 116 patients were included (mean age, 64.1 ± 6.8 years). Among them, 34 patients (29.3%) developed PJK/PJF. Mean VBQ scores were 3.13 ± 0.46 for patients with PJK/PJF and 2.46 ± 0.49 for patients without, which was significantly different between the 2 groups ( P < .001). On multivariate analysis, VBQ score was the only significant predictor of PJK/PJF (odds ratio = 1.745, 95% CI = 1.558-1.953, P < .001), with a predictive accuracy of 94.3%.

CONCLUSION

In patients undergoing ASD correction, higher VBQ was independently associated with PJK/PJF occurrence. Measurement of VBQ score on preoperative MRI may be a useful adjunct to ASD surgery planning.

Vertebral bone quality score independently predicts cage subsidence following transforaminal lumbar interbody fusion

BACKGROUND CONTEXT

Cage subsidence following transforaminal lumbar interbody fusion (TLIF) has been associated with poor bone quality. Current evidence suggests that the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score correlates with poor bone quality.

PURPOSE

To our knowledge, this is the first study to assess whether the VBQ score can predict the occurrence of postoperative cage subsidence after TLIF surgery.

DESIGN/SETTING

Retrospective single-center cohort.

PATIENT SAMPLE

Patients undergoing single-level TLIF for degenerative spine disease between February 2014 and October 2021.

OUTCOME MEASURES

Extent of subsidence.

METHODS

Demographic, procedure-related, and radiographic data were collected for study patients. VBQ scores were determined from preoperative T1-weighted MRI. Subsidence was defined as ≥2 mm of migration of the cage into the superior or inferior end plate or both. Univariate and multivariate logistic regression were used to determine the correlation between potential risk factors for subsidence and actual subsidence rates.

RESULTS

Subsidence was observed among 42 of the 74 study patients. The mean VBQ scores were 2.9±0.5 for patients with subsidence and 2.5±0.5 for patients without subsidence. The difference among groups was significant (p=.003). On multivariate logistic regression, a higher VBQ score was significantly associated with an increased risk of subsidence (OR=1.5, 95% CI=1.160-1.973, p=.004) and was the only significant independent predictor of subsidence after TLIF.

CONCLUSION

We found that a higher VBQ score was significantly associated with cage subsidence following TLIF. The MRI-VBQ score may be a valuable tool for assisting in identifying patients at risk of cage subsidence following TLIF.

Meta-analysis of overall survival and postoperative neurologic deficits after resection or biopsy of butterfly glioblastoma

Butterfly glioblastoma (bGBM) is a grade 4 glioma with a poor prognosis. Surgical treatment of these cancers has been reviewed in the literature with some recent studies supporting resection as a safe and effective treatment instead of biopsy and adjuvant therapy. This meta-analysis was designed to determine whether there are significant differences in overall survival (OS) and postoperative neurologic deficits (motor, speech, and cranial nerve) following intervention in patients who underwent tumor resection as part of their treatment, compared to patients who underwent biopsy without surgical resection. A literature search was conducted using PubMed (National Library of Medicine) and Embase (Elsevier) to identify articles from each database's earliest records to May 25, 2021, that directly compared the outcomes of biopsy and resection in bGBM patients and met predetermined inclusion criteria. A meta-analysis was conducted to compare the effects of the two management strategies on OS and postoperative neurologic deficits. Six articles met our study inclusion criteria. OS was found to be significantly longer for the resection group at 6 months (odds ratio [OR] 2.94, 95% confidence interval [CI] 1.23-7.05) and 12 months (OR 3.75, 95% CI 1.10-12.76) than for the biopsy group. No statistically significant differences were found in OS at 18 and 24 months. Resection was associated with an increased rate of postoperative neurologic deficit (OR 2.05, 95% CI 1.02-4.09). Resection offers greater OS up to 1 year postintervention than biopsy alone; however, this comes at the cost of higher rates of postoperative neurologic deficits.

Complications associated with subaxial placement of pedicle screws versus lateral mass screws in the cervical spine: systematic review and meta-analysis comprising 1768 patients and 8636 screws

Lateral mass screw (LMS) fixation for the treatment of subaxial cervical spine instability or deformity has been traditionally associated with few neurovascular complications. However, cervical pedicle screw (CPS) fixation has recently increased in popularity, especially with navigation assistance, because of the higher pullout strength of the pedicle screws. To their knowledge, the authors conducted the first meta-analysis comparing the complication rates during and/or after CPS and LMS placement for different pathologies causing cervical spine instability. A systematic literature search of PubMed and Embase from inception to January 12, 2021 was performed to identify studies reporting CPS and/or LMS-related complications. Complications were categorized into intraoperative and early postoperative (within 30 days of surgery) and late postoperative (after 30 days from surgery) complications. All studies that met the prespecified inclusion criteria were pooled and cumulatively analyzed. A total of 24 studies were conducted during the time frame of the search and comprising 1768 participants and 8636 subaxially placed screws met the inclusion criteria. The CPS group experienced significantly more postoperative C5 palsy (odds ratio [OR] = 3.48, 95% confidence interval [CI] = 1.27-9.53, p < 0.05). Otherwise, there were no significant differences between the LMS and CPS groups. There were no significant differences between the CPS and LMS groups in terms of neurovascular procedure-related complications other than significantly more C5 palsy in the CPS group.

Navigation-Guided Subaxial Cervical Pedicle Screws in Revision Spine Surgery: 2-Dimensional Operative Video

Traditionally, lateral mass screws (LMSs) have been the mainstay of posterior fixation in the subaxial spine. Although LMSs provide adequate fixation, cervical pedicle screws (CPSs) facilitate high fusion rates (90.5%) and provide for greater bone purchase, better reduction, lower rates of screw loosening or pull out, 2 times greater biomechanical advantage, superior stabilization, decreased development of pseudarthrosis, and decreased revision surgeries compared to LMSs.1-4 In addition, CPSs can be a powerful bail-out option after lateral mass construct failure. Navigation-guided CPS placement has been reported to have an accuracy of 90.3%.5 Navigation has the added advantage of mitigating screw malposition for the placement of CPS because of the smaller pedicle sizes and variability in cervical anatomy.1,3,6 The potential risks of subaxial CPS placement include the risks of vertebral artery injury, spinal cord injury, and injury to adjacent neurovasculature.2 The overall radiographic breach rate with intraoperative imaging is reported to range from 2.9% of 22.9%, with the majority of breaches occurring in the lateral direction.7,8 Despite radiographic breaches, the occurrence of nerve root injury (0.31% per screw), vertebral artery injury (0.15% per screw), and spinal cord injury (0% per screw) is rare.3,7 Here, we demonstrate navigation-assisted C1-C2 posterior fusion, with combined C1 LMSs and C2 pedicle screws with subaxial pedicle screw revision of prior failed instrumentation.3  The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary.

Spinal cord glioblastoma multiforme in a patient with Noonan syndrome: A clinical report

INTRODUCTION

Currently, there are only 3 reported cases of central nervous system malignancies in patients with Noonan syndrome in the literature, all of which are intracranial pathologies. To our knowledge, there are no cases of spinal cord glioblastoma multiforme reported in the literature.

CASE DESCRIPTION

We describe the case of a 12-year-old girl with Noonan syndrome who presented with back pain and new onset neurological deficits and was found to have a spinal cord lesion. T10-L1 laminoplasty with safe maximal resection was done. Postoperative pathological analysis identified this lesion as a high-grade astrocytoma consistent with glioblastoma multiforme.

CONCLUSIONS

Spinal cord glioblastoma multiforme is a rare occurrence in the general population, particularly in a patient with an underlying diagnosis of Noonan syndrome. Patients with spinal cord tumors can present with a multitude of clinical signs and symptoms and treatment should not be delayed.

Effect of intensity of eggshell pigment and illuminated incubation on hatchability of brown eggs

The effects of intensity of brown eggshell pigment (light (LBP), medium (MBP) and dark (DBP)) and light intensity during incubation (low and high, 900 to 1380 and 1430 to 2080 lux, respectively) on eggshell characteristics, embryonic growth, hatchability traits, chick hatching weight and hatching time were investigated using eggs from a meat-type breeder (Hybro) flock at 32, 36 and 41 weeks of age in three trials. With eggs of similar weights the intensity of brown pigment was not associated with eggshell weight and thickness, and did not influence embryo weight and egg weight loss during incubation. The shade of brown pigment of eggs laid by young hens influenced the percentage hatchability (HP) of eggs incubated under light. Illuminated incubation improved HP of LBP eggs (compared with MBP and DBP eggs) from 32- and 36-week-old hens, but had no significant effect on HP of eggs from 41-week-old hens. Light intensity during incubation did not influence egg weight loss. High intensity of light during incubation reduced HP and increased early death percentage (EDP) in the LBP and MBP groups, and did not influence HP and EDP in the DBP group. Brown eggshell pigment and intensity of light during incubation did not influence hatching time. It is concluded that the shade of brown pigment, intensity of light during incubation and age of the breeder hens influenced the hatchability performance of embryos from brown eggs. Light during incubation improved the hatchability of embryos in light brown eggs laid by young hens and the shade of brown pigment of eggs laid by older hens did not influence hatchability under illuminated incubation. High intensity of light during incubation reduced hatchability of light and medium brown eggs, but not the dark brown eggs.

Effects of electrical field on hatchability performance of eggs from a layer-type breeder

1. Eggs from a layer-type breeder flock (Baladi, King Saud University) between 50 and 63 weeks of age were used in three trials to study the effects of electrical field (EF) during incubation on albumen and yolk heights, incubation temperature, egg weight loss and hatchability traits. The effects of egg size and eggshell characteristics on hatchability traits of eggs incubated under EF were investigated. 2. Eggs were weighed and graded into three weight classes (small, medium, and large). The physical dimensions, eggshell characteristics, and conductance of eggs were examined. The incubator was divided into two compartments for the control and EF treatments. Two aluminium plates were fitted on the inside walls of the EF compartment, face to face, and connected to a step up electric transformer. Eggs were exposed constantly to the EF during the first 18 d of incubation at the level of 30 kV/m, 60 Hz. 3. Egg size influenced the physical dimensions and eggshell characteristics of eggs. Large eggs had higher egg weight, egg surface area, egg volume, eggshell conductance, and eggshell weight and lower yolk weight percentage than medium or small size eggs. Small eggs had lower egg length and higher egg density than large or medium size eggs. Large eggs had higher eggshell thickness than small size eggs. 4. EF incubation of eggs raised incubation temperature by 0.06 degrees C, and increased the percentage of egg weight loss, hatchability, and weight of hatching chicks and reduced the early embryo deaths, and length of incubation by approximately 9.8, 19.6, 1.7, 62.1 and 2.1%, respectively. 5. There was no significant difference between the two incubation treatments in the heights of albumen and yolk of incubated eggs, percentages of late embryo deaths, and pips with live and dead embryos. Hatchability traits were not significantly influenced by egg size. 6. It was concluded that EF incubation of eggs increased hatchability, chick-hatching weight, and reduced the length of incubation of Baladi eggs. Differences in the physical dimensions and eggshell characteristics of eggs did not influence hatchability traits of eggs under EF incubation.

Incubation temperature and hemoglobin dielectric of chicken embryos incubated under the influence of electric field

Eggs from a layer-type breeder flock (Baladi, King Saud University) between 61 and 63 weeks of age were used in 3 trials to study the effects of electric field (EF) during incubation on the internal temperature of incubation, and eggs and hemoglobin (Hb) dielectric of chicken embryos at 18 days of age. Dielectric relative permittivity (epsilon') and conductivity (sigma) of Hb were examined in the range of frequency from 20 to 100 kHz. The values of dielectric increment (Deltaepsilon') and the relaxation times (tau) of Hb molecules were calculated. The internal temperature of eggs was measured in empty (following the removal of egg contents) and fertilized eggs in trials 1 and 2, respectively. The level of the EF was 30 kV/m, 60 Hz. EF incubation of embryos influenced the temperature of incubation and electrical properties of Hb molecules and did not influence the temperature of incubation and internal environment of eggs when empty eggs were incubated. EF incubation of fertilized eggs significantly raised the temperature of incubation, egg air cell, and at the surface of the egg yolk by approximately 0.09, 0.60, and 0.61 degrees F, respectively and Hb epsilon', sigma, Deltaepsilon', and tau as a function of the range of frequency of 20 to 100 kHz when compared with their counterparts of the control group. It was concluded that the exposure of fertilized chicken eggs to EF of 30 kV/m, 60 Hz, during incubation altered dielectric properties of Hb and that probably affected cell to cell communication and created the right environment for enhancing the growing process and heat production of embryos consequently increasing the temperature of the internal environment of the egg, and incubation.

Efficient gene delivery with serum into human cancer cells using targeted anionic liposomes

Success of human gene therapy depends upon the development of delivery vehicles or vectors, which can selectively deliver therapeutic genes to target cells with efficiency and safety. Previous studies have shown an efficient, systemic trans-gene expression in many cell lines (in vitro) by using an anionic liposomal vector, based on the composition of retroviral envelopes (artificial viral envelopes, AVEs). The AVE-liposomes and their complexes with plasmid (DNA) were characterized according to zeta potential measurements and transmission electron microscopy (TEM). We successfully demonstrated that AVE liposomes, dispersed in 10% serum-containing growth medium, efficiently delivered plasmid DNA to HuH-7 (human hepatoma cell line) cells. We assessed the utility of liver-targeted vesicles as a drug/gene delivery system for the treatment of liver diseases. We found that small unilamellar AVE vesicles containing 15 mol% digalactosyl diglyceride (DGDG) are efficiently targeted to the liver via the hepatic asialoglycoprotein receptor.

Interaction of type-I collagen with phospholipid monolayer

The effects of type-I collagen on dipalmitoyl phosphatidylcholine (DPPC) and dimyristoyl phosphatidylcholine (DMPC) monolayer films with different compositions were studied using monolayer technique. The addition of collagen in the subphase of different monolayer films induced a considerable shift towards larger area/molecule in the compression-isotherm curves. This is either referred to the insertion of collagen into the monolayer by its hydrophobic residues or to an adsorption process causing a protein layer to be located parallel to the lipid monolayer [1]. The variation of collagen interaction with different lipid compositions was also verified through the penetration-kinetics experiment. Comparing our results to the results of Pajean et al. [2] and Pajean and Herbage [3] on the effect of collagen on the stability of lipid vesicles implies that the collagen induced stability could be explained on the basis of collagen-lipid monolayer interaction.

Interaction of Doxorubicin with phospholipid monolayer and liposomes

The effect of Doxorubicin which is (an anthracycline antibiotic with a broad spectrum of antitumor activity) on the monolayer and bilayer in the form of large Multilamellar Vesicles (MLV's) of Dipalmitoyl phosphatidylcholine (DPPC) were studied by means of monolayer techniques (surface pressure, penetration kinetics, and association constant) and light scattering technique. The monolayer technique showed that addition of DXR to a lipid film composed of (DPPC/CHOL/PEG-PE) at a molar ratio of (100:0:0) produced a less condensed Monolayer. In the (pie-A) curves, DXR induced shift towards larger area/molecule, where the area/molecule was shifted from 61 to 89 A2, and 116 A2 in the presence of 20 and 40 nM DXR, respectively. The three curves collapsed at a pressure pi = 45 mN/m. In penetration kinetics experiment (delta pi-t), the change in pressure with time was 8 and 14 mN/m for a DXR concentration of 20 and 40 nM, respectively, and the increase in surface pressure presented a plateau over a period of 30 min. The measured association constant (K) was found to be 5 x 10(5)/M. In the light scattering experiment, there was a shift of the transition temperature (Tm) of (MLV's) of the same composition of the monolayer towards a smaller value from 40.5 degrees to 34.5 degrees C. Incorporation of CHOL and PEG-PE as DPPC/CHOL/PEG-PE at a molar ratio of (100:20:0), (100:20:4) and (100:20:4) greatly counteracted the effect of DXR and made the lipid membrane more condense and rigid. Moreover, the penetration of DXR into the membrane was greatly reduced. There was a very small shift for the (pi-A) and (delta pi-t) curves, and the association constant of the drug for these different lipid compositions was greatly reduced down to 2.5 x 10(5)/M and the transition temperature (Tm) was increased up to (42.5 degrees C) in the presence of 40 nM DXR. Our results suggest that DXR has a great effect on the phospholipid membrane, and that addition of CHOL or PEG-PE to the phospholipid membrane causes stabilization for the membrane, and reduces the interaction with Doxorubicin.