Long-term efficacy and tolerability of octreotide treatment in acromegaly

Treatment Sequencing Strategies in Advanced Neuroendocrine Tumors: A Review

Neuroendocrine tumor (NET) incidence has grown. The treatment landscape for advanced NETs is rapidly evolving, but there are limited head-to-head data to guide treatment sequencing decisions. We assessed the available clinical data to aid practicing clinicians in their routine clinical decision-making. Clinical trials have demonstrated efficacy benefits for new therapies in advanced NETs. Emerging long-term data from these trials have enabled clinicians to make more accurate risk-benefit assessments, particularly for patients receiving multiple lines of therapy. However, clinical data specifically regarding treatment sequencing are limited. In lieu of definitive data, treatment sequencing should be based on disease-related factors (e.g., site of tumor origin, volume of disease) and patient-related characteristics (e.g., comorbidities, patient preferences). Clinical decision-making in advanced NETs remains highly individualized and complex; important evidence gaps regarding treatment sequencing remain. Given this, advanced NET management should be a joint effort of multidisciplinary teams at referring and high-volume centers. Additional clinical trial and real-world evidence are needed to meet the challenge of understanding how to sequence available NET therapies. Until these trials are conducted, the best practices provided in this review may serve as a guide for clinicians making treatment sequencing decisions based on the available data.

From hormone replacement therapy to regenerative scaffolds: A review of current and novel primary hypothyroidism therapeutics

Primary hypothyroidism severely impacts the quality of life of patients through a decrease in the production of the thyroid hormones T3 and T4, leading to symptoms affecting cardiovascular, neurological, cognitive, and metabolic function. The incidence rate of primary hypothyroidism is expected to increase in the near future, partially due to increasing survival of patients that have undergone radiotherapy for head and neck cancer, which induces this disease in over half of those treated. The current standard of care encompasses thyroid hormone replacement therapy, traditionally in the form of synthetic T4. However, there is mounting evidence that this is unable to restore thyroid hormone signaling in all tissues due to often persistent symptoms. Additional complications are also present in the form of dosage difficulties, extensive drug interactions and poor patience compliance. The alternative therapeutic approach employed in the past is combination therapy, which consists of administration of both T3 and T4, either synthetic or in the form of desiccated thyroid extract. Here, issues are present regarding the lack of regulation concerning formulation and lack of data regarding safety and efficacy of these treatment methods. Tissue engineering and regenerative medicine have been applied in conjunction with each other to restore function of various tissues. Recently, these techniques have been adapted for thyroid tissue, primarily through the fabrication of regenerative scaffolds. Those currently under investigation are composed of either biopolymers or native decellularized extracellular matrix (dECM) in conjunction with either primary thyrocytes or stem cells which have undergone directed thyroid differentiation. Multiple of these scaffolds have successfully restored an athyroid phenotype in vivo. However, further work is needed until clinical translation can be achieved. This is proposed in the form of exploration and combination of materials used to fabricate these scaffolds, the addition of peptides which can aid restoration of tissue homeostasis and additional in vivo experimentation providing data on safety and efficacy of these implants.

Long-Acting Octreotide and Prolonged-Release Lanreotide Formulations Have Different Pharmacokinetic Profiles

Single-dose pharmacokinetic (PK) profiles and multiple-dose PK modeling were compared for long-acting octreotide (20 or 60 mg) and prolonged-release lanreotide (90 or 120 mg) over 91 days; steady-state profiles were simulated. All treatments were well tolerated. Octreotide 20-mg profile showed increased concentration on day 1, lag from days 2 to 6, then prolonged plateau phase (days 11-41); 60-mg PK was dose proportional. Lanreotide 90-mg profile showed C(max) on day 1 then elimination (apparent t1/2 25.5 days); 120-mg profile was underproportional. Steady-state PK of octreotide 20 mg/28 d suggested a C(mean) of 1216 rhog/mL (range, 1065-1585) with low fluctuation index (43%). Steady-state PK of lanreotide 90 mg/28 d suggested a C(mean) of 4455 rhog/mL (range, 2499-9279) with high fluctuation index (152%). Long-acting octreotide had more predictable PK than prolonged-release lanreotide. Simulated steady-state profiles suggest long-acting octreotide could be optimized to meet individual patient needs. In contrast, prolonged-release lanreotide requires exposure constantly above the therapeutic target to enable monthly long-term therapy.

A Review of the Pharmacokinetics of Levothyroxine for the Treatment of Hypothyroidism

Thyroxine hormone has been recognised since the early part of the nineteenth century and levothyroxine has been available since the mid-nineteenth century as a replacement for deficient thyroid hormones. While levothyroxine remains the staple treatment for hypothyroidism even to this day, its optimal use can be challenging. As is often the case with older drugs, the pharmacokinetics of levothyroxine is often under-appreciated or misunderstood and many factors influence the optimal dosing of levothyroxine. This article will review the pharmacokinetics of levothyroxine in the treatment of hypothyroidism and highlight major concepts that should aid both clinicians and researchers.

[Dopaminergic and somatostatinergic pathways decrease serum thyrotropin in rats bearing the 256-Walker mammary carcinoma]

The hypothalamus-pituitary-thyroid axis was studied in rats with the "low T(3) syndrome" caused by the implantation of the Walker-256 mammary carcinoma. Male adult rats were injected s.c. with 1 x 106 viable tumoral cells and killed 10 days later. The tumor development was associated with decreased thyroid activity characterized by a approximately 15% reduction in the nuclear area of the thyrocytes and 131I-thyroid uptake (down by approximately 50%), as well as about 70% lower serum levels of T4 and rTg. The functional thyroidal response to exogenous TSH was decreased in the tumor-bearing rats, as well as the rTSH secretion in response to TRH (50 microg/kg). To investigate the role of other hypothalamic neuromediators in this process, tumor-bearing rats received an i.v. injection of metoclopramide (5 mg/kg) and/or physostigmine (12.5 microg/kg), with or without concomitant stimulus with TRH. Each drug improved the rTSH response to TRH, which in the case of physostigmine, almost normalized. When both drugs were injected simultaneously the rTSH response to TRH returned to normal. Thus, in addition to the well known alterations in the extrathyroidal metabolism of thyroid hormones, TSH secretion is decreased in rats with the Walker-256 tumor, indicating a generalized reduction in the thyroid function.

Volumetric measurements of peripheral oedema in clinical conditions

Water-displacement volumetry can be used for quantifying the volume of the leg. However, not much is known about its application in patients with peripheral oedema of cardiopulmonary origin. We measured the reproducibility of a water-displacement apparatus with a solid object and in ten non-oedematous clinical patients (group A). The day-to-day variability of the leg volume was assessed in the same group. The diurnal variability was assessed in ten patients with persisting peripheral oedema (group B). The effect of treatment on the severity of peripheral oedema was evaluated in another nine patients with peripheral oedema, who were in need of diuretic treatment (group C). Volumetric results were compared to the ankle circumference method and the body weight method. The coefficient of variation was 0.16% in the fixed object and 0.47% in group A. The day-to-day variability was 1.52% after 1 day and 1.76% after a mean interval of 4.8 days. In group B, leg volume and circumference increased during the day (5.9%, P<0.001, and 2.4%, P<0.01, respectively), while body weight remained unchanged. In group C, leg volume, circumference and body weight decreased significantly after treatment (13.1%, P<0.01, 7.1%, P<0.05, and 5.9%, P<0.05). The correlation between the changes in volume and body weight was poor (r=0.37, P=0.33). In conclusion, (1) water-displacement volumetry is highly reproducible, (2) a diurnal variability of peripheral oedema was found, and (3) volumetry is a suitable tool for monitoring peripheral oedema, while the body weight method appears to be less accurate.

Incidence and morbidity of cholelithiasis in patients receiving chronic octreotide for metastatic carcinoid and malignant islet cell tumors

BACKGROUND

Octreotide, a long-acting somatostatin analogue, has demonstrated clinical utility in patients with carcinoid syndrome and malignant islet cell tumors of the pancreas. Prior studies have reported a greater than expected incidence of cholelithiasis in patients treated with octreotide for acromegaly. This study attempted to determine the incidence and morbidity of cholelithiasis in a group of patients with metastatic carcinoid or malignant pancreatic islet cell tumors who were receiving chronic therapy with octreotide.

METHODS

Forty-four of 55 patients on investigational protocols with octreotide were eligible for chart review; 10 patients were excluded due to prior cholecystectomy and 1 patient due to asymptomatic cholelithiasis at presentation. Patients fell into three treatment groups. The low dose (LD) group was comprised of 17 patients receiving 150 microg of subcutaneous octreotide 3 times a day. Twenty-one patients received high dose (HD) therapy comprised of 500 microg given 3 times a day. The low dose-high dose (LD-HD) group was comprised of 6 patients who had their dose escalated from 150 microg to 225-500 microg of octreotide 3 times a day.

RESULTS

The overall incidence of cholelithiasis and/or gallbladder sludge was found to be 52.3% in all 3 treatment groups. Three of the 44 patients (6.8%) had symptomatic disease requiring emergency cholecystectomy. Five other patients underwent elective or incidental gallbladder surgery. The incidence of cholelithiasis in the LD, LD-HD, and HD groups was 35.3%, 66.6%, and 61.9%, respectively. The incidence of acute cholecystitis in the three groups was 11.8%, 0%, and 4.8%, respectively.

CONCLUSIONS

Although greater than 50% of patients receiving octreotide developed cholelithiasis, a much smaller percentage of patients had symptomatic gallbladder disease. Patients receiving chronic octreotide treatment require monitoring for the development of gallstones. However, prophylactic cholecystectomy is not indicated, unless it is performed in conjunction with bowel resection or cytoreductive hepatic surgery.

Randomized double-blind Scandinavian trial of angiopeptin versus placebo for the prevention of clinical events and restenosis after coronary balloon angioplasty

Angiopeptin, a somatostatin analogue, inhibits intimal hyperplasia after percutaneous transluminal coronary artery balloon angioplasty (PTCA) in several animal models. This pilot study sought to determine the effect of subcutaneous infusion of angiopeptin on clinical events and restenosis in patients undergoing successful PTCA. One hundred twelve patients were randomized to receive continuous subcutaneous angiopeptin (750 micrograms/day) or placebo infusion from the day before PTCA and for the following 4 days in a double-blind study. An additional subcutaneous injection of 375 micrograms of angiopeptin or saline was given immediately before PTCA. Eighty patients had a successful PTCA, and 75 of these patients with 94 lesions underwent angiography 6 +/- 2 months after PTCA. All 112 patients underwent a 12-month clinical follow-up examination. Age, sex, smoking, diabetes, hypertension, hyperlipidemia, and morphologic features of stenosis were similar in both groups. The hierarchical 12-month event rate (death, myocardial infarction, coronary artery bypass grafting, and repeated PTCA) was reduced from 34% to 25% (p = 0.30) by angiopeptin by intention-to-treat analysis. Restenosis (> or = 50% diameter stenosis) was significantly reduced in lesions treated with angiopeptin (12% vs 40%; p = 0.003). Late lumen loss also was significantly reduced after angiopeptin treatment (0.12 +/- 0.46 mm vs 0.52 +/- 0.64 mm; p = 0.003). In conclusion, continuous subcutaneous angiopeptin infusion for 5 days tended to decrease clinical events and restenosis after PTCA.

Continuous versus intermittent subcutaneous infusion of octreotide in the treatment of acromegaly

This review evaluates the efficacy, tolerability, and safety of continuous subcutaneous infusion (CSI) relative to intermittent subcutaneous injection (ISI) of the somatostatin analog, octreotide in the treatment of acromegaly. Data was extracted from five clinical series using CSI octreotide in acromegaly, six reports comparing CSI to ISI, and three studies comparing pulsatile subcutaneous infusion (PSI) to ISI. Effects of each drug regimen on the control of growth hormone (GH), insulin-like growth factor (IGF-1), clinical symptomatology, pituitary tumor size, and adverse effects were evaluated. Normalization of serum GH or IGF-1 levels, as well as improvement in clinical symptoms was reported in the majority of the patients studied. Cases in which pituitary adenomas decreased in size were also documented during the study period. When the effects of CSI were compared with ISI, a more pronounced control of GH and IGF-1 was observed. In addition, diurnal GH fluctuation during CSI was significantly reduced relative to ISI in two reports. Moreover, in two patients, CSI achieved similar clinical and biochemical effects at lower doses than when the drug was given by ISI. Finally, adverse effects with CSI may be less severe than with ISI. Continuous subcutaneous infusion of octreotide produced biochemical improvement in 67 of the 88 patients reviewed. When compared with ISI, CSI induced more pronounced biochemical control, often with less fluctuation in GH and IGF-1 levels. Because of a lack of data, definite conclusions regarding the differences between regimens on clinical symptomatology and tolerability could not be discerned. A large prospective, long-term randomized crossover study is recommended to make these determinations.

Somatostatin receptor-dependent growth inhibition of liver metastases by octreotide

Rats were administered the somatostatin analogue octreotide 15 micrograms intraperitoneally twice daily for 4 weeks after intraportal injection of somatostatin receptor-positive pancreatic tumour cells (CA-20948) and somatostatin receptor-negative colonic tumour cells (CC531). Octreotide significantly inhibited the growth and development of somatostatin receptor-positive tumour cells in the liver. The median number of liver tumours was 286 (range 146 to greater than 500) in the treated animals and more than 500 (range 250 to in excess of 500) in the controls (P < 0.05). This significant difference in tumour load was also represented in the mean(s.e.m.) liver weight (14.5(3.7) g in animals given octreotide versus 17.9(3.0) g in the controls). No effect of octreotide treatment was found on the growth and development of somatostatin receptor-negative tumour cells in the liver. The median (range) number of tumours was 6.5 (0-425) in the treated animals and 11.0 (0-475) in the controls. Mean(s.e.m.) liver weights were 14.0(5.7) g and 11.8(4.5) g respectively. There was no difference in serum levels of growth hormone, prolactin and insulin-like growth factor between control and octreotide-treated rats. The growth inhibition of somatostatin receptor-positive tumour cells was unlikely to be the result of suppressed secretion of one of these tumour growth factors. Octreotide may be useful for the treatment of patients with somatostatin receptor-positive hepatic metastases, which can be demonstrated by somatostatin receptor scintigraphy.