Population pharmacokinetic-pharmacodynamic modeling of serum biomarkers as predictors of tumor dynamics following lenvatinib treatment in patients with radioiodine-refractory differentiated thyroid cancer (RR-DTC).

Lenvatinib is a receptor tyrosine kinase (RTK) inhibitor targeting vascular endothelial growth factor (VEGF) receptors 1-3, fibroblast growth factor (FGF) receptors 1-4, platelet-derived growth factor receptor-α (PDGFRα), KIT, and RET that have been implicated in pathogenic angiogenesis, tumor growth, and cancer. The primary objective of this work was to evaluate, by establishing quantitative relationships, whether lenvatinib exposure and longitudinal serum biomarker data (VEGF, Ang-2, Tie-2, and FGF-23) are predictors for change in longitudinal tumor size which was assessed based on data from 558 patients with radioiodine-refractory differentiated thyroid cancer (RR-DTC) receiving either lenvatinib or placebo treatment. Lenvatinib PK was best described by a 3-compartment model with simultaneous first- and zero-order absorption and linear elimination from the central compartment with significant covariates (body weight, albumin <30 g/dL, ALP>ULN, RR-DTC, RCC, HCC subjects, and concomitant CYP3A inhibitors). Except for body weight, none of the covariates have any clinically meaningful effect on exposure to lenvatinib. Longitudinal biomarker measurements over time were reasonably well defined by a PK/PD model with common EC50, Emax, and a slope for disease progression for all biomarkers. Longitudinal tumor measurements over time were reasonably well defined by a tumor growth inhibition Emax model, which in addition to lenvatinib exposure, included model-predicted relative changes from baseline over time for Tie-2 and Ang-2 as having significant association with tumor response. The developed PK/PD models pave the way for dose optimization and potential prediction of clinical response.

Machine Learning Analysis of Post-Operative Tumour Progression in Non-Functioning Pituitary Neuroendocrine Tumours: A Pilot Study.

Post-operative tumour progression in patients with non-functioning pituitary neuroendocrine tumours is variable. The aim of this study was to use machine learning (ML) models to improve the prediction of post-operative outcomes in patients with NF PitNET. We studied data from 383 patients who underwent surgery with or without radiotherapy, with a follow-up period between 6 months and 15 years. ML models, including k-nearest neighbour (KNN), support vector machine (SVM), and decision tree, showed superior performance in predicting tumour progression when compared with parametric statistical modelling using logistic regression, with SVM achieving the highest performance. The strongest predictor of tumour progression was the extent of surgical resection, with patient age, tumour volume, and the use of radiotherapy also showing influence. No features showed an association with tumour recurrence following a complete resection. In conclusion, this study demonstrates the potential of ML models in predicting post-operative outcomes for patients with NF PitNET. Future work should look to include additional, more granular, multicentre data, including incorporating imaging and operative video data.

Non-functioning pituitary macroadenoma following surgery: long-term outcomes and development of an optimal follow-up strategy.

Objectives: Recurrence and regrowth of non-functioning pituitary macroadenomas (NFPMs) after surgery are common but remain unpredictable. Therefore, the optimal timing and frequency of follow-up imaging remain to be determined. We sought to determine the long-term surgical outcomes of NFPMs following surgery and develop an optimal follow-up strategy. Methods: Patients underwent surgery for NFPMs between 1987 and 2018, with a follow-up of 6 months or more, were identified. Demographics, presentation, management, histology, imaging, and surgical outcomes were retrospectively collected. Results: In total, 383 patients were included; 256 were men (256/383; 67%) with median follow-up of 8 years. Following primary surgery, 229 patients (229/383; 60%) achieved complete resection. Of those, 28 (28/229; 11%) developed recurrence, including six needed secondary surgery (6/229; 3%). The rate of complete resection improved over time; in the last quartile of cases, 77 achieved complete resection (77/95; 81%). Reoperation-free survival at 5, 10 and 15 years was 99%, 94% and 94%, respectively. NFPMs were incompletely resected in 154 patients (154/383; 40%); of those, 106 (106/154; 69%) had regrowth, and 84 (84/154; 55%) required reoperation. Surgical reintervention-free survival at 5, 10 and 15 years was 74%,49% and 35%, respectively. Young age and cavernous sinus invasion were risk factors for undergoing reoperation (P < 0.001 and P < 0.0001, respectively) and radiotherapy (P = 0.003 and P < 0.001, respectively). Patients with residual tumour required reoperation earlier than those underwent complete resection (P = 0.02). Radiotherapy to control tumour regrowth was delivered to 65 patients (65/383; 17%) after median time of 1 year following surgery. Radiotherapy was administered more in patients with regrowth of residual disease (61/106; 58%) than those who had NFPMs recurrence (4/28; 14%) (P ≤ 0.001) Following postoperative radiotherapy, one patient (1/65; 2%) had evidence of regrowth, seven (7/65; 11%) had tumour regression on imaging, and no patients underwent further surgery. Conclusions: NFPMs recurrence and regrowth are common, particularly in patients with residual disease post-operatively. We propose a follow-up strategy based on stratifying patients as "low risk" if there is no residual tumour, with increasing scan intervals, or "high risk" if there is a residual tumour, with annual scans for at least five years and extended lifelong surveillance after that.

Pituitary function at presentation and following therapy in patients with non-functional pituitary macroadenomas: a single centre retrospective cohort study.

BACKGROUND: Non-functioning pituitary macroadenomas (NFPMs) may present with hypopituitarism. Pituitary surgery and radiotherapy pose an additional risk to pituitary function. OBJECTIVES: To assess the incidence of hypopituitarism at presentation, the impact of treatment, and the likelihood of endocrine recovery during follow-up. METHODS: All patients treated surgically with and without radiotherapy for NFPMs between 1987 and 2018 who had longer than six months follow-up were identified. Demographics, presentation, investigation, treatment, and outcomes were collected. RESULTS: In total, 383 patients were identified. The median age was 57 years, with a median follow-up of 8 years. Preoperatively, 227 patients (227/375; 61%) had evidence of at least one pituitary deficiency. Anterior panhypopituitarism was more common in men (p = 0.001) and older patients (p = 0.005). Multiple hormone deficiencies were associated with large tumours (p = 0.03). Patients treated with surgery and radiotherapy had a higher incidence of all individual pituitary hormone deficiency, anterior panhypopituitarism, and significantly lower GH, ACTH, and TSH deficiencies free survival probability than those treated with surgery alone. Recovery of central hypogonadism, hypothyroidism, and anterior panhypopituitarism was also less likely to be reported in those treated with surgery and radiotherapy. Those with preoperative hypopituitarism had a higher risk of pituitary impairment at latest review than those presented with normal pituitary function (p = 0.001). CONCLUSION: NFPMs are associated with a significant degree of hypopituitarism at time of diagnosis and post-therapy. The combination of surgery and radiotherapy is associated with a higher risk of pituitary dysfunction. Recovery of pituitary hormone deficit may occur after treatment. Patients should have regular ongoing endocrine evaluation post-treatment to assess changes in pituitary function and the need for long-term replacement therapy.

Natural history of non-functioning pituitary microadenomas: results from the UK non-functioning pituitary adenoma consortium.

OBJECTIVE: The optimal approach to the surveillance of non-functioning pituitary microadenomas (micro-NFPAs) is not clearly established. Our aim was to generate evidence on the natural history of micro-NFPAs to support patient care. DESIGN: Multi-centre, retrospective, cohort study involving 23 endocrine departments (UK NFPA consortium). METHODS: Clinical, imaging, and hormonal data of micro-NFPA cases between January, 1, 2008 and December, 21, 2021 were analysed. RESULTS: Data for 459 patients were retrieved [median age at detection 44 years (IQR 31-57)-152 males/307 females]. Four hundred and nineteen patients had more than two magnetic resonance imagings (MRIs) [median imaging monitoring 3.5 years (IQR 1.71-6.1)]. One case developed apoplexy. Cumulative probability of micro-NFPA growth was 7.8% (95% CI, 4.9%-8.1%) and 14.5% (95% CI, 10.2%-18.8%) at 3 and 5 years, respectively, and of reduction 14.1% (95% CI, 10.4%-17.8%) and 21.3% (95% CI, 16.4%-26.2%) at 3 and 5 years, respectively. Median tumour enlargement was 2 mm (IQR 1-3) and 49% of micro-NFPAs that grew became macroadenomas (nearly all >5 mm at detection). Eight (1.9%) patients received surgery (only one had visual compromise with surgery required >3 years after micro-NFPA detection). Sex, age, and size at baseline were not predictors of enlargement/reduction. At the time of detection, 7.2%, 1.7%, and 1.5% patients had secondary hypogonadism, hypothyroidism, and hypoadrenalism, respectively. Two (0.6%) developed hypopituitarism during follow-up (after progression to macroadenoma). CONCLUSIONS: Probability of micro-NFPA growth is low, and the development of new hypopituitarism is rare. Delaying the first follow-up MRI to 3 years and avoiding hormonal re-evaluation in the absence of tumour growth or clinical manifestations is a safe approach for micro-NFPA surveillance.

Post-Operative Medium- and Long-Term Endocrine Outcomes in Patients with Non-Functioning Pituitary Adenomas-Machine Learning Analysis.

Post-operative endocrine outcomes in patients with non-functioning pituitary adenoma (NFPA) are variable. The aim of this study was to use machine learning (ML) models to better predict medium- and long-term post-operative hypopituitarism in patients with NFPAs. We included data from 383 patients who underwent surgery with or without radiotherapy for NFPAs, with a follow-up period between 6 months and 15 years. ML models, including k-nearest neighbour (KNN), support vector machine (SVM), and decision tree models, showed a superior ability to predict panhypopituitarism compared with non-parametric statistical modelling (mean accuracy: 0.89; mean AUC-ROC: 0.79), with SVM achieving the highest performance (mean accuracy: 0.94; mean AUC-ROC: 0.88). Pre-operative endocrine function was the strongest feature for predicting panhypopituitarism within 1 year post-operatively, while endocrine outcomes at 1 year post-operatively supported strong predictions of panhypopituitarism at 5 and 10 years post-operatively. Other features found to contribute to panhypopituitarism prediction were age, volume of tumour, and the use of radiotherapy. In conclusion, our study demonstrates that ML models show potential in predicting post-operative panhypopituitarism in the medium and long term in patients with NFPM. Future work will include incorporating additional, more granular data, including imaging and operative video data, across multiple centres.

Lenvatinib dose, efficacy, and safety in the treatment of multiple malignancies.

INTRODUCTION: Lenvatinib is an oral multitargeted tyrosine kinase inhibitor that has shown efficacy and manageable safety across multiple cancer types. The recommended starting doses for lenvatinib differ across cancer types and indications based on whether it is used as monotherapy or as combination therapy. AREAS COVERED: This review covers clinical trials that established the dosing paradigm and efficacy of lenvatinib and defined its adverse-event profile as a monotherapy; or in combination with the mTOR inhibitor, everolimus; or the anti-PD-1 antibody, pembrolizumab; and/or chemotherapy. EXPERT OPINION: Lenvatinib has been established as standard-of-care either as a monotherapy or in combination with other anticancer agents for the treatment of radioiodine-refractory differentiated thyroid carcinoma, hepatocellular carcinoma, renal cell carcinoma, and endometrial carcinoma, and is being investigated further across several other tumor types. The dosing and adverse-event management strategies for lenvatinib have been developed through extensive clinical trial experience. Collectively, the data provide the rationale to start lenvatinib at the recommended doses and then interrupt or dose reduce as necessary to achieve required dose intensity for maximized patient benefit. The adverse-event profile of lenvatinib is consistent with that of other tyrosine kinase inhibitors, and clinicians are encouraged to review and adopt relevant symptom-management strategies.

The management and outcome of hyponatraemia following transsphenoidal surgery: a retrospective observational study.

PURPOSE: Hyponatraemia is a common complication following transsphenoidal surgery. However, there is sparse data on its optimal management and impact on clinical outcomes. The aim of this study was to evaluate the management and outcome of hyponatraemia following transsphenoidal surgery. METHODS: A prospectively maintained database was searched over a 4-year period between January 2016 and December 2019, to identify all patients undergoing transsphenoidal surgery. A retrospective case-note review was performed to extract data on hyponatraemia management and outcome. RESULTS: Hyponatraemia occurred in 162 patients (162/670; 24.2%) with a median age of 56 years. Female gender and younger age were associated with hyponatraemia, with mean nadir sodium being 128.6 mmol/L on postoperative day 7. Hyponatraemic patients had longer hospital stay than normonatraemic group with nadir sodium being inversely associated with length of stay (p < 0.001). In patients with serum sodium ≤ 132 mmol/L, syndrome of inappropriate antidiuretic hormone secretion (SIADH) was the commonest cause (80/111; 72%). Among 76 patients treated with fluid restriction as a monotherapy, 25 patients (25/76; 32.9%) did not achieve a rise in sodium after 3 days of treatment. Readmission with hyponatraemia occurred in 11 cases (11/162; 6.8%) at a median interval of 9 days after operation. CONCLUSION: Hyponatraemia is a relatively common occurrence following transsphenoidal surgery, is associated with longer hospital stay and risk of readmission and the effectiveness of fluid restriction is limited. These findings highlight the need for further studies to better identify and treat high-risk patients, including the use of arginine vasopressin receptor antagonists.

Cabergoline reduces 3-methoxytyramine in a SDHC patient with metastatic paraganglioma and prolactinoma.

SUMMARY: We observed a novel therapeutic response with cabergoline in a male patient with a dopamine-secreting head and neck paraganglioma (HNPGL), macroprolactinoma and germline succinate dehydrogenase C mutation (SDHC). The macroprolactinoma was treated with cabergoline which gave an excellent response. He was found to have raised plasma 3-methoxytyramine of 1014 pmol/L (NR: 0-180 pmol/L); but it was unclear if this was a drug-induced phenomenon from dopamine agonist (DA) therapy. Cabergoline was stopped for 4 weeks and the 3-methoxytyramine level increased significantly to 2185 pmol/L, suggesting a biochemical response of his HNPGL. Subsequently, Gallium-68 Dotatate PET and MRI (Gallium-68 Dotatate PET/MRI) demonstrated a second lesion in the sacrum. Both the HNPGL and metastatic sacral deposit received external beam radiotherapy with a good biochemical and radiological response. CONCLUSION: Our case report highlights the rare potential of germline SDHC mutations causing metastatic paraganglioma and concurrent pituitary tumours. Cabergoline treatment may lower elevated 3-methoxytyramine levels and, therefore, mask the biochemical evidence of metastatic disease but also may have therapeutic relevance in dopamine-secreting pheochromocytomas/paragangliomas (PPGLs). LEARNING POINTS: Several neuroendocrine tumours (NETs) express dopamine D2 and D4 receptors. In this case report, cabergoline significantly reduced plasma 3-methoxytyramine level in a patient with functional HNPGL. Cabergoline might have therapeutic relevance in dopamine-secreting PPGLs. Paragangliomas associated with SDHC mutation classically present with asymptomatic non-functional HNPGL and have rare metastatic potential. The association of pheochromocytoma or paraganglioma and pituitary adenoma is now a well-described rare association (<1%), designated as the three P association. While the three P association is most commonly seen with succinate dehydrogenase B and D mutations, it has also been described in patients with SDHA and SDHC mutations. Cabergoline treatment may lower elevated 3-methoxytyramine levels and mask the biochemical evidence of metastatic disease. Regular functional imaging with Gallium-68 Dotatate PET/MRI provides better evidence of metastatic disease.

Temporal trends in craniopharyngioma management and long-term endocrine outcomes: A multicentre cross-sectional study.

BACKGROUND: The optimal management of craniopharyngiomas remains controversial. OBJECTIVES: To examine temporal trends in the management of craniopharyngioma with a focus on endocrine outcomes. METHODS: This was a cross-sectional, multicentre study. Patients treated between 1951 and 2015 were identified and divided into four quartiles. Demographics, presentation, treatment and outcomes were collected. RESULTS: In total, 142 patients with childhood-onset craniopharyngioma (48/142; 34%) and adult-onset disease (94/142; 66%) were included. The median follow-up was 15 years (IQR 5-23 years). Across quartiles, there was a significant trend towards using transsphenoidal surgery (P < .0001). The overall use of radiotherapy was not different among the four quartiles (P = .33). At the latest clinical review, the incidence of GH, ACTH, gonadotrophin deficiencies and anterior panhypopituitarism fell significantly across the duration of the study. Anterior panhypopituitarism was not affected by treatment modality (surgery vs surgery and radiotherapy) (P = .23). There was no difference in the incidence of high BMI (≥25 kg/m2 ) among the four quartiles (P = .14). BMI was higher in patients who treated with surgery and radiotherapy than those treated with surgery only (P = .006). Tumour regrowth occurred in 51 patients (51/142; 36%) with no difference in regrowth among quartiles over the time course of the study (P = .15). CONCLUSION: We demonstrate a significant reduction in panhypopituitarism in craniopharyngioma patients over time, most likely because of a trend towards more transsphenoidal surgery. However, long-term endocrine sequelae remain common and lifelong follow-up is required.

Rathke's cleft cysts following transsphenoidal surgery: long-term outcomes and development of an optimal follow-up strategy.

BACKGROUND: In patients with symptomatic Rathke's cleft cyst, transsphenoidal surgery is highly effective at preventing further visual loss and usually allows for some recovery of vision. However, cyst recurrence and the need for re-operation are well recognized. To this end, the aim of this study was to investigate patterns of recurrence and long-term outcomes and to use this information to develop an optimal follow-up strategy. METHOD: A prospectively maintained database was searched over a 10-year period between 1 January 2008 and the 1 January 2018 to identify all adults that underwent transsphenoidal surgery with a new diagnosis of Rathke's cleft cyst. A retrospective case note review was performed for each patient to extract data on their presentation, investigation, treatment, and outcome. RESULTS: In all, 61 eligible patients were identified. The median follow-up was 34 months (range 2-112 months). In the 22 patients with pre-operative visual loss, the outcomes at 6 months were as follows: normal vision (2/22; 9.1%), improved but not normal (7/22; 31.8%), stable (12/22; 54.5%), worse but not blind (1/22; 4.5%), and blind (0/22; 0%). The overall rate of regrowth and re-operation in our study was 19.7 and 11.5%, respectively. The only factor that was significantly associated with recurrence was the presence of residual cystic disease on the post-operative MRI (p < 0.001). CONCLUSIONS: We propose a follow-up strategy that stratifies patients at "low risk" if there is no residual cyst, with increasing interval scans, or "high risk" if there is residual cyst, with annual visual assessment and scans.

Outcomes of Patients with Nelson's Syndrome after Primary Treatment: A Multicenter Study from 13 UK Pituitary Centers.

CONTEXT: Long-term outcomes of patients with Nelson's syndrome (NS) have been poorly explored, especially in the modern era. OBJECTIVE: To elucidate tumor control rates, effectiveness of various treatments, and markers of prognostic relevance in patients with NS. PATIENTS, DESIGN, AND SETTING: Retrospective cohort study of 68 patients from 13 UK pituitary centers with median imaging follow-up of 13 years (range 1-45) since NS diagnosis. RESULTS: Management of Cushing's disease (CD) prior to NS diagnosis included surgery+adrenalectomy (n = 30; eight patients had 2 and one had 3 pituitary operations), surgery+radiotherapy+adrenalectomy (n = 17; two received >1 courses of irradiation, two had ≥2 pituitary surgeries), radiotherapy+adrenalectomy (n = 2), and adrenalectomy (n = 19). Primary management of NS mainly included surgery, radiotherapy, surgery+radiotherapy, and observation; 10-year tumor progression-free survival was 62% (surgery 80%, radiotherapy 52%, surgery+radiotherapy 81%, observation 51%). Sex, age at CD or NS diagnosis, size of adenoma (micro-/macroadenoma) at CD diagnosis, presence of pituitary tumor on imaging prior adrenalectomy, and mode of NS primary management were not predictors of tumor progression. Mode of management of CD before NS diagnosis was a significant factor predicting progression, with the group treated by surgery+radiotherapy+adrenalectomy for their CD showing the highest risk (hazard ratio 4.6; 95% confidence interval, 1.6-13.5). During follow-up, 3% of patients had malignant transformation with spinal metastases and 4% died of aggressively enlarging tumor. CONCLUSIONS: At 10 years follow-up, 38% of the patients diagnosed with NS showed progression of their corticotroph tumor. Complexity of treatments for the CD prior to NS diagnosis, possibly reflecting corticotroph adenoma aggressiveness, predicts long-term tumor prognosis.

Craniopharyngioma in children: trends from a third consecutive single-center cohort study.

OBJECTIVE: The management of children with craniopharyngioma has evolved over time, with a trend toward less invasive neurosurgical approaches as surgeons have sought to balance oncological control and treatment-related morbidity. To this end, the aim of this study was to evaluate the safety and effectiveness of the current management of children with craniopharyngioma compared to the previous management methods used at the authors' treatment center. METHODS: A prospectively maintained database was searched over a 14-year period between January 1, 2005, and December 31, 2018, to identify all children 17 years of age or younger with a new diagnosis of craniopharyngioma. A retrospective case note review was performed for each child to extract data on the presentation, investigation, treatment, and outcome of their illness. Morbidity was assessed in the same fashion as in previous cohorts, according to the following categories: visual loss, pituitary dysfunction, hypothalamic dysfunction, neurological deficits, and cognitive impairment. RESULTS: In total, 59 children were identified with craniopharyngioma during the study period. A total of 92 operations were performed, including cyst drainage (35/92; 38.0%), craniotomy and resection (30/92; 32.6%), and transsphenoidal resection (16/92; 17.4%). Approximately two-thirds of all operations were performed using image guidance (66/92; 71.7%) and one-third were performed using endoscopy (27/92; 29.3%). The majority of children had adjuvant therapy comprising proton beam therapy (18/59; 30.5%) or conventional radiotherapy (16/59; 27.1%). The median follow-up duration was 44 months (range 1-142 months), and approximately one-half of the children had no evidence of residual disease on MRI studies (28/59; 47.5%). Of the remaining 31 children, there was a reduction in the volume of residual disease in 8 patients (8/59; 13.6%), stable residual disease in 18 (18/59; 30.5%), and tumor growth in 5 patients (5/59; 8.5%). There was significantly reduced morbidity (p < 0.05) in all categories in the current cohort compared with our last cohort (1996-2004). CONCLUSIONS: The authors' institutional experience of pediatric craniopharyngioma confirms a trend toward less invasive neurosurgical procedures, most of which are now performed with the benefit of image guidance or endoscopy. Moreover, the authors have identified an expanding role for more targeted radiotherapy for children with residual disease. These advances have allowed for tumor control comparable to that achieved in previous cohorts, but with significantly reduced morbidity and mortality.

Two cases of spontaneous remission of primary hyperparathyroidism due to auto-infarction: different management and their outcomes.

Spontaneous remission of primary hyperparathyroidism (PHPT) due to necrosis and haemorrhage of parathyroid adenoma, the so-called 'parathyroid auto-infarction' is a very rare, but previously described phenomenon. Patients usually undergo parathyroidectomy or remain under close clinical and biochemical surveillance. We report two cases of parathyroid auto-infarction diagnosed in the same tertiary centre; one managed surgically and the other conservatively up to the present time. Case #1 was a 51-year old man with PHPT (adjusted (adj.) calcium: 3.11 mmol/L (reference range (RR): 2.20-2.60 mmol/L), parathyroid hormone (PTH) 26.9 pmol/L (RR: 1.6-6.9 pmol/L) and urine calcium excretion consistent with PHPT) referred for parathyroidectomy. Repeat biochemistry 4 weeks later at the surgical clinic showed normal adj. calcium (2.43 mmol/L) and reduced PTH. Serial ultrasound imaging demonstrated reduction in size of the parathyroid lesion from 33 to 17 mm. Twenty months later, following recurrence of hypercalcaemia, he underwent neck exploration and resection of an enlarged right inferior parathyroid gland. Histology revealed increased fibrosis and haemosiderin deposits in the parathyroid lesion in keeping with auto-infarction. Case #2 was a 54-year-old lady admitted with severe hypercalcaemia (adj. calcium: 4.58 mmol/L, PTH 51.6 pmol/L (RR: 1.6-6.9 pmol/L)) and severe vitamin D deficiency. She was treated with intravenous fluids and pamidronate and 8 days later developed symptomatic hypocalcaemia (1.88 mmol/L) with dramatic decrease of PTH (17.6 pmol/L). MRI of the neck showed a 44 mm large cystic parathyroid lesion. To date, (18 months later), she has remained normocalcaemic. Learning points: Primary hyperparathyroidism (PHPT) is characterised by excess parathyroid hormone (PTH) secretion arising mostly from one or more autonomously functioning parathyroid adenomas (up to 85%), diffuse parathyroid hyperplasia (<15%) and in 1-2% of cases from parathyroid carcinoma. PHPT and hypercalcaemia of malignancy, account for the majority of clinical presentations of hypercalcaemia. Spontaneous remission of PHPT due to necrosis, haemorrhage and infarction of parathyroid adenoma, the so-called 'parathyroid auto-infarction', 'auto-parathyroidectomy' or 'parathyroid apoplexy' is a very rare in clinical practice but has been previously reported in the literature. In most cases, patients with parathyroid auto-infarction undergo parathyroidectomy. Those who are managed conservatively need to remain under close clinical and biochemical surveillance long-term as in most cases PHPT recurs, sometimes several years after auto-infarction.

Exposure-response analysis and simulation of lenvatinib safety and efficacy in patients with radioiodine-refractory differentiated thyroid cancer.

PURPOSE: Once-daily lenvatinib 24 mg is the approved dose for radioiodine-refractory differentiated thyroid cancer. In a phase 3 trial with lenvatinib, the starting dose of 24 mg was associated with a relatively high incidence of adverse events that required dose reductions. We used an exposure-response model to investigate the risk-benefit of different dosing regimens for lenvatinib. METHODS: A population pharmacokinetics/pharmacodynamics modeling analysis was used to simulate the potential benefit of lower starting doses to retain efficacy with improved safety. The seven lenvatinib regimens tested were: 24 mg; and 20 mg, 18 mg, and 14 mg, all with or without up-titration to 24 mg. Exposure-response models for efficacy and safety were created using a 24-week time course. RESULTS: The approved dose of lenvatinib at 24 mg, predicted the best efficacy. However, the lenvatinib dosing regimens of 14 mg with up-titration or 18 mg without up-titration potentially provides comparable efficacy (objective response rate at 24 weeks) and a better safety profile. CONCLUSIONS: Treatment with lenvatinib at starting doses lower than the approved once-daily 24 mg dose could provide comparable antitumor efficacy and a similar or better safety profile. Based on the results from this modeling and simulation study, a comparator dose of lenvatinib 18 mg without up-titration was selected for evaluation in a clinical trial.

Clinical Pharmacokinetic and Pharmacodynamic Profile of Lenvatinib, an Orally Active, Small-Molecule, Multitargeted Tyrosine Kinase Inhibitor.

Lenvatinib is a multikinase inhibitor that targets vascular endothelial growth factor (VEGF) receptors 1-3, fibroblast growth factor receptors 1-4, platelet-derived growth factor receptor-alpha, and RET and KIT proto-oncogenes. Lenvatinib is approved for the treatment of radioiodine-refractory differentiated thyroid cancer in the United States (US), European Union (EU), Canada, Japan, and Switzerland. It is also approved in combination with everolimus for the treatment of advanced renal cell carcinoma following ≥1 VEGF-targeted treatment in the US and EU. In addition, lenvatinib is under investigation for the treatment of hepatocellular carcinoma. As lenvatinib becomes more widely available, a better understanding of its pharmacokinetic profile has become increasingly important. Following oral administration, lenvatinib is absorbed rapidly and is metabolized extensively prior to excretion. This metabolism is mediated by multiple pathways, and several metabolites of lenvatinib have been identified. The effect of food intake on lenvatinib exposure has also been studied and was found to not significantly influence overall exposure to the drug. Exposure to lenvatinib is increased in patients with severe hepatic impairment, indicating that dose reduction must be considered for those patients. The findings summarized here indicate that the clinical pharmacokinetic and pharmacodynamic profile for lenvatinib are predictable, with a dose-independent absorption and elimination profile that supports once-daily administration, and has minimal effects due to mild or moderate renal or hepatic impairment or drug interactions.

Population pharmacokinetics and exposure-response relationship of amatuximab, an anti-mesothelin monoclonal antibody, in patients with malignant pleural mesothelioma and its application in dose selection.

PURPOSE: To characterize amatuximab pharmacokinetics (PK) and the relationship of amatuximab exposure with response in patients with unresectable malignant pleural mesothelioma (MPM) receiving amatuximab with pemetrexed and cisplatin. METHODS: A nonlinear mixed effects PK model was built using data from all of the amatuximab studies conducted to date. Patients received amatuximab alone or in combination with chemotherapy. The influence of demographic, laboratory and disease characteristics on PK parameters was assessed. Exposure-response analyses explored relationships between amatuximab exposure and overall survival (OS), progression-free survival (PFS) and safety. Alternative amatuximab dosing regimens were explored with simulations using population PK and parametric survival models. RESULTS: Amatuximab PK was best described by a two-compartment model with parallel linear and nonlinear elimination pathways. Body weight and an antidrug antibodies reaction with the titer >64 affected volume of distribution and clearance, respectively. Exposure-response analyses demonstrated that the amatuximab exposure (C min) showed a significant effect on OS (log-rank test, P = 0.0202). For patients with amatuximab C min above the median (38.2 µg/mL), the median OS was 583 days (90 % CI 418 -NE). For patients with C min ≤ 38.2 µg/mL, the median OS was 375 days (90 % CI 325-486). The amatuximab exposure showed similar significant effect on PFS. Exposure-response analysis for adverse events did not reveal any relationship. CONCLUSIONS: In patients with MPM, higher amatuximab exposure in combination with chemotherapy was shown to be associated with longer OS, supporting evaluation of more frequent dosing in future trials to achieve higher exposure and subsequently longer OS.

Population pharmacokinetic analysis of lenvatinib in healthy subjects and patients with cancer.

AIMS: Lenvatinib was recently approved for the treatment of radioiodine-refractory differentiated thyroid cancer (RR-DTC). Here, we characterized the pharmacokinetic (PK) profile of lenvatinib and identified intrinsic and extrinsic factors that explain interindividual PK variability in humans. METHODS: This population PK analysis used pooled data from 15 clinical studies, including eight phase 1 studies in healthy subjects, four phase 1 studies in patients with solid tumours, two phase 2 studies in patients with thyroid cancer and one phase 3 study in patients with RR-DTC. RESULTS: The final pooled dataset included data from 779 subjects receiving 3.2-32 mg oral lenvatinib, mainly once daily as tablets or capsules. Lenvatinib PK was best described by a three-compartment model with linear elimination. Lenvatinib absorption was best described by simultaneous first- and zero-order absorption. The population mean value for lenvatinib apparent clearance (CL/F) was 6.56 l h(-1) [percent coefficient of variation (%CV) 25.5], and was independent of dose and time. The relative bioavailability of lenvatinib in capsule form was 90% vs. tablets (%CV 30.2). The final PK model included significant but marginal effects of body weight (2.8% of CL/F variation), liver-function markers [alkaline phosphatase (-11.7%) and albumin (-6.3%)] and concomitant cytochrome P450 3A4 inducers (+30%) and inhibitors (-7.8%) on lenvatinib CL/F. Lenvatinib PK was unaffected by pH-elevating agents, dose, age, sex, race, alanine aminotransferase, aspartate aminotransferase or bilirubin levels, or renal function. CONCLUSIONS: The significant effects of several covariates on lenvatinib PK variability were small in magnitude, and therefore were not considered clinically relevant, or to warrant any dose adjustment.

Population pharmacometric analyses of eribulin in patients with locally advanced or metastatic breast cancer previously treated with anthracyclines and taxanes.

Pharmacometric investigation of eribulin was undertaken in patients with metastatic breast cancer (MBC) and other advanced solid tumors. A population pharmacokinetic (PK) model used data combined from seven phase 1 studies (advanced solid tumors; n = 129), and one phase 2 (MBC; n = 211), and one phase 3 study (MBC; n = 173). Phase 3 data were also used in a PK/pharmacodynamic (PD) model of efficacy and tumor response (sum of longest diameters of target lesions). All analyses used NONMEM 7.2. Eribulin PK, described by a dose-independent, three-compartment model with allometric relationship for body weight, was similar for all tumor types. Inter-individual variability (IIV) was 52% for both exposure and clearance. Liver function markers (albumin, alkaline phosphatase, bilirubin) significantly influenced eribulin PK (7.3% of IIV in clearance). Tumor shrinkage correlated with eribulin exposure; a 36% decrease in tumor size from baseline was modeled at week 36. No patient/disease factors significantly predicted eribulin's effect on tumor size. At week 6, a decrease in tumor size was associated with longer survival than an increase (P = .0055), suggesting survival may relate indirectly to eribulin exposure. These pharmacometric analyses provide a detailed overview of eribulin exposure-efficacy relationships to inform physicians treating patients with MBC.

Population pharmacokinetic-pharmacodynamic analysis for eribulin mesilate-associated neutropenia.

AIMS: Eribulin mesilate is an inhibitor of microtubule dynamics that is approved for the treatment of late-stage metastatic breast cancer. Neutropenia is one of the major dose-limiting adverse effects of eribulin. The objective of this analysis was to develop a population pharmacokinetic-pharmacodynamic model for eribulin-associated neutropenia. METHODS: A combined data set of 12 phase I, II and III studies for eribulin mesilate was analysed. The population pharmacokinetics of eribulin was described using a previously developed model. The relationship between eribulin pharmacokinetic and neutropenia was described using a semi-physiological lifespan model for haematological toxicity. Patient characteristics predictive of increased sensitivity to develop neutropenia were evaluated using a simulation framework. RESULTS: Absolute neutrophil counts were available from 1579 patients. In the final covariate model, the baseline neutrophil count (ANC0) was estimated to be 4.03 × 10(9) neutrophils l(-1) [relative standard error (RSE) 1.2%], with interindividual variability (IIV, 37.3 coefficient of variation % [CV%]). The mean transition time was estimated to be 109 h (RSE 1.8%, IIV 13.9CV%), the feedback constant (γ) was estimated to be 0.216 (RSE 1.4%, IIV 12.2CV%), and the linear drug effect coefficient (SLOPE) was estimated to be 0.0451 µg l(-1) (RSE 3.2%, IIV 54CV%). Albumin, aspartate transaminase and receival of granulocyte colony-stimulating factor (G-CSF) were identified as significant covariates on SLOPE, and albumin, bilirubin, G-CSF, alkaline phosphatase and lactate dehydrogenase were identified as significant covariates on mean transition time. CONCLUSIONS: The developed model can be applied to investigate optimal treatment strategies quantitatively across different patient groups with respect to neutropenia. Albumin was identified as the most clinically important covariate predictive of interindividual variability in the neutropenia time course.