Tolvaptan for the treatment of the syndrome of inappropriate antidiuresis (SIAD)

The syndrome of inappropriate antidiuresis (SIAD), the commonest cause of hyponatraemia, is associated with significant morbidity and mortality. Tolvaptan, an oral vasopressin V2-receptor antagonist, leads through aquaresis to an increase in serum sodium concentration and is the only medication licenced in Europe for the treatment of euvolaemic hyponatraemia. Randomised controlled trials have shown that tolvaptan is highly efficacious in correcting SIAD-related hyponatraemia. Real-world data have confirmed the marked efficacy of tolvaptan, but they have also reported a high risk of overly rapid sodium increase in patients with a very low baseline serum sodium. The lower the baseline serum sodium, the higher the tolvaptan-induced correction rate occurs. Therefore, a lower starting tolvaptan dose of 7.5 mg has been evaluated in small cohort studies, demonstrating its efficacy, but it still remains unclear as to whether it can reduce the risk of overcorrection. Most international guidelines, except for the European ones, recommend tolvaptan as second-line treatment for SIAD after fluid restriction. However, the risk of unduly rapid sodium correction in combination with its high cost have limited its routine use. Prospective controlled studies are warranted to evaluate whether tolvaptan-related sodium increase can improve patient-related clinical outcomes, such as mortality and length of hospital stay in the acute setting or neurocognitive symptoms and quality of life in the chronic setting. In addition, the potential role of a low tolvaptan starting dose needs to be further explored. Until then, tolvaptan should mainly be used as second-line treatment for SIAD, especially when there is a clinical need for prompt restoration of normonatraemia. Tolvaptan should be used with specialist input according to a structured clinical pathway, including rigorous monitoring of electrolyte and fluid balance and, if needed, implementation of appropriate measures to prevent, or when necessary reverse, overly rapid hyponatraemia correction.

Clinical Experience of the Efficacy and Safety of Low-dose Tolvaptan Therapy in a UK Tertiary Oncology Setting

CONTEXT

In patients with cancer, hyponatremia is associated with increased morbidity and mortality and can delay systemic therapy.

OBJECTIVE

To assess the safety and efficacy of low-dose tolvaptan (7.5 mg) for hospitalized, adult patients with hyponatremia due to syndrome of inappropriate antidiuresis (SIAD), and coexisting malignancy.

METHODS

Retrospective evaluation in a tertiary cancer center.

RESULTS

Fifty-five patients with mean baseline serum sodium (sNa) 117.9 ± 4.6 mmol/L were included. In total, 90.9% had severe hyponatremia (sNa < 125 mmol/L). Mean age was 65.1 ± 9.3 years. Following an initial dose of tolvaptan 7.5 mg, median (range) increase in sNa observed at 24 hours was 9 (1-19) mmol/L. Within 1 week, 39 patients (70.9%) reached sNa ≥ 130 mmol/L and 48 (87.3%) had sNa rise of ≥5 mmol/L within 48 hours. No severe adverse events were reported. Thirty-three (60%) and 17 (30.9%) patients experienced sNa rise of ≥8 and ≥12 mmol/L/24 hours, respectively. The rate of sNa correction in the first 24 hours was significantly higher among participants that continued fluid restriction after tolvaptan administration (median [quantiles]: 14 [9-16] versus 8 [5-11] mmol/L, P = .036). Moreover, in the over-rapid correction cohort (≥12 mmol/L/24 hours) demeclocycline was appropriately discontinued only in 60% compared with 91.7% of the remaining participants (P = .047). Lower creatinine was predictive of higher sNa correction rate within 24 hours (P = .01).

CONCLUSION

In the largest series to date, although low-dose tolvaptan was demonstrated to be effective in correcting hyponatremia due to SIAD in cancer patients, a significant proportion experienced over-rapid correction. Concurrent administration of demeclocycline and/or fluid restriction must be avoided due to the increased risk of over-rapid correction.

Total Neoadjuvant Therapy (TNT) versus Standard Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Total neoadjuvant therapy (TNT) is a novel approach for locally advanced rectal cancer (LARC), which attempts to deliver both systemic chemotherapy and neoadjuvant chemoradiotherapy prior to surgery. However, its efficacy and safety remain controversial in randomized controlled trials (RCTs). We conducted this meta-analysis to assess such concerns.

MATERIALS AND METHODS

Head-to-head phase II/III RCTs were searched in Embase, PubMed, Web of Science, and the Cochrane Library, as well as other sources. The primary endpoint was pathologic complete response (pCR). Secondary endpoints were disease-free survival (DFS), overall survival (OS), local recurrence-free survival, distant metastasis-free survival, and the R0 resection rate.

RESULTS

Eight phase II/III RCTs involving 2,196 patients with LARC were assessed. The primary analysis demonstrated a statistically significant improvement in the pCR rate for TNT treatment (odds ratio, 1.77; 95% confidence interval [CI], 1.28-2.45; p = .0005). TNT treatment also showed improvements in DFS and OS outcomes compared with standard chemoradiotherapy (hazard ratio [HR], 0.83; 95% CI, 0.72-0.96; p = .03 and HR, 0.88; 95% CI, 0.74-1.05; p = .15). In addition, TNT treatment showed significant efficacy in reducing the risk of distant metastasis (HR, 0.81; 95% CI, 0.68-0.95; p = .012).

CONCLUSION

The overall pCR rate may be improved with TNT compared with standard treatment. The TNT strategy may also improve DFS and OS and reduce the risk of distant metastasis.

IMPLICATIONS FOR PRACTICE

Locally advanced rectal cancer (LARC) is a relatively common disease, with a poor prognosis because of its high metastatic potential. The role of total neoadjuvant therapy (TNT) has always been controversial. This meta-analysis found that TNT in LARC is associated with a significant improvement in overall pathologic complete response rate, disease-free survival, overall survival, and distant metastasis-free survival compared with standard treatment. TNT is a promising strategy for LARC, especially for patients who have little desire for surgery.

Hyponatremia in patients with cancer

PURPOSE OF REVIEW

Hyponatremia is seen commonly in patients with cancer and is associated with increased mortality and morbidity. Understanding the proper diagnosis and therapy of cancer-associated hyponatremia is critical to ensure improved outcomes.

RECENT FINDINGS

The most common cancers associated with hyponatremia are the various forms of lung cancer with incidences approaching 25-45%. The most common causes of hyponatremia in cancer patients are the syndrome of inappropriate antidiuretic hormone secretion [syndrome of inappropriate antidiuretic hormone (ADH)] and volume depletion. Proper diagnosis rests on clinical information supplemented by laboratory studies and is critical to ensure appropriate therapy. In recent years, the development of drugs that specifically antagonize the vasopressin type 2 receptor in the distal tubule have offered targeted and highly effective therapies for syndrome of inappropriate ADH.

SUMMARY

Hyponatremia in cancer patients generally indicates advanced or severe disease but proper therapy that targets the underlying process can improve outcomes.

Urea in cancer patients with chronic SIAD-induced hyponatremia: Old drug, new evidence

BACKGROUND

Syndrome of inappropriate antidiuresis (SIAD) is the main cause of hyponatremia in cancer patients. International guidelines indicate urea as an interesting option for chronic SIAD. Nevertheless, strong data to support its use are lacking, and its role in oncologic patients has not been described so far.

MATERIAL AND METHODS

We retrospectively analysed 36 cancer patients affected by moderate or profound SIAD-induced chronic hyponatremia, who started oral urea (initial daily dose 15 g or 30 g) without fluid restriction between July 2013 and July 2018. We analysed mean serum sodium (sNa) increase after 24 hours and percentages of patients who reached eunatremia within 14, 30 and 60 days of treatment, stratifying according to the degree of hyponatremia at diagnosis. Clinical evaluation and biochemical assessment were periodically performed.

RESULTS

Mean sNa was 123 [±4] mmol/L at baseline; after 24 hours of treatment, a mean increase of 5 [±3] mmol/L was observed. Eunatremia was reached by 55.6%, 86.1% and 91.7% patients within 14, 30 and 60 days of treatment, respectively. Trends in sNa normalization were similar in patients with moderate and profound hyponatremia at diagnosis. Rapid sNa overcorrection was avoided in all cases. Urea  was interrupted within  the first  2 months  of treatment in 10 patients, in half cases for rapid neoplastic progression and in the remaining patients for the drug taste.

CONCLUSIONS

In our study, urea was effective in correcting chronic hyponatremia among cancer patients with SIAD. Almost all patients reached eunatremia within the first month of therapy, and urea was globally well tolerated.

Endoscopic evaluation of immunotherapy-induced gastrointestinal toxicity

Immunotherapy is any treatment aimed at boosting or enhancing the immune system. It includes a wide range of options, from vaccines to treatment for conditions such as allergy and cancer. In the case of cancer, unlike other available treatments, immunotherapy is not aimed at destroying the tumor cells but at stimulating the patient’s immune system so that it attacks the tumor. In cancer, immunotherapy provides a series of advantages. Nevertheless, immunotherapy administered for treatment of cancer is associated with immune-mediated enterocolitis. Colitis mediated by monoclonal anti-cytotoxic T lymphocyte–associated antigen 4 and to programmed cell death protein 1 and its ligand PDL1 shares characteristics with chronic inflammatory bowel disease (IBD), and similar findings have been reported for both the endoscopy images and the segment involved. The most frequent lesions on endoscopy are ulcer and erythema, and the most frequently affected site is the sigmoid colon. A segmental pattern has been reported to be slightly more frequent than a continuous pattern. In addition, upper gastrointestinal lesions have been reported in up to half of patients, with the most frequent findings being gastritis and erosive duodenitis. As is the case in IBD, systemic corticosteroids and immunosuppressive treatment (anti-TNF agents) are the approaches used in patients with a more unfavorable progression. Immunotherapy must be suspended completely in some cases.

Endocrine paraneoplastic syndromes in lung cancer

Paraneoplastic syndromes are defined as a combination of clinical disorders associated with malignant diseases that are caused by the secretion of various substances by the tumor without, however, being caused by the direct growth and infiltration of the primary tumor, or due to the development of distant metastases. Despite the fact that lung cancer represents the number one cause of death from cancer worldwide, the new methods of treatment increase patient survival and the incidence of paraneoplastic syndromes. The most important ones of these are humoral hypercalcemia of malignancy, syndrome of inappropriate antidiuretic hormone, hyponatremia of malignancy, ectopic Cushing's syndrome, carcinoid syndrome, and hypoglycemia and are usually a poor prognostic marker. Early diagnosis of those syndromes is achieved using specific criteria and may lead to early diagnosis of the underlying malignancy. It is essential to treat them with the overriding objective of improving the patients' quality of life.

Rapidity of Correction of Hyponatremia Due to Syndrome of Inappropriate Secretion of Antidiuretic Hormone Following Tolvaptan

BACKGROUND

Tolvaptan effectively corrects hyponatremia due to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), but undesired overcorrection can occur. We hypothesized that pretherapy parameters can predict the rapidity of response to tolvaptan in SIADH.

STUDY DESIGN

Multicenter historical cohort study.

SETTING & PARTICIPANTS

Adults with SIADH or congestive heart failure (CHF) treated with tolvaptan for a serum sodium concentration ≤ 130 mEq/L at 5 US hospitals.

PREDICTORS

Demographic and laboratory parameters.

OUTCOMES

Rate of change in serum sodium concentration.

MEASUREMENTS

Spearman correlations, analysis of variance, and multivariable linear mixed-effects models.

RESULTS

28 patients with SIADH and 39 patients with CHF treated with tolvaptan (mean baseline serum sodium, 120.6 and 122.4 mEq/L, respectively) were studied. Correction of serum sodium concentration > 12 mEq/L/d occurred in 25% of patients with SIADH compared to 3% of those with CHF (P<0.001). Among patients with SIADH, the increase in serum sodium over 24 hours was correlated with baseline serum sodium concentration (r=-0.78; P<0.001), serum urea nitrogen concentration (SUN; r=-0.76; P<0.001), and estimated glomerular filtration rate (r=0.58; P=0.01). Baseline serum sodium and SUN concentrations were identified as independent predictors of change in serum sodium concentration in multivariable analyses. When patients were grouped into 4 categories according to baseline serum sodium and SUN median values, those with both low baseline serum sodium (≤121 mEq/L) and low baseline SUN concentrations (≤10mg/dL) exhibited a significantly greater rate of increase in serum sodium concentration (mean 24-hour increase of 15.4 mEq/L) than the other 3 categories (P<0.05). Among patients with CHF, only baseline SUN concentration was identified as an independent predictor of change in serum sodium concentration over time.

LIMITATIONS

Lack of uniformity in serial serum sodium concentration determinations and documentation of water intake.

CONCLUSIONS

Baseline serum sodium and SUN values are predictive of the rapidity of hyponatremia correction following tolvaptan use in SIADH. We advise caution when dosing tolvaptan in patients with both low serum sodium and SUN concentrations.

Managing hyponatremia in lung cancer: latest evidence and clinical implications

Hyponatremia is the most common electrolyte disorder in lung cancer patients. This condition may be related to many causes including incidental medications, concurrent diseases and side effects of antineoplastic treatments or the disease itself. Although not frequently life-threatening, it is usually associated with prolonged hospitalization, delays in scheduled chemotherapy, worsening of patient performance status and quality of life and may also negatively affect treatment response and survival. Most of the available data focus on thoracic tumors, especially small-cell lung cancer (SCLC), where hyponatremia is frequently related to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Few studies specifically focus on non-small cell lung cancer (NSCLC) patients. Hyponatremia treatment needs to be personalized based on severity and duration of sodium serum reduction, extracellular fluid volume and etiology. However, literature data highlight the importance of early correction of the serum concentration levels. To achieve this the main options are fluid restriction, hypertonic saline, loop diuretics, isotonic saline, tolvaptan and urea. The aim of this review is to analyze the role of hyponatremia in lung cancer patients, evaluating causes, diagnosis, management and clinical implications.

Efficacy and safety of two different tolvaptan doses in the treatment of hyponatremia in the Emergency Department

Hyponatremia (plasma sodium concentration or _P[Na⁺] <136 mEq/L) is the most common electrolyte unbalance in clinical practice. Although it constitutes a negative prognostic factor, it frequently remains underdiagnosed and undertreated. Tolvaptan is an oral V₂-receptor antagonist which produces aquaresis. Given its emerging role in the treatment of dilutional hyponatremia, we aimed to compare the efficacy and safety of two different doses of this drug in an Emergency Department (ED) setting. Consecutive patients with moderate-severe euvolemic or hypervolemic hyponatremia were sequentially assigned to the 15 mg Group and to the 7.5 mg Group, and were revaluated at 6, 12 and 24 h. Further evaluations and administrations were scheduled daily until _P[Na⁺] correction was achieved or the maximum period of 72 h was exceeded. A 1-month follow-up was performed. Twenty-three patients were enrolled: 12 were included in the 15 mg Group, 11 in the 7.5 mg Group. Both doses significantly elevated the _P[Na⁺] over 24 h, although the 15 mg Group showed faster corrections than the 7.5 mg Group (12 vs 6 mEq/L/24 h; P = 0.025). An optimal correction rate (within 4-8 mEq/L/24 h) was observed in 45.4 % of the 7.5 mg Group against 25.0 % (P n.s.). The standard dose led to dangerous overcorrections (>12 mEq/L/24 h) in 41.7 % of the patients, while the low dose did not cause any (P = 0.037). No osmotic demyelination syndrome was observed. A 7.5 mg tolvaptan dose can be considered both effective and safe in treating hyponatremia in the ED, while a 15 mg dose implicates too high risk of overcorrection.

[Hyponatremia in emergency admissions - often dangerous]

Hyponatremia is the most common electrolyte disorder in clinical practice and associated with increased morbidity and mortality, independent of underlying disease. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema whilst over rapid correction of chronic hyponatremia can cause serious neurologic impairment and death resulting from osmotic demyelination. Still hyponatremia is often neglected and insufficiently addressed, most likely due to limited understanding of its pathophysiological mechanisms. Being familiar with only few basic principles of body fluid regulation may be a worthwhile investment into the clinical career and save patients' lives.

Vasopressin Receptor Antagonists in Hyponatremia: Uses and Misuses

Decreases in the concentration of sodium in plasma constitute hyponatremia, the commonest electrolyte disorder in clinical medicine. It is now well established that its presence conveys an increased mortality risk even when the decrement is mild. In addition, recent evidence suggests that chronic and apparently asymptomatic hyponatremia is associated with increased morbidity including neurocognitive deficits and bone fractures. Furthermore, hyponatremia is associated with higher health care-related expenses. Consequently, exploring new therapeutic strategies that increase plasma sodium in a safe and effective manner is of paramount importance. In this regard, there are scant data to support the use of traditional management strategies for hyponatremia (fluid restriction, salt tablets, loop diuretics, and normal saline). Furthermore, data from a large hyponatremia registry reveal the limited efficacy of these therapies. More recently vasopressin receptor antagonists provide a promising treatment for hyponatremia by targeting its most common mechanism, namely, increased vasopressin activity. However, uncertainty still lingers as to the optimal indications for the use of vasopressin receptor antagonists in hyponatremia and a few reports have described complications resulting from their misuse. This review summarizes the appropriate and inappropriate uses of vasopressin receptor antagonists in the treatment of hyponatremia.

Improving care and outcomes of inpatients with syndrome of inappropriate antidiuresis (SIAD): a prospective intervention study of intensive endocrine input vs. routine care

PURPOSE

The syndrome of inappropriate antidiuresis is often undertreated with most patients discharged with persistent hyponatraemia. This study tested the hypothesis that an endocrine input is superior to routine care in correcting hyponatraemia and can improve patient outcomes.

METHODS

This single-centre prospective-controlled intervention study included inpatients admitted at a UK teaching hospital, with serum sodium ≤ 127 mmol/l, due to syndrome of inappropriate antidiuresis over a 6-month period. The prospective intervention group (18 subjects with mean serum sodium 120.7 mmol/l) received prompt endocrine input, while the historical control group (23 patients with mean serum sodium 124.1 mmol/l) received routine care. The time needed for serum sodium increase ≥ 5 mmol/l was the primary endpoint.

RESULTS

The intervention group achieved serum sodium rise by ≥5 mmol/l in 3.5 vs. 7.1 days in the control group (P = 0.005). In the intervention group, the mean total serum sodium increase was 12 mmol/l with only 5.8 % of patients discharged with serum sodium < 130 vs. 6.3 mmol/l increase (P < 0.001) and 42.1 % of the subjects discharged with serum sodium < 130 mmol/l in the control group (P = 0.012). The mean length of hospital stay in the intervention group (10.9 days) was significantly shorter than in the control group (14.5 days; P = 0.004).The inpatient mortality rate was 5.5 % in intervention arm vs. 17.4 % in control arm, but this difference was not statistically significant.

CONCLUSIONS

Since the endocrine input improved time for correction of hyponatraemia and shortened length of hospitalisation, widespread provision of endocrine input should be considered.

Role of tolvaptan in the management of hyponatremia in patients with lung and other cancers: current data and future perspectives

Hyponatremia is the most frequently observed electrolyte abnormality in clinical practice, and its frequency is almost double in hospitalized cancer patients. As a subset of cancer, hyponatremia is quite common in lung cancer patients, and it is often coupled with the diagnosis of syndrome of inappropriate antidiuretic hormone secretion. The presence of hyponatremia is consequential in that its presence adversely affects cancer patients’ prognosis and outcomes. Limited data suggest that correcting hyponatremia in lung cancer patients can increase response to anticancer treatment, may help reduce length of hospital stay and cost, and reduce morbidity and mortality. The type of treatment for hyponatremia depends on several factors; the key factors are the duration and severity of neurological symptoms of hyponatremia and the status of extracellular volume. When hyponatremia is caused by syndrome of inappropriate antidiuretic hormone, hypertonic saline is indicated for acute symptomatic cases, whereas fluid restriction is recommended in chronic asymptomatic hyponatremia. The latter allows a slower rate of correction, thus avoiding the dreaded complication of osmotic demyelination syndrome. Fluid restriction is, however, insufficient or impractical, and often the use of pharmacological therapy such as antidiuretic hormone receptor antagonists becomes necessary. Availability of these antagonists as an effective treatment in the management of hyponatremia has been a major breakthrough, and furthermore, its clinical or investigational use in cancer-related hyponatremia may offer a potential opportunity to gain further insights into the prognostic impact of hyponatremia correction on cancer patients’ outcomes. Tolvaptan is a prototype of ADH receptor antagonists that acts at renal tubular levels to increase free water excretion without inducing major systemic electrolyte abnormalities such as hypokalemia or alkalosis. The aim of this paper is to provide a brief review while focusing on cancer hyponatremia; (1) of the epidemiology of hyponatremia and its pathophysiology and diagnostic approaches and (2) of the pharmacokinetics of tolvaptan and its clinical efficacy, safety, and compliance.

Real-life experience of tolvaptan use in the treatment of severe hyponatraemia due to syndrome of inappropriate antidiuretic hormone secretion

OBJECTIVE

European guidelines do not recommend tolvaptan for treatment of syndrome of inappropriate antidiuretic hormone secretion (SIADH), principally owing to concerns about risk of overly rapid correction of hyponatraemia. This study evaluated the real-life effectiveness and safety of tolvaptan.

DESIGN

Consecutive case series.

PATIENTS

Inpatients treated with tolvaptan for SIADH in 2 UK hospitals over a 3-year period.

MEASUREMENTS

The primary outcome measures were serum sodium (sNa) correction at 24 and 48 h after tolvaptan therapy.

RESULTS

This case series included 61 patients aged 74·4 ± 15·3 years with (mean ± SD) sNa 119·9 ± 5·5 mmol/l. The mean sNa increase 24 h after tolvaptan initiation was 9 ± 3·9 mmol/l. Excessive correction of hyponatraemia was observed in 23% of patients with all these patients having baseline sNa <125 mmol/l, but no cases of osmotic demyelination syndrome were recorded. At the end of tolvaptan therapy, sNa increase was 13·5 ± 5·9 mmol/l with 96·7% of patients having sNa increase ≥5 mmol/l in 48 h. There was a negative significant correlation (P = 0·012) between baseline sNa and 24-h change; for every 1 mmol/l reduction in baseline value, sNa increased by an additional 0·23 mmol/l (95% CI 0·05-0·41).

CONCLUSIONS

Tolvaptan is effective in correcting hyponatraemia. Without rigorous electrolyte monitoring, tolvaptan carries a significant risk of overly rapid sodium correction, especially in patients with starting sNa <125 mmol/l. Tolvaptan should be used with great caution under close electrolyte monitoring.

Prevalence of Hyponatremia in Palliative Care Patients

Introduction:

Hyponatremia is an undertreated finding in clinical practice. It is the most common electrolyte abnormality. Hyponatremia can be asymptomatic or can cause symptoms ranging from nausea and lethargy to convulsions and coma. Palliative care patients have a multitude of symptoms and there are several contributing factors towards this. Hyponatremia could be one of the contributing factors. Looking at the prevalence of hyponatremia would highlight the magnitude of the problem and would prompt healthcare professionals to investigate and treat hyponatremia in palliative care patients, which in turn might reduce symptoms such as fatigue and nausea. This could improve the quality of life in palliative care patients.

Aim:

To assess the prevalence of hyponatremia among patients referred for palliative care in a tertiary care hospital.

Methodology:

This is a descriptive study, with retrospective analysis of consecutive patient charts for 5 years. The sodium levels at the time of referral for palliative care, was reviewed. Inferential statistics for the result was calculated using the Z-test.

Results:

Of the 2666 consecutive patient charts that were reviewed, sodium values were recorded in 796 charts. Among the recorded charts, 28.8 % of patients showed hyponatremia at the time of referral which was significant with a P value of 0.000 (<0.05). Of these, 61.1 % had malignancy as their diagnosis and the rest had nonmalignant diseases, ranging from trauma to chronic obstructive pulmonary disease.

Conclusions:

Prevalence of hyponatremia is significant in palliative care patients. A prospective study looking at the causes and clinical outcomes associated with hyponatremia in palliative care patients is needed.

[Hyponatremia and tolvaptan : what is the situation 5 years after approval?]

The diuretic tolvaptan has been approved for more than 5 years for the indications of euvolemic hyponatremia due to syndrome of inappropriate antidiuretic hormone (SIADH) secretion. In recent years many patients have been treated with tolvaptan and many physicians could gather practical experience. Other countries, such as the USA had already gained greater experience, also in the indications for hypervolemic hyponatremia. After approval was granted more than 5000 patients worldwide were included in the so-called hyponatremia register and 22 active centers in Germany with 317 patients participated. Although some details from this now concluded register have been published, the final publication of the multinational post-authorization safety study on tolvaptan in the treatment of SIADH has not yet been published. In the years 2012 and 2013 two warning letters were issued on tolvaptan. The first letter warned of the risk of a faster increase in serum sodium using tolvaptan and provided detailed information on how the risk of osmotic demeyelination can be minimized. So far only one proven case of osmotic demelination syndrome (ODS) is known; however, this occurred following incorrect use of tolvaptan in a monotherapy. The second warning letter provided information on the potential risk (reversible) of liver damage by tolvaptan, which resulted from the TEMPO 3:4 study. In this study tolvaptan was used in a higher dosage for therapy of autosomal dominant polycystic kidney disease. Although the European renal best practice (ERBP) guidelines from 2014 did not recommend tolvaptan for the indications of SIADH, other guidelines came to different conclusions. In summary, 5 years after the approval of tolvaptan there is still no consensus. At the current time many questions still remain unanswered. Initiation of therapy with tolvaptan remains reserved for experienced physicians in hospitals. Treatment must be adapted on the basis of a clinical estimation of the individual situation of each patient.

Efficacy and safety of long-term tolvaptan treatment in a patient with SCLC and SIADH

Hyponatremia frequently occurs in patients with cancer and is mostly due to a syndrome of inappropriate antidiuresis caused by ectopic secretion of antidiuretic hormone (SIADH). Small cell lung cancer presents with SIADH in approximately 11%-15% of cases. Recently, a new class of drugs, vasopressin V2-receptor antagonists (vaptans), emerged as a promising treatment for SIADH, but efficacy and safety data in cancer patients are lacking. We present a case of SIADH, heralding small cell lung cancer and persisting after apparent complete remission of primary tumor following chemotherapy/radiotherapy, in a patient who underwent long-term treatment with tolvaptan without any serious adverse effects.

Paraneoplastic syndromes associated with lung cancer

Paraneoplastic syndromes are signs or symptoms that occur as a result of organ or tissue damage at locations remote from the site of the primary tumor or metastases. Paraneoplastic syndromes associated with lung cancer can impair various organ functions and include neurologic, endocrine, dermatologic, rheumatologic, hematologic, and ophthalmological syndromes, as well as glomerulopathy and coagulopathy (Trousseau’s syndrome). The histological type of lung cancer is generally dependent on the associated syndrome, the two most common of which are humoral hypercalcemia of malignancy in squamous cell carcinoma and the syndrome of inappropriate antidiuretic hormone secretion in small cell lung cancer. The symptoms often precede the diagnosis of the associated lung cancer, especially when the symptoms are neurologic or dermatologic. The proposed mechanisms of paraneoplastic processes include the aberrant release of humoral mediators, such as hormones and hormone-like peptides, cytokines, and antibodies. Treating the underlying cancer is generally the most effective therapy for paraneoplastic syndromes, and treatment soon after symptom onset appears to offer the best potential for symptom improvement. In this article, we review the diagnosis, potential mechanisms, and treatments of a wide variety of paraneoplastic syndromes associated with lung cancer.

A rapid and efficient way to manage hyponatremia in patients with SIADH and small cell lung cancer: treatment with tolvaptan

Background

Hyponatremia based on syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH) is observed in up to 15% of patients with small cell lung cancer (SCLC). The electrolyte imbalance is associated with a high morbidity and mortality and often delays appropriate treatment. Management of hyponatremia proved to be challenging until new vasopressin-2 receptor antagonists such as tolvaptan became available. This is the first report which presents a prospective case series with an efficient management of hyponatremia including tolvaptan in ten patients with SCLC and severe SIADH (plasma sodium < 125 mmol/l).

Methods

Ten patients with SCLC and severe SIADH were followed after the onset of clinical symptoms of SIADH. Patients were chosen on the basis of histological proven diagnosis of SCLC and the clinical picture of a neurocognitive deficit caused by SIADH-related hyponatremia. All patient data were monitored for clinical improvement based on ECOG status, commencement of chemotherapy and correction of sodium levels.

Results

The treatment followed a diagnostic and treatment algorithm and lead to a rapid and efficient correction of both clinical symptoms and plasma sodium level.

Conclusions

Based on this algorithm all patients started chemotherapy in time. Subsequently, the treatment with tolvaptan lead to an improvement of the ECOG-performance status. In addition, all patients benefit from the effective management of SIADH which omitted prolonged hospital stays and non-elective hospitalizations due to an unstable clinical condition due to severe hyponatremia. These observations add new insight to management of SIADH in thoracic oncology and are of interest for specialists in oncology, endocrinology and pulmonary medicine.

Clinical review: the use of vaptans in clinical endocrinology

CONTEXT

Hyponatremia is the most common electrolyte disorder encountered in clinical practice and represents a clinical, social, and economic burden. Conventional treatments of hyponatremia present some pitfalls, such as suboptimal efficacy, risk of overly rapid correction, and adverse effects. Vasopressin receptor antagonists, known as vaptans, represent a new and interesting class of drugs for the treatment of the euvolemic and hypervolemic forms of hyponatremia.

EVIDENCE ACQUISITION

This review is based on a PubMed search with the following terms: "vaptans," "vasopressin receptor antagonists," "tolvaptan," "conivaptan," "vasopressin receptor antagonists and SIADH," "vasopressin receptor antagonists and congestive heart failure," "vasopressin receptor antagonists and cirrhosis," and "vasopressin receptor antagonists and polycystic kidney disease."

EVIDENCE SYNTHESIS

Overall, the studies reported in this review indicate that vaptans effectively correct hyponatremia in euvolemic and hypervolemic patients. In the latter group, vaptans generally had favorable effects on fluid balance also. To date two vaptans, ie, conivaptan and tolvaptan, have been marketed in the United States for the treatment of euvolemic and hypervolemic hyponatremia, whereas tolvaptan has been marketed in Europe with the limitation of euvolemic hyponatremia. Although these drugs have a good safety profile, caution should be used, and treatment should be initiated in a hospital setting in order to closely monitor patients and avoid overly rapid correction or overcorrection.

CONCLUSIONS

Vaptans can be considered a new effective tool for the treatment of euvolemic and hypervolemic hyponatremia. Nevertheless, more comparative research of vaptans vs other therapies on clinical grounds is needed to more accurately assess the value of these drugs in the treatment of hyponatremia.

[The syndrome of inappropriate antidiuresis]

The syndrome of inappropriate antidiuresis (SIAD; formerly the syndrome of inappropriate secretion of antidiuretic hormone) is the most frequent cause of hyponatremia. A strong association exists between mortality and hyponatremia, which reflects the severity of the underlying disease. In SIAD, hyponatremia is associated with normovolaemia but the assessment of extracellular volume can be difficult. Clinical features are mainly neurological and can lead to death but mechanisms of adaptation can limit cerebral oedema. The notion of mild asymptomatic hyponatremia was questioned by the observation of subclinical neurocognitive impairment, a greater risk of falls and fractures. Aetiologies are classified into six groups: neurologic disorders, infections mainly cerebral, meningeal and pulmonary, drugs in particular antidepressants, tumors, genetic causes, and idiopathic. Symptomatic acute hyponatremia is a therapeutic emergency that is not specific of SIAD. When hyponatremia is asymptomatic, fluid restriction with salt intake is generally sufficient but urea can be an alternative. In chronic SIAD, there is currently no recommendation. Fluid restriction is not always feasible; urea has proved its efficacy, its good tolerance and its long-term harmlessness. Vaptans have demonstrated their good tolerance and their efficacy on the correction of hyponatremia from SIAD in studies subgroups, for moderate hyponatremia and asymptomatic patients. In the only study having compared vaptans and urea, efficacy and tolerance were similar. Because of the cost difference between vaptans and urea and while waiting for follow-up studies, urea appears at present as the first-line treatment of hyponatremia in SIAD.

[Ectopic hormone secretion by neuroendocrine tumors]

Ectopic hormone production is a rare complication in neuroendocrine tumors. Tumors producing corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) are most commonly observed, leading to the classical symptoms of Cushing’s syndrome. Additionally, a very low percentage of neuroendocrine tumors can produce growth hormone-releasing hormone (GHRH) leading to classical features of acromegaly. Moreover, ectopic antidiuretic hormone (ADH) secretion has been described in neuroendocrine tumors presenting as hyponatremia due to the syndrome of inappropriate ADH secretion. Other ectopic hormone secretions, such as paraneoplastic gonadotropin release are rarely observed. Ectopic hormone secretion is not usually associated with a detectable pituitary mass and diagnosis is based on the measurement of circulating peptides. This is frequently assisted by imaging techniques, such as somatostatin receptor scintigraphy. Therapeutically a curative approach is the primary goal but in advanced tumors palliative treatment aims to control symptoms with the help of specific antihormonal compounds, such as somatostatin analogues.