Tolvaptan resistance is related with a short-term poor prognosis in patients with lung cancer and syndrome of inappropriate anti-diuresis


Purpose: Tolvaptan (TVP), a vasopressin receptor antagonist, represents a therapeutic option in the syndrome of inappropriate anti-diuresis (SIAD). The aim of this study was to evaluate the effect of TVP to treat and solve hyponatremia in oncologic patients.
Methods: 15 oncologic patients who developed SIAD have been enrolled. Patients receiving TVP belonged to group A, whereas group B was characterized by hyponatremic patients treated with hypertonic saline solutions and fluid restriction.
Results: In group A, the correction of serum sodium was achieved after 3.7±2.8 days. In group B, the target levels were obtained more slowly, after 5.2±3.1 days (p: 0.01) than in group A. The hospital stay and incidence of re-hospitalization were higher in group B than in group A. In this latter, 37% of patients had hyponatremic relapses, notwithstanding the progressive increase of doses from 7.5 to 60 mg per day of TVP, revealing a complete lack of response to TVP. In these patients, a growth of tumor mass or new metastatic lesions has been revealed.
Conclusion: TVP improved hyponatremia more efficiently and stably than hypertonic solutions and fluid restrictions. Positive consequences have been obtained about the rate of chemotherapeutical cycles concluded, hospital stay, rate of relapse of hyponatremia, and re-hospitalization.
Our study also suggested potential prognostic information that could be deduced from TVP patients, in whom sudden and progressive hyponatremia occurred, despite TVP dosage increase. A re-staging of these patients to rule out tumor mass growth or new metastatic lesions is suggested.

Keywords: hyponatremia, paraneoplastic syndrome, syndrome of inappropriate anti-diuresis, tolvaptan, vasopressin


The prognosis of oncologic patients is often related to the onset of electrolytic disorders, particularly if hyponatremia occurs [1]. The syndrome of inappropriate anti-diuresis (SIAD) represents the main cause of hyponatremia, even though differential diagnosis with concomitant comorbidities (heart failure, nephrotic syndrome, extracellular volume depletion, pulmonary disorders) and drugs (tricyclic antidepressants, selective serotonin reuptake inhibitors, opioids, chemotherapeutic agents and immunotherapy) needs to be carried out [2, 3].

In particular, SIAD is directly associated with malignancy as expression of a paraneoplastic endocrine effect mediated by an ectopic production of vasopressin (AVP) by cancer cells. Moreover, medications, particularly chemotherapic agents, such as vinca alkaloids, alkylating agents, and platinum compounds, which increase the AVP synthesis/release, could induce SIAD. Other drugs, such as cyclophosphamide, could enhance the water permeability of the distal tubule, in the absence of high AVP levels [1].


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