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Marquina et al. J Cancer Metastasis Treat 2020;6:6 I http://dx.doi.org/10.20517/2394-4722.2019.39 Page 7 of 8

The Spanish Medical Oncology Society (SEOM) has developed an algorithm which could be useful for
[29]
the management of hyponatremia secondary to SIADH in cancer patients based on the prior algorithm
[30]
developed in Spain for hyponatremia patients .
According to the SEOM algorithm, management will depend on the two scenarios mentioned above: the
patient is a candidate vs. a non-candidate for chemotherapy.

When the patient is a candidate for chemotherapy [Figure 1]
(1) Mild hyponatremia (130-135 mmol/L): proceed with chemotherapy. Re-evaluate during the next
cycle. Note that there are discrepancies in this point, as Tolvaptan would prevent the exacerbation of
[19]
hyponatremia and the development of severe hyponatremia following the first cycle of chemotherapy ;
(2) Moderate hyponatremia (120-130 mmol/L): consider Tolvaptan if chemotherapy requires pre-hydration,
hyponatremia is progressively worsening, or hyponatremia is symptomatic. As mentioned above for mild
hyponatremia, Tolvaptan could prevent worsening hyponatremia;
(3) Severe hyponatremia (< 120 mmol/L): use the same as treatment as for severe hyponatremia. Once 24-
48 h have elapsed following therapy with hypertonic saline solution, Tolvaptan could be started.

When SIADH-induced hyponatremia is caused by the anti-cancer treatment itself (for example, vincristine) , a
[8]
modification of cancer therapy should be considered. When a change in medication is not feasible, SIADH
in these cases should be treated with Tolvaptan.

When the patient is not a candidate for chemotherapy [Figure 2]
As mentioned above, supportive treatment and treatment of hyponatremia should be prioritized according
to the severity of the symptoms, rather than the level of hyponatremia per se:
(1) Mild hyponatremia (130-135 mmol/L): focus on supportive care management;
(2) Very symptomatic moderate/severe hyponatremia (< 130 mmol/L): consider Tolvaptan. If < 120 mmol/L,
treat the acute phase with hypertonic sodium solution and, once stabilized, consider Tolvaptan;
(3) Mild symptomatic moderate/severe hyponatremia (< 130 mmol/L): focus on supportive care
management.

DECLARATIONS
Authors’ contributions
Wrote and reviewed the manuscript: Marquina G, Gomez-Hoyos E, Runkle I

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Conflicts of interest
All authors declared that there are no conflicts of interest.

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Not applicable.

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