Background: I131 therapy is regarded as an "internal surgery" (i.e., a non-invasive approach involving no incision or bleeding) that supports "external surgery" (i.e., using a scalpel) in completely eradicating the root cause of thyroid cancer. Limiting iodine intake is of paramount importance in I131 therapy. I131 therapy protocols recommend that patients follow a low-iodine diet, ideally with a maximum iodine intake of 50 μg/day for two weeks before the I131 therapy. Methods: A pre-post compassion uncontrolled clinic intervention study was conducted on a group of over 70 post-thyroidectomy thyroid cancer patients with indications for I131 therapy at the Vietnam National Cancer Hospital from December 2020 to December 2022. Aim: It aimed to assess the effects of a low-iodine diet on post-thyroidectomy thyroid cancer patients with indications for I131 therapy. Results: The study found that following the intervention, the percentage of participants at risk of mild to moderate malnutrition, as assessed by the PG-SGA tool, decreased to 4.3% from 40.0% before the intervention, with a statistically significant difference of p < 0.001. There was a considerable improvement in the low calcemia level among the study participants, with 35.7% of patients experiencing hypocalcemia prior to the intervention, which reduced to 17.1% after the intervention. This difference was statistically significant (p = 0.01). The study also revealed a urinary iodine level improvement among the study participants. Before the intervention, patients' average urinary iodine level was 14.9 ± 11.3 µg/dl. Following the intervention, it reduced to 12.7 ± 3.9 µg/dl, although this difference was not statistically significant (p = 0.29). Patients' quality of life after adhering to the low-iodine diet tended to decline; however, the change in scores before and after the intervention did not show a significant difference. Conclusion: Despite its negative impact on patients' quality of life, active nutrition counseling and intervention during the low-iodine diet contributed to the substantial improvement in the hypocalcemia level and the reduced urinary iodine level among patients, which in turn could enhance the efficacy of the subsequent I131 therapy.
Keywords: Nutritional intervention; low-iodine diet; quality of life; thyroid cancer patients.