Gastric Carcinoid and elevated gastrin levels

Hi,

My father has been diagnosed with multiple gastric carcinoids in stomach. Biopsy report for these tumours classify them as (Neuro endocrine tumour(Grade 1). Triple phase CT scan rules out any other tissue growth like a gastrinoma anywhere else in the whole abdomen and thorax.
Gastrin levels are highly elevated at 2574 pg/ml. Endoscopy of the stomach confirms that tumours in stomach are less than 5 mm in size.

The patient is doing absolutely fine and is carrying out his daily activities normally without any problems.

Confusion arises as gastric carcinoids are not known to raise gastrin levels to such high extent.

What are the treatment options for this problem.