Rationale: Familial adenomatous polyposis (FAP) syndrome is characterized by the development of numerous colorectal polyps. If left untreated, these patients have a chance of nearly 100% of developing colorectal cancer (CRC) at a young age. Therefore, guidelines recommend a prophylactic colectomy during early adulthood. Even after colectomy, most patients will develop adenomas in the retained rectum or ileoanal pouch requiring further endoscopic surveillance. In a recent study in mouse models, a chemopreventive effect of Lithium was observed on the spread of Apc mutated cells within the crypts of normal intestinal mucosa, suggesting polyp formation can be prevented. Lithium is used to treat patients with bipolar disorders but has never been investigated in patients with FAP aiming to reduce polyp burden. We hypothesize that Lithium could reduce the spread of APC mutated cells within the crypt of normal intestinal mucosa potentially reducing polyp burden in patients with FAP. Objective: The aim of this study is to investigate the effect of low-dose Lithium on stem cell dynamics, the number and size of polyps and, to assess safety outcomes of this drug in FAP patients. Study design: A prospective phase II, single arm pilot trial, with a duration of 18 months. The drug will be administered between month 6 and 12. Study population: Twelve patients with FAP between the age of 18 and 35 not having undergone a colectomy (yet), having a genetically confirmed APC mutation and a family history with a classical FAP phenotype. Intervention: All patients will be treated with Lithium with an oral dose of 300mg a day for six months, achieving a therapeutic serum level between 0.2-0.4 mmol/L. Main study parameters/endpoints: The main outcome parameter is the effect of Lithium on the spread of APC mutant cells within intestinal crypts over time by using an APC specific marker NOTUM (a significance reduce of fixed crypts and reduction of fixed clone size of 50%). Nature and extent of the burden and risks associated with participation, benefit and group relatedness: A physical examination and an endoscopy with biopsies will be performed at baseline and every six months (four in total). Laboratory testing will be done at baseline and every two months during Lithium treatment. Patients will be interviewed by phone and Lithium side effect questionnaires will be obtained at baseline and during Lithium treatment. Lithium serum levels will be measured at day 12 and 22 after start of the study drug (at month 6). When the therapeutic range has been achieved, serum level testing will be done every month. Most relevant side-effects that could potential occur include polyuria, hyperparathyroidism and hypothyroidism. Most side effects are dose-dependent and will be regularly monitored. Patients with FAP could potentially benefit from a chemopreventive therapy such as Lithium to postpone or even avoid invasive types of surgery.
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Change in clone size distribution positive for NOTUM.
Timeframe: Month 0, Month 6, Month 12, Month 18