Dr. Marik on Gastric Cancer: 8 repurposed drugs (4 increase Vitamin D in cells)

Gastric Cancer: Epidemiology, Causes, Diagnosis, and Modern Treatment

Paul Marik's Cancer & Metabolic Healing Playbook (Substack), Nov 8, 2026, no DOI, https://paulmarik.substack.com/p/gastric-cancer-epidemiology-causes

GastricCancerMarik.pdf

Summary by Claude - November 2026

Practical takeaway: Clearing H. pylori infection is the biggest preventable step against stomach cancer, and treatment of advanced disease now depends on testing the tumor for HER2, PD-L1, MSI and CLDN18.2. Vitamin D appears once, as a nutrient to watch after surgery: "Iron, calcium, vitamin D, and other nutritional parameters also require monitoring."

Study type: Narrative review on Dr. Marik's Substack, 58 references. Not peer-reviewed; no new patient data.

Highlights

About 969,000 new cases and 660,000 deaths a year worldwide; rates are highest in Mongolia, Japan and South Korea.
Adding durvalumab to FLOT chemotherapy (MATTERHORN trial, 948 patients) improved overall survival (HR 0.78).
First-year drug cost: about $250,000–$320,000 for pembrolizumab + trastuzumab + chemotherapy, vs. $15,000–$65,000 for a trastuzumab biosimilar + generic chemotherapy (author's estimates).
Of 8 repurposed drugs and nutraceuticals, only metformin has a human survival signal, from retrospective studies of diabetics (HR 0.72). Marik acknowledges there is no clinical proof yet that his metabolic regimen improves survival.

Missing: vitamin D. By the review's own table, none of the 8 agents has been tested in an RCT of cancer patients; vitamin D has. In the AMATERASU RCT (417 digestive-tract cancer patients, 42% gastric, 2,000 IU/day vitamin D3 after surgery), 5-year relapse-free survival was 77% vs. 69%, not statistically significant. It was better in patients who started at 20–40 ng/mL (85% vs. 71%) and in a post hoc p53-immunoreactive subgroup of 80 patients (81% vs. 31%). In a Chinese study of 197 gastric cancer patients, those with 25(OH)D ≥20 ng/mL lived longer (Ren 2012).

What this does NOT show

It is one physician's overview, not new evidence.
Lab results for the repurposed agents (cells, organoids, mice) do not establish benefit, safe doses, or safe combinations in patients.
The vitamin D results above come from subgroups, a post hoc analysis and an observational study; AMATERASU's main result was null.

Sources:

Images

Rates of Gastric Cancer are high in some places around the world

World map: The labeled numbers match the 2022 global figures (Mongolia 35.5, Japan 27.6, South Korea 27.0, Iran 19.4, China 13.7, 968,784 cases). But Great Britain is shaded in the darkest band, which doesn't fit its low rate. That looks like a mistake in the AI-drawn map, so trust the labels more than the colors.

Conventional treatment is very expensive

Repurposed Drugs

4 of the 8 agents in Dr. Marik's table have been reported to increase vitamin D receptor (VDR) activity or amount. None of these effects has been shown in stomach tissue or in people:

Curcumin binds and activates the VDR in colon cancer cells Bartik 2010
Berberine increased VDR activity in colon cells of IBS rats Huang 2024
Metformin increased VDR in kidneys of diabetic mice Wen 2022
Sulforaphane raised VDR in growing colon cancer cells but lowered it in mature ones Hossain 2021

No VDR studies were found for ivermectin, mebendazole, EGCG or doxycycline.