L-carnitine is an amino acid compound and plays a vital role in energy metabolism.

Each cell can produce energy from the following three components: Glucose, fatty acids, and amino acids.
Glucose can be mobilized quickly and is the preferred method for energy production. However, fatty acids are more energy-rich than glucose. The fatty acids differ in the length of their chains. The longer these chains are, the more energy can be produced in the mitochondria of the cells. In contrast to short and medium-chain fatty acids, long-chain fatty acids need a transporter to get into the mitochondria. This transporter needs carnitine. I.e., in the absence of carnitine, long-chain fatty acids cannot be broken down into energy, which leads to an energy deficiency.

L-carnitine is not a substance that has direct effects against certain types of cancer.

The use of L-carnitine is currently limited to two conditions that are often found in cancer patients: fatigue and cachexia.

a.) Fatigue is a tumor-related exhaustion that occurs very often during cancer therapy.
b.) Tumor cachexia is a metabolic disorder that leads to emaciation in cancer patients.

I recommend using L-carnitine as part of a supportive measure against tumor cachexia and fatigue. During a cancer therapy, L-Carnitine can help to tolerate the treatments better.