In theory, it could happen that chemotherapy would not work well on any malignant cells (metastases) in the scalp due to scalp cooling. This leads for some patients to uncertainty.
For patients with cancer in a tissue or organ, metastases to the scalp are rare. Although scalp cooling has been used with thousands of patients over decades, a negative outcome of the disease has never been described due to scalp cooling with cancer in tissues or organs.
Research has been done with a large group of patients with breast cancer (more than 600 patients); patients who had scalp cooling developed metastases in the scalp with the same frequency as patients without scalp cooling. The patients from both groups also lived for the same amount of time. We therefore assume that scalp cooling is safe for patients with breast cancer. The risk also seems very low for other kinds of cancer, since then even fewer than 1 in 200 patients develop metastases in the scalp. (See illustration.)
Illustration: Both with and without scalp cooling, 1 in 200 patients with breast cancer develop metastases in the scalp.
A metastasis in the scalp before the start of the chemotherapy is not a reason not to use scalp cooling. This metastasis will probably shrink despite the scalp cooling, and it will not be responsible for a bad outcome of the disease.
The use of scalp cooling is not advised for patients with cancer of the blood and lymph nodes. The reason is that in these cases the cancer cells are spread throughout the body, including in the scalp. The risk of the development of metastases in the scalp skin after scalp cooling has been demonstrated with one patient with leukaemia and one patient with mycosis fungoides.
Freezing of the skin has never been reported with the use of a cooling machine; it has been reported with the use of cool caps out of the freezer.