A Chilling Thought

I have recently delved into the notion that cold caps could increase the likelihood of brain metastasis from breast cancer.  The central question is whether brain temperature reduction via cold cap therapy reduces local uptake of Taxol and Herceptin.  It turns out there is something which scientists call the Blood Brain Barrier (BBB) which helps to protect the brain from foreign nasties like viruses and bacteria in their quest to invade the brain via the bloodstream.

Apparently, an intact BBB acts like a sieve and permits sufficiently tiny particles like nutrients and hormones to flow to the brain but blocks out larger masses, where larger means having a molecular weight greater than 500 Daltons (1 Da = 1.6605402e-27 Kg).  The BBB can in certain circumstances be compromised, however, like in the presence of inflammation or especially determined bacteria such as those causing meningitis and Lyme disease.  Here are some sample molecular weights in Daltons.

Water  18.02

Oxygen (O2)   32

Tylenol   151

Glucose   180

Penicillin   313

Taxol    853.9

Herceptin   145,000

Viruses   1,000,000 – 1,000,000,000

Because both Taxol and Herceptin exceed the maximum threshold size to the brain, reducing blood flow via cold caps at least theoretically would not interrupt their uptake since they’re too large to pass through the BBB.  Accordingly, numerous studies have demonstrated very limited disbursement and therefore response of the brain to those drugs.  Scientists have been working on delivery methods to bypass the BBB, however, and have achieved success with novel methods designed to transport both Taxol and Herceptin but thus far only in animal studies.  For current breast cancer patients, this means that cold cap therapy will not jeopardize the therapeutic effect of Taxol and Herceptin because those agents cannot effectively reach the brain regardless of the surrounding temperature, a chilling thought on its own.

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