Pitch black darkness.  An empty nothingness.

When I struggle to think back to the afternoon and evening of Monday September 5 – just a month ago – I come up with a blank.  When I woke up the very next morning after that Monday, I struggled and similarly came up with another blank.


Amnesia is something I had heard of and seen in movies but to experience it first-hand is an amazing experience.  You go through life filled with memories, big and small, a continuous reel of a movie of your life.

Until it suddenly stops.

I know Monday afternoon and night existed through snippets of evidence I can follow like a detective.  I woke up at home, so obviously my ride picked me up successfully from the infusion center.  I woke up to find out that I had written a 2,000 word blog entry on Monday named "The Power of Stage IV Cancer Hope".  I woke up to almost 1,000 shares of it on Facebook.

I had no idea I had written anything – let alone what I wrote.  With some trepidation of what I had posted for the world to see, I read the post.  I may not have any memory of writing it but I often do my best writing on infusion days when my emotions are most raw.  I can see now why it became my most popular blog post ever.

But the darkness remains.

The term for this phenomenon is "Chemo brain" and it is very real.  It affects different patients in different ways and to different degrees.  Even for me, its presentation is complicated.  I often have total amnesia of chemo days from the start of infusion onward but looking at my sent email folder and social media posts, I remain perfectly lucid.

On other days, I have memory lapses I have never had before.  For example, forgetting which direction to turn when I get to an intersection on the same evening commute I have had for 17 years.  Thinking back to any day more than a week ago is fuzzy, similar perhaps to one of your memories from childhood.

This is especially noticeable to me because up until my cancer treatments I had essentially a photographic memory.  I could remember the most minute details from years before.

Interestingly, I still have close to a perfect memory when it comes to a few things.  I worry that my chemo brain may start to invade those areas but I don't think it will.  The more you continuously concentrate on subjects – for me my daughters, my personalized immunotherapy project, my science – I think the more those memories remain solidified.

So the next time a cancer survivor you know seems forgetful of a past conversation or forgets to show at an appointed time – cut them some slack.  On top of the obvious strains of dealing with cancer, you have no idea what may be going on inside their head.

Chemo brain is very real.

Dr. Tom Marsilje is a 20-year oncology drug discovery scientist with "currently incurable" stage IV colon cancer. He also writes a personal blog on life at the intersection of being both a cancer patient and researcher "Adventures in Living Terminally Optimistic," a science column for Fight Colorectal Cancer "The Currently Incurable Scientist", and posts science and advocacy updates to Twitter@CurrentIncurSci. This guest column appears on Diagnosis: Cancer through our partnership with Inspire, an Arlington, Va., company with condition-specific online support communities for over 850,000 patients and caregivers.

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