Welcome to this site.  However, I'm sorry you are having to go through treatment for anal cancer.  It's definitely a rough ride, but thank goodness, only for 6 or 7 weeks.  I received treatment in 2008, I'm still here, and doing quite well, so I hope that gives you hope!

Nadir is the point in a chemo cycle where a person's blood counts essentially hit bottom.  The following is a good description of nadir.

What Is Nadir?

When discussing chemotherapy side effects often you will hear the word nadir, mainly in reference to the blood counts, particularly white blood cell count and platelet count.  Nadir basically means low point, however further explanation may clarify this term in connection with chemotherapy treatment.

Nadir Affects Blood Cell and Platelet Counts

When chemotherapy is given it not only affects the rapidly dividing cancer cells but it also affects some of the normal cells of the body.  These effects particularly occur on normal cells that divide rapidly such as, the hair, the lining of the mouth, the cells lining the intestinal tract and the blood cells (white and red blood cells as well as platelets). 

In the bone marrow, the spongy inner core of the larger bones in the body is where blood cells are made.  There are very immature cells called stem cells, from which the various types of blood cells develop.  These stem cells do not reproduce quickly and are less likely to be affected by chemotherapy.  As cells are maturing there are certain phases in which they divide faster.  It is during these times that the cells are most sensitive to chemotherapy.  The more mature cells can continue to become fully mature cells for several days after chemotherapy is given.  When these cells live out their life span, the circulating supply is depleted and the blood counts fall to a low point, the nadir.

Emerging from the Nadir and Returning to Normal

The blood counts will return to normal within three to four weeks, after the body's feedback system has told the stem cells in the bone marrow to increase production and begin making new cells.   If chemotherapy is given at the time that the stem cells in the bone marrow are increasing their production this could cause permanent bone marrow damage.  The timing of chemotherapy cycles takes this process into account.  For example some chemotherapy drugs are given on day 1 and day 8 of a 28-day cycle.  The second dose of chemotherapy, one week after the first, is tolerated because the stem cells have not yet increased their production (they are still at the nadir).  They have not increased their production because the second treatment is given before the count of the circulating blood has reached its nadir.

The nadir time is usually about 10 days after treatment, although this may vary depending on the drugs given.  The concern during the nadir time is that the body's first line of defense against infection, white blood cells (WBC) and the platelets, which help to clot the blood, are low leaving a person more susceptible to infection and bleeding.  The next dose of chemotherapy is given only after a person's blood counts have left the nadir and recovered to a safe level."

As stated in the above information, this is a time when you need to be careful about infection and bleeding.  Some people choose to wear a mask in certain situations, especially when in public in places where germs may abound.  That might be something to consider.  During this time, a minor infection or bug can suddenly become serious, as your body's defenses may be compromised.  This is also the time of year for the flu, which is going around.  If you are concerned, I would definitely consider a mask.  Also, hand washing is important.

I remember hitting bottom around day 14 during both cycles of chemo.  I seemed very weak for about 7 days, then began feeling better.  By the time my second round of chemo was administered, I was feeling better (except for the ongoing diarrhea and burning from radiation).  For me, those two side effects were the worst and I attribute them to the radiation, not the chemo.

I'm glad you've found this site.  You will likely have more questions as you continue to move forward in your treatment, so please ask us here.  There's lots of smart people on this forum who have been through this who can offer suggestions that helped them and may help you.  Speak up and let us know what you need.  Hang in there--this treatment is definitely a difficult thing to get through, but so many of us have done it and you will too.  I wish you all the best.  Take it one day at a time and soon you'll be crossing the finish line!

Martha gave you a great explaination about nadir, I don't have anything to add to that except personal experience. I didn't feel too bad at the point you are at either- don't worry about it- just enjoy it while it lasts. Some of us got very sick and had to be hospitalized at the end of treatment like I was, others have been able to work during almost the entire treatment course, so it is pretty variable. What I remember was seeing a substitute radiation oncologist one week ( I think week 2) and him asking if I had radiation burns. When I told him I didn't, he seemed disappointed and said something like "well just wait, you will".  Two years later thinking about that it still makes me mad, and worse yet he was right, I did get terrible burns. I think men get by a bit better skin breakdown-wise just because of anatomy- not as much mucus membrane in the genital area so mens' skin is a little tougher. Best of luck in treatment, don't be afraid to ask anything on this site.

Brooklyn_bottom said:

Low WBC

Three weeks into treatment and my white blood count dropped below normal, 3.1, (my doctor said it would drop at 3 weeks, and this is 3 weeks to the day. I’ll have to ask who he likes in the Vikings/Eagles game.) I’m told if it drops much more I’ll need to get a shot to boost the WBC. 

Anyone else get a shot to boost their white blood count? What can I look forward too?

B.B. 

(Thank you Mollymaude and Strutsntoot for the support.)

I received a Neupogen injection during my first round of chemo when my WBC got very low.  My WBC did the same thing during the second round, but my doctor decided not to give me an injection at that time, perhaps because I was already so miserable with diarrhea and other side effects, I don't know.  When I got the injection, it made my bones ache for a couple of days.  That's the only side effect from Neupogen that I had. 

I had chemo and radiation the first week and I felt fine.  My husband says they removed the pump on Friday and Saturday morning I woke up with horrible mouth sores.  I gargled with salt and baking soda.  I used magic mouth wash  and nothing helped.  I felt like my esophagus was raw when I swallowed.  The doctor prescribed lidocaine liquid and that finally helped.  I received IV fluids but my blood work was always good.  The doctor lowered my chemo for week five.  I did not get mouth sores but I did have nausea on that round.  Took lots of anti nausea medication.  I think my white count never crashed because I always forced myself to eat and drink no matter how bad I felt.  I stayed home from work and I got plenty of rest.  I didn't get radiation burns until week five.  I kept worrying i wasn't getting enough but I guess I did.  My husband says I don't remember how sick I was.  He took good care of me.  The important thing is to avoid infection during Nadir.  Keep the anal area clean. Avoid being around people who may be sick.  I wore a mask to the treatment center waiting room. I pretty much stayed at home for months but it was all worth it.  One year later and I am still here.

Thanks for sharing your story about the radiation techs waiting for your burns to show up! My techs were great too. One day I just lost it and started crying and one of the techs was just so kind to me. I don't remember what she said, just how empathic she was. Some good memories in the experience!