Sue - It would all depend on the type of cancer. The only count that I am personally aware of is for Prostate Cancer, which my husband has.
The blood count for this type of cancer is called a PSA test, which means the amount of Prostate Specific Antigen present in the blood, which indicates the presence of cancer.
It is measured against something called The Gleason Scale, where 2-5 is mild, 6-7 is moderate, and 8-10 and above is aggressive.
At the intial diagnosis my husband's Gleason scale measurement was 4, and he was treated first with 3 months hormone tablets to reduce the Testosterone which feeds the cancer, followed by 32 daily treatments of Radiotherapy, this was then followed by a further 3 months of the hormone reducing tablets. Thankfully, now 2 years down the line, he is remarkably well, and has gone from 4 monthly check ups, to 6 month check up, next is at end April, and if this one is OK too, he will then go on to a once a year check up for the rest of his life. He said the treatment was not painful, but tiring, and now feels fine. I thought I would share this with you, as it's possible that the question you asked was about this type of cancer, as it is very common among men, with 30,000 a year being diagnosed, and with 20,000 a year surviving. If this answer is not any help to you. Perhaps you could post the question again in the Health & Fitness category, as I have seen questions about various types of cancers answered in that category. I do hope your question doesn't involve anyone from your family or friends. But whatever the reason for your question, I do send you my best wishes. Schutz.