Sometimes a high leukocytes level can be a sign of cancer and other things such as prostate cancer, bladder cancer or kidney cancer.
The high leukocytes levels could also be a sign of blood diseases including sickle cell anemia.
Having leukocytes in your urine is not always a sign of cancer but depending on the levels of the leukocytes in your urine it can sometimes be a sign of cancer.
If the cancer is treated soon enough then it can usually be cured and you should live a good long life but the longer you wait to treat the potential cancer due to the leukocytes levels the less chance you have of curing it.
That's why it's always a good idea to see a doctor often for checkups so that you can get checked out and find potential health issues soon enough.