I Have Been Recently Asked To Do A CA-125 Test

I have been recently asked to do a CA-125 test as I was recently diagnosed with an ovarian cyst. Subsequently an operation has been book for October with the understanding that if the blood test is ok there might not be a need to operate. Is the CA-125 test valid or accurate enough to determine the presence of cancer and grounds for operation? Would a biopsy be a better route to take? Secondly, can I continue to do strenuous work, office cleaning, with the presence of what could be ovarian cancer?