I forgot to ask my doctor. What does the letter after the stage mean? For example Stage IIIa or IIIc.
It's the grade of the tumour
Actually this website (American Cancer Society) has a good explanation of the various stages of ovarian cancer. The letter following the III indicates the depth and/or spread of the cancer, pointing out the location of any metastasis. The grade (aggressiveness/likelihood of recurrence) of the cancer is typically a number like 1, 2, 3. So your cancer might be staged at IIIc and be a grade 1.