If this is recurrent disease, it could have undergone malignant transformation to WHO III/IV. Has the recurrence been biopsied? Is there enhancement?
Regardless, chemo is standard of care for recurrent LGG s/p XRT per NCCN guidelines. Especially if the patient hasn't seen chemo before, I would do chemo with temozolomide first (or PCV I suppose, if you are a masochist), and save reirradiation for if the patient progresses on chemo. Whether and which component of FLAIR to include is complex for recurrent disease, and would depend on the original treatment fields, location of recurrence, etc.