To evaluate the patterns of recurrence following postoperative conformal radiotherapy (RT) for intracranial meningioma.

Eighty-six patients who received conformal RT for intracranial meningiomas from 2014 to 2017 were retrospectively analysed. For documented recurrences, recurrence imaging was deformably co-registered to planning CT scan. In-field recurrence was defined as recurrence within the 90% isodose line, and out-of-field recurrences were those that occurred outside the 90% isodose line. We present the demographic details, surgical and RT details, outcomes and patterns of recurrence.

The median age was 46 years (range 17–72); 82·6% underwent surgery [46·5% had subtotal resection (STR), 43·7% gross tumour resection (GTR), 5·6% biopsy] and 17·4% had no surgery. Among these, 53·5% were WHO grade 2; 27·9% grade 1; and 1·2% grade 3 meningioma. Fifty per cent received stereotactic RT (SRT), 46·5% 3D conformal RT (3DCRT) and 3·5% intensity-modulated RT (IMRT). The mean clinical target volume (CTV) and planning target volume (PTV) margins were 4·5 mm (range 0–15) and 3·9 mm (range 1–5), respectively. The doses ranged from 54 to 59·4 Gy. The median follow-up after RT was 1·7 years (range 0·2–4·7). 17·4% were lost to follow-up, 5·4% had recurrence, and the median time to recurrence after completion of RT was 2 years (range 0·7–2·9). The 3-year recurrence-free rate was 81·5%. Three patients had in-field and two had in-field and out-of-field recurrence. Among the cases with recurrence, three received SRT, one 3DCRT and one IMRT. Four were grade 2 and one was grade 3 tumour, and the CTV margin ranged from 0 to 5 mm, and the PTV margin ranged from 3 to 5 mm.

Local recurrence was seen in grade 2 and 3 meningiomas. SRT probably had more recurrence as they had lesser CTV margin. Increased CTV margin, escalated dose up to 59·4 Gy and 3DCRT/IMRT may be helpful in preventing local recurrences in grade 2 and grade 3 meningiomas.