Impact of microscopic orbital periosteum invasion in orbital preservation surgery

Objective: The orbital periosteum is considered to be a barrier to tumor spread; however, it is difficult to evaluate microscopic tumor spread during surgery. This study aimed to assess the impact of pathological status in orbital preservation surgery. Methods: We retrospectively analyzed the 3-year local control rate and treatment outcomes of patients with malignant tumors invading the orbit who were treated between 2006 and 2012. Results: In total, 27 patients were reviewed over a median follow-up period of 36 months. Pathologically, 19 had carcinomas and 8 had sarcomas. Treatment was by orbital exenteration in 6 patients and orbital preservation surgery in 21 patients. After orbital preservation surgery, poorer 3-year local control rates were significantly associated with positive surgical margins (negative vs. positive: 91% vs. 41%, P = 0.040) and microscopic orbital periosteum invasion (negative vs. positive: 90% vs. 39%, P = 0.010). These factors were independent risk factors in multivariate analysis. The locations of the positive margin were most common at the horizontal and vertical margins of the orbital periosteum and the posterior margin of the orbital apex. Moreover, in 24% of patients, invasion evaluation by preoperative imaging study was underestimated compared with postoperative microscopic evaluation. Conclusions: The positive surgical margin and microscopic orbital periosteum invasion were the risk factors of orbital recurrence. It is difficult to determine the indications for orbital preservation surgery by preoperative imaging studies because of the unpredictable accurate pathological status before surgery and the limitations of preoperative imaging evaluation.