Long-Term Outcomes of Subtotal Resection for Large Vestibular Schwannomas: Results From the Acoustic Neuroma Subtotal Resection Study—Part II- Tumor Regrowth

BACKGROUND AND OBJECTIVES: Subtotal resection (STR) of large vestibular schwannomas (VS) may achieve better facial nerve outcomes. However, this approach, involving less-than-total tumor removal, may also increase the risk of regrowth. The objective was to examine differences in the regrowth rate based on the extent of resection in patients with large VS. METHODS: A multicenter, prospective, nonrandomized cohort study was conducted on patients with large VS (≥2.5 cm) who underwent gross total resection (GTR), near-total resection (NTR), or STR. GTR was defined as no visible remnant, NTR as a remnant <0.5 cm3 on postoperative MRI or 5 × 5 × 2 mm during surgery, and STR as any larger remnant. A Cox proportional hazard model assessed the risk of tumor regrowth. RESULTS: Among 126 patients (mean follow-up: 60 ± 31 months; mean tumor diameter: 3.3 ± 0.7 cm), 35 underwent GTR, 39 NTR, and 52 STR. Tumor regrowth occurred in 22 cases (17%). STR patients (27%) had a 3-fold higher regrowth risk compared with GTR patients (8%) (P = .02). The median regrowth time for STR (24 months) was significantly shorter than for NTR or GTR (48 months, P = .03). A greater residual tumor volume percentage (TV%) was associated with regrowth (hazard ratio 1.73, 95% CI, 1.07-2.81, P = .02). A residual tumor volume of 0.7 cm3 and a TV% of 12% were identified as optimal cutoff points for predicting regrowth in NTR. CONCLUSION: STR is associated with a significantly higher likelihood of tumor regrowth. The percentage of the residual tumor remnant is positively correlated with the risk of regrowth. A residual tumor volume of 0.7 cm3 and a TV% of 12% were identified as optimal cutoffs for NTR. When feasible, GTR or NTR should be attempted to minimize the chances of tumor regrowth.