HSC Section 8_April 2017

T. R. MCRACKAN ET AL.

search terms used included ‘‘facial nerve schwannoma,’’ ‘‘facial nerve neuroma,’’ ‘‘radiotherapy,’’ ‘‘stereotactic radiosurgery,’’ ‘‘stereotactic radiotherapy,’’ ‘‘radiosurgery,’’ ‘‘radiation therapy,’’ ‘‘gamma knife,’’ and ‘‘Cyberknife.’’ In total, 13 articles were iden- tified that discussed SRS for FNSs. In lieu of repeating the data from our institutions prior manuscript, we updated our experience with longer follow-up. Institutional review board approval was obtained from our institution. Inclusion criteria for article selection included English language, treatment of FNS with SRS, follow-up period clearly identified. Two articles (2,10) were removed that described treatment of nonvestibular schwannomas with SRS but did not differentiate outcomes between FNS and other schwannomas (7,8). One article was included without individual patient follow-up periods iden- tified (9). However, the overall follow-up period was similar to the other included studies and thus was kept for analysis. In total, 10 articles were evaluated in addition to our institution data, yielding 53 patients. Hearing data were analyzed only when objective measures were used. Studies that used terms such as ‘‘hearing was stable’’ were not included when the hearing data were not clearly defined. In our analysis, hearing data were reported using the American Academy of Otolaryngology (AAO) acoustic neuroma hearing guidelines (10). FN data were included when the pre-SRS and post- SRS functional status was reported using the House-Brackmann (HB) Scale (11). We defined tumor control as either no change or a decrease in tumor size. Decrease in tumor size was reported as a separate category when studies clearly stated their definition. To make the reporting more uniform, we defined the decrease in tumor size as either 2 mm in linear direction or 20% volume loss in accordance with RECIST criteria 1.1 (12). Although it was not distinctly stated in all of the articles reviewed, all Neurofibro- matosis II patients were removed from analysis when possible.

five (55.6%) used either three dimensions or tumor volume, and one (11.1%) did not report tumor size. Three (33.3%) articles did not report post-SRS hearing data in all patients. All studies discussed FN outcomes; however, two (22.2%) used subjective ‘‘improvement’’ or ‘‘worsened’’ statements rather than the HB score and were not included for FN outcome analysis. The mean follow-up was 42.1 months (range, 12 Y 120 mo). All cases in the literature were deter- mined to be FNS by either involvement of FN segments other than CPA/IAC on magnetic resonance imaging (MRI) or based on intraoperative findings when tumor was ini- tially thought to be an acoustic neuroma. Treatment Data Including our institution’s experience, a total of 53 patients were identified who received SRS for FNS. In looking at the treatment modalities, 45 (84.9%) patients were treated with gamma knife (GK), 4 (7.5%) with LINAC, and 4 (7.5%) with fractionated SRS. Meanmargin radiation doses to the 50% isodose line based on treatment modality were the following: GK, 12.5 Gy (range, 10 Y 16 Gy); LINAC, 36.3 Gy (range, 12 Y 54 Gy); and all fractionated SRS pa- tients received 50.0 Gy administered in 25 fractions (2 Gy per fraction 4 d/wk). There were variable treatment methods used with LINAC. One patient received one single dose at 12 Gy (13). The other three received fractionated ther- apy: 2 Gy per fraction 5 days per week for 50 Gy (14), 1.8 Gy per fraction 5 days per week for 54 Gy (15), and 0.5 Gy 5 days per week for 25 Gy (13). There were minimal data available with regard to cochlear dose. Tumor Control Only patients with 2 years or longer follow-up were in- cluded in the tumor control analysis (n = 45). When defined as no tumor growth or decreased tumor size, 42(93.3%) patients had tumor control with SRS and 3(6.7%) did not (Table 1). According to the guidelines in the Methods sec- tion, 30 patients were evaluated for growth or reduction in tumor size. Of these, 15 (50.0%) showed no growth, 2 (6.7%) showed growth, and 13 (43.3%) were reduced in size after

RESULTS

Published Data Our institution’s previous article on this topic was ex- cluded because we have included updated data for these patients in this article. This left nine articles that met our criteria for inclusion for evaluation. When presenting tumor size, three (33.3%) studies used largest tumor dimension,

TABLE 1. Data extracted from the literature for patients with a minimum of 2-year follow-up

Hearing data in patients with pretreatment serviceable hearing (n = 18)

Study

n SRS type

Facial nerve

Tumor control

Follow-up

Unchanged Hearing worsened Unchanged Improved Worsened Yes

No

1 (50.0%) a

Current

7 GK 1 (50.0%) 1 LINAC n/a 14 GK 5 (100%) 11 GK 2 (66.6%) a

6 (85.7%) 0 (0%) 1 (100%) 0 (0%)

1 (14.3%) 6 (85.7%) 1 (14.3%)

57.1 30.2 31.4 39.5 48.0 30.0 46.7 67.3 62.0 48.0 47.6

Ingrosso et al. (14)

n/a

0 (0%)

1 (100%) 0 (0%) 9 (100%) 0 (0%) 8 (88.9%) 1 (11.1%) 1 (100%) 0 (0%) 2 (100%) 0 (0%) 5 (100%) 0 (0%) 4 (100%) 0 (0%) 1 (100%) 0 (0%)

Kida et al. (16) Litre et al (17)

0 (0%)

5 (55.5%) 4 (44.4%) 0 (0.0%)

1 (33.3%) a

n/a

n/a

n/a

McCelland et al. (15) 1 LINAC n/a

n/a

0 (0%) 1 (50%)

0 (0%) 1 (50%)

1 (100%)

Hillman et al. (13) Madhok et al. (18) Nishioka et al. (19) McRackan et al. (4)

2 LINAC 0 (0%)

2 (100%)

0 (0%)

6 GK 4 F-SRS 1 GK

n/a n/a n/a

n/a n/a n/a

4 (80.0%) 1 (20.0%) 0 (0%)

n/a

n/a

n/a

1 (100%) 0 (0%) 4 (66.6%) 0 (0%)

0 (0%)

6 GK 1 (50.0%) a

1 (50.0%) a 5 (36.7%)

2 (33.3%) 5 (83.3%) 1 (16.7%)

Jacob et al. (9)

Total

45

9 (64.3 %)

22 (68.8%) 6 (18.8%) 4 (12.5%) 42 (93.3%) 3 (6.7%)

a Studies where the topic of interest was reported for only a portion of the cohort. F-SRS indicates fractionation SRS; n/a, data not available.

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