Radiat Oncol J.  2018 Jun;36(2):114-121. 10.3857/roj.2018.00031.

Maximum diameter versus volumetric assessment for the response evaluation of vestibular schwannomas receiving stereotactic radiotherapy

• Choi Y
• Kim S
• Kwak DW
• Lee HS
• Kang MK
• Lee DK
• Hur WJ

• KMID: 2418871
• DOI: http://doi.org/10.3857/roj.2018.00031

Abstract

PURPOSE
To explore the feasibility of maximum diameter as a response assessment method for vestibular schwannomas (VS) after stereotactic radiosurgery or fractionated stereotactic radiotherapy (RT), we analyzed the concordance of RT responses between maximum diameters and volumetric measurements.
MATERIALS AND METHODS
Forty-two patients receiving curative stereotactic radiosurgery or fractionated stereotactic RT for VS were analyzed retrospectively. Twelve patients were excluded: 4 did not receive follow-up magnetic resonance imaging (MRI) scans and 8 had initial MRI scans with a slice thickness >3 mm. The maximum diameter, tumor volume (TV), and enhanced tumor volume (ETV) were measured in each MRI study. The percent change after RT was evaluated according to the measurement methods and their concordances were calculated with the Pearson correlation. The response classifications were determined by the assessment modalities, and their agreement was analyzed with Cohen kappa statistics.
RESULTS
Median follow-up was 31.0 months (range, 3.5 to 86.5 months), and 90 follow-up MRI studies were analyzed. The percent change of maximum diameter correlated strongly with TV and ETV (r(p) = 0.85, 0.63, p = 0.000, respectively). Concordance of responses between the Response Evaluation Criteria in Solid Tumors (RECIST) using the maximum diameters and either TV or ETV were moderate (kappa = 0.58; 95% confidence interval, 0.32-0.85) or fair (kappa = 0.32; 95% confidence interval, 0.05-0.59), respectively.
CONCLUSION
The percent changes in maximum diameter and the responses in RECIST were significantly concordant with those in the volumetric measurements. Therefore, the maximum diameters can be used for the response evaluation of VS following stereotactic RT.

Keyword

Vestibular schwannoma; Radiotherapy; Response Evaluation Criteria in Solid Tumors (RECIST)

MeSH Terms

Classification
Follow-Up Studies
Humans
Magnetic Resonance Imaging
Methods
Neuroma, Acoustic*
Radiosurgery
Radiotherapy*
Response Evaluation Criteria in Solid Tumors
Retrospective Studies
Tumor Burden