Predictive Factors of Pseudoprogression in Vestibular Schwannoma Treated with Fractionated Stereotactic Radiotherapy

Full Article

AWS Lo, SF Nyaw, WH Mui, JJ Huang, KM Kam, CS Wong

Hong Kong J Radiol 2019;22:152-9

Objective: Fractionated stereotactic radiotherapy (FSRT) is a well-established treatment for vestibular schwannoma (VS). Tumour pseudoprogression may lead to worsening symptoms leading to the necessity of urgent salvage surgery. This study aimed to assess the predictive factors of pseudoprogression and treatment related toxicities in VS treated with FSRT.
Methods: This retrospective cohort study included all patients with VS treated with FSRT between 1999 and 2015. Risk factors assessed included sex, age, previous surgical resection, tumour diameter, gross tumour volume, planning target volume, overall treatment time, equivalent dose in 2-Gy fractions, and the presence of brainstem or cerebellar compression prior to radiotherapy. Fisher’s exact test and two-sample t test were used for statistical analysis.
Results: Eighteen patients were included. The median follow-up time was 80.3 months. The overall disease control rate after FSRT was 94.4%. Of the 18 patients, one (5.6%) developed local tumour progression, seven (38.9%) underwent tumour pseudoprogression; and 10 (55.6%) had stable disease. Median time to tumour pseudoprogression was 8.63 months (range, 4.5-13.1 months). Tumours with pseudoprogression and those with at least stable disease had a mean diameter of 2.7 cm and 2.1 cm, respectively (p = 0.18). The mean treatment planning target volume in the pseudoprogression group was larger than that in the non-progression group with volume measured (22.2 cc vs. 10.0 cc; p = 0.04). Patients with brainstem or cerebellar compression observed on magnetic resonance imaging before radiotherapy were associated with a higher risk of pseudoprogression (p = 0.0498). The overall salvage surgery rate was 17.7%.
Conclusion: Upfront surgery may be more desirable than FSRT for those surgically fit patients with considerable treatment volume and evidence of mass effect. Large prospective studies are needed to confirm our findings and to identify further predictive factors for pseudoprogression.


Author affiliation(s):
AWS Lo: Department of Clinical Oncology, Prince of Wales Hospital, Shatin, Hong Kong
SF Nyaw, WH Mui, JJ Huang, CS Wong: Department of Clinical Oncology, Tuen Mun Hospital, Tuen Mun, Hong Kong
KM Kam: Comprehensive Oncology Centre, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong







方法:本回顧性隊列研究納入1999年至2015年期間接受FSRT治療的所有VS患者。評估的危險因素包括性別、年齡、手術切除史、腫瘤直徑、腫瘤總體積、計劃靶體積、總體治療時間、2 Gy分次的等效劑量,以及放療前腦幹或小腦是否受壓。使用Fisher精確檢驗和雙樣本t檢驗作統計分析。
結果:納入18名患者。中位隨訪時間為80.3個月。FSRT後的總體疾病控制率為94.4%。18名患者中,1例(5.6%)出現局部腫瘤進展惡化,7例(38.9%)出現腫瘤假性進展;10例(55.6%)病情穩定。腫瘤假性進展的中位時間為8.63個月(4.5至13.1個月)。具有假性進展的腫瘤和至少疾病穩定的腫瘤平均直徑分別為2.7 cm和2.1 cm(p = 0.18)。假性進展組的平均治療計劃靶體積大於非進展組的體積(22.2 cc比10.0 cc;p = 0.04)。在放療前通過磁共振成像觀察到腦幹或小腦受壓的患者與假性進展的風險較高相關(p = 0.0498)。整個搶救手術率為17.7%。