Prospective Registration Study for Establishing Minimal Clinically Important Differences in Patients Undergoing Surgery for Spinal Metastases
Authors: Hirota Ryosuke , Oshigiri Tsutomu , Iesato Noriyuki , Emori Makoto , Teramoto Atsushi , Shiratani Yuki , Suzuki Akinobu , Terai Hidetomi , Shimizu Takaki , Kakutani Kenichiro , Kanda Yutaro , Tominaga Hiroyuki , Kawamura Ichiro , Ishihara Masayuki , Paku Masaaki , Takahashi Yohei , Funayama Toru , Miura Kousei , Shirasawa Eiki , Inoue Hirokazu , Kimura Atsushi , Iimura Takuya , Moridaira Hiroshi , Nakajima Hideaki , Watanabe Shuji , Akeda Koji , Takegami Norihiko , Nakanishi Kazuo , Sawada Hirokatsu , Matsumoto Koji , Funaba Masahiro , Suzuki Hidenori , Funao Haruki , Hirai Takashi , Otsuki Bungo , Kobayakawa Kazu , Uotani Koji , Manabe Hiroaki , Tanishima Shinji , Hashimoto Ko , Iwai Chizuo , Yamabe Daisuke , Hiyama Akihiko , Seki Shoji , Goto Yuta , Miyazaki Masashi , Watanabe Kazuyuki , Nakamae Toshio , Kaito Takashi , Nakashima Hiroaki , Nagoshi Narihito , Kato Satoshi , Imagama Shiro , Watanabe Kota , Inoue Gen , Furuya Takeo 
Published: June 2024

Study Design.
Multicenter, prospective registry study.

Objective.
To clarify minimal clinically important differences (MCIDs) for surgical interventions for spinal metastases, thereby enhancing patient care by integrating quality of life assessments with clinical outcomes.

Background.
Despite its proven usefulness in degenerative spinal diseases and deformities, the MCID remains unexplored regarding surgery for spinal metastases.

Patients and Methods.
This study included 171 (out of 413) patients from the multicenter “Prospective Registration Study on Surgery for Metastatic Spinal Tumors” by the Japan Association of Spine Surgeons. These were evaluated preoperatively and at 6 months postoperatively using the Face Scale, EuroQol-5 Dimensions-5 Levels (EQ-5D-5L), including the Visual Analog Scale, and performance status. The MCIDs were calculated using an anchor-based method, classifying participants into the improved, unchanged, and deteriorated groups based on the Face Scale scores. Focusing on the improved and unchanged groups, the change in the EQ-5D-5L values from before to after treatment was analyzed, and the cutoff value with the highest sensitivity and specificity was determined as the MCID through receiver operating characteristic curve analysis. The validity of the MCIDs was evaluated using a distribution-based calculation method for patient-reported outcomes.

Results.
The improved, unchanged, and deteriorated groups comprised 121, 28, and 22 participants, respectively. The anchor-based MCIDs for the EQ-5D-5L index, EQ-Visual Analog Scale, and domains of mobility, self-care, usual activities, pain/discomfort, and anxiety/depression were 0.21, 15.50, 1.50, 0.50, 0.50, 0.50, and 0.50, respectively; the corresponding distribution-based MCIDs were 0.17, 15,99, 0.77, 0.80, 0.78, 0.60, and 0.70, respectively.

Conclusion.
We identified MCIDs for surgical treatment of spinal metastases, providing benchmarks for future clinical research. By retrospectively examining whether the MCIDs are achieved, factors favoring their achievement and risks affecting them can be explored. This could aid in decisions on surgical candidacy and patient counseling.

Level of Evidence.
II.