Background: Conditional survival is a measure of prognosis for patients who have already survived for a specific period of time; however, data on conditional survival after sacrectomy in patients with sacral chordoma are lacking. In addition, because sacral tumors are rare and heterogeneous, classifying them in a way that allows physicians to predict functional outcomes after sacrectomy remains a challenge.
Questions/purposes: (1) What is the overall survival and disease-free survival in patients treated by sacrectomy for chordoma? (2) What is the conditional survival probability and how do prognostic factors change over time in patients undergoing surgical resection for sacral chordoma? (3) What is the local recurrence rate after surgery, how was it treated, and what factors impact on local recurrence? (4) What is the postoperative motor, sensory, bowel, and bladder function by level of resection as determined by using a newly designed scoring method?
Methods: Between 2003 and 2012, our center treated 122 patients surgically for sacral chordoma. Of those, two died and five were lost before a minimum followup of 1 year was achieved, leaving 115 patients available for analysis in this retrospective study at a mean of 4.9 years (range, 1.3-10.8 years). Basically, single posterior or combined approaches were chosen based on the most cephalad extent of the tumor and resection level was normally at half or one sacral vertebrae above the tumor. The 5-year conditional survival rate was calculated based on Kaplan-Meier survival analysis. The effect of prognostic factors on conditional survival was also explored. A newly designed score method was proposed and adopted in the current study to critically evaluate the functional outcome after resection of the sacrum. Inter- and intraobserver reliability was tested by a preliminary study using kappa statistics and Spearman rank correlation coefficients. Significant interobserver (p < 0.01) and intraobserver agreement (κ > 0.75) were found in nine items between each observer.
Results: The estimated 5-year overall survival rate was 81% (95% confidence interval [CI], 72%-90%) at diagnosis. The 5-year disease-free survival rate was 52% (95% CI, 43%-63%). The 5-year conditional overall survival decreased with each additional year in the first 4 years (81% at diagnosis versus 60% at the fourth year, p < 0.0001) and increased slightly in the fifth year. Patients with adequate surgical margins displayed a higher 5-year survival than those with an inadequate margin (86% [95% CI, 76%-95%] versus 67% [95% CI, 48%-85%], p = 0.01) at diagnosis. Conditional survival estimates for patients who received operations elsewhere were lower than that of newly diagnosed patients treated by us at diagnosis (64% [95% CI, 46%-83%] versus 90% [95% CI, 82%-99%], p = 0.012), but with the numbers we had, we could not detect a difference in conditional survival between those treated elsewhere first compared with those initially treated by us at 5 years. The proposed score system for function evaluation was able to distinguish different levels of resection. The overall functional results for the preservation of bilateral S1, S2, and S3 were 40 ± 8%, 60 ± 12%, and 82 ± 11%, respectively. Patients who had preservation of only one S3 nerve root had more severe incontinence (1.99 ± 0.79 versus 2.60 ± 0.63, p = 0.01) and more sensory loss (1.88 ± 0.82 versus 2.31 ± 0.59, p = 0.02) than those patients with preservation of bilateral S3 nerve roots.
Conclusions: The 5-year conditional survival for sacral chordoma decreased with each additional year and began to improve after the fourth year. In addition, the effect of the surgical margin and influence of previous surgery on conditional survival were not linear over time. The level of nerve root resections corresponded with the overall function scores according to the proposed scoring method. This information and scoring system should be valuable in discussing outcomes of sacrectomy in patients with chordoma who are considering this operation and serve as the basis for further study.
Level of evidence: Level III, therapeutic study.