3. Results
3.1. Baseline characteristics of the patient sample
Between February 1, 2009, and February 1, 2017, 130 patients were
included, with 99 patients in the very low-risk group and 31 patients in
the low-risk group, according to the CHIC-HS criteria. Totally, there
were 26 and 104 patients included in the US and NC groups, respectively.
All patients received adjuvant chemotherapy postoperatively.
The baseline demographic and clinical characteristics before and after
PSM are shown in Table 2. Before PSM, there were no significant
differences in sex and serum AFP levels between the NC and US groups
(p =0.21 and p =0.437, respectively), but SMD was 0.264 for
sex and 0.189 for serum AFP levels. The mean age of the patients was
higher in the US group than in the NC group, although the difference was
not significant (702±533 vs. 561±525, mean±standard deviation,p =0.098, SMD=0.269). In contrast, the distribution of PRETEXT
stages differed significantly between the groups (p =0.001,
SMD=0.849). After PSM, all SMD values were <0.2. In the NC and
US groups, the mean age was 528.0±324.8 days and 603.7±522.1 days,
respectively (p =0.851), with 50% male participants in each group
(p =1). The distribution of PRETEXT stage and serum AFP levels was
similar between the groups (p =0.655 and p =0.806,
respectively). Overall, patient characteristics were similar for all
variables included in PS matching.
3.2. Association between NACT, surgical outcomes, and pathological
findings
Postoperative pathological results are shown in Table 3. A positive
surgical margin was observed in three (13.6%) and six (27.3%) patients
in the US and NC groups, respectively. There was no significant
difference between the groups (p =0.268). There were significant
differences in pathological classification between the groups
(p =0.031). The pathological classification in the NC and US
groups was pure fetal histology (PFH) in five (22.7%) and two (9.1%)
patients, epithelial mixed embryonal/fetal (EMEF) in nine (40.9%) and
16 (72.7%) patients, mixed epithelial-mesenchymal (MEM) in eight
(36.4%) and two (9.1%) patients, and small cell undifferentiated (SCU)
in zero (0%) and two (9.1%) patients, respectively. The number of EMEF
cases was significantly higher in the NC group than in the US group.
3.3. Patient outcomes
The median follow-up period was 64 months (95% confidence interval
[CI]: 58.2–65.5): US group, 62.18 months (interquartile range
[IQR]: 60–69) and NC group, 68.82 months (IQR: 60–75.75).
In the US group, the 5-year EFS
and OS were 81.8% (95% CI: 60.9–93.3) and 86.3% (95% CI: 65.8–96),
respectively. Events occurred in four (16.7%) patients, all of whom
experienced an event <14 months after surgery (Table S1). One
patient with EMEF pathology died during chemotherapy from sepsis, two
SCU patients and one patient with EMEF pathology experienced recurrence,
and the lesion in one patient with SCU recurred as a hepatic sarcoma.
Three patients underwent a second surgery after relapse, and the tumors
were resected. The patient with EMEF pathology survived, and the two SCU
patients died due to progression of lung metastases.
In the NC group, the 5-year EFS and OS were 81.8% (95% CI: 60.9–93.3)
and 90.9% (95% CI: 71.0–98.7), respectively. Events occurred in four
(16.7%) patients, all of whom experienced an event <9 months
after surgery (Table S1). One patient with EMEF pathology died due to
multiple organ failure, and three patients with MEM pathology developed
recurrence and underwent a second surgery; one patient died of hepatic
metastases, and two patients had long-term survival after surgery.
No significant difference was
observed between the groups in terms of EFS and OS (p =0.964 andp =0.655, respectively) (Fig. 1).
Our analysis of the putative risk
factors of interest showed that resection margin status, PRETEXT stages,
age, sex, and AFP levels were not associated with death or events,
but that pathological
classification was significantly associated (p =0.007 and p=0.032,
respectively). However, no events occurred in patients with PFH
pathology, and they survived until the last follow-up, whereas all SCU
patients died, and the sample size was thus underpowered to calculate
odds ratios and conduct further analyses.