Patient characteristics
We collected a total of 202 cases in this retrospective study, including 148 males and 54 females, with a mean age of 56.3 (median 56, range 25-89) years old. Of the 202 patients, 155 had primary OSCC in our department, and the remaining 47 had recurrent lesions after surgical treatment in other medical institutions. The mean follow-up period was 13.62 (median 10, range 1 to 56) months. The clinical parameters of all 202 patients are shown in Table 1.
Relationship between preoperative plasma DD, FIB, and PLT levels and clinicopathologic parameters
Of the 202 patients, preoperative FIB and PLT levels were closely related to each other (r=0.376, P=0.000); however, the preoperative DD level and preoperative FIB and PLT levels were not significantly related (P=0.053 and 0.636, respectively).
Preoperative plasma DD, FIB, and PLT levels and clinicopathologic parameters, including age, sex, tumour location, TNM staging, surgical treatment and duration, are summarized in Table 2. The mean preoperative DD level was 499.45 μg/L, and referring to the manufacturer’s recommendation, a plasma DD level of 500 μg/L was set as the cut-off value for normal and high DD values. The mean preoperative FIB and PLT levels were 3.33 g/L and 259.5*10^9/L, respectively, and were set as cut-off values for low and high FIB and PLT values, respectively. In this study, we found that the preoperative DD level in different sex or age groups of patients was not statistically different (P=0.187 and 0.062, respectively); however, in different tumour sites and in different T stage, N stage, and clinical stage patients, the preoperative DD level was significantly different (P=0.040, 0.000, 0.001 and 0000, respectively). However, with regard to preoperative FIB and PLT levels, we found different results: the preoperative FIB level was different based on sex and N stage category only (P=0.025 and 0.002, respectively), and the preoperative PLT level was different based on tumour site and clinical stage category only (P=0.048 and 0.040, respectively).
The means of DD, FIB and PLT in patients with primary oral cancer were 424.96 μg/L, 3.49 g/L and 249.11*10^9/L, respectively, and those in patients with recurrent tumours were 752.07 μg/L, 3.82 g/L and 283.72*10^9/L, respectively. The difference in DD and FIB levels between primary and recurrent cancer was statistically significant (P=0.018 and 0.038, respectively) (Figure 1).
Relationship between postoperative DD change and treatment-related parameters
We retrospectively observed postoperative DD levels in the first 3 days after surgery and in 96 patients with postoperative DD results. The postoperative DD level was elevated in all 96 patients on the first day after surgery and slowly decreased with time. The elevated level was correlated with the preoperative DD level (r=0.284, P=0.005) as well as the surgical type (r=0.344, P=0.001) but not the duration of surgery (P=0.244) (Table 3).
Survival analysis of patients with primary OSCC
According to the NCCN guidelines and patient desire, 155 patients with primary OSCC were prescribed to different surgical plans including 1) excision of the primary lesion (19.4%); 2) excision of the primary lesion and neck dissection (25%); 3) excision of the primary lesion and vascularized free flap transplantation (0.9%); 4) excision of the primary lesion, neck dissection and vascularized free flap transplantation (51.9%); and 5) unoperated (2.8%). Of the 155 patients with primary oral cancer, recurrence was diagnosed in 33 patients after surgical treatment in our department, rated 21.29%, and 26 of them died during the follow-up time. The time from surgery to disease progression ranged from 1 to 34 months. Univariate analyses revealed that N stage (P=0.003) and preoperative DD level (P=0.033) were predictors of PFS. In multivariate analysis, only N stage was found to be an independent prognostic factor in patients with primary OSCC (P=0.007) (Table 4, Figure 2).
In our study, PFS was 78.7%. Patients with normal preoperative DD (<500 μg/L) had a significantly better PFS than patients with high preoperative DD (≥500 μg/L) (81.7% vs. 74.2%, P=0.027).
The data that support the findings of this study are available from the corresponding author upon reasonable request.