Patient clinical characteristics
Of the 104 women with recurrent EOC, 77.9% had advanced stage (III or IV), 76.9% had high-grade disease, and57.7%hadthrombocytosisat the time of diagnosis. The median age was 53 years (range 37–81 years) and the mean platelet level was299.8000 /µl (range 108,000-545,000 cells/µl) at diagnosis.
Relationship Between Clinicopathological Parameters And Pretreatment Plasma D-dimer/fibrinogen/platelet Levels
Plasma D-dimer and fibrinogen levels pretreatment were above the normal value in 29(27.9%) and 90(86.5%) patients, respectively. The incidence of thrombocytosis was 57.7% (60 /104).Here we found that elevated platelet levels were significantly associated with FIGO stage (P = 0.021) and histological type was associated with elevated plasma D-dimer levels (P = 0.016), but not with other clinicopathological parameters. (Table 1)
Table 1
Relationship between clinicopathological parameters and different levels of plasma D-dimer, fibrinogen and platelet count in104 patients with recurrent EOC
| | Platelet count 1000cells/µl | | PlasmaFibrinogen g/l | | Plasma D-dimer mg/l | |
Variable | n | ≤ 300 | > 300 | P | 2–4 | > 4 | P | ≤ 0.3 | > 0.3 | P |
Age, y | | | | 0.340 | | | 0.386 | | | 0.566 |
≤55 | 39 | 28 | 21 | | 27 | 12 | | 5 | 34 | |
> 55 | 65 | 26 | 39 | | 48 | 17 | | 9 | 56 | |
Stage | | | | 0.335 | | | 0.473 | | | > 0.05 |
I or and II | 23 | 11 | 12 | | 16 | 7 | | 4 | 19 | |
III or and IV | 81 | 33 | 48 | | 59 | 22 | | 10 | 71 | |
Histological type | | | | 0.432 | | | 0.016 | | | 0.402 |
Serous | 64 | 28 | 36 | | 41 | 23 | | 6 | 58 | |
Non serous | 40 | 16 | 24 | | 34 | 6 | | 8 | 32 | |
Grade | | | | 0.021 | | | 0.273 | | | > 0.05 |
Low | 24 | 15 | 9 | | 19 | 5 | | 4 | 20 | |
High | 80 | 29 | 51 | | 56 | 24 | | 10 | 70 | |
Postoperative residual disease | | | | 0.069 | | | 0.514 | | | 0.402 |
Microscopic | 66 | 32 | 34 | | 48 | 18 | | 8 | 58 | |
Macroscopic | 38 | 12 | 26 | | 27 | 11 | | 6 | 32 | |
CI: confidence interval; HR: hazard ratio. |
Factors affecting progression free survival and overall survival: by univariate and multivariate analyses
Of the 104 women with recurrent EOC, pretreatment thrombocytosis was associated with worse median progression free survival (11.6 vs.14.1months, P = 0.003, Fig. 1A) and median overall survival (15.6vs. 21.3months, P = 0.009, Fig. 1B).However, elevated plasma D-dimer and fibrinogen were not confirmed in univariate analysis and multivariate analysis (Table 2 and Table 3). Next we investigated the association between the percentage of reduction of platelet count relative to the pretreatment level and patient survival. Intriguingly, we found that a reduction less than 25% in platelet count post-treatment was associated with poor PFS and OS (P = 0.021, P = 0.009, Fig. 1C and 1D). After adjustment for tumor stage, histological grading, and residual disease after cytoreductive surgery, multivariate analysis rendered decrease of platelets to a cut-off value of less than25% reduction after treatment as an independent, unfavorable prognostic factor for PFS. (Table 2 and Table 3)
Table 2
Univariate and multivariate analysis of prognostic factors in progression free survival
| Univariate analysis | Multivariate analysis |
Variable | HR | 95.0% CI | Pvalue | HR | 95.0% CI | P value |
Age (y) ≤ 55 vs.>55 | 1.351 | 0.903 | -2.020 | 0.143 | - | - | - | - |
Postoperative residual disease Microscopic vs. Macroscopic | 3.637 | 2.376 | -5.566 | 0.000 | 2.761 | 1.752 | -4.351 | 0.000 |
Grade Low vs. High | 2.499 | 1.535 | -4.067 | 0.000 | 1.912 | 1.141 | -3.202 | 0.014 |
Stage I or II vs. III or IV | 2.344 | 1.360 | -4.039 | 0.002 | 1.592 | 0.883 | -2.872 | 0.122 |
Platelet count (1000/µl) ≤ 300 vs. >300 | 1.820 | 1.214 | -2.728 | 0.004 | 1.626 | 1.073 | -2.466 | 0.022 |
Platelet count reduction > 25% vs. ≤25% | 1.594 | 1.068 | -2.378 | 0.023 | 1.651 | 1.100 | -2.478 | 0.015 |
Plasma fibrinogen(g/l) 2–4 vs. >4 | 0.914 | 0.592 | -1.411 | 0.685 | - | - | | - |
Plasma D-dimer (mg/l) ≤0.3 vs.>0.3 | 0.894 | 0.507 | -1.574 | 0.697 | - | - | - | - |
CI: confidence interval; HR: hazard ratio. |
Table 3
Univariate and multivariate analysis of prognostic factors in overall survival
| Univariate analysis | Multivariate analysis |
Variable | HR | 95.0% CI | P value | HR | 95.0% CI | P value |
Age (y) ≤ 55 vs.>55 | 1.606 | 0.844 | -3.058 | 0.149 | - | - | - | - |
Postoperativeresidual disease Microscopic vs. Macroscopic | 5.811 | 3.019 | -11.182 | 0.000 | 4.300 | 2.124 | -8.703 | 0.000 |
Grade Low vs. High | 2.695 | 1.225 | -5.928 | 0.014 | 1.714 | 0.733 | -4.004 | 0.214 |
Stage I or II vs. III or IV | 2.972 | 1.195 | -7.393 | 0.019 | 1.799 | 0.656 | -4.930 | 0.254 |
Plateletcount (1000/µl) ≤ 300 vs. >300 | 2.298 | 1.208 | -4.373 | 0.011 | 2.363 | 1.202 | -4.645 | 0.013 |
Platelet count reduction > 25% vs. ≤25% | 2.222 | 1.200 | -4.113 | 0.011 | 2.363 | 1.262 | -4.423 | 0.007 |
Plasmafibrinogen(g/l) 2–4 vs. >4 | 1.092 | 0.573 | -2.083 | 0.789 | - | - | - | - |
Plasma D-dimer (mg/l) ≤0.3 vs.>0.3 | 0.712 | 0.315 | -1.608 | 0.413 | - | - | - | - |
CI: confidence interval; HR: hazard ratio. |
Platelet count and CA125 trends: during treatment and until the clinical diagnosis of recurrence
To consider platelet and CA125 trends, data of 104 patients was recorded through primary diagnosis, primary treatment and until the clinical diagnosis of recurrence. Of the patients with recurrent EOC (n = 104),86.5%patients had a normal platelet count(mean 197,000 cells/µl) after primary therapy ,and mean platelet counts at the diagnosis of recurrence were found to be increased to 227,000 cells/µl compared to that after primary therapy (P = 0.007, Fig. 2A).CA125 is a standard tumor marker followed in ovarian cancer to track the efficacy of primary therapy and in surveillance for recurrence. The mean CA125 level at diagnosis was 1034.8 IU/mL (normal < 35 IU/mL). In contrast, 81.4%had a normal CA125 level at the conclusion of primary therapy with a mean 75.1 IU/mL, and the mean post-treatment CA125 level was 12.8 IU/mL. At the clinical diagnosis of disease recurrence, CA125 was elevated in 80.8% of patients, with a median 323.1 IU/mLcompared to that after treatment (P < 0.001, Fig. 2B).Among patients with a CA125 < 35 IU/mL at the time of recurrence, mean platelet levels at the diagnosis of recurrence were increased to 249.700 cells//µl compared to that (197.100 cells/µl) at the conclusion of primary therapy (P = 0.046).
Normalization of platelet counts post-treatment is associated with disease response to therapy
In the patients with recurrent EOC who experienced a compete response to therapy > 6 months, 56.0% (51/91) had thrombocytosis at diagnosis, and 92.3% (84/91) of these patients had normalized platelet levels by the end of primary therapy. In the treatment resistant cohort (n = 13) who experienced a complete response to primary therapy that was durable for < 6 months, 76.9% (10/13) patients had thrombocytosis at begining of primary therapy. At the end of primary therapy, only 46.2% (6/13) had normalized platelet counts. These data indicate a correlation between the normalization of platelet counts at the end of primary therapy and disease response to therapy (P < 0.001).
Platelets Resistance Against Chemotherapy-induced Apoptosis
Tissue co-culture with platelets demonstrated consistent protection against apoptosis with and without exposure to docetaxel. Platelet activation was evident by the aggregation of platelets within the initial hours of 37℃incubation. Incubation of SKOV3 cells with platelets in serum-free conditions reduced apoptosis 59.9% (p = 0.008). After incorporating docetaxel, incubation of the SKOV-3 cell line with platelets reduced apoptosis by 37.6% (p = 0.0015).(Fig. 3B and 3D)
We next compared the apoptotic rates of different platelet concentrations and tumor cells. To observe these changes in apoptotic rates, ovarian cancer cells were incubated with different concentrations of platelets for 72 hours in a serum free environment with and without docetaxel 5 nM. Incubation of SKOV3 cells with platelets of the dose 0.5 × 108platelets/mL,1 × 108platelets/mL,2 × 108 platelets/mL,4 × 108platelets/mL in serum-free conditions reduced apoptosis by 55.4%(p = 0.01),59.9%(p = 0.008) ,43.9%(p = 0.044),8.3%(p = 0.706), respectively (Fig. 3A and 3C). After incorporating docetaxel, incubation of theSKOV3cellwith platelets of the dose 0.5 × 108platelets/mL,1 × 108 platelets/mL,2 × 108platelets/mL,4 × 108platelets/mL reduced apoptosis by 30.2%(p = 0.03),37.6% (p = 0.015),21.5%(p = 0.098),17.4% (p = 0.26), respectively (Fig. 3B and 3D). These data suggest that platelets have an anti-apoptotic effect on SKOV3 cell, and they suggest that the anti-apoptotic performance of platelets in vitro was comparable at the different seeding density. Since the culture of the SKOV3 cell with platelets incubated with 4 × 108platelets/mL did not reduce a significantly greater number of apoptosis rates than that with 1 × 108platelets/mL, the lower seeding density was preferable.