Assessment of oxidative stress markers was perfomed in prostate cancer (PCa) patients subjected to high-dose brachytherapy (HDR) with external beam radiotherapy (EBRT). Sixty men with PCa were subjected to combined two-fraction treatment with HDR (tot. 20 Gy) and EBRT (46 Gy). Blood samples were taken before treatment, immediately afterwards, after 1.5–3 months, and approx. 2 years. Control group consisted of 30 healthy men. Erythrocyte glutathione peroxidase activity in the patients was lower than in healthy subjects by 34% (
Prostate cancer (PCa) is among the most frequently diagnosed malignancies in men [
The source of many diseases, including tumours, lies in an increased generation of reactive oxygen species (ROS) resulting in an oxidative stress. States of prostatic hyperplasia and enlargement are often concomitant with inflammation accompanied by increased generation of ROS, reactive nitrogen species (RNS), and oxidizing halogen derivatives [
In search of effective methods of PCa therapy, oncology centres introduce their own therapeutic procedures. These may affect the ongoing cellular oxidation-reduction processes in different ways. There are very few reports on oxidative stress in the circulating blood of PCa patients undergoing HDR-BT combined with EBRT. The aim of this study was to assess the activity of SOD, CAT, and GPx, as well as the concentration of the thiobarbituric acid reactive substances (TBARS) as products of lipid peroxidation in the blood of PCa patients subjected to HDR-BT combined with EBRT. We also aimed to determine the direct effect of radiotherapy on oxidative stress levels and compare the results obtained in the patients with those of the control group composed of healthy men with no malignancies.
The study included 60 men aged 53–80 with prostate cancer limited to prostate gland (T1ABCN0M0, T2ABCN0M0Gx, and T1ABCN0M0Gx), treated at the Department of Oncology and Brachytherapy, Collegium Medicum of Nicolaus Copernicus University, Toruń, Poland (Franciszek Łukaszczyk Oncology Center in Bydgoszcz, Poland). The patients were administered a combined treatment employing two-fraction interstitial HDR brachytherapy and radiation with external beams.
The study was authorized by Collegium Medicum Bioethical Committee of Nicolaus Copernicus University (No. KB/605/2007). The patients provided their written informed consent to participate in the scientific study. They were treated according to the adopted procedures. Characteristics of the examined cohort are presented in Table
Patient characteristics.
Mean | SD | |
---|---|---|
Age (years) | 67.4 | 7.41 |
PSA (ng/mL) | 11.12 | 7.25 |
Gleason score | 5.67 | 1.37 |
TNM | 1.66 | 0.63 |
Haemoglobin (g/dL) | 13.63 | 1.3 |
HDR-BT was applied in two fractions, before and after external beam radiation. The volume and stadium of the tumour were preliminarily assessed, which permitted us to appropriately plan the positioning of needle drivers, so that radiation would cover the entire prostate gland and its sheath. BT was administered to the patients under lumbar anaesthesia and in gynaecological position, by inserting TRUS-controlled needle driver into prostate gland. Subsequently, a moving radiation source with iridium 192 was attached using a perforated template with multiple holes, delivering a dose of 10 Gy. During the entire surgery, lasting for approx. 2 hours, two dosimeters recorded radiation levels in the urethra and anus. The patients had also a Foley catheter inserted into the bladder prior to the surgery and removed on the following day. Postoperative hospitalization lasted 2 days and was followed by 4-field technique of external beam radiation (23 sessions delivering a total dose of 46 Gy) for 4-5 weeks. EBRT therapy was then followed by another BT administration, which increased the final delivered dose to 66 Gy (biological dose of 90 Gy).
Blood was taken for analysis from the patients’ basilic vein four times: on the day of admittance to the ward prior to therapy administration, immediately after therapy administration, after 1.5–3 months of the end of therapy and finally after approx. 2 years (during follow-up visits). Ten patients participated in the last analysis. The control group members had their blood taken once, following the same procedure as in the patients.
SOD activity was determined using a method based on enzymatic inhibition of adrenaline autoxidation to adrenochrome in basic medium [
TBARS concentration was determined using a method based on coloured complexes formed by the products of lipid peroxidation and thiobarbituric acid at 100°C in acidic medium [
Statistical analysis was conducted using the ANOVA (analysis of variance) method (
No statistically significant differences were found by comparing SOD and CAT activity in the erythrocytes of PCa patients before brachytherapy with that of the control group or by comparing SOD and CAT activity in the patients at different times of analysis (Table
Markers of oxidative stress in blood of prostate cancer patients and in control group.
Control | Patients | ||||
---|---|---|---|---|---|
Before therapy | After radiotherapy | ||||
Immediately | 1.5–3 months | 2 years | |||
SOD (U/g Hb) |
|
|
|
|
|
CAT (104 IU/g Hb) |
|
|
|
|
|
GPx (U/g Hb) |
|
8.1** ± 3.9 | 6.1** ± 3.1 | 8.5*a ± 4.2 | 4.8** ± 1.9 |
TBARSeryth. (nmol MDA/g Hb) |
|
43.0** ± 19.7 | 38.5* ± 19.7 | 41.0** ± 16.3 |
|
TBARSplasma (10−2 nmol MDA/mL) |
|
44.6** ± 19.7 | 45.7** ± 19.7 | 43.2** ± 16.3 | 46.4* ± 15.6 |
SOD: superoxide dismutase; CAT: catalase; GPx: glutathione peroxidase; TBARSs: thiobarbituric acid reactive substances.
Data expressed as mean
a
GPx activity in the erythrocytes of PCa patients prior to therapy administration was lower by approx. 34% (
TBARS concentration in the erythrocytes of PCa patients was significantly higher at all times of analysis than that in the control group, with the exception of lipid peroxidation product levels 2 years after treatment (Table
Statistically significant correlation coefficients between measured parameters.
Group | Parameters |
|
---|---|---|
Control | ||
CAT/TBARSplasma | −0.37* | |
CAT/TBARSeryth. | 0.39* | |
SOD/GPx | 0.44* | |
SOD/TBARSeryth. | 0.37* | |
GPx/TBARSeryth. | 0.49** | |
| ||
Patients | ||
Before therapy | SOD/TBARSplasma | 0.39** |
GPx/TBARSeryth. | −0.30* | |
TNM/TBARSeryth. | -0.30* | |
Gleason score/GPx | 0.27* | |
Age/ASA class | 0.27* | |
Gleason score/TBARSeryth. | −0.33* | |
Hb/TBARSeryth. | −0.31* | |
Leukocyte count/TBARSeryth. | −0.32* | |
Immediately after radiotherapy | SOD/TBARSeryth. | 0.45** |
1.5–3 months after | CAT/TBARSplasma | −0.37* |
2 years after radiotherapy | CAT/TBARSplasma | −0.67* |
*
SOD: superoxide dismutase; CAT: catalase; GPx: glutathione peroxidase; TBARSs: thiobarbituric acid reactive substances, ASA: American Society of Anesthesiologists score.
TBARS concentrations in blood plasma and erythrocytes of prostate cancer patients before treatment were found to be higher than that in the control group, which indicates a disturbance in the oxidant-antioxidant balance induced by this tumour, as well as intensification of lipid peroxidation processes. The presence of oxidative stress in PCa patients has been confirmed in other studies, which, similarly to our study, report higher TBARS concentrations in blood plasma [
After radiotherapy, no changes in erythrocyte SOD and CAT activity, as well as plasma and erythrocyte TBARS concentrations were found. After approx. 2 years of radiotherapy conclusion, CAT activity in patients’ blood decreased in a statistically insignificant way and reached values similar to those of the control group. Erythrocyte TBARS concentration was also similar to that of the control group, which may indicate a tendency to normalize the oxidation-reduction processes at the systemic level. However, plasma TBARS concentration did not decrease, which proves that a complete restoration of oxidant-antioxidant balance has not been obtained. Two years may not be a sufficient period for the oxidation-reduction processes to reach correct parameters. The results of prostatic HDR-BT combined with EBRT are probably more long lasting. It has been demonstrated that, as opposed to surgical treatment, radiation requires several to 20 months for PSA concentration to decrease, while normalization may often be observed as late as 2-3 years after treatment [
Conversely, the results obtained immediately after treatment may indicate a lack of significant effect of HDR-BT combined with EBRT on oxidant-antioxidant processes in PCa patients. Increased ROS generation induced by radiation may only occur in neoplastically transformed tissues not analysed in this study, while local processes may not be sufficiently intense to manifest systemically as statistically significant changes in the determined markers.
The results confirm that in the course of PCa, imbalance of oxidant-antioxidant processes occurs. HDR-BT combined with EBRT and used in PCa treatment limited to prostate gland did not induce changes in the levels of oxidative stress markers at the systemic level, which may prove its applicability in assessing oxidation-reduction processes in the treatment of patients with tumour at this stadium. A tendency to normalize oxidation-reduction processes after 2 years of therapy conclusion is visible, although this is too a short period to restore the oxidant-antioxidant balance.
The authors declare that they have no conflict of interests.