Reducing biochemical recurrence rates in EBRT-treated prostate cancer patients: the influence of dose and dose per fraction

External beam radiotherapy for prostate cancer: What are the current research trends and hotspots?

Background

The external beam radiotherapy (EBRT) applied for prostate cancer (PCa) has been one of the most important and hottest research fields over recent decades. This study aimed to explore the research hotspots of EBRT in PCa and help the researchers have a clear and intuitive reference basis for later researches.

Methods

The literature scientometric analysis related to “EBRT applied for PCa” was conducted via the Web of Science Core Collection from 2010 to 2019. The Microsoft Office Excel 2019 and CiteSpace V. 5.7.R1 software were introduced for visualizing and analyzing the data.

Results

A total of 7860 relevant papers were extracted and downloaded. A total of 7828 papers were extracted and analyzed after data cleansing by CiteSpace. The tendency of published papers was comprehensively increasing from 2010 to 2019. Among all 73 countries/regions, USA published the most papers, accounting for 39%, which was the most active contributor with most publications. Australia (Centrality: 0.18), England (Centrality: 0.12) were cooperating most cohesively with other countries. Univ Toronto was the most productive institute (229), while Harvard Univ (Centrality: 0.67) had extensive collaborations with other institutes. The International journal of Radiation Oncology Biology Physics had the largest number of publications and the highest number of co‐citations. Briganti A had the largest volume of publications. D'Amico AV had the highest number of co‐citations. Four latest and largest clusters were identified as oligometastases, salvage therapy (SRT), prostate‐specific membrane antigen (PSMA), and hypofractionation. Thirteen references became strongest burst citations lasting until 2019. The studies of “oligometastases,” “SRT,” “PSMA,” “hypofractionation,” “postoperative radiotherapy,” and “dose and fraction regimen changes” were prevailing in the recent years.

Conclusion

The “oligometastases,” “SRT,” “PSMA,” “hypofractionation,” “postoperative radiotherapy,” and “dose and fraction regimen changes” may be the state‐of‐art research frontiers, and related studies will advance in this field over time.

Optimization of treatment planning parameters used in tomotherapy for prostate cancer patients

BACKGROUND AND PURPOSE

Tomotherapy treatment planning depends on parameters that are not used conventionally such as: field width (FW), pitch factor (PF) and modulation factor (MF). The aim of this study is to analyze the relationship between these parameters and their influence on the quality of treatment plans and beam-on time.

MATERIAL AND METHODS

Ten prostate cancer patients were included in the study. For each patient, two cases of irradiation were considered depending on the target volume: PTV1 included the prostate gland, seminal vesicles, pelvic lymph nodes and a 1 cm margin, whereas PTV2 included only the prostate gland with a 1 cm margin. For each patient and each case of irradiation (PTV1 and PTV2) 8 treatment plans were created - all consisted of a different combination of planning parameters (FW = 1.05, 2.5, 5 cm; PF = 0.107, 0.215, 0.43; MF = 1.5, 2.5, 3.5). Default values used in this study were FW = 2.5 cm, PF = 0.215 and MF = 2.5. Hence, for plans with different FWs, parameters of PF and MF were 0.215 and 2.5, respectively; for different PFs, FW and MF were 2.5 and 2.5, respectively; finally for different MFs, FW and PF were 2.5 and 0.215, respectively. The reference plan was optimized for FW = 1.05 cm, PF = 0.107 and MF = 3.5, which was assumed to result in the best dose distribution and the longest treatment time. As a result, 160 plans were created. Each plan was analyzed for dose distribution and execution time.

RESULTS AND CONCLUSION

: Treatment plans with FW of 5 cm resulted in the shortest execution time compromising the dose distribution. Moreover, the dose fall off in the longitudinal direction was not sharp. FW of 1.05 cm and PF of 0.107 were not recommended for routine prostate plans due to long execution time, which was 3 times longer than for plans with FW = 5 cm. There was no substantial decrease of irradiation time when PF was increased from 0.215 to 0.43 for both cases (PTV1 and PTV2); however, the dose distribution was slightly compromised. Finally, decreasing MF from 2.5 to 1.5 was useless because it did not change the beam-on time; however, it did remarkably decrease the dose distribution. Nevertheless, increasing MF up to 3.5 could be considered. The lowest EUD for the rectum and intestines, could be observed for PF = 0.107. For the other plans the differences were rather small (the EUD was almost the same). By reducing PF from 0.43 to 0.107 or FW from 5 to 1.05 the EUD for bladder (in PTV1 case) decreased by 3.13% and 2.60%. When PTV2 was a target volume, the EUD for bladder decreased by 4.54% and 3.43% when FW was changed from 5 to 1.05 and MF from 1.5 to 3.5, respectively. For optimal balance between beam-on time and dose distribution in OARs for routine patients, the authors would suggest to use: FW = 2.5, PF = 0.215 and MF = 2.5.

The tissue plasminogen activator gene promoter: a novel tool for radiogenic gene therapy of the prostate?

BACKGROUND

Radiation therapy is a treatment modality routinely used in cancer management so it is not unexpected that radiation-inducible promoters have emerged as an attractive tool for controlled gene therapy. The human tissue plasminogen activator gene promoter (t-PA) has been proposed as a candidate for radiogenic gene therapy, but has not been exploited to date. The purpose of this study was to evaluate the potential of this promoter to drive the expression of a reporter gene, the green fluorescent protein (GFP), in response to radiation exposure.

METHODS

To investigate whether the promoter could be used for prostate cancer gene therapy, we initially transfected normal and malignant prostate cells. We then transfected HMEC-1 endothelial cells and ex vivo rat tail artery and monitored GFP levels using Western blotting following the delivery of single doses of ionizing radiation (2, 4, 6 Gy) to test whether the promoter could be used for vascular targeted gene therapy.

RESULTS

The t-PA promoter induced GFP expression up to 6-fold in all cell types tested in response to radiation doses within the clinical range.

CONCLUSIONS

These results suggest that the t-PA promoter may be incorporated into gene therapy strategies driving therapeutic transgenes in conjunction with radiation therapy.