Dosimetric analysis of testicular doses in prostate intensity-modulated and volumetric-modulated arc radiation therapy at different energy levels

The Effect of Prostate Cancer Radiotherapy on Testosterone Level: A Systematic Review and Meta-analysis

INTRODUCTION

In the current study, a systematic search and meta-analysis were performed to evaluate the effect of prostate cancer radiotherapy on testosterone levels of patients.

METHODS

To illuminate the effect of radiotherapy on the testosterone level of prostate cancer patients, a systematic search was conducted in accordance with the PRISMA guideline in electronic databases of Scopus, Embase, PubMed, Web of Science, and clinical trials up to December 2018 using relevant keywords. Based on a certain set of inclusion and exclusion criteria, 12 eligible studies that had data on the testosterone level following prostate cancer radiotherapy were included in the meta-analysis.

RESULTS

According to the various techniques of prostate cancer radiotherapy, the dose values scattered to the testicular tissues ranged from 0.31 to 10 Gy. Combining the findings from 12 studies, it was found that prostate cancer radiotherapy leads to a significant reduction in the testosterone level (Weighted Mean Difference [WMD]: -51.38 ng/dL, 95% CI: -75.86, -26.90, I2=0.0%, P<0.05). Furthermore, subgroup analysis by the patient number showed a significant reduction in the testosterone level at patient number < 50 (WMD: -80.32 ng/dL, 95% CI: -125.10, -35.55, I2= 0.0%) and 50 < patient number < 100 (WMD: -46.99 ng/dL, 95% CI: - 87.15, -6.82, I2= 0.0%). Subgroup analysis based on treatment technique type revealed a significant reduction in testosterone level after conventional radiotherapy (WMD: -56.67, 95% CI: -100.45,-12.88, I2= 34.3%) and IMRT/SBRT technique (WMD: -57.42, 95% CI: -99.39, -15.46, I2= 0.0%) in comparison with the proton therapy (WMD: 0.00, 95% CI: -80.24, 80.24).

CONCLUSION

The findings showed a significant decrease in the testosterone level of prostate cancer patients after radiotherapy compared with pre-treatment levels.

Optimal tumor coverage with different beam energies by IMRT, VMAT and TOMO: Effects on patients with proximal gastric cancer

To compare the effects of different photon energies on radiation planning by intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and helical tomotherapy (TOMO) for proximal gastric cancer (PGC). Network analysis with microarray procession and gene ontology were used to identify the effect of radiotherapy (RT) on PGC. Then, we retrospectively analyzed 8 PGC patients after receiving irradiation with a prescribed dose of 50.4 Gy. The Pinnacle treatment planning system (TPS, V9.8) was used to generate IMRT and VMAT plans by using 6 or 10 MV. TOMO plans were calculated on the Tomotherapy Planning Station Hi-Art Version 4.2.3 workstation (Tomotherapy Incorporated, Madison, WI, USA). PGC is associated with high DNA repair ability. TOMO plan results in higher tumor coverage and a better conformity index than IMRT and VMAT. 10-MV VMAT yields better dosimetric quality of the gradient index than 6-MV VMAT (P = .012). TOMO was associated with a lower irradiation dose in the mean dose to the right kidney (P = .049), left kidney and heart than 6-MV IMRT and 6-MV VMAT. 6-MV IMRT plan presented a higher dose of lung Dmean (P = .017) than 10-MV IMRT. Additionally, VMAT, using a planning energy of 6 MV, was associated with a significantly higher left kidney Dmean (P = .018) and V10 (P = .036) than a planning energy of 10 MV. TOMO is a better RT plan not only for tumor coverage but also for sparing organs at risk. IMRT and VMAT plans with 10 MV beams are more suitable than 6 MV beams for PGC treatment.

Incidental testicular doses during volumetric-modulated arc radiotherapy in prostate cancer patients

PURPOSE

To compare the incidental testicular doses during volumetric-modulated arc therapy (VMAT) in patients receiving prostate-only and pelvic lymphatic irradiation.

MATERIALS AND METHODS

Testicular doses in 40 intermediate- and high-risk prostate cancer patients were determined on treatment planning system (TPS) using the VMAT technique at 6 MV. Scattered testicular doses were also measured by MOSFET detectors placed on testis surface. The testicular doses of patients treated with prostate-only and pelvic field irradiation were compared.

RESULTS

The median testicular doses measured per 200 cGy fraction by TPS and MOSFET detectors were 1.7 cGy (0.7-4.1 cGy) and 4.8 cGy (3.6-8.8 cGy), respectively. The TPS doses and MOSFET readings showed a significant strong correlation (Pearson r = 0.848, p < 0.001). The testicular doses measured by TPS (1.34 ± 0.36 cGy vs. 2.60 ± 0.95 cGy; p < 0.001) and MOSFET (4.52 ± 0.64 cGy vs. 6.56 ± 1.23 cGy; p < 0.001) were significantly lower in patients with prostate-only irradiation than in those with pelvic field irradiation. The mean cumulative scattered dose for prostate-only field delivering 78 Gy was 1.8 Gy and that for pelvic field irradiation was 2.6 Gy, consistent with the reported findings.

CONCLUSIONS

The patients with prostate-only irradiation received lower testicular doses than those with additional pelvic field irradiation possibly due to the increased scattered doses in large field irradiation using the VMAT technique. The clinical response to increased incidental testicular doses due to pelvic field irradiation remains unknown, and it warrants further investigation.

A systematic review of radiation-induced testicular toxicities following radiotherapy for prostate cancer

BACKGROUND

Prostate cancer is the second most common malignancy in men in the world, and radiotherapy is used as a standard treatment modality for this cancer. Although this treatment modality effectively kills prostate cancerous cells, it unavoidably irradiates the organs/tissues that are away from the treatment site. In this regard, radiation-induced testicular toxicities following prostate radiotherapy can affect sexual function, reproduction, and quality of life in cancer survivors. This review summarizes the available data on testicular exposure to radiation during prostate radiotherapy and the consequences on testicular function.

METHODS

To illuminate the radiation-induced testicular toxicities following prostate radiotherapy, a systematic search was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline in PubMed, Web of Science, Scopus, Embase, and clinical trials electronic databases up to September 2018. According to a set of prespecified inclusion and exclusion criteria, 31 eligible articles providing data on testicular function following radiotherapy in patients with prostate cancer were included in the study.

RESULTS

According to the different radiotherapeutic techniques used for prostate cancer treatment, the total tumor dose and scattered testicular dose values were ranging from 36.25 to 78.00 Gy and 0.06 to 6.48 Gy, respectively. Luteinizing hormone and follicle-stimulating hormone levels after prostate radiotherapy were significantly higher in comparison with the pretreatment levels. Around 60% of the studies showed that testosterone levels after prostate radiotherapy were significantly lower than the pretreatment levels. Furthermore, erectile dysfunction (ED), as an adverse side effect resulting from prostate radiotherapy, was reported and this complication is significantly correlated with lower satisfaction with sexual life. Testicular atrophy following prostate radiotherapy has also been observed and its frequency in patients with prior prostate radiotherapy is 2.5 times more than that in the patients without prior radiotherapy.

CONCLUSION

The data revealed that the scattered dose to testicular tissues during prostate radiotherapy can lead to testicular atrophy, variation of the male sex hormones, and quality of sexual life.