Modelling second malignancy risks from low dose rate and high dose rate brachytherapy as monotherapy for localised prostate cancer

Normal Tissue Integral Dose as a Result of Prostate Radiation Therapy: A Quantitative Comparison Between High-Dose-Rate Brachytherapy and Modern External Beam Radiation Therapy Techniques

Purpose

Quantification of integral radiation dose delivered during treatment for prostate cancer is lacking. We performed a comparative quantification of dose to nontarget body tissues delivered via 4 common radiation techniques: conventional volumetric modulated arc therapy, stereotactic body radiation therapy, pencil-beam scanning proton therapy, and high-dose-rate brachytherapy.

Methods and Materials

Plans for each radiation technique were generated for 10 patients with typical anatomy. For brachytherapy plans, virtual needles were placed to achieve standard dosimetry. Standard planning target volume margins or robustness margins were applied as appropriate. A "normal tissue" structure (entire computed tomography simulation volume minus planning target volume) was generated for integral dose computation. Dose-volume histogram parameters for targets and normal structures were tabulated. Normal tissue integral dose was calculated by multiplying normal tissue volume by mean dose.

Results

Normal tissue integral dose was lowest for brachytherapy. Pencil-beam scanning protons, stereotactic body radiation therapy, and brachytherapy resulted in 17%, 57%, and 91% absolute reductions compared with standard volumetric modulated arc therapy, respectively. Mean nontarget tissues receiving 25%, 50%, and 75% of the prescription dose were reduced by 85%, 76%, and 83% for brachytherapy relative to volumetric modulated arc therapy, by 79%, 64%, and 74% relative to stereotactic body radiation therapy, and 73%, 60%, and 81% relative to proton therapy. All reductions observed using brachytherapy were statistically significant.

Conclusions

High-dose-rate brachytherapy is an effective technique for reducing dose to nontarget body tissues relative to volumetric modulated arc therapy, stereotactic body radiation therapy, and pencil-beam scanning proton therapy.

GEC-ESTRO ACROP prostate brachytherapy guidelines

This is an evidence-based guideline for prostate brachytherapy. Throughout levels of evidence quoted are those from the Oxford Centre for Evidence based Medicine (https://www.cebm.ox.ac.uk/resources/levels-of-evidence/oxford-centre-for-evidence-based-medicine-levels-of-evidence-march-2009). Prostate interstitial brachytherapy using either permanent or temporary implantation is an established and evolving treatment technique for non-metastatic prostate cancer. Permanent brachytherapy uses Low Dose Rate (LDR) sources, most commonly I-125, emitting photon radiation over months. Temporary brachytherapy involves first placing catheters within the prostate and, on confirmation of accurate positioning, temporarily introducing the radioactive source, generally High Dose Rate (HDR) radioactive sources of Ir-192 or less commonly Co-60. Pulsed dose rate (PDR) brachytherapy has also been used for prostate cancer [1] but few centres have adopted this approach. Previous GEC ESTRO recommendations have considered LDR and HDR separately [2-4] but as there is considerable overlap, this paper provides updated guidance for both treatment techniques. Prostate brachytherapy allows safe radiation dose escalation beyond that achieved using external beam radiotherapy alone as it has greater conformity around the prostate, sparing surrounding rectum, bladder, and penile bulb. In addition there are fewer issues with changes in prostate position during treatment delivery. Systematic review and randomised trials using both techniques as boost treatments demonstrate improved PSA control when compared to external beam radiotherapy alone [5-7].

Radioactive Iodine-125 in Tumor Therapy: Advances and Future Directions

Radioactive iodine-125 (I-125) is the most widely used radioactive sealed source for interstitial permanent brachytherapy (BT). BT has the exceptional ability to deliver extremely high doses that external beam radiotherapy (EBRT) could never achieve within treated lesions, with the added benefit that doses drop off rapidly outside the target lesion by minimizing the exposure of uninvolved surrounding normal tissue. Spurred by multiple biological and technological advances, BT application has experienced substantial alteration over the past few decades. The procedure of I-125 radioactive seed implantation evolved from ultrasound guidance to computed tomography guidance. Compellingly, the creative introduction of 3D-printed individual templates, BT treatment planning systems, and artificial intelligence navigator systems remarkably increased the accuracy of I-125 BT and individualized I-125 ablative radiotherapy. Of note, utilizing I-125 to treat carcinoma in hollow cavity organs was enabled by the utility of self-expandable metal stents (SEMSs). Initially, I-125 BT was only used in the treatment of rare tumors. However, an increasing number of clinical trials upheld the efficacy and safety of I-125 BT in almost all tumors. Therefore, this study aims to summarize the recent advances of I-125 BT in cancer therapy, which cover experimental research to clinical investigations, including the development of novel techniques. This review also raises unanswered questions that may prompt future clinical trials and experimental work.

Efficacy of Surgical Excision and Brachytherapy in the Treatment of Keloids: A Retrospective Cohort Study

OBJECTIVE

To demonstrate the efficacy of a protocol combining surgical excision and high-dose-rate brachytherapy for treatment of keloids.

METHODS

The authors performed a unicentric retrospective cohort study between 2013 and 2018. The minimum follow-up was 12 months. All patients treated for keloids at the authors' institution were included. Extralesional excision was performed with placement of a brachytherapy sheath under the skin. The total dose of irradiation was 18 Gy. The postoperative results were evaluated for aesthetic and functional outcomes with a validated scale, as well as the presence or absence of recurrence.

RESULTS

Fifteen patients were lost to follow-up. Thirty-eight patients with 67 keloids were included. The control rate was 94%. The aesthetic and functional outcomes were considered good in 62% of cases. The main limitation of the study was the small patient population.

CONCLUSIONS

Extralesional excision combined with postoperative high-dose-rate brachytherapy seems to be one of the most effective invasive protocols to treat and prevent keloids.

High prevalence of secondary bladder cancer in men on radiotherapy for prostate cancer: evidence from a meta-analysis

Objective

To assess whether radiotherapy (RT) for prostate cancer (PCa) was a risk factor for secondary bladder cancer (BLCa) through a meta-analysis.

Materials and methods

The MEDLINE, Embase, and the Cochrane Library were systematically searched for all studies investigating the risk of BLCa in patients with RT. The association between RT and risk of BLCa was summarized using hazard ratio with a 95%CI. The protocol for this meta-analysis is available from PROSPERO (CRD42018090075).

Results

Overall, 619,479 participants (age: 57-79 years) were included from 15 studies, 206,852 of whom were patients who received RT. Synthesis of results indicated that RT was significantly associated with an increased risk of BLCa compared with the risk in those who received radical prostatectomy or non-RT (overall HR=1.6, 95%CI: 1.33-1.92, P<0.001). The results were consistent when restricted to a 5-year lag period (HR=1.84, 95%CI: 1.26-2.69, P=0.002) and multivariable adjustment (HR=1.96, 95%CI: 1.47-2.62, P<0.001), but not for 10-year lag period (HR=1.93, 95%CI: 0.9- 4.16, P=0.093) and brachytherapy subgroup (HR=1.33, 95%CI: 0.87-2.05, P=0.188). The GRADE-profiler revealed that the rate of events of BLCa on average in the RT-patients and the non-RT control was 2,462/183,669 (1.3%) and 4,263/382,761(1.1%), respectively; the overall quality of the evidence was low.

Conclusion

Patients who received RT for PCa was associated with higher risks of developing secondary BLCa compared to those unexposed to RT, but the absolute effect was low.

Low dose rate prostate brachytherapy

Low dose rate (LDR) prostate brachytherapy is an evidence based radiation technique with excellent oncologic outcomes. By utilizing direct image guidance for radioactive source placement, LDR brachytherapy provides superior radiation dose escalation and conformality compared to external beam radiation therapy (EBRT). With this level of precision, late grade 3 or 4 genitourinary or gastrointestinal toxicity rates are typically between 1% and 4%. Furthermore, when performed as a same day surgical procedure, this technique provides a cost effective and convenient strategy. A large body of literature with robust follow-up has led multiple expert consensus groups to endorse the use of LDR brachytherapy as an appropriate management option for all risk groups of non-metastatic prostate cancer. LDR brachytherapy is often effective when delivered as a monotherapy, although for some patients with intermediate or high-risk disease, optimal outcome are achieved in combination with supplemental EBRT and/or androgen deprivation therapy (ADT). In addition to reviewing technical aspects and reported clinical outcomes of LDR prostate brachytherapy, this article will focus on the considerations related to appropriate patient selection and other aspects of its use in the treatment of prostate cancer.