Development of Late Toxicity and International Prostate Symptom Score Resolution After External-Beam Radiotherapy Combined With Pulsed Dose Rate Brachytherapy for Prostate Cancer

Multisource Rotating Shield Brachytherapy Apparatus for Prostate Cancer

PURPOSE

Our purpose is to present a novel multisource rotating shield brachytherapy (RSBT) apparatus for the simultaneous precise angular and linear positioning of partially shielded ¹⁵³Gd brachytherapy sources in interstitial needles for the treatment of locally advanced prostate cancer. It is designed to lower the dose to nearby healthy tissues, the urethra in particular, relative to conventional high-dose-rate brachytherapy techniques.

METHODS AND MATERIALS

Following needle implantation through the patient template, an angular drive mechanism is docked to the patient template. Each needle is coupled to a multisource afterloader catheter by a connector passing through a shaft. The shafts are rotated about their axes by translating a moving template between 2 stationary templates. The shafts' surfaces and moving template holes are helically threaded with the same pattern such that translation of the moving template causes simultaneous rotation of the shafts. The rotation of each shaft is mechanically transmitted to the catheter-source-shield combination, inside the needles, via several key-keyway pairs. The catheter angles are simultaneously incremented throughout treatment, and only a single 360° rotation of all catheters is needed for a full treatment. For each rotation angle, source depth in each needle is controlled by a multisource afterloader, which is proposed as an array of belt-driven linear actuators, each of which drives a wire that controls catheter depth in a needle.

RESULTS

Treatment plans demonstrated that RSBT with the proposed apparatus reduced urethral D_0.1cm³ (the minimum dose delivered to the hottest 0.1cm³ of the urethra) below that of conventional high-dose-rate brachytherapy by 31% for urethral dose gradient volume within 3 mm of the urethra surface. Treatment time to deliver 20 Gy with the proposed multisource RSBT apparatus by use of nineteen 62.4-GBq ¹⁵³Gd sources was 122 minutes.

CONCLUSIONS

The proposed RSBT delivery apparatus enables a mechanically feasible urethra-sparing treatment technique for prostate cancer in a clinically reasonable time frame.

Urinary quality of life outcomes in men who were treated with image-guided intensity-modulated radiation therapy for prostate cancer

PURPOSE

Quality of life (QoL) outcomes play a major role in the treatment selection for prostate cancer (CaP). We evaluated the urinary QoL outcomes in men who were treated with image-guided intensity-modulated radiation therapy (IG-IMRT) for CaP.

METHODS AND MATERIALS

We enrolled men who were diagnosed with CaP and underwent IG-IMRT in a large urological group practice into a prospectively maintained database. The typical radiation treatment dosage to prostates and seminal vesicles was 8100 cGy in 45 fractions. Urinary QoL was self-assessed using the standardized incontinence grade and International Prostate Symptom Score (IPSS) at baseline and at each follow-up visit. We evaluated the cumulative incidence of urinary incontinence and changes in both continence and IPSS over time.

RESULTS

Of the 3602 men who were eligible for analysis, 3086 (85.7%) had no urinary incontinence; 479 (13.3 %) had minimal incontinence (no requirement for pads), and 37 (1.0 %) had significant urinary incontinence that required the use of pads or interfered with activities of daily living, at baseline. After a median follow-up of 24 months (range: 12.0-41.0 months), these numbers were 80.6%, 17.4%, and 2.0%, respectively. Radiation therapy appeared to have a beneficial effect on some men: 54.1% of men with minimal incontinence became completely continent of urine during follow-up. Of those with significant urinary incontinence, 29.7% reported resolution and 27.0% reported improved symptoms with no requirement for pads. Of the 1276 men with moderate IPSS, the mean IPSS decreased from 12 to 9.8 at the time of the last follow-up (P < .001). Similarly, of the 233 men with severe IPSS, the mean IPSS decreased from 24 to 13 at the time of the last follow-up (P < .001).

CONCLUSION

IG-IMRT for clinically localized CaP is associated with a relatively low incidence of urinary incontinence. Although unexplained, IG-IMRT seems to improve symptoms in some men with baseline urinary incontinence and moderate-to-severe IPSS.

A review of the clinical experience in pulsed dose rate brachytherapy

Pulsed dose rate (PDR) brachytherapy is a treatment modality that combines physical advantages of high dose rate (HDR) brachytherapy with the radiobiological advantages of low dose rate brachytherapy. The aim of this review was to describe the effective clinical use of PDR brachytherapy worldwide in different tumour locations. We found 66 articles reporting on clinical PDR brachytherapy including the treatment procedure and outcome. Moreover, PDR brachytherapy has been applied in almost all tumour sites for which brachytherapy is indicated and with good local control and low toxicity. The main advantage of PDR is, because of the small pulse sizes used, the ability to spare normal tissue. In certain cases, HDR resembles PDR brachytherapy by the use of multifractionated low-fraction dose.

Prostate volume and implant configuration during 48 hours of temporary prostate brachytherapy: limited effect of oedema

BACKGROUND

In pulsed-dose rate prostate brachytherapy the dose is delivered during 48 hours after implantation, making the treatment sensitive to oedematic effects possibly affecting dose delivery. The aim was to study changes in prostate volume during treatment by analysing catheter configurations on three subsequent scans.

METHODS

Prostate expansion was determined for 19 patients from the change in spatial distribution of the implanted catheters, using three CT-scans: a planning CT (CT1) and two CTs after 24 and 48 hours (CT2, CT3). An additional 4 patients only received one repeat CT (after 24 hours). The mean radial distance (MRD) of all dwell positions to the geometric centre of all dwell positions used was calculated to evaluate volume changes. From three implanted markers changes in inter-marker distances were assessed. The relative shifts of all dwell positions were determined using catheter- and marker-based registrations. Wilcoxon signed-rank tests were performed to compare the results from the different time points.

RESULTS

The MRDs measured on the two repeat CTs were significantly different from CT1. The mean prostate volume change derived from the difference in MRD was +4.3% (range -9.3% to +15.6%) for CT1-CT2 (p < .05) and +4.4% (range -7.5% to +16.3%) for CT1-CT3 (p < .05). These values represented a mean increase of 1.2 cm(3) in the first 24 hours and 1.5 cm(3) in the subsequent 24 hours. There was no clear sign of prostate expansion from the change in inter-marker distance (CT1-CT2: 0.2 ± 1.8 mm; CT1-CT3: 0.6 ± 2.2 mm). Catheter configuration remained stable; shifts in catheter positions were largest in the C-C direction: 0 ± 1.8 mm for CT1-CT2 and 0 ± 1.4 mm for CT2-CT3.

CONCLUSIONS

The volume changes derived from catheter displacements were small and therefore considered clinically insignificant. Implant configuration remains stable during 2 days of treatment, confirming the safety of this technique.

Focal radiotherapy as focal therapy of prostate cancer

PURPOSE OF REVIEW

Focal radiotherapy treatment procedures play an increasingly important role in function-preservation and organ-preservation treatment techniques. As an alternative to traditional whole-gland radiotherapy regimes, focal prostate radiotherapy may be of benefit for both primary tumor as well as locally recurrent disease. This is a review of the current literature on the topic, including patient selection, preliminary toxicity, and outcome data as well as a technical overview on treatment delivery techniques.

RECENT FINDINGS

Partial organ treatment in early prostate cancer (PCa) is now technically feasible with both newer external-beam and brachytherapy technology. To date, only small and generally monoinstitutional series have been published in the literature. Early feasibility and toxicity data are encouraging, and demonstrate potential advantages for the role of focal brachytherapy in early PCa. Although some advanced external-beam techniques can also be used to deliver focal therapy within the prostate, there is no relevant publication in the literature.

SUMMARY

Radiotherapy, especially interventional radiotherapy (brachytherapy), is a technically feasible treatment technique to deliver focal radiotherapy for PCa. To date, only preliminary results are available for all forms of interventional radiotherapy (high dose rate, low dose rate, and pulsed dose rate) for focal PCa treatment and no large cohort comparative results are published. As interventional radiotherapy (brachytherapy) as yet lacks any such long-term studies, comparative outcome data are not available to suggest differences in efficacy for one form of brachytherapy or another.