Interstitial Low Dose Rate Brachytherapy for Prostate Cancer — A Focus on Intermediate- and High-risk Disease

An open-source genetic algorithm for determining optimal seed distributions for low-dose-rate prostate brachytherapy

PURPOSE

An open source optimizer that generates seed distributions for low-dose-rate prostate brachytherapy was designed, tested, and validated.

METHODS

The optimizer was a simple genetic algorithm (SGA) that, given a set of prostate and urethra contours, determines the optimal seed distribution in terms of coverage of the prostate with the prescribed dose while avoiding hotspots within the urethra. The algorithm was validated in a retrospective study on 45 previously contoured low-dose-rate prostate brachytherapy patients. Dosimetric indices were evaluated to ensure solutions adhered to clinical standards. The SGA performance was further benchmarked by comparing solutions obtained from a commercial optimizer (inverse planning simulated annealing [IPSA]) with the same cohort of 45 patients.

RESULTS

Clinically acceptable target coverage by the prescribed dose (V100) was obtained for both SGA and IPSA, with a mean ± standard deviation of 98 ± 2% and 99.5 ± 0.5%, respectively. For the prostate D90, SGA and IPSA yielded 177 ± 8 Gy and 186 ± 7 Gy, respectively, which were both clinically acceptable. Both algorithms yielded reasonable dose to the rectum, with V100 < 0.3 cc. A reduction in dose to the urethra was seen using SGA. SGA solutions showed a slight prostate volume dependence, with smaller prostates (<25 cc) yielding less desirable, although still clinically viable, dosimetric outcomes. SGA plans used, on average, fewer needles than IPSA (21 vs. 24, respectively), which may lead to a reduction in urinary toxicity and edema that alters post-implant dosimetry.

CONCLUSIONS

An open source SGA was validated that provides a research tool for the brachytherapy community.

MRI-based sector analysis enhances prostate palladium-103 brachytherapy quality assurance in a phase II prospective trial of men with intermediate-risk localized prostate cancer

PURPOSE

Palladium-103 ((103)Pd) may be superior to other isotopes in brachytherapy for localized intermediate-risk prostate cancer because of its relatively short half-life, higher initial dose rate, and greater dose heterogeneity within the target volume; these properties also underscore the need for accurate target delineation and postimplant quality assurance. We assessed the use of prostate sector analysis based on MRI for quality assurance after (103)Pd monotherapy.

METHODS AND MATERIALS

Fifty men with intermediate-risk prostate cancer underwent (103)Pd monotherapy in a prospective phase II trial at MD Anderson Cancer Center. Dosimetric analyses on day 30 after the implant were done using both CT and fused CT/MRI scans. Dosimetric variables were assessed for the entire prostate and for each of three or six sectors. Volumes and dosimetric variables were compared with paired t tests.

RESULTS

Postimplant dosimetric variables for the entire prostate were significantly different on CT vs. CT/MRI (p = 0.019 for V100 and p < 0.01 for D90). Prostate volumes were smaller on the CT/MRI scans (p < 0.00001). The base sector contributed the greatest difference, with doses based on CT/MRI lower than those based on CT (p < 0.01 for V100 and D90). To date, these lower base doses have not affected biochemical outcomes for patients with disease in prostate base biopsy samples.

CONCLUSIONS

CT/MRI is more precise than CT for prostate volume delineation and dosimetric quality assessment and thus provides superior heterogeneity control assessment after (103)Pd monotherapy implants.

Prostate cancer, androgen deprivation therapy, obesity, the metabolic syndrome, type 2 diabetes, and cardiovascular disease: a review

Prostate cancer is the most frequently diagnosed malignancy among UK men and accounts for 12% of male deaths. Androgen deprivation therapy (ADT) is commonly used as part of the treatment for prostate cancer. It is effective at suppressing prostate-specific antigen, stabilizing disease, alleviating symptoms in advanced disease, and potentially prolonging survival. However ADT, presumably at least in part owing to low testosterone levels is associated with insulin resistance, the development of metabolic syndrome plus increased overall and cardiovascular disease mortality. We have reviewed the relationship between prostate cancer, ADT, metabolic syndrome, type 2 diabetes, and cardiovascular disease. We have not reviewed other potential medical problems such as osteoporosis. We suggest that there should be a baseline assessment of patients' risk for cardiovascular disease before starting ADT. Consideration should be given to starting appropriate therapies including lifestyle advice, antihypertensive and lipid-lowering agents, insulin sensitizer, plus possibly aspirin. Having started ADT, the patients should have a regular (possibly annual) assessment of their cardiovascular risk factors.

Low-dose rate brachytherapy for men with localized prostate cancer

BACKGROUND

Localized prostate cancer is a slow growing tumor for many years for the majority of affected men. Low-dose rate brachytherapy (LDR-BT) is short-distance radiotherapy using low-energy radioactive sources. LDR-BT has been recommended for men with low risk localized prostate cancer.

OBJECTIVES

To assess the benefit and harm of LDR-BT compared to radical prostatectomy (RP), external beam radiotherapy (EBRT), and no primary therapy (NPT) in men with localized prostatic cancer.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1950), and EMBASE (from 1980) were searched in June 2010 as well as online trials registers and reference lists of reviews.

SELECTION CRITERIA

Randomized, controlled trials comparing LDR-BT versus RP, EBRT, and NPT in men with clinically localized prostate cancer.

DATA COLLECTION AND ANALYSIS

Data on study methods, participants, treatment regimens, observation period and outcomes were recorded by two reviewers independently.

MAIN RESULTS

We identified only one RCT (N = 200; mean follow up 68 months). This trial compared LDR-BT and RP. The risk of bias was deemed high. Primary outcomes (overall survival, cause-specific mortality, or metastatic-free survival) were not reported. Biochemical recurrence-free survival at 5 years follow up was not significantly different between LDR-BT (78/85 (91.8%)) and RP (81/89 (91.0%)); P = 0.875; relative risk 0.92 (95% CI: 0.35 to 2.42).For severe adverse events reported at 6 months follow up, results favored LDR-BT for urinary incontinence (LDR-BT 0/85 (0.0%) versus RP 16/89 (18.0%); P < 0.001; relative risk 0) and favored RP for urinary irritation (LDR-BT 68/85 (80.0%) versus RP 4/89 (4.5%); P < 0.001; relative risk 17.80, 95% CI 6.79 to 46.66). The occurrence of urinary stricture did not significantly differ between the treatment groups (LDR-BT 2/85 (2.4%) versus RP 6/89 (6.7%); P = 0.221; relative risk 0.35, 95% CI: 0.07 to 1.68). Long-term information was not available.We did not identify significant differences of mean scores between treatment groups for patient-reported outcomes function and bother as well as generic health-related quality of life.

AUTHORS' CONCLUSIONS

Low-dose rate brachytherapy did not reduce biochemical recurrence-free survival versus radical prostatectomy at 5 years. For short-term severe adverse events, low-dose rate brachytherapy was significantly more favorable for urinary incontinence, but radical prostatectomy was significantly more favorable for urinary irritation. Evidence is based on one RCT with high risk of bias.

Three-Dimensional Prostate Mapping Biopsy Has a Potentially Significant Impact on Prostate Cancer Management

Purpose

To compare a new staging, three-dimensional prostate mapping biopsy (3D-PMB) method with traditional transrectal ultrasound (TRUS) biopsy and assess its possible impact on patient management.

Patients and Methods

One hundred eighty patients with unilateral cancer on TRUS biopsy, who were considering conservative management, underwent restaging with 3D-PMB. The 3D-PMB was carried out transperineally using a brachytherapy grid under TRUS guidance. Biopsies were taken every 5 mm throughout the volume of the prostate, and labeling of the specimen coordinates allowed accurate reconstruction of the location and extent of a patient's cancer.

Results

3D-PMB obtained a median of 50 cores (standard deviation, ± 20.61). One hundred ten patients (61.1%) were positive bilaterally, and 41 patients (22.7%) had Gleason scores increased to 7 or higher. Thirty-six patients had negative results on 3D-PMB. Complications of 3D-PMB were self-limited and included 14 patients (7.7%) who required short-term indwelling catheter drainage and two patients with hematuria, one of whom required overnight bladder irrigation.

Conclusion

3D-PMB is a transperineal biopsy that can be safely used to accurately stage prostate cancer patients. At the present time, when patient management is increasingly based on the extent and characteristics of prostate cancer, 3D-PMB could have a profound effect on patient management.

High dose rate brachytherapy in combination with external beam radiotherapy in the radical treatment of prostate cancer: initial results of a randomised phase three trial

BACKGROUND AND PURPOSE

A randomised phase III trial has compared external beam radiotherapy alone with a dose escalated schedule using high dose rate brachytherapy. Patients with histologically confirmed prostate cancer, no evidence of metastases, a PSA <50, no previous TURP and fit for general anaesthetic were included.

METHODS

Patients were randomised to receive either standard radiotherapy 55 Gy in 20 fractions treating Monday to Friday over 4 weeks or a combined schedule comprising external beam treatment delivering 35.75 Gy in 13 fractions treating daily Monday to Friday over 2.5 weeks followed by a temporary high dose rate afterloading implant delivering 17 Gy in two fractions over 24h.

RESULTS

A total of 220 patients were randomised, balanced for important prognostic parameters including tumour stage, presenting PSA, Gleason score and use of adjuvant anti-androgens. With a median follow up of 30 months (range 3-91) a significant improvement in actuarial biochemical relapse-free survival is seen in favour of the combined brachytherapy schedule (p=0.03). A lower incidence of acute rectal discharge was seen in the brachytherapy group (p=0.025) and other acute and late toxicities were equivalent. Patients randomised to brachytherapy had a significantly better FACT-P score at 12 weeks (p=0.02).

CONCLUSIONS

The use of high dose rate brachytherapy in combination with external beam radiotherapy resulted in an improved biochemical relapse-free survival compared to external beam radiotherapy alone with less acute rectal toxicity and improved quality of life in this randomised trial.