Technology Insight: Combined external-beam radiation therapy and brachytherapy in the management of prostate cancer

The evolution of brachytherapy for prostate cancer

Brachytherapy (BT), using low-dose-rate (LDR) permanent seed implantation or high-dose-rate (HDR) temporary source implantation, is an acceptable treatment option for select patients with prostate cancer of any risk group. The benefits of HDR-BT over LDR-BT include the ability to use the same source for other cancers, lower operator dependence, and - typically - fewer acute irritative symptoms. By contrast, the benefits of LDR-BT include more favourable scheduling logistics, lower initial capital equipment costs, no need for a shielded room, completion in a single implant, and more robust data from clinical trials. Prospective reports comparing HDR-BT and LDR-BT to each other or to other treatment options (such as external beam radiotherapy (EBRT) or surgery) suggest similar outcomes. The 5-year freedom from biochemical failure rates for patients with low-risk, intermediate-risk, and high-risk disease are >85%, 69-97%, and 63-80%, respectively. Brachytherapy with EBRT (versus brachytherapy alone) is an appropriate approach in select patients with intermediate-risk and high-risk disease. The 10-year rates of overall survival, distant metastasis, and cancer-specific mortality are >85%, <10%, and <5%, respectively. Grade 3-4 toxicities associated with HDR-BT and LDR-BT are rare, at <4% in most series, and quality of life is improved in patients who receive brachytherapy compared with those who undergo surgery.

Do theoretical potential and advanced technology justify the use of high-dose rate brachytherapy as monotherapy for prostate cancer?

Low-dose rate brachytherapy (LDR-BT), involving implantation of radioactive seeds into the prostate, is an established monotherapy for most low-risk and select intermediate- and high-risk prostate cancer patients. High-dose rate brachytherapy (HDR-BT) is an advanced technology theorized to be more advantageous than LDR-BT from a radiobiological and radiophysics perspective, to the patient himself, and in terms of resource allocation. Studies of HDR-BT monotherapy have encouraging results in terms of biochemical control, patient survival, treatment toxicity and erectile preservation. However, there are still certain limitations that preclude recommending HDR-BT monotherapy for prostate cancer outside the setting of a clinical trial. HDR-BT monotherapy should be considered experimental at present.

Combining theoretical potential and advanced technology in high-dose rate brachytherapy boost therapy for prostate cancer

External beam radiation therapy (EBRT) combined with brachytherapy (BT) is an attractive treatment option for select patients with clinically localized prostate cancer. Either low- or high-dose rate BT may be combined with EBRT ('LDR-BT boost,' 'HDR-BT boost,' respectively). HDR-BT boost has potential theoretical benefits over LDR-BT boost or external beam radiation therapy monotherapy in terms of radiobiology, radiophysics and patient convenience. Based on prospective studies in this review, freedom from biochemical failure (FFBF) rates at 5 years for low-, intermediate- and high-risk patients have generally been 85-100%, 68-97%, 63-85%, respectively; late Radiotherapy and Oncology Group Grades 3 and 4 genitourinary and gastrointestinal toxicities are seen in <8% of patients. HDR-BT boost is now a relatively well-established treatment modality for certain intermediate-risk and high-risk prostate cancer patients, though limitations exist in drawing conclusions from the currently published studies.

Impact of intraoperative MRI/TRUS fusion on dosimetric parameters in cT3a prostate cancer patients treated with high-dose-rate real-time brachytherapy

Purpose

The purpose of this study was to evaluate the impact of intraoperative MRI/TRUS fusion procedure in cT3a prostate cancer patients treated with high-dose-rate (HDR) real-time brachytherapy.

Material and methods

Prostate gland, dominant intraprostatic lesions (DILs), and extracapsular extension (ECE) were delineated in the pre-brachytherapy magnetic resonance images (MRI) of 9 consecutive patients. The pre-implant P-CTV_US (prostate clinical target volume) was defined as the prostate seen in the transrectal ultrasound (TRUS) images. The CTV_MR includedthe prostate with the ECE image (ECE-CTV) as defined on the MRI. Two virtual treatment plans were performed based on the MRI/TRUS fusion images, the first one prescribing 100% of the dose to the P-PTV_US, and the second prescribing to the PTV_MR. The implant parameters and dose-volume histogram (DVH) related parameters of the prostate, OARs, and ECE were compared between both plans.

Results

Mean radial distance of ECE was 3.6 mm (SD: 1.1). No significant differences were found between prostate V₁₀₀, V₁₅₀, V₂₀₀, and OARs DVH-related parameters between the plans. Mean values of ECE V₁₀₀, V₁₅₀, and V₂₀₀ were 85.9% (SD: 15.1), 18.2% (SD: 17.3), and 5.85% (SD: 7) when the doses were prescribed to the PTV_US, whereas ECE V₁₀₀, V₁₅₀, and V₂₀₀ were 99.3% (SD: 1.2), 45.8% (SD: 22.4), and 19.6% (SD: 12.6) when doses were prescribed to PTV_MR (p = 0.028, p = 0.002 and p = 0.004, respectively).

Conclusions

TRUS/MRI fusion provides important information for prostate brachytherapy, allowing for better coverage and higher doses to extracapsular disease in patients with clinical stage T3a.

Intensity-modulated radiation therapy, proton therapy, or conformal radiation therapy and morbidity and disease control in localized prostate cancer

CONTEXT

There has been rapid adoption of newer radiation treatments such as intensity-modulated radiation therapy (IMRT) and proton therapy despite greater cost and limited demonstrated benefit compared with previous technologies.

OBJECTIVE

To determine the comparative morbidity and disease control of IMRT, proton therapy, and conformal radiation therapy for primary prostate cancer treatment.

DESIGN, SETTING, AND PATIENTS

Population-based study using Surveillance, Epidemiology, and End Results-Medicare-linked data from 2000 through 2009 for patients with nonmetastatic prostate cancer.

MAIN OUTCOME MEASURES

Rates of gastrointestinal and urinary morbidity, erectile dysfunction, hip fractures, and additional cancer therapy.

RESULTS

Use of IMRT vs conformal radiation therapy increased from 0.15% in 2000 to 95.9% in 2008. In propensity score-adjusted analyses (N = 12,976), men who received IMRT vs conformal radiation therapy were less likely to receive a diagnosis of gastrointestinal morbidities (absolute risk, 13.4 vs 14.7 per 100 person-years; relative risk [RR], 0.91; 95% CI, 0.86-0.96) and hip fractures (absolute risk, 0.8 vs 1.0 per 100 person-years; RR, 0.78; 95% CI, 0.65-0.93) but more likely to receive a diagnosis of erectile dysfunction (absolute risk, 5.9 vs 5.3 per 100 person-years; RR, 1.12; 95% CI, 1.03-1.20). Intensity-modulated radiation therapy patients were less likely to receive additional cancer therapy (absolute risk, 2.5 vs 3.1 per 100 person-years; RR, 0.81; 95% CI, 0.73-0.89). In a propensity score-matched comparison between IMRT and proton therapy (n = 1368), IMRT patients had a lower rate of gastrointestinal morbidity (absolute risk, 12.2 vs 17.8 per 100 person-years; RR, 0.66; 95% CI, 0.55-0.79). There were no significant differences in rates of other morbidities or additional therapies between IMRT and proton therapy.

CONCLUSIONS

Among patients with nonmetastatic prostate cancer, the use of IMRT compared with conformal radiation therapy was associated with less gastrointestinal morbidity and fewer hip fractures but more erectile dysfunction; IMRT compared with proton therapy was associated with less gastrointestinal morbidity.

Advances in permanent 125I seed implantation for colorectal liver metastases

Colorectal cancer is one of the most common cancers worldwide and the second most common type of cancer in the Western world. Colorectal cancer is the most common source of metastatic liver cancer, and liver metastasis is an important prognostic factor for colorectal cancer. Hepatic resection is the treatment of choice for colorectal liver metastases. The postoperative 5-year survival rate for patients with colorectal liver metastase now exceeds 50%. However, hepatic resection is indicated for only 10%-25% of patients with colorectal liver metastases. Therefore, non-surgical methods have attracted increasing attention. Permanent ¹²⁵I seed implantation is now becoming a hotspot for treatment of colorectal liver metastases. This review will focus on the recent advances in permanent ¹²⁵I seed implantation for colorectal liver metastases.