Sabr Radiotherapy For Prostate Cancer

Specific Examples Of Sbrt/sabr

Specific examples of SBRT/SABR include:

Lung SBRT/SABR is a established treatment option for early stage non-small cell lung cancer and patients with one or a few lung metastasis . It is understood that very high radiation doses are required to control non-small cell lung cancer. The doses with this technique are much higher than achieved with conventional radiation therapy techniques in the past. Lung SBRT was initially used for peripheral lung tumours however is being used for more central tumours . The movement of patient breathing can be adjusted for meaning that very high and focused radiation doses can be given. In several clinical trials, the chance of controlling the cancer in the lung with this technique is up to 98% better than using older techniques. Lung SBRT may also be a treatment option for patients with small amount of metastatic lung disease .

Bone/Spine SBRT/SABR is largely used for metastatic disease in the spine. The aim is to improve symptoms, such as pain, and quality of life by controlling the cancer in the spine over the longer term. SBRT to the spine and other bones provides better control of the tumour in that bone and also allows re-treatment to occur . As the spinal cord is often right next to the area being treated, very strict and accurate delivery measures are used to ensure that this treatment remains safe.

Patient And Treatment Characteristics

Baseline patient characteristics are presented in . Median follow-up was 23 months , and median age was 71 years . Eighty-nine patients with 128 total metastatic lesions treated were included in the analysis. Fifty-eight patients had one lesion, 23 had two lesions, and eight had three lesions. Nine of the 89 subjects received conventional radiotherapy as noted in the methods . Median PSA before SABR was 0.7 ng/mL , and 64% had PSA < 2 ng/mL. Prior to SABR , 61%, 44%, and 19% had disease progression while receiving chemotherapy, abiraterone, or enzalutamide, respectively. Significantly, 38% of the cohort had progressed on both chemotherapy and at least one second-generation antiandrogens. Seventy-one percent of patients had received prior SABR to the prostate or prostate fossa. Patients were maintained on the same systemic therapy before and after SABR until clinical failure.

PSA progression-free survival

The number of metastatic sites correlated with PSA progression-free survival . Patients with three treated metastatic sites experienced significantly inferior PSA progression-free survival relative to patients with two metastases or one metastasis .

Local progression of SABR-treated metastases and distant progression

Twenty-one patients experienced LF after radiotherapy. Median time to LF was not reached. Local PFS was 84.4% and 75.3% at 1 and 2 years, respectively .

Treatment Planning And Planning Objectives

Plans were generated utilizing 10 F and 6 F as well as 6 MV flattened photon beams. Maximum dose rates were used for each energy, 2400, 1400, and 600MU/min for 10 F, 6 F and 6MV, respectively. Several arc arrangements were investigated. Single VMAT arcs were used for PO plans while, after initial investigations for PPLN plans, dosimetrically acceptable plans were only achieved using two VMAT arcs.

Prostate only plans

Prostate and pelvic lymph nodes plans

For prostate and pelvic lymph nodes planning, after initial investigations of several arc combinations, two arc arrangements were investigated further

• Two full arcs .

• Two partial 300° arcs .

Similar to PO plans, 40Gy was prescribed to the CTV and 36.25Gy to PTV. Additionally, 25Gy was prescribed to the PTV to be delivered simultaneously in 5 fractions. Dose objectives and constraints are also presented in Table .

The equivalent dose as 2Gy fractions from a hypo-fractionated course for tumours and OARs could be calculated using the equation: \, where D is the total dose given at dose d per fraction. This hypo-fractionated dose regime corresponds to a CTV EQD2Gy of 108.6Gy, PTV EQD2Gy of 90.6Gy \ \), a normal tissue late effect EQD2Gy of 74.3Gy \ \), and an acute toxicity EQD2Gy of 52.1Gy \ \).

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Radiation Therapy For Prostate Cancer

There are several types of radiation therapy used for prostate cancer treatment, but generally, radiation therapy is delivered either externally or internally. With external beam radiation, a machine is used to direct targeted radiation to the tumor site from outside the patients body. Internal radiation therapy, or brachytherapy, involves delivering radiation from inside the patients body with radioactive pellets that are placed in or near the tumor.

Moffitt Cancer Centers Radiation Oncology Program uses a wide range of radiation therapy techniques, including the most advanced options available today. Some of the most common radiation delivery methods for treating prostate cancer include:

In addition to offering these radiation therapies, Moffitt is the only cancer center in the United States that can provide internal radiation treatment for prostate cancer using an absorbable Duraseal gel that reduces radiation dosage to the rectum. Additionally, Moffitt is an American College of Radiology-accredited center a designation that speaks not only to the high quality of our equipment, but also to the ability of our team. Radiation therapy is a complex, state-of-the-art treatment, and it is the team, not the machine, that matters most.

Is It For Me

This treatment is for men with localised prostate cancer that is low- or intermediate-risk and if your cancer hasnt spread to other nearby tissues or organs, such as the bladder or pelvic wall, or anywhere else in your body.

SABR can also be used if you’ve previously undergone external beam radiotherapy for prostate cancer and have relapsed with the disease in the prostate only. This is known as prostate cancer reirradiation.

Your GenesisCare Consultant Oncologist will discuss your diagnosis, treatments to date and overall health with a multidisciplinary team of SABR and MRIdian specialists. Together, theyll decide if this treatment is right for you. Your consultant will explain the treatment plan to you, including any side effects you might experience and the outcome we can expect to achieve. Youll have time to ask questions before you decide whether you want to proceed.

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Stereotactic Body Radiation Therapy

Stereotactic body radiation therapy or radiotherapy and stereotactic ablative radiation therapy or radiotherapy both describe an advanced form of radiation therapy that is used to treat many different types of cancer. The two terms are interchangeable. It is used to treat both primary cancer , or where a cancer may have spread . Secondary cancers treated with SBRT include those in the bone, lung or liver.

This technique differs from other external beam radiation therapy as it involves the delivery of higher doses of radiation to the cancer. This is why the word ablative is part of the name sometimes given for this type of treatment. These higher doses are given to the patient from Xray beams directed from outside the body and using a small number of treatments . Typically, one to five treatments are used over a few days. The delivery technique is extremely precise which is what the term stereotactic refers to. There are several technologies available in Australia that can be used to deliver this technique including Linac based, Cyberknife, Tomotherapy and Gammaknife.

Plan Analysis Patient Specific Qa And Statistical Analysis

For the PTVs, the near maximum dose D2% and near minimum dose D98% were recorded. Several dose metrics were assessed for each OAR. Additionally, dose conformity index : \ , conformation number : \ \) , heterogeneity index : \, were evaluated.

Population-averaged dose-volume histograms for the PTVs and selected OARs are presented. Medium and low-dose spillage outside the PTVs were also assessed for each plan: \, where Volx%pres is the tissue volume receiving at least x% of the PTV prescribed dose . Patient specific size parameters were also recorded and analysed for correlation with dose spillage . The number of monitor units and estimated treatment delivery times were also assessed.

For a subset of PO and PPLN plans, pre-treatment dose verification was conducted using OCTAVIUS-4D phantom consisting of a motorized cylindrical phantom with a ±360° angular range . For this investigation, a PTW OCTAVIUS 729 2D array was inserted into the centre of the phantom. The detector size is 0.5×0.5×0.5cm3 . Moreover, 30 plans representing high dose region, were delivered to a PTW OCTAVIUS 1000 SRS 2D array . The detector size is 2.3 mm×2.3 mm×0.5 mm. The detector spacing in the inner area is 2.5 mm centre-to-centre and in the outer area is 5 mm centre-to-centre .

A 3D gamma analysis was conducted using Verisoft software version which creates 3D dose maps from the multiple 2D doses obtained . Global gamma criteria were used with a 10% minimum dose threshold .

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What Does Sabr Mean For You

The first step is usually a four-dimensional computed tomography scan captured while you lie in a specialised body support that will help you hold perfectly still. Your radiation therapy team will use these scans to design an individualised SABR treatment to deliver the large radiation dose to the tumour while avoiding surrounding healthy tissues.

SABR treatments use a number of radiation beams from different angles, each shaped to precisely target the tumour. Before the treatment is delivered, the radiation therapy team will take x-ray and CT images to ensure treatment accuracy. The treatment appointment can take about an hour, and your radiation therapists will help to ensure you are relaxed and comfortable throughout.

How Is Sbrt Delivered What Technology Is Used

SBRT consists of a much shorter course of radiotherapy than the conventional approaches, with only five treatment sessions. This is accomplished by delivering a higher dose per day, which requires significant precision and accuracy with expertise from the treating radiation oncologist as well as a team of medical physicists, medical dosimetrists, and radiation therapists. Modern and advanced linear accelerator technology is also required. Overall, SBRT planning and treatment delivery requires six visits to the department .

Because the prostate can move due to filling up and emptying of the bladder and rectum, pinpoint accuracy is required for SBRT. There are two ways to achieve this level of accuracy:

CT-guidance: In order to make sure that the prostate is accurately targeted and tracked, we place 3 implanted markers into the prostate. All of our treatment devices are equipped with onboard X-ray imagers or cone-beam CT technology that allow us to triangulate these markers . Also, prior to each treatment session, a cone-beam CT is obtained in order to make sure the anatomy is stable for treatment. This generally means having a full bladder and an empty rectum. We do provide detailed instructions on preparation for treatment to each patient.

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Immunologic Parameters And Outcomes

We previously validated CD8+ CD11ahigh TTR T-cell populations as significant in anti-tumor immunity . To determine whether these cells or other known anti-tumor T cell populations predict patient outcomes, we measured these cells in systemic circulation before and after radiotherapy .

Baseline TTR levels predicted significantly improved PSA PFS, local PFS, and distant PFS . Patients with baseline TTR levels above the cutoff experienced prolonged median time to PSA progression compared with patients with levels below the cutoff . Similarly, patients with baseline TTR above the cutoff did not reach median time to LF while their counterparts achieved a median 23 months local PFS . Interestingly, patients with PD-1+ TTR at baseline above the cutoff experienced shorter median time to LF .

Patients with increasing TTR at day 1 achieved superior median time to DF . In addition, patients with increasing TEM at day 14 achieved superior median time to PSA progression .

Stereotactic Ablative Radiotherapy For Low Risk Prostate Cancer With Injectable Rectal Spacer

A phase II study to assess safety and efficacy of the spacer injection process, ability of the spacer to effectively provide the space necessary to reduce acute events in the rectum, and also meet the SABR based rectal constraints, and to monitor stability of this process during SABR. Unlike IMRT, which uses smaller dose/fraction, when using such high dose/fraction, even a few mm of shift in spacer positioning may impact the dose that the rectum receives, and therefore, a rigorous study of stability of material during the SABR treatments will need to be determined. If there is some shift, by doing this study, we may be able to determine the margin of error that will be necessary in considering rectal organ dosimetry, based on the possible shift in positiong that may occur with the spacer over time.

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Contouring And Planning For Sabr

Contouring was aided by fusing patients diagnostic MRI scans with their planning CT scans in the Varian Eclipse treatment planning system version 13.5 . Three clinical target volumes were defined 1) prostate and proximal 10 mm of seminal vesicles CTV, 2) remaining SV CTV, 3) pelvic lymph nodes CTV. The planning target volumes were constructed to create two distinct PTVs 1) PTV which is the CTV expanded with 5 mm margins in all directions except posteriorly 2) PTV consisting of the CTV+CTV+7 mm isotropic margin. Organs at risk contoured were bladder, rectum, sigmoid colon, bowel, femoral heads, and penile bulb. The prostatic urethra and neurovascular bundles were also contoured with reference to both the diagnostic MR and to standard anatomical references. All planning was conducted in Eclipse TPS using the Progressive Resolution Optimization and Acuros XB dose calculation algorithm for a Varian TrueBeam-STx Linac with a HD MLC. The dose calculation grid size used was 2.5 mm and the heterogeneity correction and jaw tracking settings were enabled. A subset of plans, were recalculated using 1.25 mm grid size to assess the effect of using a finer grid size on dose and optimization time.

What Is Stereotactic Body Radiotherapy

Traditionally, prostate cancer radiotherapy has been delivered over the course of multiple treatment sessions with a low dose per treatment session. In order to deliver the total dose needed to eradicate prostate cancer, up to 45 treatments were needed, which translates to nine weeks of daily treatments . It has since become appreciated that prostate cancer appears to be uniquely sensitive to a higher dose per treatment session, such that prostate cancer could be eradicated in a much shorter amount of time with significantly fewer treatments. Various ways of doing this have been explored. Among them, stereotactic body radiotherapy , also known as stereotactic ablative radiotherapy, is a radiation therapy technique that allows the prostate radiotherapy course to be condensed to just five treatment sessions. With SBRT, advanced treatment delivery technologies and radiation planning parameters are used to deliver higher doses per day in a safe and effective manner.

SBRT is now supported by high level evidence as a safe and effective treatment. The UCLA SBRT Prostate Cancer program is led by Dr. Amar Kishan and Dr. Michael Steinberg.

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A Trial Using Stereotactic Radiotherapy To Treat Prostate Cancer

Please note – this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Phase:

This trial is looking at whether a new targeted type of radiotherapy called SABR is a useful treatment for prostate cancer.

Some of the men taking part will have their lymph nodes treated as well as their prostate gland and the others will not.

Sabr Treatment Planning And Delivery

Treatment planning, dose constraints, simulation, setup, and treatment delivery parameters were conducted as previously reported . All patients were instructed to have a full bladder and empty their rectum with enemas at the time of CT simulation and treatment planning MRIs. Gold fiducial markers and a perirectal hydrogel spacer were placed 5 days before simulation. Three fiducials were placed in the right lateral base, right apex, and left anterior mid gland. The hydrogel was injected transperineally on the posterior side of Denonvilliers fascia and the anterior rectal wall to minimize risk of pushing cancer cells away from a high-dose radiation field. Prophylactical but optional therapy included 4 mg of dexamethasone before each fraction of SAbR and use of alpha-blocker for at least the duration of treatment.

Table 1 A. Prescription dose and target coverage.

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Treatment Planning Ct Scan

During this session, the patients custom body mold will be created and a CT scan of the patient in this device will be performed immediately thereafter. Patients prepare for the scan with a self-administered enema to achieve an empty rectum and by drinking a moderate amount of water prior to the procedure to achieve a full bladder.

What Does Sabr Involve

Your treatment will involve an initial appointment with your consultant, who has the appropriate experience, either in person or via a secure video consultation. Youll then need to attend one of our SABR centres for a radiotherapy planning scan, which is used to plan the treatment delivery.

You may be required to have a rectal spacer inserted to help protect the surrounding healthy tissue and reduce side effects from prostate radiotherapy. You may also need to have fiducial markers inserted during the same one-off insertion procedure. These are tiny gold markers, the size of a grain of rice, that show up clearly on your planning scans, helping your consultant deliver your radiotherapy with greater accuracy.

If youre interested in knowing more about 5# SABR on the MRIdian MR linac at our centres in Oxford and London find out more here.

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