Proton Therapy Spot Placement for Prostate Cancer

Recruiting in Palo Alto (17 mi)

Overseen by Samantha Hedrick, PhD

Age: 18+

Sex: Male

Travel: May Be Covered

Time Reimbursement: Varies

Trial Phase: Academic

Waitlist Available

Sponsor: Thompson Cancer Survival Center

No Placebo Group

Trial Summary

What is the purpose of this trial?

This purpose of this study is to examine the placement of proton spots during pencil beam scanning proton therapy for low and intermediate risk prostate cancer. The researchers will test a unique technique called "Spot Delete" to control the placement of spots during treatment planning. They will also use a special computer model to study how the energy of the proton beam (linear energy transfer) is related to rectal and bladder side effects. The study involves creating a treatment plan based on a CT scan, which helps guide the proton beam in the body. The clinical team uses this CT scan to find the best placement for the protons. The "Spot Delete" method prevents protons from stopping in the rectum, sigmoid, and small bowel, which is thought to be related to acute or late toxicities, such as tenesmus, diarrhea, fecal incontinence, proctitis, and rectal hemorrhage.

Do I have to stop taking my current medications for the trial?

The trial protocol does not specify whether you need to stop taking your current medications. However, since prior systemic therapy for prostate cancer is an exclusion criterion, you may need to discuss your current medications with the trial team.

What data supports the idea that Proton Therapy Spot Placement for Prostate Cancer is an effective treatment?

The available research shows that Proton Therapy Spot Placement for Prostate Cancer can effectively target the cancer while reducing the impact on surrounding healthy organs. For example, one study found that by deleting certain spots in the treatment plan, the dose to nearby organs like the rectum and bladder was reduced, which means less potential damage to these areas. Another study highlighted that reducing the number of spots can shorten treatment times without losing effectiveness, making the therapy more efficient. These findings suggest that Proton Therapy Spot Placement is a promising option for treating prostate cancer, offering precise targeting and potentially fewer side effects compared to traditional methods. ^{1 2 3 4 5}

What safety data is available for proton therapy spot placement in prostate cancer treatment?

The safety data for proton therapy spot placement, including techniques like spot deletion and pencil beam scanning, indicate that these methods can reduce dose exposure to organs at risk (OAR) such as the rectum and bladder, without compromising the treatment's effectiveness. Studies have shown that spot deletion can decrease the dose to OARs and improve beam delivery time. Additionally, early toxicity and patient-reported quality-of-life outcomes from proton therapy for prostate cancer have been prospectively recorded, suggesting manageable toxicity levels. Comparative analyses also highlight the dosimetric benefits of pencil beam scanning over traditional methods, although more data is needed to fully understand the comparative toxicity rates. ^{2 3 4 6 7}

Is Spot Delete planning for proton therapy a promising treatment for prostate cancer?

Yes, Spot Delete planning for proton therapy is promising for prostate cancer. It can reduce treatment time by cutting down the number of proton spots without losing quality. This method also helps protect healthy organs and tissues from unnecessary radiation, making it a safer option. ^{1 2 3 5 8}

Research Team

Samantha Hedrick, PhD

Principal Investigator

Thompson Proton Center

Eligibility Criteria

Men over 18 with low to intermediate risk prostate cancer, not previously treated with pelvic radiotherapy, cryotherapy, hyperthermia or chemotherapy. They must have a clinical stage T1-T2c prostate cancer, PSA < 20 ng/mL, Gleason Score ≤ 7 and be in good physical condition (ECOG status 0-1). Participants should also be willing to complete quality of life surveys.

Inclusion Criteria

My prostate cancer has a Gleason score of 7 or less.

I am fully active or can carry out light work.

I am 18 years old or older.

Exclusion Criteria

I have had radiation therapy to my pelvic area before.

I have had cryotherapy or hyperthermia for prostate cancer.

I have received chemotherapy for prostate cancer.

Treatment Details

Interventions

• Spot Delete planning for proton therapy (Proton Beam Therapy)
• Traditional proton treatment planning system (Proton Beam Therapy)

Trial Overview The trial is testing 'Spot Delete' planning for proton therapy against traditional methods. It aims to reduce side effects by avoiding proton spots in sensitive areas like the rectum and bowel during treatment for prostate cancer.

Participant Groups

Group I: "Spot Delete" Experimental Treatment 1 Intervention

A unique technique called "Spot Delete" will be utilized to control the placement of spots during treatment planning, to prohibit proton spots from being placed in the rectum, sigmoid, and small bowel. A specialized computer model will be used to study how the energy of the proton beam (linear energy transfer) is related to rectal and bladder side effects.

Group II: Control Arm Active Control 1 Intervention

The proton spots that are placed by the treatment planning system are not modified

Spot Delete planning for proton therapy is already approved in United States, European Union for the following indications:

🇺🇸 Approved in United States as Proton Therapy for:

• Prostate cancer
• Brain tumors
• Breast cancer
• Cancer in children
• Eye melanoma
• Esophageal cancer
• Head and neck cancers
• Liver cancer
• Lung cancer
• Lymphoma
• Pancreatic cancer
• Pituitary gland tumors
• Sarcoma
• Tumors affecting the spine
• Tumors in the base of the skull

🇪🇺 Approved in European Union as Proton Therapy for:

• Prostate cancer
• Brain tumors
• Breast cancer
• Cancer in children
• Eye melanoma
• Esophageal cancer
• Head and neck cancers
• Liver cancer
• Lung cancer
• Lymphoma
• Pancreatic cancer
• Pituitary gland tumors
• Sarcoma
• Tumors affecting the spine
• Tumors in the base of the skull

Find a Clinic Near You

Research Locations Nearby Select from list below to view details:

Thompson Proton Center Knoxville, TN

Who Is Running the Clinical Trial?

Thompson Cancer Survival Center

Lead Sponsor

Trials

4

Patients Recruited

800+

References

1. United States pubmed.ncbi.nlm.nih.gov

Robust treatment planning in whole pelvis pencil beam scanning proton therapy for prostate cancer. [2021] Whole-pelvis pencil beam scanning (PBS) proton therapy is utilized in both the intact and post-operative settings in patients with prostate cancer. As whole pelvis prostate radiotherapy has traditionally been delivered with standard photon beams, limited evidence and technical descriptions have been reported regarding the use of proton therapy. Here we present two robust three-field treatment planning approaches utilized to maximize target coverage in the presence of anatomic and delivery uncertainties. Both techniques, conventional optimization (CO) and robust optimization (RO), create treatment plans with acceptable target coverage and sparing of organs at risk (OAR). While the RO method is less time intensive and may theoretically allow for superior OAR sparing and improved robustness, the CO method can be implemented by institutions who do not have RO capabilities.

2. England pubmed.ncbi.nlm.nih.gov

Impact of spot reduction on the effectiveness of rescanning in pencil beam scanned proton therapy for mobile tumours. [2022] Objective. In pencil beam scanning proton therapy, individually calculated and positioned proton pencil beams, also referred to as 'spots', are used to achieve a highly conformal dose distributions to the target. Recent work has shown that this number of spots can be substantially reduced, resulting in shorter delivery times without compromising dosimetric plan quality. However, the sensitivity of spot-reduced plans to tumour motion is unclear. Although previous work has shown that spot-reduced plans are slightly more sensitive to small positioning inaccuracies of the individual pencil beams, the resulting shorter delivery times may allow for more rescanning. The aim of this study was to assess the impact of tumour motion and the effectiveness of 3D volumetric rescanning for spot-reduced treatment plans.Approach.Three liver and two lung cancer patients with non-negligible motion amplitudes were analysed. Conventional and probabilistic internal target volume definitions were used for planning considering single or multiple breathing cycles respectively. For each patient, one clinical and two spot-reduced treatment plans were created using identical field geometries. 4D dynamic dose calculations were then performed and resulting target coverage (V95%), dose homogeneity (D5%-D95%) and hot spots (D2%) evaluated for 1-25 rescans.Main results. Over all patients investigated, spot reduction reduced the number of spots by 91% in comparison to the clinical plan, reducing field delivery times by approximately 50%. This reduction, together with the substantially increased dose per spot resulting from the spot reduction process, allowed for more rescans in the same amount of time as for clinical plans and typically improved dosimetric parameters, in some cases to values better than the reference static (3D calculated) plans. However, spot-reduced plans had an increased possibility of interference with the breathing cycle, especially for simulations of perfectly repeatable breathing.Significance.For the patients analysed in this study, spot-reduced plans were found to be a valuable option to increase the efficiency of 3D volumetric rescanning for motion mitigation, if attention is paid to possible interference patterns.

3. England pubmed.ncbi.nlm.nih.gov

Simulation study using the spots deletion technique in spot scanning proton beam therapy for prostate cancers. [2021] The aim of the present study was to investigate the effects on the dose distribution and beam delivery time in spot scanning proton beam therapy (PBT) incorporating the spot deletion technique. A spot scanning plan was created for 30 patients with prostate cancer. The plan was then modified via two processes: Spots with lower weighting depositions were deleted (process A) and spots that were distant from the clinical target volume (CTV) were deleted (process B). The dose distribution to the organs at risk (OAR), the expanded CTV (exCTV), which was defined by a uniform expansion of the CTV by a radius of 5 mm, and the beam delivery time were compared among initial and modified plans. The V50 Gy [relative biological effectiveness (RBE)] to the rectum and bladder, and V60 Gy(RBE) to the urethral bulb, inhomogeneity index (INH) of the exCTV showed a difference (P=1.1x10-14, P=6.4x10-14, P=2.7x10-7, P=3.2x10-17), although only changes by process B were significant. Modified plan by process B showed the V50 Gy(RBE) to the rectum and bladder decreased by -2.4&#177;1.6 and -2.3&#177;1.4%, and the V60 Gy (RBE) to the urethral bulb decreased by -15.9&#177;19.4%. The INH of the exCTV increased by 0.05&#177;0.03%. On the other hand, modification of the initial plan by process A did not affect the dose of the OAR, exCTV or beam delivery time. In spot scanning PBT, modification of the initial radiotherapy plan by systemic deletion of spots distant from the CTV could result in a dose reduction to the OAR.

4. England pubmed.ncbi.nlm.nih.gov

Dosimetric impact of random spot positioning errors in intensity modulated proton therapy plans of small and large volume tumors. [2022] To study dosimetric impact of random spot positioning errors on the clinical pencil beam scanning proton therapy plans.

5. England pubmed.ncbi.nlm.nih.gov

Shortening delivery times for intensity-modulated proton therapy by reducing the number of proton spots: an experimental verification. [2020] Delivery times of intensity-modulated proton therapy (IMPT) can be shortened by reducing the number of spots in the treatment plan, but this may affect clinical plan delivery. Here, we assess the experimental deliverability, accuracy and time reduction of spot-reduced treatment planning for a clinical case, as well as its robustness. For a single head-and-neck cancer patient, a spot-reduced plan was generated and compared with the conventional clinical plan. The number of proton spots was reduced using the iterative 'pencil beam resampling' technique. This involves repeated inverse optimization, while adding in each iteration a small sample of randomly selected spots and subsequently excluding low-weighted spots until plan quality deteriorates. Field setup was identical for both plans and comparable dosimetric quality was a prerequisite. Both IMPT plans were delivered on PSI Gantry 2 and measured in water, while delivery log-files were used to extract delivery times and reconstruct the delivered dose via Monte-Carlo dose calculations. In addition, robustness simulations were performed to assess sensitivity to machine inaccuracies and errors in patient setup and proton range. The number of spots was reduced by 96% (from 33 855 to 1510 in total) without compromising plan quality. The spot-reduced plan was deliverable on our gantry in standard clinical mode and resulted in average delivery times per field being shortened by 46% (from 51.2 to 27.6 s). For both plans, differences between measured and calculated dose were within clinical tolerance for patient-specific verifications and Monte-Carlo dose reconstructions were in accordance with clinical experience. The spot-reduced plan was slightly more sensitive to machine inaccuracies, but more robust against setup and range errors. In conclusion, for an example head-and-neck case, spot-reduced IMPT planning provided a deliverable treatment plan and enabled considerable shortening of the delivery time (∼50%) without compromising plan quality or delivery accuracy, and without substantially affecting robustness.

6. England pubmed.ncbi.nlm.nih.gov

Early toxicity and patient reported quality-of-life in patients receiving proton therapy for localized prostate cancer: a single institutional review of prospectively recorded outcomes. [2019] We report prospectively captured clinical toxicity and patient reported outcomes in a single institutional cohort of patients treated for prostate cancer with proton beam therapy (PBT). This is the largest reported series of patients treated mostly with pencil beam scanning PBT.

7. Ireland pubmed.ncbi.nlm.nih.gov

Proton beam therapy delivered using pencil beam scanning vs. passive scattering/uniform scanning for localized prostate cancer: Comparative toxicity analysis of PCG 001-09. [2022] Patient-level benefits of proton beam therapy (PBT) relative to photon therapy for prostate cancer (PC) continue to be the focus of debate. Although trials comparing the two modalities are underway, most are being conducted using "conventional" PBT (passive scattering/uniform scanning [PS/US]) rather than pencil beam scanning (PBS). The dosimetric benefits of PBS are well-known, but comparative data are limited. This analysis compares PBS toxicity rates with those of PS/US in a prospective multicenter registry.

8. Netherlands pubmed.ncbi.nlm.nih.gov

A comparison of proton therapy and IMRT treatment plans for prostate radiotherapy. [2019] Proton therapy (PT) is becoming a more widely available treatment option on the world stage and there is some interest in investment in this treatment option in Australia. The benefit of PT has been shown for a number of tumour sites, particularly for paediatric patients. The workload from these patients may not completely fill the maximum yearly workload of a machine. This work aims to ascertain if prostate cancer would be a suitable candidate to fill the rest of the workload at an Australian PT facility. Passive and intensity modulated proton therapy (IMPT) plans were generated for a prostate patient. These were compared to 7 field sliding window and step and shoot IMRT plans. All plans used a prescription dose of 78 CGE. IMRT and IMPT plans used inverse planning for optimisation. Homogeneity in the PTV was best for the IMPT plan. IMPT also gave the best rectal sparing. The bladder and femoral heads were exposed to less dose in both proton plans. Proton plans exposed normal tissue outside the PTV to less than 50% of the dose given by the IMRT plans. PT, particularly IMPT, is a suitable treatment option for the prostate cancer patient presented here.