Rectal CancerREBOOTNCT07616297
Higher Radiation Dose to the Tumor May Help Avoid Surgery in Rectal Cancer Patients
A study testing Simultaneous integrated boost to the tumor and positive mesorectal lymph nodes in people with Rectal Cancer and Radiation Oncology, run by Claudia Schuurhuizen at 1 site in Netherlands.
Trial summary
The goal of this prospective study is to evaluate if a higher radiation dose to the tumor can increase the organ preservation rate in non-locally advanced rectal cancer. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Rectal Cancer, Radiation Oncology
- What is being tested?
- Simultaneous integrated boost to the tumor and positive mesorectal lymph nodes
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 25 participants
- Where
- 1 siteNetherlands
- Study dates
- 27 Jan 2026to 1 Aug 2030
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Age ≥18 years
- Eastern cooperative oncology group (ECOG) performance status ≤2
- Histologically confirmed rectal adenocarcinoma
- Non-locally advanced rectal cancer, defined as (magnetic resonance imaging (MRI)-based) T1-3, N0/N1 (≤3 positive mesorectal lymph nodes), MX/M0
- Indication for curative treatment with organ preservation
- Discussed in the multidisciplinary tumor board (MTB)
- Written informed consent
Who cannot join
- Previous radiotherapy in the pelvic area
- Other malignancies, except for adequately treated basal cell carcinoma (BCC), at time of inclusion or within 3 years prior to inclusion
- Contra-indications for (chemo)radiotherapy or surgery
- Presence of lateral lymph nodes, cN2 status, extramural vascular invasion (EMVI) or mesorectal fascia involvement as seen on MRI
- Mucinous defined tumor on MRI
- Prior local excision of the primary tumor
- DPD (dihydropyrimidine dehydrogenase) deficiency
- Unable to understand the requirements of the study and to give written informed consent, as determined by the treating physician
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Netherlands1 site, 1 recruiting
- Recruiting
Erasmus MC
Rotterdam, South Holland, 3015 GD
Judith Sluijter, MSc, +31107035792, j.sluijter@erasmusmc.nl
Claudia Schuurhuizen, PhD, MD
About this study
Official title: REctal Organ Preservation With a BOost Approach Using CBCT-based Online Adaptive radioTherapy
The goal of this prospective study is to evaluate if a higher radiation dose to the tumor can increase the organ preservation rate in non-locally advanced rectal cancer.
Read the detailed description
Rationale:
Organ preservation has emerged as a promising alternative to total mesorectal excision (TME) for non-locally advanced rectal cancer, aiming to reduce long-term functional impairments and improve quality of life. While magnetic resonance (MR)-guided radiotherapy boosts have shown potential in enhancing organ preservation rates, their high costs, prolonged treatment times and limited accessibility prevent widespread adoption. To address this gap in current treatment options, this study investigates a more accessible online adaptive boost strategy based on cone-beam computed tomography (CBCT) imaging, with the aim of expanding organ-preserving treatment options for rectal cancer patients.
Objective:
The primary objective of this study is to evaluate the organ preservation rate at two-year follow-up in patients with non-locally advanced rectal cancer. Secondary objectives include the assessment of clinical and pathological response rates, recurrence and survival outcomes, biological effects, treatment-related toxicities, bowel function, quality of life, tumor regression, CBCT-based workflow, and target and organ motion during treatment.
Study design:
This study is designed as a non-randomized, single arm, monocenter, phase II clinical trial.
Study population:
Patients (n=25) older than 18 years with non-locally advanced rectal cancer (defined as cT1-3N0-IM0) and a wish for organ preservation, who are referred for treatment.
Intervention (if applicable):
Addition of a simultaneous integrated boost (SIB) to the standard chemoradiotherapy (CRT) scheme of 2.0 Gy to the mesorectum. The radiotherapy scheme consists of 25 fractions, delivering 2.0 Gy per fraction to the mesorectum and 2.4 Gy per fraction to the tumor and positive mesorectal lymph nodes.
Main study parameters/endpoints:
This study aims to demonstrate that the investigated treatment approach results in an increased organ preservation rate of 70% at two year follow-up compared to historical data.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
Preclinical data confirmed the feasibility of the investigated SIB-CRT approach, demonstrating limited and clinically acceptable increases in organ at risk doses compared to the standard CRT scheme, all remaining well within clinical constraints. Furthermore, current literature supports the safety of dose escalation CRT strategies for rectal cancer, reporting manageable acute toxicity profiles, with symptoms typically returning to baseline after treatment. Based on these data, the investigated SIB-CRT strategy is expected to result in only minimal additional toxicities compared to standard CRT therapy.
The additional burden for the participants includes five MRI scans (approximately five hours total), scheduled alongside routine visits to minimize inconvenience. Patients will also be asked to complete three questionnaires at five time points, requiring approximately two hours in total, and to provide one additional 20 mL blood sample during three routine blood withdrawals.
The principal investigators consider the additional potential risk and burden for patients in the study to be acceptable. This study aims to significantly improve organ preservation rates, offering a meaningful benefit to individual patients by potentially avoiding TME surgery.
- Conditions
- Rectal Cancer, Radiation Oncology
- Being tested
- Simultaneous integrated boost to the tumor and positive mesorectal lymph nodes
- Keywords
- Radiation Oncology, Rectal cancer, Organ Preservation
- Medical subject headings
- Rectal Neoplasms
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Simultaneous integrated boost to the tumor and positive mesorectal lymph nodesRadiation
Addition of a simultaneous integrated boost (SIB) to the standard chemoradiotherapy (CRT) scheme of 2.0 Gy to the mesorectum. The radiotherapy scheme consists of 25 fractions, delivering 2.0 Gy per fraction to the mesorectum and 2.4 Gy per fraction to the tumor and positive mesorectal lymph nodes.
| Study group | Role | What they receive |
|---|---|---|
| Simultaneous integrated boost | Experimental | Treatment arm, in which all participating patients will receive the simultaneous integrated boost (SIB) Receives: Radiation: Simultaneous integrated boost to the tumor and positive mesorectal lymph nodes |
What is being measured
The primary outcome is the main question the study is designed to answer.
Organ preservation
Organ preservation is considered unsuccessful if the rectum is surgically removed, a stoma is present, or a non-salvageable locoregional cancer recurrence is developed.
Measured: During two-year follow-up
Secondary outcomes (13)
Rate of clinical complete response
Defined as the proportion of patients showing complete resolution of the tumor, assessed through endoscopy and MRI
Measured: Assessed at the two response assessments (14-16 weeks and 26 weeks after the start of treatment)
Rate of pathological complete response
Evaluated in patients undergoing surgical resection who did not achieve cCR. pCR is defined as the absence of any residual tumor in surgical specimens, assessed via histopathological examination.
Measured: During two-year follow-up
Local progression-free survival
Defined as the absence of tumor regrowth at or near the primary tumor site. Assessed through clinical evaluation and radiological imaging during the follow-up period.
Measured: During two-year follow-up
Distant progression-free survival
Defined as the absence of distant metastasis or death from any cause. Monitored with regular imaging and clinical evaluations during the follow-up period.
Measured: During three-year follow-up
Overall survival
Defined as the time from the start of treatment to death from any cause.
Measured: During three-year follow-up
Biological effect of the treatment
Blood analyses to assess circulating tumor DNA (ctDNA) as a potential biomarker to predict treatment response.
Measured: An additional 20 mL blood sample will be collected during scheduled blood withdrawal moments at three time points: (1) at baseline, (2) 2 weeks after start of treatment, and (3) 14-16 weeks after start of treatment.
Toxicities
Acute and late toxicities will be evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 6.0. Both patient- and clinician-reported toxicity will be assessed during regular follow-up visits. Toxicities will be scored using the CTCAE scale, which ranges from Grade 0 (no toxicity) to Grade 5 (death), with higher grades indicating more severe adverse outcomes.
Measured: During two-year follow-up
Bowel function
Evaluated using the low anterior resection syndrome (LARS) score, completed by the patient through a self-administered questionnaire. by a questionnaire which the patient fills in by themself. The total score ranges from 0 to 42 points, with higher scores indicating more severe symptoms. The following categories are used: 0-20 points: No LARS, 21-29 points: Minor LARS, 30-42 points: Major LARS
Measured: Baseline and 3, 6, 12 and 24 months after start of treatment
Quality of Life (QoL)
Measured using the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 questionnaire, filled in by the patient. All of the scales and single-item measures range in score from 0 to 100. A high score for the functional scale and functional single-items represents a high or healthy level of functioning. A high score for the global health status/QoL scale represents a high QoL, whereas a high score for the symptom scale and single items represents a high level of symptomatology or problems.
Measured: Baseline and 3, 6, 12 and 24 months after start of treatment
Quality of Life (QoL)
Measured using the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-CR29 questionnaire, filled in by the patient. All of the scales and single-item measures range in score from 0 to 100. A high score for the functional scale and functional single-items represents a high or healthy level of functioning, whereas a high score for the symptom scales and single-items represents a high level of symptomatology or problems.
Measured: Baseline and 3, 6, 12 and 24 months after start of treatment
Tumor regression during treatment, monitored through weekly MRI scans
Weekly information to evaluate tumor regression during treatment. This includes five MRI scans in total, each requiring approximately one hour, including waiting time. Retrospectively, these scans will also be used to assess inter- and intrafractional motion of the target and OARs to investigate the potential for further margin reduction.
Measured: Baseline, and treatment week 2, 3, 4 and 5
Target and organ intra- and interfraction motion
Daily CBCT scans acquired pre-, intra-, and post-treatment will be retrospectively analyzed to assess inter- and intrafractional motion of the target and OARs to investigate the potential for further margin reduction in millimeters.
Measured: CBCT data is gathered daily as standard-of-care during the 5-week treatment
Feasibility of the CBCT-based SIB online adaptive workflow
Feasibility of the CBCT-based SIB online adaptive workflow including treatment time in minutes will be evaluated using treatment logs.
Measured: During the 5-week treatment course
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted1 Jun 2026
- Study start27 Jan 2026
- Primary completion1 Aug 2029 (estimated)
- Study completion1 Aug 2030 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Rectal CancerStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 25 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Claudia Schuurhuizen
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor-investigator, Claudia Schuurhuizen, Erasmus Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07616297
- Sponsor's protocol ID
- NL-010517
- Acronym
- REBOOT
- Status last verified
- May 2026
- First submitted
- 13 Mar 2026
- Last updated
- 1 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 1 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- REctal Organ Preservation With a BOost Approach Using CBCT-based Online Adaptive radioTherapy
- ClinicalTrials.gov ID
- NCT07616297
- Acronym / sponsor ID
- REBOOT / NL-010517
- Conditions
- Rectal Cancer, Radiation Oncology
- Keywords
- Radiation Oncology, Rectal cancer, Organ Preservation
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 25 participants (estimated)
- Lead sponsor
- Claudia SchuurhuizenUniversity, hospital or other
- Study start
- 27 Jan 2026 (actual)
- Primary completion
- 1 Aug 2029 (estimated)
- Study completion
- 1 Aug 2030 (estimated)
- First posted
- 1 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this prospective study is to evaluate if a higher radiation dose to the tumor can increase the organ preservation rate in non-locally advanced rectal cancer.
Detailed description
Rationale:
Organ preservation has emerged as a promising alternative to total mesorectal excision (TME) for non-locally advanced rectal cancer, aiming to reduce long-term functional impairments and improve quality of life. While magnetic resonance (MR)-guided radiotherapy boosts have shown potential in enhancing organ preservation rates, their high costs, prolonged treatment times and limited accessibility prevent widespread adoption. To address this gap in current treatment options, this study investigates a more accessible online adaptive boost strategy based on cone-beam computed tomography (CBCT) imaging, with the aim of expanding organ-preserving treatment options for rectal cancer patients.
Objective:
The primary objective of this study is to evaluate the organ preservation rate at two-year follow-up in patients with non-locally advanced rectal cancer. Secondary objectives include the assessment of clinical and pathological response rates, recurrence and survival outcomes, biological effects, treatment-related toxicities, bowel function, quality of life, tumor regression, CBCT-based workflow, and target and organ motion during treatment.
Study design:
This study is designed as a non-randomized, single arm, monocenter, phase II clinical trial.
Study population:
Patients (n=25) older than 18 years with non-locally advanced rectal cancer (defined as cT1-3N0-IM0) and a wish for organ preservation, who are referred for treatment.
Intervention (if applicable):
Addition of a simultaneous integrated boost (SIB) to the standard chemoradiotherapy (CRT) scheme of 2.0 Gy to the mesorectum. The radiotherapy scheme consists of 25 fractions, delivering 2.0 Gy per fraction to the mesorectum and 2.4 Gy per fraction to the tumor and positive mesorectal lymph nodes.
Main study parameters/endpoints:
This study aims to demonstrate that the investigated treatment approach results in an increased organ preservation rate of 70% at two year follow-up compared to historical data.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
Preclinical data confirmed the feasibility of the investigated SIB-CRT approach, demonstrating limited and clinically acceptable increases in organ at risk doses compared to the standard CRT scheme, all remaining well within clinical constraints. Furthermore, current literature supports the safety of dose escalation CRT strategies for rectal cancer, reporting manageable acute toxicity profiles, with symptoms typically returning to baseline after treatment. Based on these data, the investigated SIB-CRT strategy is expected to result in only minimal additional toxicities compared to standard CRT therapy.
The additional burden for the participants includes five MRI scans (approximately five hours total), scheduled alongside routine visits to minimize inconvenience. Patients will also be asked to complete three questionnaires at five time points, requiring approximately two hours in total, and to provide one additional 20 mL blood sample during three routine blood withdrawals.
The principal investigators consider the additional potential risk and burden for patients in the study to be acceptable. This study aims to significantly improve organ preservation rates, offering a meaningful benefit to individual patients by potentially avoiding TME surgery.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Simultaneous integrated boost | Experimental | Radiation: Simultaneous integrated boost to the tumor and positive mesorectal lymph nodesTreatment arm, in which all participating patients will receive the simultaneous integrated boost (SIB) |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- Age ≥18 years
- Eastern cooperative oncology group (ECOG) performance status ≤2
- Histologically confirmed rectal adenocarcinoma
- Non-locally advanced rectal cancer, defined as (magnetic resonance imaging (MRI)-based) T1-3, N0/N1 (≤3 positive mesorectal lymph nodes), MX/M0
- Indication for curative treatment with organ preservation
Key exclusion criteria (8 listed)
- Previous radiotherapy in the pelvic area
- Other malignancies, except for adequately treated basal cell carcinoma (BCC), at time of inclusion or within 3 years prior to inclusion
- Contra-indications for (chemo)radiotherapy or surgery
- Presence of lateral lymph nodes, cN2 status, extramural vascular invasion (EMVI) or mesorectal fascia involvement as seen on MRI
- Mucinous defined tumor on MRI
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Simultaneous integrated boost to the tumor and positive mesorectal lymph nodesAddition of a simultaneous integrated boost (SIB) to the standard chemoradiotherapy (CRT) scheme of 2.0 Gy to the mesorectum. The radiotherapy scheme consists of 25 fractions, delivering 2.0 Gy per fraction to the mesorectum and 2.4 Gy per fraction to the tumor and positive mesorectal lymph nodes. | Radiation | Simultaneous integrated boost |
Primary outcome
Organ preservation
Time frame: During two-year follow-up
Organ preservation is considered unsuccessful if the rectum is surgically removed, a stoma is present, or a non-salvageable locoregional cancer recurrence is developed.
13 secondary outcomes
Rate of clinical complete response
Time frame: Assessed at the two response assessments (14-16 weeks and 26 weeks after the start of treatment)
Rate of pathological complete response
Time frame: During two-year follow-up
Local progression-free survival
Time frame: During two-year follow-up
Distant progression-free survival
Time frame: During three-year follow-up
Overall survival
Time frame: During three-year follow-up
Biological effect of the treatment
Time frame: An additional 20 mL blood sample will be collected during scheduled blood withdrawal moments at three time points: (1) at baseline, (2) 2 weeks after start of treatment, and (3) 14-16 weeks after start of treatment.
Toxicities
Time frame: During two-year follow-up
Bowel function
Time frame: Baseline and 3, 6, 12 and 24 months after start of treatment
Quality of Life (QoL)
Time frame: Baseline and 3, 6, 12 and 24 months after start of treatment
Quality of Life (QoL)
Time frame: Baseline and 3, 6, 12 and 24 months after start of treatment
Tumor regression during treatment, monitored through weekly MRI scans
Time frame: Baseline, and treatment week 2, 3, 4 and 5
Target and organ intra- and interfraction motion
Time frame: CBCT data is gathered daily as standard-of-care during the 5-week treatment
Feasibility of the CBCT-based SIB online adaptive workflow
Time frame: During the 5-week treatment course
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 1 Jun 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Simultaneous integrated boost to the tumor and positive mesorectal lymph nodes in people with Rectal Cancer and Radiation Oncology, run by Claudia Schuurhuizen at 1 site in Netherlands.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 1 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Netherlands. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Each site lists its own contact: choose the nearest one under Trial locations. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Organ preservation (time frame: During two-year follow-up). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 1 Jun 2026.