A Phase II Prospective Study of Maastro Applicator Brachytherapy for Rectal Cancer

NCT07402486 | Not Yet Recruiting Phase 2

• 1 other identifier: Si1005/2568(IRB4)
• Study Type: interventional
• Target: 20
• Locations: 0 countries
• Sites: N/A

Brief Summary

Rectal cancer is a common type of cancer and an important cause of illness and death worldwide. In 2020, cancers of the colon and rectum were the fourth most common cancers globally, and about one third of these cases were rectal cancer. Surgery is the main treatment for rectal cancer. In more advanced cases, chemotherapy and external beam radiotherapy are often given before surgery. However, surgery can sometimes result in a permanent stoma (an opening on the abdomen for bowel movements) and carries higher risks of complications, especially in older patients or those with other medical problems. Because of this, there is growing interest in treatment approaches that can control the cancer while avoiding major surgery when possible. Some studies suggest that in carefully selected patients, rectal cancer can be treated without removing the rectum if the tumor responds well to radiation and chemotherapy. In these patients, survival outcomes may be similar to those who undergo surgery, although the risk of the cancer growing back locally can be slightly higher. This means that careful and long-term follow-up is very important. One of the key challenges with non-surgical treatment is determining how much radiation is needed to completely eliminate the tumor while minimizing side effects. Contact X-ray brachytherapy is a type of radiation treatment that delivers a high dose of radiation directly to the tumor using low-energy X-rays. Because the radiation is given very close to the tumor, it can better target the cancer while reducing radiation exposure to surrounding healthy tissues. This technique has been used in Europe for many years and is recommended by international guidelines in selected patients, mainly within research settings. Other forms of brachytherapy using modern radiation sources can achieve similar dose distributions and may also support organ-preserving treatment strategies. A new medical device called the Maastro applicator has been developed for use with high-dose-rate (HDR) brachytherapy systems. This applicator is designed to deliver radiation in a way that closely mimics low-energy X-ray treatments, while being compatible with widely available HDR brachytherapy equipment. Early technical studies suggest that it can deliver radiation accurately and safely, but its clinical effectiveness and safety in patients with rectal cancer have not yet been fully studied. This phase II prospective study aims to evaluate the feasibility, safety, and early treatment outcomes of using the Maastro applicator for brachytherapy in patients with rectal cancer. The study will assess how often the tumor completely disappears after treatment, how well the cancer is controlled over time, the side effects of treatment, and how patients' quality of life changes. The results of this study will help determine whether this treatment approach is suitable for wider clinical use and will contribute to improving future treatment options for patients with rectal cancer.

Conditions

Rectal Cancer

Keywords

HDR brachytherapy; Ractal cancer; Contact brachytherapy; MAASTRO applicator

Outcome Measures

Primary Outcomes (1)

• Clinical Complete Response (cCR) Rate

  Clinical complete response is defined as the absence of detectable residual tumor within the treated rectal wall following Maastro applicator HDR brachytherapy, as determined by a combination of clinical examination, endoscopic assessment, and imaging (pelvic MRI), with biopsy performed when clinically indicated. Complete response requires no visible tumor, no ulceration suspicious for malignancy, and no radiologic evidence of residual disease at the treated site.

  Within 6 months after completion of Maastro applicator HDR brachytherapy

Secondary Outcomes (7)

• Local Control Rate

  Up to 2 years after completion of Maastro applicator HDR brachytherapy

• Regional Control Rate

  Up to 2 years after completion of Maastro applicator HDR brachytherapy

• Progression-Free Survival (PFS)

  Up to 2 years after initiation of Maastro applicator HDR brachytherapy

• Overall Survival (OS)

  Up to 2 years after initiation of Maastro applicator HDR brachytherapy

• Incidence of Acute and Late Treatment-Related Toxicities

  From treatment initiation up to 2 years after completion of Maastro applicator HDR brachytherapy

Study Arms (1)

Rectal HDR brachytherapy

EXPERIMENTAL

The patient will be given HDR brachytherapy via Maastro Applicator either as a monotherapy or boost

Radiation: Rectal HDR brachytherapy via Maastro Applicator

Interventions

Rectal HDR brachytherapy via Maastro Applicator RADIATION

Participants in this study will receive endorectal high-dose-rate (HDR) brachytherapy using the Maastro applicator as part of an organ-preserving treatment approach for rectal cancer. The Maastro applicator is a specially designed endorectal device intended for use with a standard HDR afterloading brachytherapy system (Ir-192 source). It enables delivery of a high, localized radiation dose directly to the rectal tumor with a steep dose fall-off, thereby minimizing radiation exposure to surrounding normal tissues. Procedure and delivery The brachytherapy procedure will be performed in a controlled procedural or operating room environment. Prior to treatment, patient identity, informed consent, and procedural safety checks will be confirmed. Local anesthesia and/or sedation will be administered according to institutional practice and patient needs. A rectoscope will be gently inserted to visualize the rectal lumen. Tumor localization and treatment geometry will be confirmed using direct

Rectal HDR brachytherapy

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age ≥ 18 years at the time of informed consent Histologically confirmed rectal cancer Any T, N, or M stage, provided the primary rectal lesion is suitable for endorectal HDR brachytherapy Tumor characteristics deemed suitable for treatment with the Maastro applicator (per investigator assessment) Rectal lesion accessible for applicator placement and adequate visualization Adequate organ function to undergo sedation/anesthesia and brachytherapy, as judged by the investigator Ability to comply with study procedures, imaging, and scheduled follow-up Written informed consent obtained prior to study participation

You may not qualify if:

• Active inflammatory bowel disease with moderate to severe disease activity Uncontrolled proctitis not attributable to tumor involvement Severe anorectal conditions that preclude safe applicator placement (e.g., severe anal stenosis, uncontrolled hemorrhoidal bleeding, severe radiation-induced proctopathy in the target area) Any medical, psychiatric, or social condition that, in the opinion of the investigator, would interfere with safe study participation or interpretation of results

Sponsors & Collaborators

• Siriraj Hospital: lead

MeSH Terms

Conditions

Rectal Neoplasms

Condition Hierarchy (Ancestors)

Colorectal Neoplasms; Intestinal Neoplasms; Gastrointestinal Neoplasms; Digestive System Neoplasms; Neoplasms by Site; Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Intestinal Diseases; Rectal Diseases

Central Study Contacts

Wiwatchai Sittiwong, MD

CONTACT

66830081877; wiwatchai.sit@gmail.com

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Dr.

Study Record Dates

• First Submitted: February 4, 2026
• First Posted: February 11, 2026
• Study Start: March 1, 2026
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): December 31, 2027
• Last Updated: February 11, 2026

Record last verified: 2026-01