Shortening Radiation Course Duration Using Simultaneous Integrated Boost With Lower Intensity Elective Nodal Dosing and Concurrent Chemotherapy for High-Risk Anal Squamous Cell Carcinoma (SSIBLING)

Shortening Radiation Course Duration Via Simultaneous Integrated Boost With Lower Intensity Elective Nodal Dosing While Giving Concurrent Chemotherapy for High-risk Anal Squamous Cell Carcinoma - a Phase 2 Study

This phase 2 single-arm study will evaluate whether a shortened course of mildly hypofractionated radiation therapy given with standard concurrent chemotherapy (mitomycin C and capecitabine) can provide acceptable tumor control in patients with high-risk non-metastatic anal squamous cell carcinoma. Standard chemoradiation for anal cancer typically requires approximately 5.5 to 6 weeks of daily radiation, which can create substantial logistical burden for patients and caregivers, particularly those in rural settings.

The investigational approach uses a 23-fraction radiation regimen designed to shorten treatment duration while maintaining biologically equivalent tumor-directed dosing compared with standard treatment. The primary question is whether this shorter chemoradiation regimen can achieve an acceptable 6-month complete clinical response rate while maintaining manageable toxicity.

Study Overview

• Status: Not yet recruiting
• Conditions: Anal Cancer
• Intervention / Treatment: Radiation: Hypofractionated Radiation Therapy

Detailed Description

Standard chemoradiation for high-risk non-metastatic anal squamous cell carcinoma typically requires approximately 27 to 30 fractions of radiation delivered over 5.5 to 6 weeks with concurrent chemotherapy. While effective, this prolonged treatment course creates substantial logistical burden for patients and caregivers, particularly for those living in rural regions with limited access to radiation oncology facilities.

This phase 2, single-arm study evaluates a shortened hypofractionated chemoradiation approach designed to reduce treatment duration while maintaining biologically comparable tumor-directed dosing relative to conventional treatment regimens. The investigational radiation regimen uses a simultaneous integrated boost (SIB) approach delivering 23 fractions over approximately 4.5 weeks, with reduced elective nodal dosing and concurrent standard-of-care chemotherapy consisting of mitomycin C and capecitabine.

The study focuses on patients with high-risk non-metastatic anal squamous cell carcinoma, including larger primary tumors and/or node-positive disease, a population for whom treatment de-escalation strategies are generally not appropriate. The primary objective is to evaluate whether this shortened regimen achieves an acceptable 6-month complete clinical response rate. Secondary objectives include assessment of survival outcomes, disease control, treatment interruptions, clinician- and patient-reported toxicity, quality of life, and treatment burden.

Exploratory correlative analyses will evaluate circulating tumor DNA (ctDNA) collected at protocol-specified time points to assess correlations between circulating biomarkers and clinical outcomes. The study also includes optional qualitative patient and caregiver interviews to better understand treatment experience and logistical burden associated with cancer therapy.

• Study Type: Interventional
• Enrollment (Estimated): 24
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Chris Anker, MD; Phone Number: 1 (802) 656-2021; Email: chris.anker@uvmhealth.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 18 years or older
• Histologically or cytologically confirmed non-metastatic anal squamous cell carcinoma meeting one of the following criteria:

T2 tumor measuring ≥4 cm T3 or T4 disease Any node-positive disease

• Patients with HPV-associated (p16-positive) perianal cancer are eligible if the tumor extends to the anal verge
• Karnofsky Performance Status >60
• Creatinine clearance >30 mL/min
• Considered by the investigator to be appropriate candidates for concurrent capecitabine and mitomycin C chemotherapy
• Ability to understand and willingness to provide informed consent
• For participants of childbearing potential: negative pregnancy test or documented absence of pregnancy per institutional standard within 14 days prior to registration
• Participants of reproductive potential must agree to use adequate contraception during study treatment and for 90 days after completion of therapy

Exclusion Criteria:

• Prior pelvic radiation therapy
• Uncontrolled intercurrent illness that, in the opinion of the investigator, would prevent safe receipt of radiation therapy or capecitabine
• Prior or concurrent malignancy that, in the opinion of the investigator, could interfere with assessment of safety or efficacy
• Current receipt of another investigational agent for treatment of anal squamous cell carcinoma

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Experimental: Hypofractionated Chemoradiation; Participants receive mildly hypofractionated radiation therapy delivered in 23 fractions using a simultaneous integrated boost approach with concurrent standard-of-care mitomycin C and capecitabine chemotherapy.	Radiation: Hypofractionated Radiation Therapy; Participants receive mildly hypofractionated radiation therapy delivered in 23 fractions using a simultaneous integrated boost approach, given concurrently with standard-of-care mitomycin C and capecitabine chemotherapy.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Complete Clinical Response Rate at 6 Months	Proportion of participants achieving complete clinical response, defined as absence of tumor and malignant ulceration in the anal canal and perianal skin on digital rectal examination and/or anoscopy, with resolution of palpable inguinal lymphadenopathy if present at baseline. Biopsy may be used when clinically indicated to confirm persistent disease.	6 months after start of radiation therapy

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Colostomy-Free Survival	Time from completion of treatment to colostomy placement or last follow-up without colostomy.	2 years
Disease-Free Survival	Time from study registration to disease progression, recurrence, or death from any cause.	2 years
Locoregional Control	Proportion of participants without locoregional disease failure involving the primary tumor or regional lymph node sites.	2 years
Local Control Rate	Proportion of participants without local recurrence at the primary tumor site.	2 years
Regional Control Rate	Proportion of participants without recurrence in regional lymph node sites.	2 years
Elective Regional Control Rate	Proportion of participants without recurrence in electively treated nodal regions.	2 years
Distant Metastasis-Free Survival	Time from study registration to development of distant metastatic disease or death.	2 years
Overall Survival	Time from study registration to death from any cause.	2 years
Treatment Interruption Rate	Proportion of participants experiencing interruption or delay in planned protocol treatment.	During treatment (approximately 5 weeks)
Treatment-Related Toxicity	Incidence of clinician-reported treatment-related adverse events graded according to CTCAE version 6.0.	Baseline through 24 months
Patient-Reported Treatment-Related Symptoms	Patient-reported gastrointestinal, genitourinary, skin, and functional symptoms assessed using PRO-CTCAE.	Baseline through 24 months
Fecal Incontinence Severity Index Score	The Fecal Incontinence Severity Index is a patient-reported measure of fecal incontinence severity based on the frequency of accidental leakage of gas, mucus, liquid stool, and solid stool. Total scores range from 0 to 61, with higher scores indicating more severe fecal incontinence.	Baseline through 24 months
Hazard Ratio for Clinical Recurrence According to HPV ctDNA Detection Status	HPV ctDNA will be measured in serial plasma samples using a laboratory-based HPV ctDNA assay and categorized as detectable or undetectable. We will assess the correlation between baseline HPV ctDNA levels and selected clinical features via a Wilcoxon test. We will test for correlations between HPV ctDNA detection and recurrence-free survival using a landmark Cox proportional hazards model, with recurrence-free survival compared using the log-rank test Clinical recurrence will be based on radiographic imaging, endoscopic assessment, and/or clinical examination, as determined by the evaluating physician. HPV ctDNA detection will not be considered a recurrence event.	Baseline through 24 months
Patient and Caregiver Treatment Experience Assessed Through Qualitative Interviews	Patient and caregiver experiences will be assessed using semi-structured Patient and Caregiver/Support Person Experience Interviews. Interview responses will be reviewed to identify common themes related to treatment burden, convenience, travel requirements, caregiver impact, treatment tolerance, and perceptions of the shortened treatment course.	Approximately 3 months after treatment
Fecal Incontinence Quality of Life Scale Domain Scores	The Fecal Incontinence Quality of Life Scale measures quality of life across four domains: lifestyle, coping/behavior, depression/self-perception, and embarrassment. Domain scores range from 1 to 5, with higher scores indicating better quality of life.	Baseline through 24 months
Baseline HPV ctDNA Levels According to Selected Clinical Features	Baseline HPV ctDNA levels will be measured in plasma using a laboratory-based HPV ctDNA assay. Correlations between baseline HPV ctDNA levels and selected demographic and disease-related clinical features will be assessed using a Wilcoxon test.	Baseline

Collaborators and Investigators

• Sponsor: University of Vermont Medical Center
• Investigators: Principal Investigator: Christopher L Anker, MD, University of Vermont Cancer Center

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2029
• Primary Completion (Estimated): May 1, 2039
• Study Completion (Estimated): April 1, 2040

Study Registration Dates

• First Submitted: August 2, 2026
• First Submitted That Met QC Criteria: August 17, 2026
• First Posted (Actual): August 20, 2026

Study Record Updates

• Last Update Posted (Actual): August 20, 2026
• Last Update Submitted That Met QC Criteria: August 17, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Circulating Tumor DNA; Hypofractionated Radiation Therapy; anal squamous cell carcinoma
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Intestinal Diseases; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Colorectal Neoplasms; Intestinal Neoplasms; Rectal Diseases; Anus Diseases; Rectal Neoplasms; Anus Neoplasms
• Other Study ID Numbers: UVMCC2604; temp (Other Grant/Funding Number: University of Vermont Cancer Center)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared because no IPD-sharing plan has been established for this small investigator-initiated study. Study findings may be reported in aggregate form.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No