This Phase II single-arm clinical trial investigates the safety, tolerability, and therapeutic potential of high-bioavailability curcumin (BCM-95®) administered concurrently with neoadjuvant chemoradiotherapy (nCRT) in patients with mid- to low-rectal adenocarcinoma. The study is designed and conducted at Chang Gung Memorial Hospital, Linkou (Taiwan), under IRB approval and in accordance with Good Clinical Practice (GCP) guidelines.
Scientific Background and Rationale
Curcumin (diferuloylmethane) is a hydrophobic polyphenol extracted from Curcuma longa with extensive anti-inflammatory, antioxidant, and anti-neoplastic properties mediated through suppression of NF-κB, STAT3, COX-2, and multiple cell-signaling pathways. In preclinical models, curcumin inhibits radiation-induced activation of NF-κB and enhances radiosensitivity of colorectal-cancer cell lines, while protecting normal intestinal epithelium from irinotecan-induced mucosal injury by mitigating oxidative and endoplasmic-reticulum stress. Despite its excellent oral safety record (FDA GRAS Notice No. 686), conventional curcumin suffers from extremely low systemic bioavailability due to poor solubility and rapid metabolism.
BCM-95® Curcumin is a patented formulation that combines 95 % curcuminoids with turmeric essential oils, improving absorption approximately seven-fold compared with standard curcumin. Given its dual ability to radiosensitize tumor tissue and protect normal mucosa, BCM-95® Curcumin may attenuate radiation-induced enteritis while enhancing tumor regression and pathological complete-response (pCR) rates following nCRT.
Objectives
Primary Objective: To evaluate whether oral BCM-95® Curcumin can reduce the incidence and severity of radiation-induced gastrointestinal toxicity, particularly grade ≥ 3 proctitis/enteritis, during nCRT.
Secondary Objectives: To assess improvement in treatment response (clinical and pathological CR rates, tumor-regression grade), treatment completion rate, and quality-of-life indices; and to explore anti-cancer and immunomodulatory mechanisms through translational analyses of tumor and blood specimens.
Study Overview
A total of 72 patients with stage II-III (mid- to low-) rectal adenocarcinoma will receive standard long-course nCRT (50.4 Gy in 28 fractions with concurrent fluoropyrimidine-based chemotherapy) or equivalent short-course radiotherapy plus chemotherapy, along with oral BCM-95® Curcumin 3 g per day. Treatment begins concurrently with chemotherapy and continues through the full nCRT period. Follow-up includes surgical resection or a watch-and-wait strategy based on clinical response.
Each participant undergoes serial evaluations:
Baseline: history, colonoscopy, pelvic MRI, CT staging, laboratory profile, and CEA.
During therapy: bi-weekly hematology and biochemistry tests; adverse-event assessment (CTCAE v5.0, RTOG/EORTC criteria).
Post-radiation (2-3 weeks): colonoscopy graded by Vienna Rectoscopy Score to quantify acute proctitis.
At completion of nCRT: pelvic MRI and colonoscopy for clinical response evaluation.
Surgery or watch-and-wait: histopathologic examination for pCR and tumor-regression grade.
Translational research includes multiplex immunohistochemistry on paired tumor and adjacent mucosa (pre-treatment, post-radiation, post-CRT) and peripheral-blood analyses for immune-cell phenotyping (BD FACSymphony panel), cytokine profiling (MILLIPLEX array), and circulating-tumor-DNA (ctDNA) monitoring. These studies aim to correlate molecular and immune alterations with clinical outcomes.
Run-in Cohort (Safety Lead-in)
A run-in phase enrolling 6 patients will precede full recruitment. Dose-limiting toxicities (DLTs) include grade ≥ 3 non-hematologic AEs (except expected nausea/vomiting), ALT/AST \> 3×ULN (confirmed) or \> 5×ULN any time, bilirubin \> 2×ULN with hepatic enzyme elevation, grade 4 hematologic toxicity \> 7 days, or any toxicity requiring treatment interruption \> 2 weeks. If ≤ 1/6 patients develops a DLT, the study proceeds to full Phase II enrollment (n = 72).
Endpoints
Primary Endpoint: Incidence of grade ≥ 3 gastrointestinal toxicity (enteritis/proctitis) evaluated by NCI CTCAE v5.0 and RTOG/EORTC criteria.
Secondary Endpoints: (1) Vienna Rectoscopy Score; (2) any grade III AEs during therapy; (3) clinical CR rate (RECIST v1.1); (4) pathological CR rate; (5) treatment completion rate.
Exploratory Endpoints: three-year disease-related failure rate, five-year overall survival, and molecular/immunologic correlates.
Statistical Considerations
The sample size (n = 72, 64 evaluable) was calculated by an exact one-proportion test (80 % power, α = 0.05) to detect a 15 % absolute reduction in acute radiation proctitis (30 % → 15 %). Efficacy and safety analyses follow the intent-to-treat principle. Categorical variables will be analyzed by χ² or Fisher's exact test; continuous variables by t or Mann-Whitney U test; survival by Kaplan-Meier and log-rank tests (p \< 0.05 two-sided). Analyses will be performed in SPSS v24.
Safety Monitoring and Ethics
Safety is assessed continuously through bi-weekly labs and AE documentation. Curcumin is paused if ALT/AST \> 3×ULN until recovery. Serious adverse events (SAEs) are reported to the Chang Gung IRB per institutional policy. The study follows the Declaration of Helsinki and GCP standards. All participants provide written informed consent. Confidentiality is maintained via coded identifiers; data access is restricted to authorized investigators.
Data and Safety Monitoring Plan (DSMP)
Enrollment review every 3 months by PI.
SAE review quarterly by Safety Officer.
Protocol deviation audit monthly by Clinical Research Coordinator.
Data integrity checked continuously by Data Manager. All findings are reported to the sponsor and IRB.
Anticipated Impact
This study will provide clinical and molecular evidence for the potential of high-bioavailability curcumin as a safe adjunct to neoadjuvant chemoradiotherapy in rectal cancer, with the dual goals of reducing treatment-related toxicity and enhancing tumor response and long-term oncologic outcomes. If proven beneficial, curcumin could be a cost-effective, natural, and readily implementable adjuvant strategy for improving tolerance and quality of life in rectal cancer patients undergoing multimodality therapy.
