This randomized phase II trial studies how well veliparib or pembrolizumab work with combination chemotherapy and radiation therapy in treating patients with rectal cancer that has spread from where it started to nearby tissue or lymph nodes (locally advanced). Veliparib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Drugs used in chemotherapy, such as modified (m)FOLFOX6 regimen, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Radiation therapy uses high-energy x-rays to kill tumor cells and shrink tumors. Giving veliparib or pembrolizumab with combination chemotherapy and radiation therapy may kill more tumor cells, make the tumor smaller, and reduce the amount of normal tissue that needs to be removed.
PRIMARY OBJECTIVE: I. To demonstrate an absolute improvement in neoadjuvant rectal cancer (NAR) score for the experimental regimen as compared to concurrently randomized control patients. SECONDARY OBJECTIVES: I. To compare overall survival (OS). II. To compare disease-free survival (DFS). III. To compare the rate of pathologic complete response (pCR) (nodes and tumor). IV. To compare the rate of sphincter preservation. TERTIARY OBJECTIVES: I. To compare the proportion of patients who have a tumor resection overall, conditional on beginning induction chemotherapy, and conditional on beginning chemoradiotherapy. II. To compare time from initiation of chemoradiotherapy to surgery in the subset of patients with tumor resection. EXPLORATORY OBJECTIVES: I. To estimate the rate of disease progression during chemotherapy (prior to chemoradiation). II. To compare the rate of clinical complete response rate (cCR). III. To compare the rate of negative circumferential margin. IV. To compare the rate of completion of all cycles of neoadjuvant chemotherapy. V. To compare the rate of completion of full course of chemoradiation. VI. To compare the toxicity and safety between interventions. VII. To explore the correlative molecular predictors of response and distant failure. VIII. To explore the relationship between radiographic findings and pathologic outcomes. OUTLINE: Patients are sequentially randomized to treatment arms, initially ARM I or ARM II and then later either ARM I or ARM III. ARM I: Patients receive mFOLFOX6 regimen consisting of oxaliplatin intravenously (IV) over 2 hours, leucovorin calcium IV over 2 hours on day 1, and fluorouracil IV continuously over 46-48 hours on days 1-2. Treatment repeats every 2 weeks for 8 cycles in the absence of disease progression or unacceptable toxicity. 3-4 weeks after last does of mFOLFOX6 patient undergo radiation therapy (RT) and receive capecitabine orally (PO) twice daily (BID) Monday-Friday for 5 weeks in the absence of disease progression or unacceptable toxicity. ARM II: Patients receive mFOLFOX6 regimen consisting of oxaliplatin IV over 2 hours, leucovorin calcium IV over 2 hours on day 1, and fluorouracil IV continuously over 46-48 hours on days 1-2. Treatment repeats every 2 weeks for 8 cycles in the absence of disease progression or unacceptable toxicity. 3-4 weeks after last does of mFOLFOX6 patient undergo RT and receive capecitabine PO BID and veliparib PO BID Monday-Friday for 5 weeks in the absence of disease progression or unacceptable toxicity. ARM III: Patients receive mFOLFOX6 regimen consisting of oxaliplatin IV over 2 hours, leucovorin calcium IV over 2 hours on day 1, and fluorouracil IV continuously over 46-48 hours on days 1-2. Treatment repeats every 2 weeks for 8 cycles in the absence of disease progression or unacceptable toxicity. 3-4 weeks after last does of mFOLFOX6 patient undergo RT and receive capecitabine PO BID Monday-Friday for 5 weeks. They also receive pembrolizumab IV over 30 minutes every 3 weeks beginning on day 1 of RT for up to 6 cycles in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 days and every 6 months for up to 3 years.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
363
Given PO
Given IV
Undergo intensity modulated radiation therapy
Given IV
Given IV
Given IV
Given PO
University of Alabama at Birmingham Cancer Center
Birmingham, Alabama, United States
Southern Cancer Center PC-Mobile
Mobile, Alabama, United States
Southern Cancer Center PC-Providence
Mobile, Alabama, United States
Southern Cancer Center PC-Springhill
Mobile, Alabama, United States
University of South Alabama Mitchell Cancer Institute
Mobile, Alabama, United States
Neoadjuvant Rectal Cancer (NAR) Score
A linear regression model that controls for the stratification factors (cT-stage and cN-stage) will be used. Mean NAR scores along with standard errors and confidence intervals will be reported by treatment. The NAR score ranges from zero to 100 with lower values corresponding to better prognosis.
Time frame: Baseline to up to 3 years
Overall Survival
Analyzed using the stratified log rank test with strata cT-stage and cN-stage. Kaplan-Meier plots will illustrate the distribution of these endpoints by treatment. Cox regression models will be used to estimate hazard ratios and associated confidence intervals.
Time frame: Time from randomization, assessed up to 3 years
Disease Free Survival
Analyzed using the stratified log rank test with strata cT-stage and cN-stage. Kaplan-Meier plots will illustrate the distribution of these endpoints by treatment. Cox regression models will be used to estimate hazard ratios and associated confidence intervals.
Time frame: Time from randomization, assessed up to 3 years
Rate of Pathologic Complete Response (Nodes and Tumor) ypT0 and ypN0
Pathologic Complete Response means no remaining cancer detectable in the pathology sample. Analyzed by a logistic regression model that controls for the stratification factors (cT-stage and cN-stage). Observed proportions along with confidence intervals will be presented by treatment.
Time frame: Up to 3 years
Rate of Sphincter Preservation
Sphincter preservation means that the surgical procedure used to remove the tumor did not disturb the sphincter muscle. Analyzed by a logistic regression model that controls for the stratification factors (cT-stage and cN-stage). Observed proportions along with confidence intervals will be presented by treatment.
Time frame: Up to 3 years
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