Inclusion Criteria:
* Documented informed consent of the participant and/or legally authorized representative
* Assent, when appropriate, will be obtained per institutional guidelines
* Agreement to allow the use of archival tissue from diagnostic tumor biopsies
* If unavailable, exceptions may be granted with study principal investigator (PI) approval
* Age: ≥ 18 years
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
* Histologically or cytologically confirmed appendiceal or colorectal cancer peritoneal metastases
* No extraperitoneal metastases except lung ≤ 5 lesions with largest ≤ 1cm as identified on CT imaging or MRI. CT scan or MRI to assess measurable disease must have been completed within 28 days prior to registration
* Visible peritoneal metastatic disease on cross-sectional imaging or diagnostic laparoscopy (does not have to be measurable by RECIST (v1.1)
* Completed at least 4 months (8 cycles) of first-line standard-of-care oxaliplatin-based systemic therapy without progression of disease. Or completed less than 4 months of oxaliplatin based therapy due to intolerance and without progressive disease. Or progressed on first-line standard-of-care oxaliplatin-based systemic therapy. Permissible first-line systemic therapies include leucovorin calcium, fluorouracil, and oxaliplatin (FOLFOX) or capecitabine and oxaliplatin (XELOX) or fluorouracil, leucovorin, oxaliplatin and irinotecan (FOLFOXIRI). Receipt of anti-EGFR, anti-VEGF, or anti-BRAF therapy in the first-line is acceptable. Mismatch repair-deficient patients are permissible if they have progressed on first-line immunotherapy
* Not a candidate for cytoreductive surgery as determined by site investigator
* Fully recovered from the acute toxic effects of prior anti-cancer therapy to Common Terminology Criteria for Adverse Events (CTCAE) grade 1 or lower except alopecia, hearing loss, neuropathy, or non-clinically significant laboratory abnormalities
* Complete medical history and physical exam (To be performed within 28 days prior to Day 1 of protocol therapy)
* Absolute neutrophil count (ANC) ≥ 1,500/mcL (To be performed within 28 days prior to Day 1 of protocol therapy)
* Platelets ≥ 100,000/mcL (To be performed within 28 days prior to Day 1 of protocol therapy)
* Hemoglobin ≥ 8 g/dL (To be performed within 28 days prior to Day 1 of protocol therapy)
* Serum albumin ≥ 2.8 g/dL (To be performed within 28 days prior to Day 1 of protocol therapy)
* Total bilirubin ≤ 1.5 X upper limit of normal (ULN) (unless has Gilbert's disease, then direct bilirubin \< 1.5 mg/dL) (To be performed within 28 days prior to Day 1 of protocol therapy)
* Aspartate aminotransferase (AST) ≤ 5 x ULN (To be performed within 28 days prior to Day 1 of protocol therapy)
* Alanine aminotransferase (ALT) ≤ 5 x ULN (To be performed within 28 days prior to Day 1 of protocol therapy)
* Calculated creatinine clearance of ≥ 45 mL/min per 24-hour urine test or the Cockcroft-Gault formula (To be performed within 28 days prior to Day 1 of protocol therapy)
* Women of childbearing potential (WOCBP): Negative urine or serum pregnancy test (To be performed within 28 days prior to Day 1 of protocol therapy)
* If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required
* Agreement by females and males of childbearing potential to use an effective method of birth control (e.g. licensed hormonal/barrier methods or surgery intended to prevent pregnancy \[or with a side effect of pregnancy prevention\]) or abstain from heterosexual activity for the course of the study through at least 14 months after the last dose of protocol therapy
* Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for \> 1 year (women only)
* CROSS-OVER ARM INCLUSION: Documented informed consent of the participant and/or legally authorized representative
* Assent, when appropriate, will be obtained per institutional guidelines
* CROSS-OVER ARM INCLUSION: Agreement to allow the use of archival tissue from diagnostic tumor biopsies
* If unavailable, exceptions may be granted with Study PI approval
* CROSS-OVER ARM INCLUSION: Age: ≥ 18 years
* CROSS-OVER ARM INCLUSION: ECOG performance status of 0 or 1
* CROSS-OVER ARM INCLUSION: No extraperitoneal metastases except lung ≤ 5 lesions with largest ≤ 1cm as identified on CT imaging or MRI. CT scan or MRI to assess measurable disease must have been completed within 28 days prior to registration
* CROSS-OVER ARM INCLUSION: Progression on Control Arm of the Study as determined by RECIST v1.1. Non-radiographic progression will need to be assessed on a case-by-case basis by central review
* CROSS-OVER ARM INCLUSION: Fully recovered from the acute toxic effects of prior anti-cancer therapy to CTCAE grade 1 or lower except alopecia, hearing loss, neuropathy, or non-clinically significant laboratory abnormalities
* CROSS-OVER ARM INCLUSION: Complete medical history and physical exam (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: ANC ≥ 1,500/mcL (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: Platelets ≥ 100,000/mcL (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: Hemoglobin ≥ 8 g/dL (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: Serum albumin ≥ 2.8 g/dL (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: Total bilirubin ≤ 1.5 X ULN (unless has Gilbert's disease, then direct bilirubin \<1.5 mg/dL) (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: AST ≤ 5 x ULN (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: ALT ≤ 5 x ULN (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: Calculated creatinine clearance of ≥ 45 mL/min per 24-hour urine test or the Cockcroft-Gault formula (To be performed within 28 days prior to Day 1 of protocol therapy)
* CROSS-OVER ARM INCLUSION: Women of childbearing potential (WOCBP): negative urine or serum pregnancy test (To be performed within 28 days prior to Day 1 of protocol therapy)
* If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required
* CROSS-OVER ARM INCLUSION: Agreement by females and males of childbearing potential to use an effective method of birth control (e.g. licensed hormonal/barrier methods or surgery intended to prevent pregnancy \[or with a side effect of pregnancy prevention\]) or abstain from heterosexual activity for the course of the study through at least 14 months after the last dose of protocol therapy
* Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for \> 1 year (women only)
Exclusion Criteria:
* More than 8 cycles of first line irinotecan therapy
* Progression on irinotecan
* Receipt of any second-line systemic chemotherapy (Note: Sequential administration of FOLFOX followed by FOLFIRI is considered second line therapy. However, FOLFOXIRI followed by FOLFIRI is considered first line as long as no more than 8 cycles of irinotecan are given)
* Any concurrent chemotherapy, investigational product, biologic, or hormonal therapy for cancer treatment. Concurrent use of hormonal therapy for non-cancer-related conditions (e.g., hormone replacement therapy) is acceptable
* Strong CYP3A4 inducers/inhibitors within 14 days prior to Day 1 of protocol therapy
* Prior peritoneal-directed chemotherapy (Prior cytoreductive surgery is permitted)
* Participation in another clinical study with an investigational product administered in the last 2 months
* Concurrent enrollment in another clinical study, unless it is an observational (non-interventional) clinical study or during the follow-up period of an interventional study
* Low-grade appendiceal mucinous neoplasm or low-grade appendiceal mucinous adenocarcinoma
* Extraperitoneal metastases (except lung ≤ 5 lesions with largest being ≤ 1cm)
* Any history of bowel obstruction requiring nasogastric tube, percutaneous endoscopic gastrostomy, or need for total parenteral nutrition. Even if the bowel obstruction resolved with conservative measures, the patient would be excluded. The exception is if the bowel obstruction was surgically addressed with ostomy, resection or bypass. This exception should be documented
* Fused mesenteric disease-causing mesenteric shortening and bowel sequestration ("cauliflowering")
* Bulky mesenteric disease where chemotherapy is unlikely to penetrate the tumor
* Contraindication to laparoscopy
* Rapid weight loss (\> 10% in \< 3 months)
* Ascites (\> 2L drained per month)
* Adhesions involving \> 50% of abdominal cavity on diagnostic laparoscopy
* Life expectancy \< 6 months
* Treatment with therapeutic oral or IV antibiotics within 14 days prior to Day 1 Cycle 1 of treatment
* Patients receiving prophylactic antibiotics are eligible, provided the signs of active infection have resolved
* Any prior malignancy except adequately treated basal or squamous cell skin cancer, in situ cervical cancer, adequately treated stage I or II cancer from which the patient is currently in complete remission, or any other cancer from which the patient has been disease-free for two years
* History of allergic or hypersensitivity reactions attributed to compounds of similar chemical or biologic composition to study agents (platinum-based compounds, etc.)
* History of allogeneic organ transplantation or other active primary immunodeficiency
* Active and uncontrolled infection, including tuberculosis (clinical evaluation that includes clinical history, physical examination and radiographic findings, and tuberculosis testing in line with local practice), or human immunodeficiency virus (positive HIV 1/2 antibodies)
* Clinically significant uncontrolled illness, including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina pectoris, uncontrolled cardiac arrhythmia, active interstitial lung disease (ILD), serious chronic gastrointestinal conditions associated with diarrhea, or psychiatric illness/social situations that would limit compliance with study requirement, substantially increase the risk of incurring AEs, or compromise the ability of the patient to give written informed consent
* Females only: Pregnant or breastfeeding
* Any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
* Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)
* CROSS-OVER ARM EXCLUSION: Any concurrent chemotherapy, investigational product, biologic, or hormonal therapy for cancer treatment. Concurrent use of hormonal therapy for non-cancer-related conditions (e.g., hormone replacement therapy) is acceptable
* CROSS-OVER ARM EXCLUSION: Strong CYP3A4 inducers/inhibitors within 14 days prior to Day 1 of protocol therapy
* CROSS-OVER ARM EXCLUSION: Participation in another clinical study with an investigational product administered in the last 2 months other than the current study
* CROSS-OVER ARM EXCLUSION: Concurrent enrollment in another clinical study, unless it is an observational (non-interventional) clinical study or during the follow-up period of an interventional study
* CROSS-OVER ARM EXCLUSION: Extraperitoneal metastases (except lung ≤ 5 lesions with largest being ≤ 1cm)
* CROSS-OVER ARM EXCLUSION: Any history of bowel obstruction requiring nasogastric tube, percutaneous endoscopic gastrostomy, or need for total parenteral nutrition. Even if the bowel obstruction resolved with conservative measures, the patient would be excluded. The exception is if the bowel obstruction was surgically addressed with ostomy, resection or bypass. This exception should be documented
* CROSS-OVER ARM EXCLUSION: Fused or bulky mesenteric disease-causing mesenteric shortening and bowel sequestration
* CROSS-OVER ARM EXCLUSION: Contraindication to laparoscopy
* CROSS-OVER ARM EXCLUSION: Rapid weight loss (\> 10% in \< 3 months)
* CROSS-OVER ARM EXCLUSION: Ascites (\> 2L drained per month)
* CROSS-OVER ARM EXCLUSION: Adhesions involving \> 50% of abdominal cavity on diagnostic laparoscopy
* CROSS-OVER ARM EXCLUSION: Life expectancy \< 6 months
* CROSS-OVER ARM EXCLUSION: Treatment with therapeutic oral or IV antibiotics within 14 days prior to Day 1 Cycle 1 of treatment
* Patients receiving prophylactic antibiotics are eligible, provided the signs of active infection have resolved