Ph II Intraperitoneal Paclitaxel + System Therapy in GI Ca w/Peritoneal Carcinomatosis (STOPGAP-B)

Inclusion Criteria:

* Cohort A: Patients must have histologically or cytologically confirmed primary gastric or gastroesophageal adenocarcinoma with a clinical diagnosis of metachronous PC with a history of prior gastric cancer resection. Extraperitoneal metastases are allowed.
* Cohort B: Patients must have histologically or cytologically confirmed primary colorectal or appendiceal adenocarcinoma with PC . Extraperitoneal metastases are allowed. Patients with PC amenable to cytoreductive surgery (CRS) without the need for upfront systemic therapy as determined by a peritoneal malignancy surgeon within 4 weeks prior to enrollment are excluded.
* Cohort C: Patients must have adenocarcinomas of the digestive tract with PC not included in Cohorts A and B (including but not limited to carcinomas of the small bowel and hepatobiliary tract).
* Must have peritoneal cytology positive disease or peritoneal carcinomatosis detected by imaging, laparoscopy or laparotomy
* Age ≥ 18
* Performance status: ECOG performance status ≤ 2 (Appendix A) . ECOG 2 allowed if attributed to malignancy (rather than comorbidities)
* Life expectancy of greater than 3 months
* Adequate organ and marrow function as defined below: Leukocytes: ≥ 2,000/mcL; Absolute neutrophil count: ≥ 1,500/mcL (may receive gcsf); Platelets: ≥ 70,000/mcl (may receive TPO); Total bilirubin: within 2x of normal institutional limit; AST(SGOT)/ALT(SPGT): ≤5 X institutional upper limit of normal; Creatinine: \< 2 X institutional upper limit of normal; Hemoglobin: Hemoglobin \> 8.0 g/dL (may be transfused); Serum albumin: ≥ 2.5 g/dL
* Ability to understand and the willingness to sign a written informed consent

Exclusion Criteria:

* Any evidence of small or large bowel obstruction with the exception of gastric outlet obstruction due to primary malignancy
* Uncontrolled intercurrent illness including, but not limited to, the following conditions: Ongoing or active infection; Symptomatic congestive heart failure; Stroke (including transient ischemic attack \[TIA\]), myocardial infarction (MI), or other ischemic event,) within 3 months before initiation of treatment; Unstable angina pectoris; Cardiac arrhythmia
* History of another primary cancer within the last 3 years with the exception of non-melanoma skin cancer, early-stage prostate cancer, or curatively treated cervical carcinoma in-situ and not treated with systemic therapy.
* History of prior iterative intraperitonealtherapy administered either as HIPEC, PIPAC or NIPEC. Single exposure to HIPEC at the time of cytreduction is not an exclusion
* Inability to comply with study and follow-up procedures as judged by the Investigator
* Patients must not be pregnant or nursing due to the potential for congenital abnormalities and the potential of this regimen to harm nursing infants.
* Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 90 days following completion of therapy. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately.
* Has an active infection requiring systemic therapy.
* Prior surgery that would preclude safe diagnostic laparoscopy and port placement
* Has a known history of active tuberculosis (TB; Bacillus tuberculosis).
* Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the study, interfere with the participant's participation for the full duration of the study, or is not in the best interest of the participant to participate, in the opinion of the treating investigator.