Inclusion Criteria:

• ≥ 12 years of age at the time of informed consent.
• New-onset moderate or severe cGVHD, as defined by the 2014 NIH Consensus Development Project Criteria for Clinical Trials in cGVHD, requiring systemic therapy.
• History of allo-HCT from any donor HLA type (related or unrelated donor with any degree of HLA matching) using any graft source (bone marrow, peripheral blood stem cells, or cord blood). Recipients of myeloablative, nonmyeloablative, or reduced-intensity conditioning are eligible.
• Adequate hematologic function with ANC ≥ 0.5 × 109/L independent of growth factors for at least 7 days prior to study entry.
• Willingness to avoid pregnancy or fathering children.

Exclusion Criteria:

• Received more than 1 prior allo-HCT. Prior autologous HCT is allowed.
• Has overlap cGVHD, defined as simultaneous presence of features or characteristics of aGVHD in a patient with cGVHD.
• Received more than 7 days of systemic corticosteroid treatment for cGVHD or unable to begin a prednisone dose ≥ 1.0 mg/kg per day (or methylprednisolone equivalent) for cGVHD.
• Received previous systemic treatment for cGVHD, including extracorporeal photopheresis.
• Systemic treatment with CNIs or mTOR inhibitors started within 2 weeks prior to C1D1.
• Prior treatment with CSF-1R targeted therapies.
• Active, uncontrolled bacterial, fungal, parasitic, or viral infection.
• Evidence of relapse of the primary hematologic disease or treatment for relapse after the allo-HCT was performed, including DLIs for the treatment of molecular relapse.
• History of acute or chronic pancreatitis.
• Active symptomatic myositis.
• History or current diagnosis of cardiac disease indicating significant risk of safety for participation in the study, such as uncontrolled or significant cardiac disease.
• Severe renal impairment, that is, estimated CrCl < 30 mL/min measured or calculated by Cockcroft-Gault equation in adults and Schwartz formula in pediatric participants, or endstage renal disease on dialysis.
• Impaired liver function, defined as total bilirubin > 1.5 × ULN and/or ALT and AST > 3 × ULN in participants with no evidence of liver cGVHD.
• Pregnant or breastfeeding.

Other protocol-defined Inclusion/Exclusion Criteria may apply.

Inclusion Criteria:

• Patients must be 5 to 60 years of age at the time of enrollment
• Patients with newly diagnosed untreated histologically confirmed classic Hodgkin lymphoma (cHL) (nodular sclerosis, mixed cellularity, lymphocyte-rich, or lymphocyte-depleted, or not otherwise specified [NOS]) with stage I or II disease
• Patients must have bidimensionally measurable disease (at least one lesion with longest diameter >= 1.5 cm)
• Patients must have a whole body or limited whole body PET scan performed within 42 days prior to enrollment. PET-CT is strongly preferred. PET-MRI allowed if intravenous contrast enhanced CT is also obtained
• Pediatric patients (age 5-17 years) with known or suspected mediastinal disease must have an upright posteroanterior (PA) chest X-ray (CXR) for assessment of bulky mediastinal disease.
• Note: Pediatric patients who have received both a CT chest and upright PA CXR may meet the definition of bulk through either modality.
• Patients >= 18 years must have a performance status corresponding to Zubrod scores of 0, 1 or 2
• Patients =< 17 years of age must have a Lansky performance score of >= 50
• Pediatric patients (age 5-17 years): A serum creatinine based on age/sex as follows (within 28 days prior to enrollment):
• 2 to < 6 years (age): 0.8 mg/dL (male), 0.8 mg/dL (female)
• 6 to < 10 years (age): 1 mg/dL (male), 1 mg/dL (female)
• 10 to < 13 years (age): 1.2 mg/dL (male), 1.2 mg/dL (female)
• 13 to < 16 years (age): 1.5 mg/dL (male), 1.4 mg/dL (female)
• >= 16 years (age): 1.7 mg/dL (male), 1.4 mg/dL (female) OR a 24 hour urine creatinine clearance >= 50 mL/min/1.73 m^2 (within 28 days prior to enrollment) OR a glomerular filtration rate (GFR) >= 50 mL/min/1.73 m^2 (within 28 days prior to enrollment). GFR must be performed using direct measurement with a nuclear blood sampling method OR direct small molecule clearance method (iothalamate or other molecule per institutional standard)
• Note: Estimated GFR (eGFR) from serum or plasma creatinine, cystatin C or other estimates are not acceptable for determining eligibility
• For adult patients (age 18 years or older) (within 28 days prior to enrollment): Creatinine clearance >= 30 mL/min, as estimated by the Cockcroft and Gault formula or a 24-hour urine collection. The creatinine value used in the calculation must have been obtained within 28 days prior to registration. Estimated creatinine clearance is based on actual body weight
• Total bilirubin =< 2 x upper limit of normal (ULN) (within 28 days prior to enrollment)
• Unless due to Gilbert's disease, lymphomatous involvement of liver or vanishing bile duct syndrome
• Aspartate aminotransferase (AST) =< 3 x ULN (within 28 days prior to enrollment)
• Unless due to Gilbert's disease, lymphomatous involvement of liver or vanishing bile duct syndrome
• Alanine aminotransferase (ALT) =< 3 x ULN (within 28 days prior to enrollment)
• Unless due to Gilbert's disease, lymphomatous involvement of liver or vanishing bile duct syndrome
• Shortening fraction of >= 27% by echocardiogram (ECHO), multigated acquisition scan (MUGA), or functional cardiac imaging scan (within 28 days prior to enrollment) or ejection fraction of >= 50% by radionuclide angiogram, ECHO, MUGA, or cardiac imaging scan (within 28 days prior to enrollment)
• Diffusion capacity of the lung for carbon monoxide (DLCO) >= 50% of predicted value as corrected for hemoglobin by pulmonary function test (PFT) (within 28 days prior to enrollment). If unable to obtain PFTs, the criterion is: a pulse oximetry reading of > 92% on room air
• Known human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial
• For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated. Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load

Exclusion Criteria:

• Patients with nodular lymphocyte predominant Hodgkin lymphoma
• Patients with a history of active interstitial pneumonitis or interstitial lung disease
• Patients with a diagnosis of inherited or acquired immunodeficiency that is poorly controlled or requiring active medications, such as primary immunodeficiency syndromes or organ transplant recipients
• Patients with any known uncontrolled intercurrent illness that would jeopardize the patient's safety such as infection, autoimmune conditions, cardiac arrhythmias, angina pectoris, and gastrointestinal disorders affecting swallowing and/or absorption of pills
• Patients with a condition requiring systemic treatment with either corticosteroids (defined as equivalent to > 10 mg daily predniSONE for patients >= 18 years or > 0.5 mg/kg [up to 10 mg/day] for patients < 18 years) or other immunosuppressive medications within 14 days prior to enrollment
• Note: Replacement therapy such as thyroxine, insulin, or physiologic corticosteroid for adrenal or pituitary insufficiency is not considered a form of systemic treatment. Inhaled or topical steroids, and adrenal replacement doses (=< 10 mg daily for patients >= 18 years or =< 0.5 mg/kg [up to 10 mg/day] predniSONE equivalents) are permitted in the absence of active autoimmune disease
• Note: Steroid use for the control of Hodgkin lymphoma symptoms is allowable, but must be discontinued by cycle 1, day 1
• Short term use of corticosteroids for premedication or treatment of an allergy or hypersensitivity is considered an acceptable use of corticosteroids.
• Patients with peripheral neuropathy > grade 1 at the time of enrollment or patients with known Charcot-Marie-Tooth syndrome
• Patients with a prior or concurrent malignancy whose natural history or treatment has the potential to interfere with the safety or efficacy assessment of the investigational regimen
• Administration of prior chemotherapy, radiation, or antibody-based treatment for cHL
• Prior solid organ transplant
• Prior allogeneic stem cell transplantation
• Live vaccine within 30 days prior to planned day 1 of protocol therapy (e.g., measles, mumps, rubella, varicella, yellow fever, rabies, bacillus Calmette Guerin [BCG], oral polio vaccine, and oral typhoid). Administration of messenger ribonucleic acid (mRNA) vaccines are permitted
• Female patients who are pregnant since fetal toxicities and teratogenic effects have been noted for several of the study drugs. A pregnancy test within 28 days prior to enrollment is required for female patients of childbearing potential
• Lactating females who plan to breastfeed their infants starting with the first dose of study therapy and for at least 6 months after the last treatment
• Sexually active patients of reproductive potential who have not agreed to use a highly effective contraceptive method for the duration of their study drug therapy. Following therapy, patients will be advised to use contraception as per institutional practice or as listed below for investigational agents, whichever is longer
• Men and women of childbearing potential (WOCBP) must use effective contraception during the study and for 2 months for WOCBP and 4 months for men, after last dose of brentuximab vedotin
• WOCBP must continue contraception for a period of at least 5 months after the last dose of nivolumab
• All patients and/or their parents or legal guardians must sign a written informed consent
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met

Inclusion Criteria:

• Participants of any sex who are ≥60 years of age on day 1, cycle 1.
• The participant must be willing and able to provide written informed consent for the trial and participate in all planned study procedures.
• Histologically confirmed diagnosis of classical Hodgkin lymphoma
• PET-avid, measurable disease (≥1.5cm bi-dimensional measurement)
• Have an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 to
• PS 2 may be allowed at the discretion of the treating investigator if impairment is considered to be primarily lymphoma-related. Evaluation of ECOG is to be performed within 10 days prior to the date of registration.
• Participants who have received involved field radiation will be allowed. However, they will be excluded if any of the following are true: 1. Radiation was dosed ≤6 months from registration. 2. Radiation was delivered to > 1 lymph node group as defined by the NCCN criteria. 3. The radiation dose was ≥30 Gy. 4. The participant has radiation-related toxicities ≥ Grade 2 at the time of registration. 5. The participant requires corticosteroids for radiation-related toxicities at the time of registration (regardless of dose). 6. The participant has ever experienced radiation pneumonitis.
• Have adequate organ function as defined per protocol. Specimens must be collected within 10 days prior to registration (confirmation of eligibility).

Exclusion Criteria:

• Nodular lymphocyte-predominant Hodgkin lymphoma
• Life expectancy < 6 months for any reason excluding lymphoma
• Has received prior therapy with an immune checkpoint inhibitor, against targets including but not limited to PD1, PDL1, PDL2, CTLA-4, OX40, or LAG 3 unless given with curative intent for reasons other than lymphoma AND the last dose was more than 3 years from registration. Any participant who received prior immune checkpoint inhibitor therapy will be excluded if they experienced any toxicity related to or possibly related to the immunotherapy that required discontinuation of drug.
• Prior systemic therapy for cHL, with the exception of steroids
• If participant received major surgery, they must have recovered adequately from the toxicity and/or complications from the intervention prior to starting study treatment.
• Presence of Grade ≥ 2 sensory and/or motor neuropathy
• Prior solid organ or stem cell transplant.
• Clinical suspicion or evidence of active involvement of lymphoma into the spinal cord, cerebral spinal fluid, or brain. External compression of the spinal cord or nerve roots is not considered involvement.Has received a live vaccine or live-attenuated vaccine within 30 days prior to the firstdose of study drug. Administration of killed vaccines, subunit vaccines, and nucleic acidvaccines is allowed.
• Is currently participating in or has participated in a study of an investigational agent or has used an investigational device within 4 weeks prior to the first dose of study treatment.Note: Participants who have entered the follow-up phase of an investigational study mayparticipate as long as it has been 4 weeks after the last dose of the previousinvestigational agent.
• Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent [excluding steroids needed for lymphoma related symptoms]) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study drug.
• Known additional malignancy that is progressing or has required active treatment within the past 3 years. Note: Participants with basal cell carcinoma of the skin, squamous cell carcinoma of the skin or carcinoma in situ (excluding carcinoma in situ of the bladder) that have undergone potentially curative therapy are not excluded.
• Has known severe hypersensitivity (≥Grade 3) to pembrolizumab and/or any of its excipients.
• Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs). Replacement therapy (eg., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment.
• Interstitial lung disease or a history of (non-infectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease.
• Any known history of pancreatitis as defined by Gandhi et al. 201432,36.
• Has an active infection requiring oral or intravenous systemic therapy.
• Has a known history of Human Immunodeficiency Virus (HIV).
• Has a known history of Hepatitis B (defined as Hepatitis B surface antigen [HBsAg] reactive) or known active Hepatitis C virus (defined as HCV RNA [qualitative] is detected) infection. Prior exposure to hepatitis B is allowed as long as there are no HBsAg detected (ie positive Hepatitis B core antibody with negative HBsAg). Prior treatment with Hepatitis C is allowed if the screening HCV RNA by PCR is negative.
• Has a known history of active tuberculosis (TB; Mycobacterium tuberculosis).
• Is currently taking a strong CYP3A4 modulator. Subjects taking strong CYP34A modulators that can safely stop these medications prior to treatment should complete a washout period of 4 weeks or 5 times the half-life of a particular drug, whichever is shorter.
• 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.
• Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.
• Is pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the study, starting with the screening visit through 120 days after the last dose of trial treatment.Note: given older age at enrollment, WOCBP are not anticipated to enroll on this study.

Inclusion Criteria:

• Participants must have a histologically confirmed diagnosis of classic follicular lymphoma (cFL). cFL was previously categorized as grade 1-3A per World Health Organization (WHO)-HAEM4R, but grading of classic follicular lymphoma (FL) is no longer mandatory.
• NOTE: Participants with follicular lymphoma with uncommon features (uFL) are eligible, including FL with diffuse growth pattern (dFL). Diagnosis is as per local pathology. Lymphoma fluorescence in situ hybridization (FISH) is not required. Molecular testing is not required.
• Participants must not have follicular lymphoma with "blastoid" or "large centrocyte" cytological features, or follicular large B-cell lymphoma (FLBL) (previously categorized as follicular lymphoma grade 3B)
• Participants must have low-tumor burden follicular lymphoma defined as:
• Nodal or extra-nodal tumor mass with diameter less than 7 cm in its greater diameter
• Involvement of no more than 3 nodal or extra nodal sites with diameter greater than 3 cm.
• Absence of B symptoms
• No symptomatic splenomegaly
• No compression syndrome (ureteral, orbital, gastrointestinal)
• No pleural or peritoneal serous effusion related to follicular lymphoma Participants must have Ann Arbor stage II, III, or IV follicular lymphoma. Participants with stage I disease may be included if they do not wish to undergo radiation or are not candidates for radiation
• Participants must either be experiencing distress due to their disease or would prefer active management of their disease rather than a watch and wait approach
• Participants must have staging imaging performed within 49 days prior to registration, as follows. PET-CT baseline scans are preferred. If a baseline PET-CT scan cannot be obtained, CT scans of the chest, abdomen, and pelvis, along with a bone marrow biopsy, are acceptable. If CT scans are used for staging at baseline, a CT scan of the neck is recommended. All measurable dominant lesions must be assessed within 49 days prior to registration. Tests to assess non-measurable disease must be performed within 49 days prior to registration. All disease must be assessed and documented on the Baseline Tumor Assessment Form.
• NOTE: if the initial evaluation is insufficient to detect measurable disease, treating investigators may obtain a CT scan with contrast
• Participants must have bi-dimensionally measurable disease (at least one lesion with longest diameter > 1.5 cm)
• Participants must not have had prior systemic therapy for follicular lymphoma. Radiation therapy for a previous diagnosis of early-stage follicular lymphoma is allowed
• Participant must be ≥ 18 years of age at the time of registration
• Participant must have Zubrod performance status of 0-2
• Participant must have a complete medical history and physical exam within 28 days prior to registration
• Leukocytes ≥ 3 x 10^3/uL (within 28 days prior to registration)
• Hemoglobin > 9.0 g/dL (within 28 days prior to registration)
• Absolute neutrophil count ≥ 1.5 x 10^3/uL (within 28 days prior to registration)
• Platelets ≥ 100 x 10^3/uL (within 28 days prior to registration)
• Total bilirubin ≤ 2 x institutional upper limit of normal (ULN) unless history of Gilbert's disease. Participants with history of Gilbert's disease must have total bilirubin ≤ 5 x institutional ULN (within 28 days prior to registration)
• Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ≤ 3 × institutional ULN (within 28 days prior to registration)
• Lactate dehydrogenase (LDH) < institutional ULN (within 28 days prior to registration)
• Participants must have a calculated creatinine clearance ≥ 30 mL/min using the following Cockcroft-Gault Formula. This specimen must have been collected and processed within 28 days prior to registration
• Participants must not have an active or uncontrolled infection before initiation of study treatment in the opinion of the treating investigators
• Participants must not have uncontrolled diabetes within 14 days prior to registration in the opinion of the treating investigators
• Participants must not have uncontrolled blood pressure and hypertension within 14 days prior to registration in the opinion of the treating investigators
• Participants with known human immunodeficiency virus (HIV)-infection must be on effective anti-retroviral therapy at registration and have undetectable viral load test on the most recent test results obtained within 6 months prior to registration
• Participants with evidence of chronic hepatitis B virus (HBV) infection must have undetectable HBV viral load while on suppressive therapy on the most recent test results obtained within 6 months prior to registration, if indicated. Participants with a positive total hepatitis (Hep) B core antibody and negative hepatitis B virus surface antigen (HBsAg) at screening are at high risk for reactivation and should receive prophylactic antivirals (e.g., entecavir) before and throughout the treatment
• Participants must not have active autoimmune disease requiring systemic therapy
• Participants must not have had undergone organ transplants requiring ongoing systemic immunosuppressive therapy
• Participants with a history of hepatitis C virus (HCV) infection must have been treated and cured. Participants currently being treated for HCV infection must have undetectable HCV viral load test on the most recent test results obtained within 6 months prior to registration, if indicated
• Participants must not have known chronic active Epstein Barr Virus infection (CAEBV); testing in asymptomatic participants is not required
• Participants must not have a positive test result for COVID-19 within seven (7) days prior to registration
• Participants must not have a prior or concurrent malignancy whose natural history or treatment (in the opinion of the treating physician) has the potential to interfere with the safety or efficacy assessment of the investigational regimen
• Participants must not have a history of confirmed progressive multifocal leukoencephalopathy (PML)
• Participants must not have received allogeneic stem cell transplantation
• Participants must not have a history of macrophage activation syndrome (MAS) or hemophagocytic lymphohistiocytosis (HLH)
• Participants with known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, must have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification. Participant must not have significant cardiovascular disease such as class III or IV cardiac disease, myocardial infarction within 6 months prior to registration. Participants with unstable arrhythmias, or unstable angina, should be excluded
• Participants must not be pregnant or nursing (nursing includes breast milk fed to an infant by any means, including from the breast, milk expressed by hand, or pumped). Individuals who are of reproductive potential must have agreed to use an effective contraceptive method with details provided as a part of the consent process. A person who has had menses at any time in the preceding 12 consecutive months or who has semen likely to contain sperm is considered to be of "reproductive potential." In addition to routine contraceptive methods, "effective contraception" also includes refraining from sexual activity that might result in pregnancy and surgery intended to prevent pregnancy (or with a side-effect of pregnancy prevention) including hysterectomy, bilateral oophorectomy, bilateral tubal ligation/occlusion, and vasectomy with testing showing no sperm in the semen
• Participants must be offered the opportunity to participate in specimen banking. With participant consent, specimens must be collected and submitted via the Southwest Oncology Group (SWOG) Specimen Tracking System
• NOTE: As a part of the Oncology Patient Enrollment Network (OPEN) registration process the treating institution's identity is provided in order to ensure that the current (within 365 days) date of institutional review board approval for this study has been entered in the system.
• Participants must be informed of the investigational nature of this study and must sign and give informed consent in accordance with institutional and federal guidelines
• For participants with impaired decision-making capabilities, legally authorized representatives may sign and give informed consent on behalf of study participants in accordance with applicable federal, local, and Central Institutional Review Board (CIRB) regulations

Patients do not need to participate in both; however, preferentially both study partsshould be performed.**************Part I: Pregnancy, delivery and maternal health**************Patients must meet the following inclusion criteria:

• Histologically proven cancer in association with a pregnancy (during pregnancy or cancer dagnosis within 5 years after pregnancy)
• > 18 years of age, premenopausal
• Patients who have given their signed and written informed consent to participate in the trial after fully understanding the implication of the protocol
• Women receiving any cytotoxic drug or radiation therapy during pregnancy are allowed for the assessment of the maternal and fetal outcome (Part II).

Exclusion Criteria:

• Mentally disabled or significantly altered mental status that would prohibit the understanding and giving of informed consent**************Part II: Follow-up of children**************

  Inclusion Criteria:

  • Children that were prenatally exposed to cancer of cancer treament. Informed Consent isasked from parents. From the age of 12 years, informed assent is additionally asked fromthe child. After the age of 18 years, informed consent is solely asked of the offspring.

  Exclusion Criteria:

  • Mentally disabled or significantly altered mental status that would prohibit the understanding and giving of informed consent