Inclusion Criteria:

• Has histologically confirmed diagnosis of classical Hodgkin lymphoma (cHL) that is 2-fluorodeoxyglucose-avid (FDG-avid).
• Has relapsed (defined as disease progression after most recent therapy) or refractory (defined as failed to achieve CR or PR to most recent therapy) cHL and exhausted all available treatment options with known clinical benefit.
• Has progressed on treatment with an anti-PD-(L)1 monoclonal antibody (mAb) administered either as monotherapy or in combination with other checkpoint inhibitors or other therapies.
• Submits an archival (<5 years) or newly obtained tumor tissue sample which has not been previously irradiated.

Exclusion Criteria:

• Diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy or any other form of immunosuppressive therapy.
• History of central nervous system (CNS) metastases or active CNS involvement.
• Has an active autoimmune disease that has required systemic treatment in past 2 years except replacement therapy.
• History of (noninfectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease.
• Has an active infection requiring systemic treatment.
• History of hemophagocytic lymphohisticytosis.
• Has an active seizure disorder that is not well controlled.
• Has clinically significant (ie, active) cardiovascular disease.
• Received prior systemic anticancer therapy including investigational agents within 4 weeks before randomization.
• Received prior radiotherapy within 2 weeks of start of study intervention or radiation related toxicities requiring corticosteroids.
• Has not adequately recovered from major surgical procedure.
• Known additional malignancy that is progressing or has required active treatment within the past 3 years.
• History of human immunodeficiency virus (HIV).
• Has had an allogeneic hematopoietic stem cell or solid organ transplantation within the last 5 years.

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) must have an upright posteroanterior (PA) chest X-ray (CXR) for assessment of bulky mediastinal disease. Adult patients must have either a CXR or CT chest
• 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/gender as follows (within 7 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 7 days prior to enrollment) OR a glomerular filtration rate (GFR) >= 50 mL/min/1.73 m^2 (within 7 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 7 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 7 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 7 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 7 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 7 days prior to enrollment) or ejection fraction of >= 50% by radionuclide angiogram, ECHO, MUGA, or cardiac imaging scan (within 7 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 7 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
• 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 (failure rate of < 1% per year when used consistently and correctly) 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 must continue contraception for a period of 6 months after last dose of brentuximab vedotin
• Women of child-bearing potential (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 first dose of study drug. Administration of killed vaccines, subunit vaccines, and nucleic acid vaccines 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 may participate as long as it has been 4 weeks after the last dose of the previous investigational 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.

Patients do not need to participate in both; however, preferentially both study parts should 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 is asked from parents. From the age of 12 years, informed assent is additionally asked from the 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