This study will validate a previously developed pediatric prognostic biomarker algorithm aimed at improving prediction of risk for the later development of chronic graft-versus-host disease (cGvHD) in children and young adults undergoing allogeneic hematopoietic stem cell transplant.

By developing an early risk stratification of patients into low-, intermediate-, and high-risk for future cGvHD development (based upon their biomarker profile, before the onset of cGvHD), pre-emptive therapies aimed at preventing the onset of cGvHD can be developed based upon an individual's biological risk profile.

This study will also continue research into diagnostic biomarkers of cGvHD, and begin work into biomarker models that predict clinical response to cGvHD therapies.

Chronic graft-versus-host disease (cGvHD) occurs when the new donor immune system "attacks" tissues in the recipient following allogeneic hematopoietic stem cell transplantation (HSCT), leading to chronic inflammation, scarring and fibrosis, impaired immunity (including immune deficiency and immune dysregulation), and altered organ system functioning. Almost any organ or system has the potential to be affected by cGvHD, although eight organ systems are classically involved, including the skin, eyes, mouth, lungs, liver, gastrointestinal tract, genitourinary tract, and the musculoskeletal system.

The investigators will be enrolling allogeneic HSCT recipients before conditioning, following these patients prospectively until 12-months (+/- 1 month) post-transplant for the development of all forms of GvHD (classical acute, late acute and chronic GvHD), collecting blood samples at day +60 (+/- 7 days), day +100 (+/- 14 days), and at the onset of either late acute or chronic GvHD. Two extra blood samples will be collected exclusively from HAPLO transplant recipients, who never developed any late-acute GvHD or chronic GVHD at the 6- and 12-month post-transplant time points. In addition, clinical data will be collected at different time points.

Case report forms of standard transplant related data will be completed and entered into a REDCap database.

Blood samples will be drawn and shipped to the Central Laboratory in Vancouver, BC, Canada, processed, analyzed, and the final biomarker risk algorithm completed. Selected clinicians will be offered to complete a short survey asking about their perception of the feasibility of altering their approach to cGvHD management based upon these results.

If chronic GvHD develops at any time after transplant (day 0 to 1 year), or if any form of GvHD occurs at or after day +100 (whether late acute, chronic GvHD, or overlap syndrome), a blood sample will be drawn before escalating immune suppression, and the onset GvHD case report form will be completed following the protocol. If chronic GvHD is confirmed, an additional CRF will be submitted at 24-months (+/- 3 months) post-transplant to document new chronic GvHD manifestations, severity, and response to therapy.

Study participants will have between 2 and 4 blood samples drawn over the course of 1-year post-transplant, depending upon their event and GvHD status.

INCLUSION CRITERIA:

1. Any indication for allogeneic hematopoietic stem cell transplant (malignant or non-malignant)
2. Age 0 - 24.99 years at the time of transplant (on day 0)
3. Any conditioning regimen (including myeloablative or reduced-toxicity/reduced-intensity)
4. Any graft source (bone marrow, peripheral blood, cord blood)
5. Any graft-versus-host disease prophylaxis strategy, including serotherapy such as ATG or alemtuzumab
6. Haploidentical transplants, including post-transplant cyclophosphamide and alpha-beta TCR depletion, are allowed

EXCLUSION CRITERIA:

1. Second or greater allogeneic transplant
2. Weight 7 kg or less
3. Pure CD34+ selected haploidentical stem cell transplant (not including CD34 enrichment used in alpha-beta TCR depleted haploidentical transplants, which is allowed)
4. Inability of a center to follow a patient for the development of late-acute and chronic GVHD until 1-year post-transplant (referral sites who transplant patients from outside institutions should not enroll participants if sending back to the referring site early, such that long-term follow up, blood, and data collection cannot be assured).

Pediatric and adult (under age of 25 y.o.) patients undergoing allogeneic HSCT (hematopoietic stem cell transplantation) before the start of the conditioning regimen.