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Parinda A. Mehta, MD

SALT LAKE CITY—A “risk-adjusted” approach leads to “excellent” survival in patients with Fanconi anemia (FA) undergoing alternative donor hematopoietic stem cell transplant (HSCT), according to a speaker at the 2018 BMT Tandem Meetings.

All FA patients who received personalized doses of busulfan in place of total body irradiation (TBI) were alive and disease-free after undergoing HSCT for bone marrow failure or myelodysplastic syndrome (MDS).

None of the patients developed graft-vs-host disease (GVHD), and the most common toxicity was viral infection.

Parinda A. Mehta, MD, of Cincinnati Children’s Hospital Medical Center in Ohio, presented these results at this year’s BMT Tandem Meetings as abstract 109.*

“We all know that inherent chemotherapy and radiation sensitivity makes transplant for patients with Fanconi anemia quite challenging,” Dr Mehta began. “In our recently published, prospective, multi-institutional study, we showed excellent outcomes of alternative donor transplant in patients with Fanconi anemia without using radiation.”

“In that study,** TBI was replaced by pharmacokinetically adjusted busulfan. It proved that, yes, we can do alternative donor transplant successfully without radiation by showing an overall survival of 80% for a total of 45 patients. We were quite ecstatic to see these numbers.”

The study also showed that younger patients fared better with this regimen, and younger patients did best with the lowest dose of busulfan tested (0.6 mg/kg vs 0.8 to 1.0 mg/kg). In addition, patients who underwent HSCT for bone marrow failure had better outcomes than patients who had MDS.

This led Dr Mehta and her colleagues to hypothesize that adjusting busulfan dosing based on a patient’s age and disease status at HSCT could minimize toxicity and improve outcomes.

Patients

The researchers tested their theory in 22 FA patients. They had a median age of 7 (range, 4-27), and most (n=13) were female.

Twelve patients had pancytopenia, 6 had severe single-lineage cytopenia, 3 had low-grade MDS, and 1 patient had acute myeloid leukemia (AML).

Eighteen patients had a history of transfusions, and 3 had a history of androgen use.

Treatment

The preparative regimen consisted of 4 doses of busulfan (every 12 hours on day -7 to -6), followed by cyclophosphamide at 10 mg/kg/day (on day -5 to -2), fludarabine at 35 mg/m2/day (on day -5 to -2), and rabbit antithymocyte globulin at 2.5 mg/kg/day (on day -5 to -2).

Busulfan doses were adjusted according to age and disease status.

Children (age 18 and younger) with bone marrow failure received busulfan at 0.6 to 0.8 mg/kg. Children with MDS/AML received busulfan at 0.8 to 1.0 mg/kg. Adults (19 and older) received the lowest dose of busulfan—0.4 mg/kg—regardless of disease status.

“At the first sight, this will look counterintuitive . . . ,” Dr Mehta said. “However, based on our previous experience, in general and also from results of our previous study, this was specifically designed to avoid upfront TRM [transplant-related mortality] for these adult patients.”

All 22 patients received CD34-selected, T-cell-depleted peripheral blood stem cells from unrelated donors. Eleven patients received a fully matched graft (10/10), 8 patients had a 9/10 match, and 3 had an 8/10 match.

The median number of CD34+ cells/kg was 23.9 x 106 (range, 4.9-76.6), and the median number of CD3 cells/kg was 1 x 104 (range, 0.003-3.1).

T-cell depletion was the only GVHD prophylaxis used.

Patients with MDS/AML could receive azacitidine at day 42 after HSCT, an option intended to prevent relapse in these patients.

Toxicity

There were no cases of acute or chronic GVHD.

Toxicities included infections (n=24), oral mucositis (n=14), hyperbilirubinemia (n=2), pulmonary hemorrhage (n=1), and sinusoidal obstruction syndrome (n=1).

There were 20 viral infections, 4 bacterial infections, and no fungal infections. Viral infections included BK virus (n=7), cytomegalovirus (n=6), Epstein-Barr virus (n=6), and adenovirus (n=1).

Dr Mehta noted that viral infections are “not unexpected in a T-cell-depleted graft setting.”

“Because we know this complication [can occur], and we worry about our patients, one of the things that, in recent years, we have done is, we manufacture viral-specific CTLs [cytotoxic T lymphocytes] for all of these patients ahead of time whenever possible,” she said.

“To give you an example, 19 out of these 20 patients’ viral infections—or rather, viremias—are completely under control with the use of either antivirals or donor-specific CTLs, including a third-party CTL in one of the patients.”

Response and survival

All 22 patients engrafted. The median time to neutrophil engraftment was 9 days (range, 8-10), and the median time to platelet engraftment was 16 days (range, 11-40).

Twenty-one of the 22 patients (95%) were alive and disease-free at last follow-up. The median follow-up was 21 months (range, 6-44).

The single AML patient achieved remission but died of post-transplant lymphoproliferative disorder (PTLD) on day 202 after HSCT. Dr Mehta said this was due to partial loss of follow-up and noncompliance with medical recommendations during PTLD treatment.

The AML patient also had “significant upfront toxicity” but “recovered very nicely,” according to Dr Mehta. He had severe mucositis, herpetic stomatitis, and sinusoidal obstruction syndrome that responded to defibrotide.

“Overall, we are quite excited to see 95% overall survival for this cohort and conclude that the current risk-adjusted approach leads to excellent overall survival and disease-free survival in patients undergoing alternative donor transplant either for marrow failure or MDS/AML,” Dr Mehta said.

“Enrollment is ongoing, and we hope to see continued success in patients with MDS/AML as well as in adult patients.”

*Data in the abstract differ from the presentation.

**Mehta PA et al. Radiation-free, alternative donor HCT for Fanconi anemia patients: results from a prospective multi-institutional study. Blood 2017; doi: https://doi.org/10.1182/blood-2016-09-743112.


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