Conference Coverage

HSCT may be best option for therapy-related ALL



Therapy-related acute lymphoblastic leukemia (tALL) is less common and less well known than therapy-related acute myeloid leukemia, but tALL also appears to be associated with poor-prognosis features, compared with de novo ALL, investigators said.

“Currently, this condition is not fully recognized by the [World Health Organization] classification, but it has emerged as a relevant and increasingly common form of ALL. There is no standardized therapy for tALL at this time due to the rarity of the condition. Therefore, more information regarding characteristics, prognosis, and treatment is needed,” wrote Brayan Merchán, MD, and colleagues at Princess Margaret Hospital in Toronto.

At their center, the median overall survival (OS) among 58 patients with tALL who received front line induction therapy was 13 months, although patients who were able to undergo hematopoietic stem cell transplant had a 400% longer OS than patients who did not receive HSCT, they reported in an electronic poster presented as part of the virtual annual congress of the European Hematology Association.

A hematologist-oncologist who has studied tALL agreed that it appears to be a distinct clinical entity from de novo ALL.

“It is distinct from the other ALL because the age [at diagnosis] is different, the cytogenetic and molecular profiles are different, and while responses are the same, it seems that survival is lower in cases who don’t go through bone marrow transplant as consolidation,” said Ibrahim Aldoss, MD, from City of Hope Medical Center in Duarte, Calif.

Dr. Aldoss, who was not involved in the study, was the lead author of a study published in 2018 which found that, “[a]lthough survival of therapy-related acute lymphoblastic leukemia was inferior to de novo cases, allogeneic hematopoietic cell transplantation outcomes were comparable for the two entities” (Haematologica. 2018 Oct; 103[10]:1662-8).

He noted that induction regimen options for patients with tALL may be limited because some patients may had previous exposures to cytotoxic chemotherapy agents – such as anthracyclines used in standard regimens for breast cancer – that have cumulative toxicities and lifetime dose limits.

In addition, “these patients tend to be older, because they went through another cancer and then developed therapy-related ALL, and usually they’re not eligible for pediatric-inspired regimens that we use more frequently in younger patients,” he said.

Retrospective study

Dr. Merchán and colleagues conducted a retrospective study of all consecutive adults with ALL treated at their center from 1999 to 2019 and followed until January 2020. Of this group, they identified 59 patients who had been exposed to chemotherapy or radiation for other diseases prior to their ALL diagnosis.

The mean age of the 59 patients (31 women and 28 men) was 54.7 years. In all, 34 had solid cancers and 25 had hematologic malignancies before their ALL diagnosis. The most common diagnosis was breast cancer in 15 patients, followed by multiple myeloma in 11, lymphoma in 7, and AML in 5. Other prior diagnoses were not specified.

Prior therapies included chemotherapy alone in 18 patients, radiotherapy alone in 19, and 20 had both treatment modalities (information about 2 remaining patients was not presented).

For the overall population the median time to tALL diagnosis was 5 years, but for 9 patients with the poor-prognosis MLL gene rearrangement the median time to tALL was just 21 months. The disease latency period was 21 months for patients who received chemotherapy, compared with 117 months for patients treated with radiotherapy.

The majority of patients (53) had B-phenotype ALL. Of the 49 for whom cytogenetic data were available, 41 had cytogenetic abnormalities, including the MLL rearrangement in 9, and complex karyotype in 7. Of all 59 patients, 12 had translocation t(9;22).

One patient did not undergo induction therapy for ALL because of poor performance status. All of the other patients received induction therapy, either a Dana-Farber Cancer Institute protocol in 44 patients, hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, and dexamethasone) in 5, or blinatumomab in 3.

A complete response was seen in 41 patients (70%); 7 patients died during induction from causes attributed to therapy.

The mean follow-up for all patients was 27 months, and median overall survival was 13 months.

Median overall survival was 98 months for patients who underwent allogeneic HSCT versus a median of 19 months for patients who did not undergo transplant. This difference was not statistically significant, however, likely because of the small sample size.

Causes of death in 11 patients after transplant included relapse in 4 and graft-versus-host disease in 2 (other causes were not specified). Among the 34 patients who did not undergo HSCT following induction, 15 died from disease progression.

“From our results, tALL patients who were able to receive HSCT had better OS. Our data also supports the notion that tALL may be distinct entity with poor prognosis features compared to de novo ALL,” the investigators concluded.

The authors did not disclose a funding source. Dr. Merchán and Dr. Aldoss reported no relevant disclosures.

SOURCE: Merchán B et al. EHA25, Abstract EP391.

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