Systemic Immunotherapy Effective for Refractory Extramedullary Acute Myeloid Leukemia

In his book, A Commotion in the Blood: Life, Death, and the Immune System, Stephen S. Hall¹ beautifully captured the earliest trials of stimulating the immune system to fight cancer. It started with an observation: some tumors regressed after severe infection, Dr Coley noted. Not letting the exception pass by unnoticed, Dr Coley harnessed this observation and injected a number of his patients with bacterial toxins (Coley’s toxin). This toxin represented a powerful superantigen, leading to dramatic immune system upregulation, including massive polyclonal T-cell activation and cytokine release leading to tumor regression in a notable minority of cases. Although the mechanism was not understood at that time, this observation captures an important concept: cancer is dependent on immune escape.²

Immunity for the treatment of hematologic malignancies, including acute myelogenous leukemia (AML), has been leveraged for decades in the form of allogeneic stem-cell transplantation.^3-5 Aside from allogeneic stem-cell transplantation, other immune-based strategies have been evaluated in AML, including Bacillus Calmette–Guérin vaccination, interleukin-2, and interferon alfa, all of which have shown inferior results compared with standard chemotherapy.^2,6-10 However, those strategies were not specific and were not directed against specific immune escape pathways used by malignant cells. More recently, with the discovery of immune checkpoint inhibitors (ICPI) and the successful redirection of the immune system for the treatment of various solid tumors, using the same concept in hematologic malignancy is alluring.

We herein report on a 68-year-old man with refractory extramedullary AML who successfully achieved remission using ICPI. The patient was originally diagnosed at age 65 years with stage IIIA melanoma in the left upper posterior arm (Appendix Fig A1), which was treated with surgical excision and lymph node resection, followed by radiation therapy in 2014. The patient went into remission without evidence of recurrence on follow-up imaging (Fig 1).

FIG 1.

Patient timeline. Each point represents diagnosis, treatment, or response. Space between events does not represent real time. CLIA, cladribine, idarubicin, and cytarabine.

One year later (October 2015), the patient was referred to the leukemia department with pancytopenia. Bone marrow aspirate and biopsy revealed myelodysplastic syndrome, 2% blasts, with complex cytogenetics and mutation in nucleophosmin 1 (NPM1) and DNA methyltransferase 3 alpha (DNMT3A). The patient was treated with the hypomethylating agent guadecitabine (SGI-110). He received a total of 19 cycles, with complete remission, including full hematologic recovery, resolution of dysplastic morphology on subsequent bone marrow examinations, and cytogenetic remission. Eighteen months after his original myelodysplastic syndrome diagnosis, the patient was noted to have a dark-colored skin lesion on the left upper arm that was suggestive of melanoma recurrence (Fig 2). Positron emission tomography/computed tomography scan showed a single fluorodeoxyglucose-avid lesion in the skin and subcutaneous region of the left upper arm (Fig 2). A skin biopsy revealed myeloid sarcoma with monocytic differentiation. Immunohistochemical studies were positive for CD45, CD33, lysozyme, CD11c, CD68, CD4, and myeloperoxidase in the neoplastic cells. They were negative for a pan-melanocytic cocktail (human melanoma black [HMB45], anti–Mart-1, anti-tyrosinase), Sox10, pan-keratin cocktail (AE1/AE3, MNF116, Zym5.2, and Cam5.2), and CD3, CD8, CD20, CD117, CD30, and CD34, supporting the diagnosis of myeloid sarcoma (Fig 2). Repeat bone marrow studies revealed a persistent morphologic remission with diploid cytogenetics and less than 1% NPM1 and DNMT3A mutations by polymerase chain reaction. The patient then received two cycles of intensive cytarabine-based chemotherapy with cladribine 5 mg/m², idarubicin 10 mg/m², and cytarabine 1 g/m² days 1 to 3 every 28 days, with follow-up positron emission tomography scan after two cycles showing progressive disease (Fig 3). A repeat skin biopsy was again consistent with myeloid sarcoma (Fig 3). Surveillance bone marrow examination showed myelodysplasia with 2% blasts, diploid cytogenetics, and DNMT3A mutation identified, and NPM1 mutation no longer detected at variant allele frequency level of sensitivity of approximately 1%. Given the progressive yet self-contained extramedullary disease to sites within the left upper arm, the patient was then treated with nine fractions of radiotherapy (10 Gy), without evidence of response to radiation therapy. He was then enrolled in a phase II trial of the hypomethylating agent azacitidine with dual checkpoint inhibition. The treatment regimen consisted of azacitidine 75 mg/m² (days 1 to 7) and nivolumab 3 mg/kg (day 1 and day 14) every 28 days, in addition to ipilimumab 1 mg/kg every 42 days. A skin biopsy after the first cycle demonstrated ongoing myeloid sarcoma. The patient continued receiving treatment for another cycle, and a skin biopsy after cycle 2 was negative for CD33 myeloid sarcoma, instead demonstrating predominant T-cell lymphocyte (CD3+) infiltration, with predominance of CD8 over CD4+ lymphocytes (including CD4+ histiocytes; Fig 4). The patient has continued receiving this combination therapy and so far received six cycles, with continued clinical and radiologic clearance of his skin lesion (Fig 4) and ongoing bone marrow response.

FIG 2.

(A, B) Positron emission tomography/computed tomography in April 2017 showing 1.5 × 0.8 cm fluorodeoxyglucose-avid nodule in the skin and subcutaneous region of the left upper arm posteriorly (arrows) with a maximum standardized uptake value of 3.8. (C) Skin lesion at the time of presentation. Immunohistochemical studies demonstrating neoplastic cells positivity for (D) CD33, (E) myeloperoxidase (MPO), and (F) CD43.

FIG 3.

(A, B) Skin lesion post cycle 2 of cladribine, idarubicin, and cytarabine. (C) Positron emission tomography/computed tomography post cycle 2 of cladribine, idarubicin, and cytarabine shows previously identified cutaneous nodule within the left posterior arm has increased in number and fluorodeoxyglucose activity. There are multiple new foci of fluorodeoxyglucose activity now seen along the musculatures and subcutaneous/cutaneous tissues of the left arm.

FIG 4.

(A-D) Skin immunohistochemical studies post cycle 2 of azacitidine with dual checkpoint inhibition showing negative CD 33, T-cell lymphocyte (CD3-positive) infiltration, and predominance of CD8 over CD4+ lymphocytes. (E, F) Complete clinical resolution of previously identified lesions in the left arm taken after six cycles. (G) Positron emission tomography/computed tomography post cycle 6 of azacitidine with dual checkpoint inhibition demonstrates complete metabolic response to therapy in terms of previously identified multiple cutaneous and subcutaneous nodules in the left arm.

Immune checkpoint inhibitors are antibodies directed against T-cell inhibitory signals to modulate the interaction between cytotoxic T cells and tumor cells. Activating programmed cell death protein 1 (PD-1) prevents CD28/B7 signaling that is crucial for CD8 T-cell activation.¹¹ PD-1 and programmed death-ligand 1 (PD-L1) interactions inhibited antitumor immune responses in a murine AML model.¹² Treatment with anti–PD-1 antibody improved survival in those models, indicating the importance of the PD-1/PD-L1 pathway in immune evasion by AML blasts as well as providing a rationale for clinical trials targeting this pathway in AML (eg, with nivolumab).¹² Seventeen-color multiparameter flow cytometry was reported on 38 patients with relapsed AML, 36 patients with untreated AML, and eight healthy controls. All T-cell subpopulations (CD3+, CD4+, and CD8+ T cells) had significantly higher PD1 expression in relapsed AML (P < .006) and untreated AML (P < .05) compared with healthy controls.¹³ This suggests that PD1 overexpression is an escape route used by leukemia. This finding was also supported in other reports.^14-16 In a report, T-cell receptor (TCR) clonotypes that were minimal or undetectable became enriched after nivolumab administration, and one patient had marked reduction in TCR diversity indexes and clearance of measurable residual disease with TCR clone directed against Wilms Tumor 1 (WT1).¹⁷ In an ongoing phase IB/II study of nivolumab in combination with azacitidine in relapsed AML (ClinicalTrials.gov identifier: NCT02397720), 70 evaluable patients were reported with 63% overall response rate, which compared favorably to historical response rate of 15% to 20% treated at the same institute. The durability of these responses is also notable, with no relapses among 34% of patients who achieved complete remission (CR)/complete remission with incomplete hematologic recovery/hematological improvement (CR duration, not reached), with median follow-up 13.3 months.^18,19

On the other hand, CD80/CD86 expressed on AML blasts binds to CTLA-4 on the T cell, where it acts as T-cell coinhibitory signal, diverting T cells into an exhausted state. Expression of CD86 was reported on AML blasts in more than half of 100 samples tested, and, in some cases, the level of expression was so high that it was equivalent to that of mature monocytes and activated B lymphocytes,²⁰ which gives a rationale for targeting this pathway (eg, with ipilimumab). In a phase I/Ib multicenter trial of ipilimumab in patients with relapsed hematologic cancers after allogeneic stem cell transplantation, 12 patients with relapsed AML and another four with extramedullary relapsed disease were included. Out of those patients, three patients with leukemia cutis achieved CR and one patient with myeloid sarcoma involving lymph nodes also achieved CR. All CRs were reported to occur in the 10 mg/kg cohort.²¹

Hypomethylating agents, standardly used in AML therapy, may enhance immune response by promoting tumor antigen expression, antigen presentation, and enhanced effector T-cell function.²² Simultaneously, hypomethylating agents (HMAs) therapy may also epigenetically modify inhibitory molecule expression; exposure to hypomethylating agents has demonstrated partial demethylation of PD-1 gene locus¹⁶ and dose-dependent upregulation of PD-L1, PD-L2, PD-1, and cytotoxic T-lymphocyte associated protein 4 (two-fold or greater).¹⁶ There was trend toward increased expression of those checkpoints in HMA-resistant patients compared with sensitive patients, suggesting upregulation of inhibitory immune signals as a mechanism of resistance to HMAs. This has led to the hypothesis that concomitant administration of immune checkpoint inhibitors in combination with HMAs may overcome resistance via immune evasion.¹⁶

AML with mutant NPM1 is considered to be of favorable risk, and, interestingly, one suggested explanation relates to immune responses developed against epitopes derived from the mutated region of NPM1. Higher PD-L1 expression in NPM1 mutated patients, particularly in leukemic stem/progenitor cells, has been noted, potentially making this particular subgroup of AML more likely to benefit from ICPI treatment.^23-25

In this particular case, myeloid sarcoma arising from a previous melanoma site, in a patient with complete remission from previously diagnosed myelodysplastic syndrome, highlights important questions, as does the excellent response to ICPI. We wondered if the local microenvironment has immune-based hosting and homing characteristics (ie, poor immune surveillance), which leads to weak containment of neoplastic cell expansion. This poor immune surveillance is reversible using ICPI. Also, it is interesting to note that, in this patient, leukemia cutis started as single lesion, then had what we think was an in-transit metastasis with multiple sentinel lesions (Fig 3). This raises the question of local evolution of myeloid sarcoma and suggests that metastasis can originate from myeloid sarcoma rather than homing from existing bone marrow disease. Although no clear data exist to date, this case and previous cases of myeloid sarcoma and leukemia cutis suggest ICPI therapy may be an effective treatment modality for patients with isolated extramedullary AML.

In conclusion, we report on the successful treatment of primary refractory myeloid sarcoma with hypomethylating agent therapy in combination with PDL1 and cytotoxic T-lymphocyte associated protein 4 inhibition. Additional studies should evaluate the effectiveness of this strategy for this difficult-to-treat patient population and whether particular patient subgroups are more sensitive to this treatment approach.

Appendix

FIG A1.

Initial diagnosis of melanoma on the left upper posterior arm.

AUTHOR CONTRIBUTIONS

Conception and design: Mansour Alfayez, Naval Daver, Courtney D. DiNardo

Financial support: Naval Daver, Courtney D. DiNardo

Provision of study material or patients: Naval Daver, Courtney D. DiNardo

Collection and assembly of data: Mansour Alfayez, Doina Ivan, Naveen Pemmaraju, Courtney D. DiNardo

Data analysis and interpretation: All authors

Manuscript writing: All authors

Final approval of manuscript: All authors

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The following represents disclosure information provided by authors of this manuscript. All relationships are considered compensated. Relationships are self-held unless noted. I = Immediate Family Member, Inst = My Institution. Relationships may not relate to the subject matter of this manuscript. For more information about ASCO's conflict of interest policy, please refer to www.asco.org/rwc or ascopubs.org/po/author-center.

Naveen Pemmaraju

Honoraria: Incyte, Novartis, LFB Biotechnologies, Stemline Therapeutics, Celgene

Consulting or Advisory Role: Incyte, Novartis, LFB Biotechnologies, Stemline Therapeutics, Celgene

Research Funding: Novartis, Stemline Therapeutics, Incyte, Samus Therapeutics, AbbVie, Cellectis, Affymetrix/Thermo Fisher Scientific, Daiichi Sankyo, Plexxikon

Travel, Accommodations, Expenses: Stemline Therapeutics, Celgene, Mustang Bio

Naval Daver

Consulting or Advisory Role: Celgene, Agios Pharmaceuticals, Jazz Pharmaceuticals, Pfizer, AbbVie, Astellas Pharma, Daiichi Sankyo, Novartis, Bristol-Myers Squibb

Research Funding: Bristol-Myers Squibb, Pfizer, Immunogen, Genentech, Nohla Therapeutics, AbbVie, Astellas Pharma, Servier, Daiichi Sankyo

Courtney D. DiNardo

Honoraria: Jazz, Karyopharm Therapeutics, Bayer, MedImmune

Consulting or Advisory Role: AbbVie, Celgene, Agios Pharmaceuticals

Research Funding: AbbVie, AGIOS, Celgene, Daiichi Sankyo

No other potential conflicts of interest were reported.