Response to therapy with interferon alpha-2b and prednisolone in aggressive systemic mastocytosis: report of five cases and review of the literature

Leukemia Research 28 (2004) 249–257

Response to therapy with interferon alpha-2b and prednisolone in aggressive systemic mastocytosis: report of five cases and review of the literature Alexander W. Hauswirth a , Ingrid Simonitsch-Klupp b , Martin Uffmann c , Elisabeth Koller d , Wolfgang R. Sperr a , Klaus Lechner a , Peter Valent a,∗ a

Department of Internal Medicine I, Division of Hematology and Hemostaseology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria b Department of Clinical Pathology, University of Vienna, Vienna, Austria c Department of Radiology, University of Vienna, Vienna, Austria d Medical Department for Hematology and Oncology, Hanusch-Hospital, Vienna, Austria Received 28 February 2003; accepted 12 July 2003

Abstract Aggressive systemic mastocytosis (ASM) is a hematopoietic neoplasm characterized by infiltration of visceral organs by neoplastic mast cells (MCs) with consecutive organopathy and respective clinical and laboratory findings (so called C-Findings). Whereas, it is generally appreciated that patients with ASM are candidates for pharmacological intervention, no ideal drug or drug combination have been identified yet. One drug proposed to work in ASM is interferon alpha-2b (IFN-␣2b). However, little is known so far about the quality of responses to IFN-␣2b and actual response rates. We here report on five ASM patients treated with either a combination of IFN-␣2b (3 × 3 million units per week) and prednisolone (n = 4), or IFN-␣2b alone (n = 1). During therapy, two of the five patients showed a major response defined by complete resolution of C-Finding(s), one a partial response (partial regression of C-Findings), and one a stable disease (no changes in C-Findings). In one patient, progression to mast cell leukemia was seen after 3 months. In contrast to the other patients, this patient exhibited >10% MCs in his bone marrow (bm) smear at first presentation. In summary, our data confirm beneficial effects of IFN-␣2b (plus prednisolone) for a group of patients with ASM, whereas patients with mast cell leukemia may require more aggressive therapy. Prospective trials with more patients are now required to further document these drug effects and to better define subgroups of patients with ASM who show good and long-lasting responses to IFN-␣2b. © 2003 Elsevier Ltd. All rights reserved. Keywords: Mast cells; C-Findings; Interferon-␣2b; Prednisolone; Tryptase

1. Introduction Mastocytosis is a term collectively used for a group of disorders characterized by abnormal proliferation and accumulation of mast cells (MCs) in one or multiple organs. Cutaneous and systemic variants of the disease have been described [1–6]. Cutaneous mastocytosis (CM) typically develops in childhood and shows a benign clinical course. In many cases, spontaneous regression is seen during puberty [7]. Systemic mastocytosis (SM) can develop at any age and is characterized by involvement of one or more visceral or∗ Corresponding author. Tel.: +43-1-40400-5488/6085; fax: +43-1-402-69-30. E-mail address: [email protected] (P. Valent).

0145-2126/$ – see front matter © 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0145-2126(03)00259-5

gans with or without skin involvement [1–6]. In contrast to CM, SM is a persistent disease. In fact, systemic MC disorders represent clonal myeloid neoplasms arising from MC-committed or multi-lineage hematopoietic progenitors. This concept has been supported by the recurrent transforming c-kit mutation Asp-816-Val that is detectable in a majority of patients with SM [8–12]. Thus, depending on the subtype of SM, this mutation can be found in MCs, and also in other cell types of myelomonocytic origin or even in B lymphocytes [8,13,14]. In addition, MCs in SM, but not in other disorders, frequently display CD2 and CD25 on their surface supporting their clonal origin [15,16]. Both indolent and aggressive variants of SM have been described [1–5,17–25]. Aggressive SM (ASM) is characterized by massive infiltration of diverse organs by MCs with consecutive impairment of organ function [17–21,25].

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Some of these patients may show slow progression. In other cases, rapid progression with fatal outcome is seen. Some of the patients with ASM may develop an associated clonal hematologic non-mast cell lineage disease (ASM–AHNMD) [1–5,20–25], and in a few of them, progression to mast cell leukemia is observed [23–25]. The organ systems most frequently affected in ASM are the bone marrow (bm), liver, spleen, gastrointestinal tract, and the skeletal system [17–25]. These patients variably suffer from significant cytopenia(s), hepatosplenomegaly with decreased liver function and ascites, malabsorption, or osteolytic (or diffuse osteopenic) bone lesions with pathologic fractures [17–25]. Respective clinical and laboratory findings have been termed C-Findings [25]. In contrast to indolent SM, patients with ASM frequently present without skin lesions [1–5,17–25]. So far, no established standard therapy for patients with ASM has become available. In recent years, some beneficial effects have been described for interferon alpha-2b (IFN-␣2b) and prednisolone [26–38]. However, treatment–responses have been reported to be variable and were only seen in a subgroup of patients [26–38]. In addition, it has not been clarified so far which subgroup(s) of ASM show a long-lasting response. We have recently established criteria to classify treatment–responses in patients with ASM [38]. In the current study, five patients with ASM were treated with interferon alpha-2b four of them receiving additional prednisolone. In these patients, treatment–responses were determined using recently defined response criteria [38]. In addition, we compared responses to IFN-␣2b + prednisolone observed in our patients with those documented in patients with ASM in the available literature. 2. Case reports and methods 2.1. Patient 1 In January 2000, a 22-year-old male patient presented with SM involving the bone marrow and skeletal system (Table 1). Two months earlier, he had started to complain about pain in his right thigh. An X-ray revealed huge osteolyses in the right femur (8 cm × 4.5 cm), skull, and vertebral column. A biopsy of the femoral lesion revealed a focal MC infiltrate. Small MC infiltrates were also detected in bm biopsy sections (tryptase staining). The bm smear showed a normal myelopoietic compartment without signs of dysplasia and only a few atypical MCs. The spleen size amounted to 13 cm in diameter (sonography). However, no palpable splenomegaly or lymphadenopathy and no skin lesions were found (Table 1). The serum tryptase level amounted to 78 ng/ml. An elevated alkaline phosphatase (270 U/l) was also recorded. All other routine laboratory parameters were normal. After admission, combination treatment with IFN-␣2b (3 × 3 million units per week s.c.) and pred-

nisolone (50 mg per day orally) was started. The patient received prednisolone without IFN-␣2b during the first 2 days, and was observed in the hospital during the first days of treatment with IFN-␣2b. He also received prophylactic H1 and H2 blockers because of known peptic ulcer (case history) as well as paracetamol p.o. and pamitronate (90 mg i.v. every 4–8 weeks) (Table 1). During the observation period (29 months), prednisolone was slowly tapered down to 5 mg p.o. daily, whereas IFN-␣2b was continuously administered at the same dosage. However, due to side effects (flu-like symptoms, fever), the patient refused therapy with IFN-␣2b between September 2001 and November 2001. Therapy was accompanied by an improvement of symptoms (bone pain) and decrease in alkaline phosphatase levels to normal values (Fig. 1). A re-examination of the X-ray after 9 months showed a partial regression of osteolyses, and no new lesions were found. By contrast, no significant changes in bone marrow results (MC infiltration) were seen after 8 months. 2.2. Patient 2 A 52-year-old female patient was referred in December 2000 because of SM involving the skeleton, bone marrow (bm), liver, and spleen (Table 1). Clinical symptoms had first occurred in September 2000, with abdominal discomfort and diarrhea. A few weeks later, she also suffered from fatigue, weight loss, and bone pain. Physical examination and radiologic tests revealed hepato-splenomegaly as well as diffuse osteosclerotic and osteopenic changes in the skeletal system, especially in the vertebral column, long bones, and pelvis. In addition, she suffered from gastrointestinal (GI)-tract ulcerative disease. Skin lesions or lymphadenopathy were not recorded. A liver biopsy, bone biopsy (os ileum), and bm biopsy (iliac crest) were performed, and revealed MC infiltrates at all sites. Bm MC-infiltrates were found to be focal and diffuse with an additional involvement of bony trabeculae. The bm smear showed marked trilineage dysplasia and an increase in (partly immature) monocytic cells. In addition, numerous atypical MCs were recorded (1% of nucleated bone marrow cells). A significant proportion of these cells exhibited bi- or poly-lobed nuclei suggesting the presence of promastocytes (atypical MCs type II). Laboratory examinations revealed an elevated serum tryptase (379 ng/ml) and markedly elevated serum alkaline phosphatase (916 IU/l). The blood picture showed thrombocytopenia, anemia as well as monocytosis. Based on bm and blood examinations and overt organopathy, the diagnosis ASM associated with chronic myelomonocytic leukemia (CMML) was established. On 16th January 2001, a pathologic fracture of the right femoral neck was detected requiring surgical intervention (hemiprothesis). A few days earlier, combination treatment with IFN-␣2b (3 × 3 million units per week) and prednisolone (50 mg per day orally) had been initiated. Prednisolone was started 12 days prior to IFN-␣2b. She also received H1- and H2-receptor antagonists. During

No.

Diagnosis

Male/ female

Age at onset of disease

UP-like skin lesions

GI ulcer

Diarrhoea

Palpable hepatomegaly

Palpable splenomegaly

Osteolysis

Osteoporosis

Concomitant therapy in addition to IFN-␣2b ± prednisolone

1

ASM

Male

22

No

Yes

No

No

No

Yes

No

2

ASM–CMML

Female

52

No

Yes

Yes

Yes

Yes

Yes

Yes

3

ASM–CMML

Male

53

No

No

Yes

Yes

Yes

No

No

4

ASM

Male

59

No

Yes

No

Yes

No

No

No

5

ASM

Female

40

No

No

No

No

No

No

Yes

Ranitidine, diphenhydramine, omeprazole, pamidronate, paracetamol Ranitidine, diphenhydramine, omeprazole, clodronate, paracetamol Ranitidine, diphenhydramine, cetirizine, spironolactone, allopurinol, paracetamol Ranitidine, pantoprazole, diphenhydramine, paracetamol, cetirizine Ranitidine, pantoprazole, pamidronate

ASM: aggressive systemic mastocytosis; CMML: chronic myelomonocytic leukemia; UP: urticaria pigmentosa; GI: gastrointestinal.

A.W. Hauswirth et al. / Leukemia Research 28 (2004) 249–257

Table 1 Patients’ characteristics, clinical findings, and concomitant therapy

251

252

A.W. Hauswirth et al. / Leukemia Research 28 (2004) 249–257 300

200

60 150

50 40

100

30 20

50

10 0 2

4

6

8

tryptase, ng/ml

800

400

700 300

600 500

200

400 100

300

0

(C)

4

5

6

7

8

9

300

150

200 100 4

6

8

10

12

14

0 16

months of treatment 1000 600

900

500

800

400

700 600

300

500 200 400 100

300

0

200 10 11 12 13 14

months of treatment

2

200 0

(D)

alkaline phosphatase, U/l

900

3

400

200

700

alkaline phosphatase, U/l

500

2

500

250

(B)

1000

1

600

300

0

1100

0

350

50

1200

600

700

400

10 12 14 16 18 20 22 24 26

700

800

450

0

months of treatment

(A)

900

100

0 0

1000

550 500

tryptase, ng/ml

tryptase, ng/ml

70

600

alkaline phosphatase, U/l

250

80

alkaline phosphatase, U/l

90

tryptase, ng/ml

100

1

2

3

4

5

months of treatment

Fig. 1. Monitoring of disease-related parameters during therapy. In four patients with ASM, serum alkaline phosphatase levels (䊉) and serum tryptase levels (䉬) were serially determined during therapy with IFN-␣2b and prednisolone. (A and B) In two patients (patients 1 and 2), alkaline phosphatase levels returned to normal values. (C) In third patient (patient 3), alkaline phosphatase levels decreased, but did not reach the normal range. (D) In patient 4, alkaline phosphatase levels did not decrease significantly, and after a few weeks, a further increase in alkaline phopshatase was seen. In this particular patient, no decrease in tryptase was seen, and mast cell leukemia occurred after 3 months. In all other patients, serum tryptase levels decreased over time.

the observation period (18 months), treatment with IFN-␣2b was maintained at a constant dosage, whereas prednisolone was tapered down to 6.25 mg p.o. daily. During therapy, the clinical symptoms improved (stable weight, regression of gastrointestinal symptoms, no further bone pain), and the alkaline phosphatase level decreased to normal after 2 months (Fig. 1). The tryptase level also decreased, but did not return to normal range (lowest value: 146 ng/ml). Similarly, the platelet count increased slightly, but did not remain constantly above 100,000 ␮l. A re-examination of the X-ray showed stable disease without signs of new lesions or progression of pre-existing bone lesions. 2.3. Patient 3 A 53-year-old male patient suffering from SM was first presented in April 2001 because of hepatosplenomegaly with marked ascites, anemia, and thrombocytopenia. First symptoms were noted in September 2000. At that time, he complained about diarrhea, weight loss, and pruritus. Physical examination revealed palpable hepatosplenomegaly as well as ascites. Typical skin lesions or lymphadenopathy

were not found. At admission, a bone marrow and liver biopsy were performed and showed MC infiltrates in both organs. In bm sections, focal and diffuse MC infiltrates were found. The bm smear revealed myelodysplasia as well as an increase in immature monocytic cells. The percentage of MCs amounted to 1%. Most of these cells were found to be atypical MCs type I. The blood picture showed anemia (Hb: 8.8 g/dl), leukocytosis (27,950 ␮l), monocytosis (10%), and thrombocytopenia. The serum tryptase level (610 ng/ml) as well as the alkaline phosphatase level (944 U/l) were elevated. Based on clinical and laboratory parameters, the diagnosis ASM associated with CMML was established. Symptomatic treatment of ascites (paracenthesis, furosemid, spironolactone) was followed by a transient improvement. In May 2001, combination treatment with IFN-␣2b (3 × 3 million units per week) and prednisolone (50 mg p.o. daily) was initiated. In addition, he received H1- and H2-antihistamines as well as paracetamol. Therapy was well tolerated without any side effects. During the first months of treatment, the situation of the patient improved gradually. In fact, the ascites disappeared and no further paracenthesis was required. Also, the pruritus resolved, and

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the patient’s weight returned back to normal (pre-diagnostic) values. Moreover, therapy was accompanied by a decrease in alkaline phosphatase levels and serum tryptase levels, although both parameters remained above normal range (Fig. 1). During the first months of therapy, the blood picture showed marked improvement with decrease of leukocytes to normal range (<10,000 ␮l), disappearance of monocytosis, complete regression of anemia (Hb >10 g/dl after 3 months, and >14 g/dl after 7 months), and improvement of thrombocytopenia (platelets >100,000 ␮l) (Table 1). In September 2001, however, leukocytes again increased (at that time neutrophilia and monocytosis were noted). Therefore, the dose of IFN-␣2b was switched to 5 × 3 million units per week in October 2001, and to 7 × 3 million units per week in July 2002. During the same time, prednisolone was tapered down to 12.5 mg p.o. daily. Until May 2002, no recurrence of anemia or ascites were noted, and the levels of alkaline phosphatase and tryptase remained at a constant range. 2.4. Patient 4 In December 2001, a 59-year-old male patient was referred because of SM with involvement of the bm and liver. First symptoms had occurred during summer 2001. Symptoms included fever, night sweats, abdominal pain, and weight loss. Consecutive investigations revealed anemia, thrombocytopenia, and an elevated alkaline phosphatase level. Physical examination showed hepatomegaly without palpable splenomegaly or lymphadenopathy. Skin lesions were not found. A liver biopsy and bm biopsy were performed and showed marked MC infiltrates in both organs. The MC infiltrates in the bm were focal and dense with an additional diffuse component. The bm smear revealed a marked increase in atypical MCs (14% of all nucleated bm cells). Many of these MCs showed bi- or multi-lobed nuclei. At the time of admission, the serum alkaline phosphatase level amounted to 494 U/l, and the serum tryptase level was 326 ng/ml. Combination therapy with IFN-␣2b (3 × 3 million units per week) and prednisolone (50 mg per day orally) was initiated starting with prednisolone 4 days prior to IFN-␣2b. He also received H1- and H2-blockers and paracetamol (Table 1). Therapy was well tolerated without major side effects. During the first 2 months of treatment, laboratory parameters remained at a constant range. After 2 months, however, the alkaline phosphatase- and tryptase-level showed a further increase, and the hemoglobin concentration decreased. In March 2002, a re-investigation of the bm was performed and revealed progression to mast cell leukemia with a percentage of 28% of atypical MCs in a bm smear. 2.5. Patient 5 In December 2000, a 40-year-old female patient with known SM was referred because of back pain. Routine laboratory parameters were normal at that time. There were

253

no clinical signs of hepatosplenomegaly or lymphadenoathy, and also no urticaria pigmentosa-like skin lesions. Radiologic investigations revealed pathologic fractures in thoracical vertebral bodies Th8 and Th11 and several ribs as well as osteolyses in the right os ileum. In addition, marked osteopenia was found in densitometric analyses. Therapy with IFN-␣2b (3 × 3 million units per week without prednisolone) was started and maintained until December 2001. Treatment was accompanied by severe side effects including fever and flu-like symptoms, whereas no improvement in clinical symptoms (bone pain) was noted. IFN-␣2b was stopped in December 2001. A re-examination of the densitometry showed no substantial improvement. No new bone lesions (osteolysis or pathologic fractures) were found in an X-ray at that time (stable disease). 2.6. Evaluation of disease-related parameters Tissue sections of affected organs were subjected to histopathological examination including immunohistochemistry. In all cases, MCs were made visible by applying anti-tryptase antibody G3 (Chemicon, Temecula, CA) as described [39]. Bm smears were examined for the presence and morphology of MCs according to published guidelines [40]. Serum tryptase levels were determined serially before and during therapy using a fluoro-enzymeimmunoassay (FIA) (Pharmacia, Uppsala, Sweden) [41,42]. Routine laboratory parameters were also determined serially during therapy. 2.7. Evaluation of responses to therapy–response criteria Responses to treatment with IFN-␣2b (with or without additional prednisolone) were evaluated according to recently proposed response criteria [38]. Employing these criteria, responses were classified as (i) major response (MR = complete dissolution of C-Finding[s]); (ii) partial response (PR = partial regression of C-Finding[s]); and (iii) no response (NR = persistence or progression of C-Findings) [38]. An overview of response criteria is shown in Table 2. 3. Results 3.1. Clinical responses to treatment and comparison to literature-cases The median observation period in our five patients was 18 months (range: 6–29 months). Two of the five patients (40%) showed a major response defined by complete resolution of C-Finding(s), one patient a good partial response (after 9 months), and one patient a stable disease (Table 3). In the group of responding patients, improvement of C-Findings was seen in one or more organ systems affected. In particular, during treatment with IFN-␣2b and prednisolone, variable improvements in liver function, bone marrow function,

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Table 2 Response criteria for patients with aggressive mastocytosis—modified from [38] I

Major response

Examples:

Disappearance of pre-therapeutic C-Finding(s) (at least one C-Finding dissolves and no progression in other C-Findings is seen) ANC < 1.0∗ → ANC >1.0∗ Hb < 10 → Hb > 10 plt < 100∗ → plt > 100∗ Ascites → no ascites Increased liver enzymes → normal liver enzymes Hypalbuminemia → normal serum albumin Weight loss → normal weight Osteolysis with bone fracture → resolution of osteolysis

II

Partial response

Incomplete regression of C-Finding(s)∗∗ without progress in other C-Findings (a) Good partial response: > 50% regression (b) Minor response: ≤50% regression

III

No Response

C-Finding(s) persistent or progressive∗∗∗ (a) Stable disease: C-Findings unchanged (b) Progressive disease: C-Finding(s) show progression

∗ ANC: absolute neutrophil count (×103 ␮l); Hb: hemoglobin concentration (g/dl); plt: platelet count (×103 ␮l). ∗∗ With or without decrease in mast cell infiltrates, serum tryptase, or organomegaly. ∗∗∗ In case of progressive C-Findings and documented response in other C-Finding(s), the final diagnosis is still: progressive disease.

and of skeletal changes were noted (Table 3). However, not all organ systems affected appeared to respond to therapy in these patients in the same way (Table 3). In one patient, progression to mast cell leukemia was seen after 3 months. In

contrast to the other patients with ASM, this patient exhibited >10% MCs in bone marrow smears at first presentation. In a survey of the available literature, 14 well-documented patients with aggressive MC disease receiving IFN-␣ with or without prednisolone [26–37], were examined by applying response criteria in a retrospective fashion [38]. Of these 14 patients, 3 (21.4%) were classified as having a major response, and 5 patients (35.7%) a partial response, whereas six cases did not show a response to therapy (progression or stable disease). In those with a major response, complete dissolution of C-Findings was documented for abnormal liver function and/or ascites in three patients [27,33,34], and for abnormal hematologic parameters (cytopenias) in one patient [34]. A partial response was described for severe osteopenia or osteolysis in three patients, for hepatic dysfunction and severe skin infiltration in one, and for malabsorption in another patient [28,30,35,37]. 3.2. Monitoring of disease-related parameters during therapy In four of the five patients, serum tryptase and alkaline phosphatase levels were measured before and serially during therapy with IFN-␣2b + prednisolone with ASM. In these four patients, both parameters were clearly above normal range at diagnosis. In patient 1, the increase in alkaline phosphatase was judged as being related to the involvement of the skeletal system and therefore not counted as C-Finding. In the remaining three patients, the increased alkaline phosphatase appeared to be associated with hepatic involvement (=C-Finding). During therapy, a decrease in alkaline phosphatase was seen in all four patients examined. In two of them (patients 1 and 2), the enzyme levels returned back to

Table 3 Responses to IFN-␣2b (with or without prednisolone (P)) in five patients with ASM Patient no.

Diagnosis

Affected organ

C-Finding(s)

Treatment

Best response

1

ASM

Bone

Osteolysis

IFN-␣2b + P

P.R.

9

No

2

ASM–AHNMD (CMML)

Bone marrow

Thrombocytopenia (86 × 103 ␮l) Elevated aP (916 IU/l) Osteolysis, osteopenia and pathologic fracture

IFN-␣2b + P

M.R. (136 × 103 ␮l) M.R. (139 IU/l) N.R. (S.D.)

1

No

2 –

Bone marrow

Anemia (8.8 g/dl)

IFN-␣2b + P

M.R. (10.7 g/dl)

3

Bone marrow

Thrombocytopenia (53 × 103 ␮l) Ascites Elevated aP (944 IU/l)

M.R. (103 × 103 ␮l) M.R. P.R. (281 IU/l)

8

Liver Bone 3

ASM–AHNMD (CMML)

Liver 4

5

ASM

ASM

Bone marrow

Anemia

Liver

Elevated aP

Bone

Osteopenia and pathologic fracture

IFN-␣2b + P

IFN-␣2b

Time to best response (months)

Progression (after n months)

No

1 12

N.R. (P.D.)

–

N.R. (P.D.)

–

N.R. (S.D.)

–

Mast cell leukemia (3 months) No

ASM: aggressive systemic mastocytosis; AHNMD: associated clonal hematologic non-mast cell lineage disease; P: prednisolone; aP: alkaline phosphatase; N.R.: no response; P.D.: progressive disease; S.D.: stable disease; M.R.: major response; P.R.: partial response.

A.W. Hauswirth et al. / Leukemia Research 28 (2004) 249–257

normal range after 1 and 2 months, respectively (Fig. 1A and B). In one patient (patient 3), alkaline phosphatase levels showed a substantial decrease, but normal levels were not reached during the observation period (Fig. 1C). In patient 4 (progressing to MCL), alkaline phosphatase levels showed a slight decrease during the first month, and thereafter increased again despite therapy (Fig. 1D). A sustained decrease in serum tryptase levels was only seen in two of four patients examined (patients 2 and 3, Fig. 1B and C). Interestingly, in these two patients, tryptase levels started to decrease several months after alkaline phosphatase levels had started to decrease (Fig. 1B and C). In patient 4 (Fig. 1D), no decrease in serum tryptase was noted. This patient progressed to MCL after 3 months. 3.3. Side effects Side effects recorded during treatment with IFN-␣2b were mild and tolerable in three of five patients. However, in two patients (patients 1 and 5), substantial side effects (fever, flu-like symptoms) were noted. Patient 5 refused further therapy with IFN-␣2b after 1 year. Patient 1 refused therapy between September 2001 and November 2001. Side effects that could have been attributed to prednisolone were not recorded. In patient 5, no prednisolone was given because of severe osteoporosis and because of lack of apparent involvement (C-Findings) of the liver or other organ systems.

4. Discussion So far, no standard treatment for ASM or MCL is available. However, a number of reports have suggested beneficial effects for treatment with IFN-␣2b ± corticosteroids [26–37]. In the present study, we were able to confirm beneficial effects of IFN-␣2b and prednisolone in ASM. Moreover, we have evaluated the quality of treatment–responses by employing recently established response criteria [38]. Utilizing these criteria, it was found that IFN-␣2b ± prednisolone can produce major responses with dissolution of organopathy in a subset of patients. About 10 years ago, IFN-␣2b was first described as an effective agent in a patient with aggressive MC disease [27]. Similar observations have subsequently been reported in other ASM patients [26–37]. However, the response rate (major response) was found to be rather low with an overall rate of MR of approximately 20% [38]. Similarly, in this study, only a subset of patients were found to enter MR in response to IFN-␣2b ± prednisolone. The higher response rate in our study (40%) may be explained by the fact that in previous studies a higher percentage of patients received IFN-␣2b without additional prednisolone. Another important point may be that our patients were treated with IFN for a prolonged time. In fact, it is recommended to administer IFN-␣2b in ASM patients as long as a response is seen or until significant side effects occur [38].

255

We have recently defined treatment–response criteria for patients with ASM [38]. Our current study shows that these criteria are applicable and useful, although several specific points have to be taken into account. Likewise, it is of importance to consider the existence of an AHNMD. In these patients, it may be difficult to define whether splenomegaly or cytopenia(s) is due to mastocytosis (C-Finding) or due to the AHNMD. In two of our patients, criteria for CMML were fulfilled in addition to ASM, and it was impossible to judge whether thrombocytopenia was due to ASM or CMML. Remarkably, in both patients, platelet counts improved in response to therapy. This may point to the fact that thrombocytopenia was ‘ASM-related’. Alternatively, however, this response was due to improvement of CMML or of an immunologic component of thrombocytopenia. Another important aspect is that in patients with ASM, several different organ systems may be involved and that respective organopathies may show differential responses to treatment [25,38]. Likewise, we observed that in patients treated with IFN-␣2b + prednisolone, some C-Findings improved, whereas other C-Findings did not. In such situation, it is recommended that the C-Finding that shows the best response, counts [38]. So far, little is known about clinical and laboratory parameters indicative of disease progression, prognosis, or survival in SM [25,38]. However, some adverse prognostic signs have been described such as the absence of skin lesions, elevated alkaline phosphatase, elevated numbers of MCs in bone marrow smears (or peripheral blood), or presence of an AHNMD [1–4,20,25,40]. In this study, all five patients were found to lack UP-like skin lesions. In two of them, an AHNMD was found, and four of five patients had elevated alkaline phosphatase levels. In one patient, the percentage of MCs in bone marrow smears exceeded 10%. It is of interest, that in this particular patient, but not in the others, the disease rapidly progressed to mast cell leukemia. This observation suggests that this patient had a prephase of MCL, and that more aggressive therapy was required to counteract malignant cell growth in this patient. In addition, this observation underlines the prognostic impact of an elevated percentage (>10%) of MCs in bone marrow smears [40,43]. Two disease-related laboratory parameters were found to be useful for monitoring ASM patients, namely alkaline phosphatase and MC tryptase. Serum tryptase levels are known to be elevated in patients with SM and to reflect the burden of neoplastic MCs [41,42,44]. Correspondingly, all ASM patients analyzed exhibited an elevated serum enzyme level. Moreover, we were able to show that in patients with major or good partial responses, tryptase levels decreased substantially after a certain latency period, which may be explained by a direct inhibitory effect of IFN-␣2b on immature hematopoietic (MC-committed) progenitors [45]. In fact, MC development takes a long time [46,47], and any drug effect on MCs that results from inhibition of MC progenitors must be expected to occur after a latency period of several months. By contrast, the relatively fast decrease in

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alkaline phosphatase may be reflective of a direct response of hepatic (mast) cells to therapy [46]. In this regard, it is also noteworthy that our results confirm the known beneficial effects of corticosteroids on liver function parameters and ascites-production in SM [48,49]. The exact mechanisms of action of prednisolone in ASM remain unknown. Apart from a direct effect on MC progenitors, corticosteroids may influence MC production in tissues by interfering with expression of SCF in stromal cells [46,50]. A number of side effects are known to occur in patients receiving IFN-␣. Such side effects include flu-like symptoms, fever, or bone pain. These symptoms also occurred in two of our five patients with ASM: one patient decided to stop IFN-␣2b after 1 year of treatment because of such side effects, and a second patient discontinued IFN-␣2b + prednisolone for 2 months despite a good response. Thus, side effects can be an important limitation of treatment with IFN-␣ in patients with ASM. In summary, we provide further evidence that combination treatment with IFN-␣2b and prednisolone acts beneficial in a group of patients with ASM. Based on our results, we recommend IFN-␣2b + prednisolone as first line treatment for those patients who suffer from slowly progressing ASM without an excessive increase of MCs in bone marrow smears or definitive signs of MC leukemia. Still, however, placebo-controlled clinical trials are required to confirm our results, to better define the groups of responding patients, and to determine treatment effects on survival.

Acknowledgements This study was supported by Fonds zur Förderung der Wissenschaftlichen Forschung in Österreich (FWF) grant no. P-14031. Contributions. Alexander W. Hauswirth contributed in collection and assembly of data, Ingrid Simonitsch-Klupp contributed in analysis and interpretation of histologic data, Martin Uffmann contributed in analysis and interpretation of radiologic data, Elisabeth Koller contributed in patients, Wolfgang R. Sperr contributed to the concept and design of the study and patients, Klaus Lechner contributed administrative and logistic support, and Peter Valent contributed the concept and design of study, drafting of the article, and final approval. The draft was written by A.W. Hauswirth.

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