Twin Pregnancy and Childbirth after Reduced-intensity Conditioning Allogeneic Haematopoietic Stem Cell Transplantation Combined with Imatinib Mesylate for Chronic Myeloid Leukaemia: Case Report and Literature Review

Abstract

The successful outcome of a pregnancy in a woman who had received reduced-intensity conditioning (RIC) allogeneic haematopoietic stem cell transplantation (allo-HSCT) for chronic myeloid leukaemia is reported; publications on recovery of ovarian function and pregnancy following myeloablative conditioning (MAC) or RIC allo-HSCT for haematological disorders are reviewed. Research suggests that RIC allo-HSCT may facilitate ovarian recovery. Indeed, in the case study presented, the patient had a successful twin pregnancy and delivery, subsequent to treatment. After a 5-year follow-up, the patient survives disease-free with a sustained molecular response; her children are both healthy, with no physical defects. These findings suggest that RIC allo-HSCT combined with short-term imatinib mesylate does not necessarily have profound effects on female fertility.

Introduction

An increasing number of patients with leukaemia or other malignant or nonmalignant disorders are being treated successfully with allogeneic haematopoietic stem cell transplantation (allo-HSCT). Chronic myeloid leukaemia (CML) is associated with a chromosomal translocation called the Philadelphia chromosome, whereby parts of two chromosomes (9 and 22) swap places to result in a fusion gene consisting of the V-abl Abelson murine leukaemia viral oncogene homolog 1 (ABL1) gene on chromosome 9 and the breakpoint cluster region (BCR) on chromosome 22, denoted as t(9;22)(q34;q11). Although imatinib mesylate (imatinib) – a tyrosine kinase inhibitor – is one of the most effective, low-toxicity drugs available for treating CML, since second-generation tyrosine kinase inhibitors (such as nilotinib and dasatinib) became available, HSCT remains the only curative approach that can produce a sustained absence of BCR-ABL. HSCT therefore continues to play an important role in some specific cases.

Chemotherapy or irradiation immediately prior to transplantation is called the conditioning regimen. Use of a standard myeloablative conditioning (MAC) regimen has been limited due to high rates of transplant-related mortality, especially in patients of advanced age or with comorbidities. ¹ This conditioning method also raises concerns about future adverse effects. Ovarian failure and permanent infertility occur in nearly all women of child-bearing age who are treated with MAC allo-HSCT;^2,3 few successful pregnancies have been documented. ⁴

A reduced-intensity conditioning (RIC) HSCT regimen, combined with pre- and post-transplant imatinib therapy for patients with CML in the first chronic phase, has been shown to have a good safety and efficacy profile, improving the overall survival rate and reducing the incidence of transplant-related mortality. ⁵ The effect of this treatment on reproductive function in female patients remains unclear, however. Here, we describe the case of a 23-year-old female with CML who had a successful twin pregnancy and delivery 2.5 years after RIC allo-HSCT with imatinib. To our knowledge, this is the first reported case of pregnancy after this type of treatment for CML.

Case report

Presentation and Diagnosis

An 18-year-old female was diagnosed with Philadelphia chromosome-positive CML in the chronic phase, in June 2006 (after a routine annual examination), at the Bone Marrow Transplantation Centre, The First Affiliated Hospital, School of Medicine, Zhejiang University, China. Physical examination was normal, without splenomegaly. Haemoglobin level was 10.5 g/dl; white blood cell and platelet counts were 173 × 10⁹/l and 50.3 × 10⁹/l, respectively. Bone marrow examination revealed granulocytic hyperplasia without an excess of immature white blood cells (blasts). Karyotyping of chromosomes showed 46, XX, t(9;22)(q34;q11) in 100% of metaphases. Real-time polymerase chain reaction (PCR) showed that the patient was 100% positive for the BCR-ABL fusion gene.

Treatment

Cytoreductive therapy with 1 – 3 g/day hydroxyurea, administered orally according to the patient's peripheral white blood cell count, began in June 2006 at the Bone Marrow Transplantation Centre and continued until November 2006. In October 2006, treatment resulted in complete haematological remission, according to international guidelines. ⁶ In November 2006, 400 mg/day imatinib was administered orally for 6 months. After ∼5 months' treatment, karyotyping showed disappearance of the Philadelphia chromosome and real-time PCR showed that the breakpoint cluster region (BCR)-ABL fusion gene was below detectable levels. The patient could not continue imatinib therapy > 6 months, for economic reasons. With the consent of the patient and her human leucocyte antigen-identical sister, allo-HSCT was performed in March 2007. The conditioning regimen included 30 mg/m² per day fludarabine (administered intravenously, 10 days before HSCT, for 5 days), 3.2 mg/kg per day busulphan (administered orally, 6 days before HSCT, for 2 days), and 5 mg/kg per day anti-T-lymphocyte globulin (administered intravenously, 4 days before HSCT, for 4 four days). Anti-graft-versus-host disease (GVHD) prophylaxis included 2.5 mg/kg per day cyclosporin A, administered orally from day –1 with a target blood level of 200 – 300 ng/ml, 500 mg/day myco phenolate mofetil, administered orally from day 1 until day 28 inclusive, and 10 mg/day methotrexate, administered orally on days 1, 3 and 6 only. The dosage of cyclosporin A was tapered during the second to third month post-transplant, according to the patient's chimeric status (i.e., BCR-ABL fusion status, as assessed by real-time PCR) and evidence of GVHD.

Prophylactic imatinib therapy (400 mg/day, administered orally) commenced 100 days after allo-HSCT to prevent relapse and was discontinued 24 months after transplantation. The patient did not present with obvious acute or chronic GVHD. ⁷ Recovery of spontaneous menstruation occurred ∼6 months after allo-HSCT.

Follow-up Assessment

In October 2009, 2.5 years after allo-HSCT and 7 months after withdrawal of imatinib, the patient was found to be pregnant. In June 2010, she delivered healthy twins of normal birthweight, after a full-term pregnancy. There were no complications during pregnancy and no evidence of recurrence of CML after delivery. After a total follow-up of 5 years, a complete molecular response was sustained; real-time PCR showed that the BCR-ABL fusion gene was below detectable levels. Both children were growing healthily without any physical defects at the time of last follow-up. The overall treatment and follow-up schedule is summarized in Fig. 1.

Figure 1:

Treatment schedule for a 23-year-old female patient with chronic myeloid leukaemia, undergoing reduced intensity conditioning haematopoietic stem cell transplantation (RIC allo-HSCT) and therapy with imatinib mesylate (imatinib; 400 mg/day, administered orally)

Literature review

To explore in more detail natural pregnancy or recovery of ovarian function following MAC/RIC allo-HSCT for the treatment of haematological disorders, a review of English-language publications was undertaken (Table 1).^{8 – 17} Two authors (K-N.W., L-Z.L.) independently performed searches of the PubMed database (entrez dates between January 1990 and May 2012), using broad search strategies to identify prospective and retrospective controlled clinical trials that evaluated natural pregnancy or recovery of ovarian function, following MAC/RIC allo-HSCT for the treatment of haematological disorders. The search strategies used the following terms: (pregnancy OR ovarian function OR ovarian failure OR childbirth OR menstruation); (hematopoietic stem cell transplantation [MESH] OR HSCT OR allo-HSCT).

Table 1:

Recovery of ovarian function and successful pregnancy following myeloablative conditioning (MAC) or reduced-intensity conditioning (RIC) prior to allogeneic haematopoietic stem cell transplantation (allo-HSCT) for the treatment of haematological disorders

Conditioning type	Preparative regimens	Patients, n	Ovarian recovery, %	Pregnancy, n (%)	Reference
MAC	BU (TBI)/CYC (LPAM)	15	6.7	NA	Shimizu et al. 8
MAC	TBI	∼237	NA	5 (2.1)	Carter et al. 9
MAC	BU/CYC (BEAM minority)	45	13.3	NA	Tauchmanovà et al. 10
MAC	TBI	74	13.5	NA	Bakker et al. 11
MAC	TBI	65	NA	12 (18.5)	Salooja et al. 12
MAC	BU/CYC	8	12.5	NA	Afify et al. 13
MAC	BU/CYC	73	1	0	Sanders et al. 14
MAC	TBI	532	10	7 (1.3)	Sanders et al. 14
MAC	TBI	500	NA	11 (2.2)	Sanders et al. 15
RIC	FLU/LPAM/(ATG)	11	81.8	NA	Shimizu et al. 8
RIC	TBI/CYC	17	NA	2 (11.8)	Fuchs et al. 16
RIC	CYC	103	54.4	25 (24.3)	Sanders et al. 14
RIC	CYC	43	74	NA	Spinelli et al. 17
RIC	CYC	99	NA	24 (24.2)	Sanders et al. 15

BU, busulphan; TBI, total body irradiation; CYC, cyclophosphamide; LPAM, melphalan; BEAM, bischolorethylnitrosourea, etoposide, ara-C, melphalan; FLU, fludarabine; ATG, anti-T-lymphocyte globlin; NA, not applicable.

A priori defined inclusion criteria were used: (1) studies including recovery of ovarian function and/or natural pregnancy in women following allo-HSCT for the treatment of haematological disorders; (2) use of either MAC or RIC with any specific programme for allo-HSCT; (3) studies that reported data on demographic, conditioning programme, transplant, treatment and outcome variables. Editorials, comments, letters and abstracts without full text were excluded because of a lack of detail. Assisted reproduction cases and case reports were also excluded. References in each article identified were scanned to identify other relevant studies. When there was more than one publication from the same patient cohort, the one with longest follow-up was included.

Discussion

The present study describes a rare case of successful twin pregnancy and childbirth after RIC allo-HSCT combined with imatinib, for the treatment of CML. It is well established that most MAC regimens include alkylating agents and/or irradiation, either of which can cause germinal epithelium depletion and infertility. ¹ Compared with MAC allo-HSCT, RIC is not only associated with reduced transplant-related morbidity and mortality,^18,19 but also shows advantages in preserving fertility.

The literature review demonstrated that a MAC regimen with busulphan and cyclophosphamide is associated with a high incidence of gonadal failure in females. Sanders et al. ¹⁴ reported that only one of 73 females treated with busulphan and cyclophosphamide recovered ovarian function, and that this patient was unable to become pregnant after allo-HSCT. In another study using a MAC regimen with busulphan and cyclophosphamide, 13.3% of female patients recovered gonadal function after transplanation. ¹⁰ Female children with acute myeloid leukaemia who underwent allo-HSCT with busulphan and cyclo phosphamide also showed prominent gonadal dysfunction. ¹³ There have been only two reported cases of successful pregnancy after busulphan and cyclophosphamide conditioning: one CML patient and one case of thalassaemia.^20,21 The majority of patients given total body irradiation-conditioning also experience gonadal failure. Recovery of gonadal function occurs in 10 – 13.5% of female patients, and the incidence of pregnancy reported by one centre was 1.3%.^8,13 In contrast, the RIC regimen generally increases the recovery rate for ovarian function. Recovery of gonadal function has been reported in 54.4 – 74% of female patients receiving a RIC regimen with cyclophosphamide 200 mg/kg, and the incidence of pregnancy was 24.3% in one centre.^14,17 It was reported that two out of 17 female patients of child-bearing age who received RIC allo-HSCT for lymphoma had successful pregnancies. ¹⁶ Additionally, nine of 11 (82%) female patients receiving RIC consisting of fludarabine/melphalan showed recovery of ovarian function, compared with only one of 15 (7%) controls receiving a MAC regimen. ⁸ The present case and those reported previously^{8 – 17} suggest that a RIC regimen may facilitate the recovery of ovarian function in patients undergoing allo-HSCT. The present case study is the first to report a successful pregnancy using a RIC regimen consisting of fludarabine, busulphan and anti-T-lymphocyte globulin.

To avoid CML relapse after RIC allo-HSCT, the present case received imatinib both pre-(to improve remission status), and post-transplant (to create a window of opportunity for graft versus leukaemia effects). ²² Thus, it is necessary to observe the effect of imatinib on reproduction, as ovarian failure has been reported to be a complication of such treatment.^23,24 The underlying reason for this effect may be that imatinib inhibits the expression of kinases (such as c-kit, c-abl and platelet-derived growth factor receptor, which are enzymes that appear to be important in multiple aspects of growth and development of oocytes and follicles) in mammalian ovaries:^23,24 Christopoulos et al. ²³ reported a case of primary ovarian insufficiency associated with 2 years' imatinib treatment (400 mg/day for 18 months, increasing to 600 mg/day for a further 6 months). In the present case, imatinib was administered at a dose of 400 mg/day for 6 months before transplantation, to reduce the burden of leukaemia. Prophylactic 400 mg/day imatinib commenced 100 days post-HSCT to prevent relapse, and was discontinued ∼24 months after transplantation, resulting in a cumulative treatment duration and dose of 27 months and 324000 mg, respectively. This suggested that short-term treatment and a low cumulative dose of imatinib may not have profound effects on female fertility.

Current guidelines recommend that women should not become pregnant during administration of imatinib because of possible teratogenic effects. ²⁵ The patient presented here became pregnant 7 months after withdrawal of imatinib, so was able to continue the pregnancy. The subsequent delivery of healthy twins in this patient suggested that pregnancy after stopping imatinib treatment does not present a safety issue for the fetus.

Although it is not recommended to attempt pregnancy while on imatinib, there are a few reports of successful unplanned pregnancy during such therapy (reviewed by Ali et al.). ²⁶ Two cases of twin pregnancy in women on imatinib have been reported: one case of homozygous and one case of heterozygous twins.^27,28 Homozygous twinning occurs when the early blastocyst cell loses adhesion and splits into separate embryos that are each capable of developing into a fully formed fetus. Since tyrosine kinases are involved in several cell-signalling processes and some (such as focal adhesion kinase), modulate cell adhesion and motility, it is conceivable that inhibition of tyrosine kinases at the time of conception and during early pregnancy may disturb this process and lead to homozygotic twinning. ²⁷ Although a relationship between imatinib therapy and twin pregnancy has not been confirmed, it deserves further investigation.

The introduction of imatinib has changed the therapeutic algorithm for CML. In China, however, most patients cannot afford the high cost of such therapy and are not covered by medical insurance. Furthermore, although there are increasing numbers of young patients with CML in China, with a median age of onset of 40 years, ²⁹ the long-term administration of imatinib is not possible for many young patients. In view of this situation, allo-HSCT for CML as a curative therapy is still meaningful in China, and is also a favoured choice for many patients, particularly the young. ³⁰ In our centre, the regimen of RIC allo-HSCT combined with imatinib has been used for a cohort of CML patients and showed reliable efficacy. ⁵ The present case suggests another advantage related to its reduced impact on ovarian function. A study investigating the recovery of ovarian function under this regimen is currently underway to confirm whether, in addition to curing CML, it can also improve health-related quality of life for young female patients with CML.