Background
Systemic lupus erythematosus (SLE) remains a therapeutic challenge. One of the most successful therapies for severe SLE has been administration of monthly intravenous cyclophosphamide (IVCY) for 6 months followed by quarterly maintenance infusions for 2 years (traditional/NIH IVCY regimen) [
1‐
3]. However, the side effects of long-term exposure to cyclophosphamide include infection, bone marrow damage, malignancy, hemorrhagic cystitis, and ovarian dysfunction [
2]. Ovarian dysfunction may result in physiological changes associated with menopause, including loss of bone mineral density, hypercholesterolemia, onset of vasomotor and genitourinary symptoms, psychological distress, weight gain, and infertility [
4]. Because SLE mainly affects premenopausal women, ovarian dysfunction is a particularly serious adverse event in SLE and may be particularly distressing for women who have not completed their family.
The incidence of cyclophosphamide-induced amenorrhea is generally related to age and cumulative dosage of cyclophosphamide [
4]. Although most data for understanding the biological characteristics of cyclophosphamide gonadotoxicity comes from the oncology literature, several studies have examined cyclophosphamide-induced amenorrhea in women receiving traditional IVCY regimens in SLE [
5‐
11]. In an attempt to reduce toxicity of cyclophosphamide, a low-dose IVCY regimen (6 fortnightly pulses at a fixed dose of 500 mg, followed by azathioprine) was proposed on the basis of the results of the Euro-Lupus Nephritis Trial; clinical results comparable to those obtained using the traditional regimen have been reported [
12]. However, the incidence of major side effects did not differ significantly between the traditional and the low-dose IVCY regimen groups, perhaps because of the low number of subjects included in the original study [
12]. Thus, the effects of low-dose IVCY on cyclophosphamide-induced amenorrhea have not been elucidated.
We conducted a retrospective analysis of the menstrual function of women with SLE before and after receiving low-dose IVCY (500 mg/pulse/month; the duration of treatment was modified depending on clinical response). The objective of this study was to gain a better understanding of the rate of amenorrhea in premenopausal women who were given low-dose IVCY with high-dose glucocorticoid or high-dose glucocorticoid alone. The incidence of the resumption of menses was also assessed. The results of this study will assist physicians in counseling their SLE patients about the benefits and risks of low-dose IVCY and allow women to make better informed decisions. Improved knowledge will also facilitate earlier intervention and treatment of menopausal-related complications.
Discussion
The important findings of this study are that i) patients < 40 years old have a minimum risk for sustained amenorrhea with low-dose IVCY treatment; ii) irrespective of treatment regimen, sustained amenorrhea developed frequently in patients ≥ 40 years old at initiation of treatment; iii) even low-dose IVCY may increase the risk of transient amenorrhea; and iv) the strongest risk factor for developing amenorrhea in SLE patients treated with high-dose glucocorticoids with or without low-dose IVCY is being ≥ 40 years old at the initiation of treatment.
The low-dose IVCY treatment regimen was initially proposed as an attempt to reduce the toxicity of cyclophosphamide [
12]. However, the incidence of major side effects, including menopause, did not differ significantly between traditional and low-dose IVCY regimen groups (menopause; 2/45 and 2/44, respectively) in the original study [
12]. Although patients treated with high-dose or traditional IVCY regimens were not included in the present study, the proportion of sustained amenorrhea in patients < 40 years old in our study (0/51) was much lower than similar figures for patients treated with the traditional IVCY regimen in other studies. At initiation of traditional IVCY therapy, Boumpas et al. reported that sustained amenorrhea developed in 19% (6/31) of women ≤ 30 years old [
5], Mok et al. reported that sustained amenorrhea developed in 19% (10/54) of women < 40 years old [
7], Park et al. reported that sustained amenorrhea developed in 11% (7/62) of women ≤ 40 years old [
8], and Ioannidis et al. reported that sustained amenorrhea developed in 11% (5/44) of women ≤ 31 years old [
11]. Thus, when considering the benefits of low-dose IVCY and the risk for amenorrhea, treatment with low-dose IVCY would have a lower risk for sustained amenorrhea than higher-dose regimens and should be well tolerated in premenopausal patients < 40 years old. In addition, previous reports demonstrate that the rates of amenorrhea following short-term high-dose IVCY are also lower than those following long-term high-dose IVCY: 0-12% [
5,
8,
10]. Because our IVCY protocol in the present study was mostly both low-dose and short-term, the duration of IVCY treatment and cumulative dose of cyclophosphamide also affect the resumption of menses. However, our study shows that even low-dose IVCY may increase the risk of transient amenorrhea, an important clinical consideration that should not be overlooked.
Consistent with previous studies using the traditional IVCY regimen [
5,
7,
8,
11] and with breast cancer studies [
4,
16], sustained amenorrhea developed frequently in patients ≥ 40 years old at initiation of treatment, irrespective of treatment regimen. The strongest risk factor for developing amenorrhea in SLE patients treated with high-dose glucocorticoids with or without low-dose IVCY was being ≥ 40 years old at the initiation of treatment in the present study. Older women are more likely to progress to premature ovarian failure after therapy because they have a smaller number of oocytes at the initiation of treatment [
17]. Thus, the higher risk of sustained amenorrhea from IVCY therapy should be a serious consideration in patients > 40 years old. In addition, when the patients were divided into the age groups of 32, 35, or 37 years, there was no or only weaker statistical association, although there might be an increasing risk for amenorrhea after the age of 35 years. Age at the initiation of treatment did not differ significantly between subjects with and without amenorrhea, and the logistic regression analysis did not reveal significant correlation between age and amenorrhea. Thus, we speculate that the age of 40 was a threshold for the patients in the present study.
Cyclophosphamide toxicity in women may arise from direct effects on the oocyte, or indirectly through its effects on the supporting granulosa cells of the follicle through gap junctions connecting these "nursing cells" to the oocyte [
17]. DNA cross-linking occurs in granulosa cells of animals treated with cyclophosphamide within 2 hours of administration, as well as increased nuclear size, which is thought to result from a cell-cycle block in G
2 phase [
17]. Following exposure to cyclophosphamide, human ovaries are fibrosed, and follicles are destroyed [
17]. Ovarian dysfunction can be partially mitigated during IVCY therapy by using gonadotrophic-releasing hormone analogues, which reduce proliferation within the ovary [
17]. However, the risk of precipitating a disease flare with hormonal stimulation must be considered when treating SLE [
17].
One of the limitations of the present study is the selection bias inherent in a single-center retrospective study, although rarity of the disease makes performing prospective studies difficult. In addition, our subject number was insufficient for definitive conclusions about association between amenorrhea and low-dose IVCY, and we lacked controls such as age-matched healthy subjects or SLE patients who were not treated with glucocorticoids. However, the size of our study population is comparable to similar previously reported studies, and treatment without glucocorticoids in active SLE is impractical. Another potential weakness arises from the lack of uniformity of the follow-up duration and treatment regimens, although all study subjects were followed up for at least 1 year, usually sufficient time to evaluate drug-induced amenorrhea and menses resumption. Evaluation of ovarian function could not be included because we did not measure the hormone levels of all of the subjects. The fact that the SLEDAI-2K score was higher in the IVCY group compared with the steroid group may be a limitation of this study because high disease activity has previously been associated with the development of amenorrhea in SLE [
18]. However, in the present study, there was no association between the SLEDAI-2K score and amenorrhea. Finally, because this study was not designed to assess the effectiveness of low-dose IVCY, it is not clear whether our low-dose IVCY regimen is applicable to severe manifestations of SLE. Considering that the patients that could not respond to the questionnaire due to severe or fatal disease were excluded from the study and that some of the study subjects required additional therapy, our low-dose IVCY regimen would not necessarily be suitable for all severe manifestations of SLE.
In conclusion, SLE patients < 40 years old have a minimum risk for sustained amenorrhea with low-dose IVCY treatment, whereas higher-dose IVCY reportedly has a higher risk even in this younger population. In contrast, sustained amenorrhea developed frequently in patients ≥ 40 years old at the initiation of treatment; this higher risk of sustained amenorrhea with IVCY therapy requires serious consideration when treating SLE patients ≥ 40 years old. However, our study demonstrates the possibility that even low-dose IVCY may increase the risk of amenorrhea, an important clinical consideration that should not be overlooked.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
SB and YKatsumata conceived the study and drafted the manuscript. YKawaguchi, TG, TS and TK participated in acquisition of data and patient recruitment. MH and HY participated in the design and coordination of the study. All authors read and approved the final manuscript.