Gynecology and Minimally Invasive Therapy 4 (2015) 76e80

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Original article

Clinical practice and short-term efﬁcacy of 2.45-GHz microwave
endometrial ablation to treat menorrhagia
Naoki Matsumoto*, Nobuyuki Ikeda, Toshifumi Takenaka, Satoshi Yazaki, Yuichi Sato
Department of Obstetrics and Gynecology, Tatedebari Sato Hospital, 96 Wakamatsucho, Takasaki City, Gunma, Japana r t i c l e i n f o

a b s t r a c t

Article history:
Received 10 November 2014
Received in revised form
22 February 2015
Accepted 13 March 2015
Available online 9 May 2015

Objective: To evaluate the clinical practice and short-term efﬁcacy of microwave endometrial ablation(MEA) to treat menorrhagia, and to identify prognostic factors for optimal outcomes.
Methods: We performed MEA in 22 women with menorrhagia between October 2012 and December
2013. To evaluate efﬁcacy, objective and subjective variables were measured using medical records andpatients' pre- and postoperative responses to a written questionnaire with a visual analog scale (VAS)
scored from 0 to 10 for each symptom. MEA outcome was evaluated 6 months after treatment. Patientswith amelioration of menorrhagia and no anemia were deﬁned as the effective group, and the others
were deﬁned as the noneffective group. Effective patients requiring no hormonal therapy were deﬁned
as the highly effective group. To identify prognostic factors, background factors were compared between
the highly effective group and the other groups.
Results: Uterine ﬁbroids and adenomyosis were diagnosed in 68% and 32% of patients, respectively. The
median VAS score of postoperative pain was 1.0, and that of satisfaction was 8.1. Hemoglobin concentration, menstrual bleeding volume, menstrual duration, menstrual pain, vaginal discharge, and fatigue
were ameliorated in the postoperative period. The effective group, the highly effective group, and thenoneffective group included 95%, 84%, and 5% of patients, respectively. The uterine corpus cavity wassigniﬁcantly shorter in the highly effective group than in the other groups.
Conclusion: MEA was safe and effective. The short-term efﬁcacy rate of MEA for alleviating menorrhagia
symptoms was 95%. Optimal outcomes were correlated with a shorter uterine corpus cavity.
Copyright © 2015, The Asia-Paciﬁc Association for Gynecologic Endoscopy and Minimally Invasive
Therapy. Published by Elsevier Taiwan LLC. All rights reserved.

Keywords:
dysmenorrhea
endometrial ablation
menorrhagia
microwave
minimally invasive surgery

Endometrial ablation is considered an important surgical option
for the treatment of menorrhagia.1 In Japan, microwave endometrial ablation (MEA) using a frequency of 2.45 GHz was describedand developed as an original applicator for use by Kanaoka et al2 in
2001. After the Japanese Ministry of Health, Labour, and Welfare
authorized the use of MEA as an advanced medical therapy in 2009,
MEA has been offered in a few approved institutions and facilities.

In April 2012, MEA was approved by the national health insurance
system in Japan as a covered treatment for menorrhagia. At thattime, we began providing MEA in our hospital. Several researchers
evaluated the efﬁcacy of MEA based on the condition during 3e24months after operations. Ishikawa et al3 showed that no patient
experienced recurrent menorrhagia for > 6 months after MEA.
Therefore, the short-term postoperative condition was evaluated in
6 months in this research. The purposes of this research were toevaluate the clinical practice and short-term efﬁcacy of 2.45-GHz
MEA to treat menorrhagia and to identify the prognostic factors
associated with optimal MEA outcomes.

Conﬂicts of interest: The authors have no conﬂicts of interest relevant to thisarticle.

Materials and methods

Introduction

A summary of this report was presented at the 66th Academic Conference of theJapan Society of Obstetrics and Gynecology, Tokyo, Japan, 2014.
* Corresponding author. Tatedebari Sato Hospital, 96 Wakamatsucho, Takasaki
City, Gunma 370-0836, Japan.
E-mail address: research@matsumotoc.org (N. Matsumoto).

Patient selection
Patients with symptoms of menorrhagia who were no longer
bearing children and with no uterine malignancy were initially

http://dx.doi.org/10.1016/j.gmit.2015.03.002
2213-3070/Copyright © 2015, The Asia-Paciﬁc Association for Gynecologic Endoscopy and Minimally Invasive Therapy. Published by Elsevier Taiwan LLC. All rights reserved.

N. Matsumoto et al. / Gynecology and Minimally Invasive Therapy 4 (2015) 76e80

deemed eligible to receive MEA. After initial screening, eligibility toreceive MEA was individually decided on the basis of preoperative
assessment using ultrasonography and/or magnetic resonanceimaging. In principle, patients whose menorrhagia was not easy tocontrol by conservative therapy were deemed to be good candidates. Patients whose uterine cavity was too large or too complex inshape to appropriately and safely provide MEA were excluded.
Patients who preferred hysterectomy, which would furnish a perfect effect for menorrhagia in exchange for the invasiveness, were
excluded as well. Before undergoing MEA, patients received an ironsupplement, pseudomenopausal therapy (subcutaneous leuprolide
acetate), and an oral hormonal medication (dienogest or an estrogeneprogestin combination) if necessary.
Ablation procedure
The microwave system used in this research was composed of a
Microtaze device and a Sounding Applicator (Alfresa Pharma,
Osaka, Japan). The former is a power generator of 2.45-GHz microwaves, and the latter is an intrauterine applicator that irradiates
microwaves from its tip. The applicator is 4 mm in diameter andcurved to access the endometrium easily, and it reaches to a
maximum distance of 18 cm. MEA was performed according to theprocedure guidelines described previously.4 The microwave generator's output was set to 70 watts for 50 seconds for each irradiation. Transabdominal ultrasonography was used for intraoperative
monitoring. Immediately before and after the procedure, as well as
during the procedure if necessary, hysteroscopy was used to visualize the ablated area. Microwave irradiation was repeated until a
sufﬁcient area of the uterine corpus endometrium had been ablated. General anesthesia was used, and a nonsteroidal antiinﬂammatory drug was administered intraoperatively.
Research design
We performed MEA in 22 women with menorrhagia between
October 2012 and December 2013. To evaluate MEA efﬁcacy, subjective and objective variables were measured. Objective variabledata were drawn from patients' medical records, including theirlaboratory test results, and subjective variables were measured
using patients' responses to a written questionnaire survey. Preand postoperative subjective symptom ratings of each patient wereobtained using a questionnaire with a visual analog scale (VAS)
scored from 0 to 10 for each symptom. The questionnaire survey
was performed and MEA outcome was evaluated by each patient 6
months after treatment. At that time, patients with amelioration ofmenorrhagia and no anemia were deﬁned as the effective group,and the others were deﬁned as the noneffective group. Amelioration of menorrhagia was deﬁned by self-report as mentioned in thepatient's medical record 6 months after MEA, or by a subjective
estimate of postoperative menstrual bleeding volume that was
decreased to half or less than the preoperative volume in the patient. Moreover, the effective group was subdivided into twogroups: those whose postoperative symptoms required no hormonal therapy comprised the highly effective group, whereas those
who continued to use additional hormonal therapy in the postoperative period were classiﬁed as the fairly effective group.
To evaluate MEA efﬁcacy in detail, each patient's pre- andpostoperative variables were compared. To identify the prognostic
factors associated with the optimal outcomes, background factors
were compared between the highly effective group and the othergroups. Correlation was measured between the length of theuterine corpus cavity (from the anatomical internal os to the upperedge of the endometrium) and the number of microwave irradiation sessions required.

77

This research was planned and performed on the basis of theapproval of the research ethics committee in our hospital. Eachpatient's written informed consent to the research was obtained
along with the responses to the questionnaire.
Data were analyzed using JMP version 8.0 (SAS Institute, Cary,
NC, USA) and R version 2.13. Two-tailed p values were calculatedusing univariate methods including the ManneWhitney U test,
Wilcoxon signed rank test, McNemar test, Chi-square test, andPearson product-moment correlation coefﬁcient. A p value < 0.05
was considered signiﬁcant.
Results
The characteristics of the 22 patients who received MEA are
shown in Table 1. No patients received a diagnosis of functional
menorrhagia; all patients had either uterine ﬁbroids or adenomyosis. Summarized data concerning the MEA procedures areshown in Table 2. On the whole, MEA yielded high levels of patientsatisfaction with minimal postoperative pain. The only clinicallyproblematic adverse event occurred in a patient with a single
intramural ﬁbroid of 55 mm in diameter. The patient had a feverwith purulent vaginal discharge 1 week after MEA. The condition
was diagnosed as bacterial endometrisis, and she had to be brieﬂy
admitted to our hospital for intravenous antibiotics.
To evaluate MEA efﬁcacy in detail, pre- and postoperative variables of each patient were compared. An iron supplement wasadministered to 81.8% and 5.3% of patients (p < 0.001 by McNemartest), pseudomenopausal therapy was administered to 68.2% and10.5% (p < 0.001), and oral hormonal medication was administered
to 5.3% and 10.5% (p ¼ 1.0) of the 22 women in the pre- and postoperative periods, respectively. Changes in hemoglobin concentration and patients' subjective symptom ratings are presented in
Figure 1. Hemoglobin concentration (median preoperative score,
median postoperative score, and median variation were 8.6, 13.5,
and þ5.3, respectively), menstrual bleeding volume (10, 1.0,
and 8.0, respectively), menstrual duration (7.0, 2.5, and 3.5,
respectively), menstrual pain (7.5, 0.5, and 4.0, respectively),vaginal discharge (4.8, 1.6, and 2.4, respectively), and fatigue (7.5,
2.0, and 5.0, respectively) ameliorated in the postoperative
period.

Table 1
Characteristics of the 22 patients who received microwave endometrial ablation totreat menorrhagia.
Factors

MedianRange

Age (y)ParityPrevious cesarean delivery
Obesity (BMI  25)
Initial anemiaa
Initial hemoglobin concentration (g/dL)
Organic diagnosis causing menorrhagia
Uterine ﬁbroids
Multiple ﬁbroids
Submucosal ﬁbroids
Adenomyosis
Functional menorrhagia
Patient complaints
Heavy menstrual bleeding
Prolonged menstruation
Painful menstruation
Uterine corpus cavity length (cm)
Preoperative use of iron supplement
Preoperative pseudomenopausal therapy
Preoperative oral hormonal medication

46.5
2

39e54
0e4

8.6

5.5

BMI ¼ body mass index.
aInitial hemoglobin concentration < 12.0 g/dL.

n

%

6
4
18

27.3
18.2
81.8

15
9
8
7
0

68.2
60.0
53.3
31.8
0

22
10
11

100
45.5
50.0

18
15
1

81.8
68.2
4.5

4.0e13.6

3.4e7.5

78

N. Matsumoto et al. / Gynecology and Minimally Invasive Therapy 4 (2015) 76e80

Table 2
Summarized data concerning microwave endometrial ablation procedures.
Variables

Median Range

No. of microwave irradiation sessions per operation 7.0
Operative time (min)a18
Postoperative use of painkiller on the operative day
Postoperative use of painkiller on and after the
next day
VAS score of postoperative pain (points)b
1.0
VAS score of satisfaction (points)c
8.1

n %

5e12
10e43
6 27.3
4 18.20e10
2.5e10VAS ¼ visual analog scale.
a
The duration from starting the ﬁrst irradiation to ascertaining necessary andsufﬁcient ablation by hysteroscopy.
b
A lower score indicates milder pain.
c
A higher score indicates a higher level of satisfaction.

In the 19 patients whose postoperative conditions were obtained, amenorrhea was observed in 52.6% (10/19) in the postoperative period. Only one patient reported no improvement in the
menstrual bleeding volume. She received a diagnosis of multiple
uterine ﬁbroids, including a 56-mm submucosal ﬁbroid. Her uterine corpus cavity measured 7.5 cm, and the operator performed 12
microwave irradiation sessions during the patient's MEA procedure. Her pre- and postoperative ratings of menstrual bleeding
volume were 10 and 10, respectively.
The MEA outcomes were largely positive: 94.7% (18/19) of patientswere classiﬁed in the effective group, and 84.2% (16/19) also met thecriteria for the highly effective group, whereas only 5.3% (1/19) of
patients were classiﬁed into the noneffective group. Subsequent

hysterectomies were performed in two patients, although these
events occurred after the postoperative study period of 6 months. One
case was the aforementioned patient who underwent hysterectomy
11 months after MEA. The second patient received a diagnosis ofadenomyosis and pelvic endometriosis with severe anemia anddysmenorrhea. Although MEA reduced the patient's reported menstrual bleeding volume, her dysmenorrhea was not relieved and pelvic
endometriosis was exacerbated. After MEA, she received pseudomenopausal therapy, which also did not produce sufﬁcient improvement
in her symptoms. Therefore, the patient underwent hysterectomy
with affected-side salpingo-oophorectomy 1 year after MEA.
To identify the prognostic factors associated with the optimal
outcomes, background factors were compared between the highly
effective group and the other groups (Table 3). The mean uterine
corpus cavity length was signiﬁcantly shorter in the highly effective
group than in the other groups, and no patients in this group had acavity length greater than 7 cm.
The correlation between the uterine corpus cavity length andthe number of microwave irradiation sessions required for treatment was analyzed (Figure 2), and a positive linear correlation wasobserved (r ¼ 0.54, p ¼ 0.008).
Discussion
MEA was safely and effectively provided in our hospital. The
short-term efﬁcacy rate of MEA for the treatment of menorrhagia wasestimated to be 94.7%. The optimal MEA outcomes were associatedwith a shorter uterine corpus cavity. A positive linear correlation was

Figure 1. Changes in hemoglobin concentration and patients' subjective symptom ratings to evaluate the efﬁcacy of microwave endometrial ablation in detail. The p values arecalculated using Wilcoxon signed-rank tests.

N. Matsumoto et al. / Gynecology and Minimally Invasive Therapy 4 (2015) 76e80
Table 3Comparison of background factors between the highly effective group and the othergroups in the 19 patients whose postoperative ratings were obtained.
Factors

Highly effective Otherpgroup
groupsAge (y)45.5
46
Parity22Previous cesarean delivery (%)
37.5
0Obesity (BMI  25; %)25.0
0Initial hemoglobin concentration (g/dL)
8.4
9.7
Organic diagnosis causing menorrhagia (%)
Uterine ﬁbroids
68.8
33.3
Multiple ﬁbroids
63.6
100
Submucosal ﬁbroids
63.6
100
Adenomyosis
33.3
68.8
Patient complaints (%)
Prolonged menstruation
43.8
33.3
Painful menstruation
50.0
100
Uterine corpus cavity length (cm)5.5
7.2
VAS scores of patients' subjective preoperative conditions (points)
Menstrual bleeding volume
10
7.5
Menstrual duration
7
5
Abnormal vaginal bleeding
05
Menstrual pain
58Chronic pelvic pain
2.5
0
Vaginal discharge
5
2.4
Fatigue
7.5
5Preoperative pseudomenopausal therapy (%) 68.8
66.7

0.96
0.39
0.20
0.33
0.91
0.25
0.46
0.46
0.25
0.74
0.11
0.010
0.18
0.19
0.068
0.21
0.79
0.27
0.28
0.95

Data are presented as the median or proportion in each group. The p values were
calculated using Chi-square or ManneWhitney U tests.
BMI ¼ body mass index; VAS ¼ visual analog scale.

Figure 2. Correlation between the uterine corpus cavity length and the number ofmicrowave irradiation sessions, measured using the Pearson product-moment correlation coefﬁcient.

79

observed between the uterine corpus cavity length and the numberof microwave irradiation sessions required for treatment.
To perform MEA safely, Kanaoka et al4 presented guidelines for
2.45-GHz MEA procedures. Among the reported adverse events
caused by MEA, the most severe outcomes are uterine perforationand heat damage to the extrauterine organs. To avoid the former
event, ongoing ultrasonographic monitoring and hysteroscopic examination during the procedure are recommended to allow observation of the ablated endometrial area. To avoid the latter event, it isrecommended that the myometrial layer of the area to be ablatedshould have a depth of at least 10 mm. This recommendation is basedon the results of the original study, which showed that a single session of 2.45-GHz microwave irradiation with an output of 70 watts
for 50 seconds formed a lemon-shaped necrotic area with a width of
16 mm and a length of 20 mm around the tip of the applicator.4,5
Endometrial ablation, including MEA, has a higher latent risk in patients who underwent a previous cesarean delivery.4,6 If the operator
grasps the thinness on the previous cesarean scar properly, he or she
can provide MEA and avoid irradiation sessions on the thin scar wall.
In the current study, six patients with a history of cesarean delivery
received MEA. They were safely treated with careful provision inconsideration of the thinness around the previous cesarean scar. Allof them obtained highly effective outcomes.
The short-term efﬁcacy rate of MEA for the treatment ofmenorrhagia was estimated to be 94.7%. Moreover, a highly effective outcome was obtained in 84.2% of patients. Short-term efﬁcacy
of MEA reported in the recent literature is summarized inTable 4.3,7e10 On the whole, the efﬁcacy rate for reducing themenstrual bleeding volume is estimated to be ~90%, and the
postoperative amenorrhea rate is 20e40%. The effectiveness forrelieving concomitant menstrual pain is reportedly high as well. In
the current study, similar results were observed.
The optimal MEA outcomes were associated with a shorter
uterine corpus cavity. This result does not suggest that the factor
had a robust inﬂuence on the highly effective outcome because theresult was determined by univariate analysis. However, this prognostic factor may help clinicians determine the likelihood that MEA
will produce positive outcomes in a particular patient. Women witha uterine corpus cavity length of < 7 cm may obtain better outcomes, whereas those with a longer uterine corpus cavity may be
more likely to require subsequent hormonal therapy or hysterectomy postoperatively. A trend was observed that patients withlower preoperative levels of menstrual pain and abnormal vaginal
bleeding may obtain better MEA outcomes, but this was not signiﬁcant. Peeters et al6 similarly reported that short uterine depth
and no dysmenorrhea were prognostic factors for the success ofendometrial ablation to treat menorrhagia. This information may
help physicians plan individual therapeutic strategies in the management of menorrhagia.
A positive linear correlation was observed between the uterine
corpus cavity length and the number of microwave irradiation

Table 4
Short-term efﬁcacy of microwave endometrial ablation reported in the recent literature.
Year

Researchersn

Period of assessment fortherapeutic effect (mo after MEA)

Reduction in menstrual
bleeding volume

Postoperative
amenorrhea rate

2009
2012
2012
2012
2014
2014

Sambrook et al7
Singh et al8
Tsuda9Ishikawa et al3
Nakayama et al10This research

157
68
25
55
76
19

12
6e18
3
6e24
6
6

76
84
96
92
95
95

41
41
32
31
34
53

Data are presented as %, unless otherwise indicated.
VAS ¼ visual analog scale.
a
These were performed after the postoperative study period of 6 months.

Amelioration of menstrual pain

72
81
VAS score of 4.2 improved to 1.3
VAS score of 7.5 improved to 0.5

Subsequent
hysterectomy rate
4
7
2
9a

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N. Matsumoto et al. / Gynecology and Minimally Invasive Therapy 4 (2015) 76e80

sessions required for treatment. As a rough estimate, a uterine
corpus cavity with a length of 5 cm generally required six microwave irradiation sessions, one of 6 cm needed seven sessions, andone of 7 cm required eight sessions. This guideline may assist MEA
operators in selecting the number of microwave irradiation sessions, taking into account uterine size, uterine shape, organic
diagnosis, and previous history of cesarean delivery.
Since the introduction of MEA for the treatment of menorrhagia
in our hospital in 2012, the procedures have been shown to be both
effective and safe. In our experiences, the cases that do not havevery large cavities, protuberating submucosal myomas, and severe
endometriosis outside the uterus are considered to be positive indications for MEA. Particularly for a case with large submucosal
myomas, Kanaoka et al11 developed and reported the system oftranscervical microwave myolysis. It seems to have potency;
however, it cannot be applied yet for approved treatment. We hope
to continue contributing to improvements in the provision andresearch of this novel and useful therapy in Japan.
References
1. Reid PC. Endometrial ablation in Englanddcoming of age? An examination of
hospital episode statistics 1989/1990 to 2004/2005. Eur J Obstet Gynecol Reprod
Biol. 2007;135:191e194.

2. Kanaoka Y, Hirai K, Ishiko O, Ogita S. Microwave endometrial ablation at afrequency of 2.45 GHz. A pilot study. J Reprod Med. 2001;46:559e563.
3. Ishikawa M, Katayama K, Yoshida H, Hirahara F. Therapeutic outcomes andpostoperative courses in microwave endometrial ablation for menorrhagia.
J Microwave Surg. 2012;30:253e257.
4. Kanaoka Y, Ishikawa N, Asakawa Y, Nakayama K. Practice Guideline of MEA;
2012.
Availablefrom:
http://www.alfresa-pharma.co.jp/microtaze/
MEAguideline2012.pdf.
5. Kanaoka Y, Hirai K, Ishiko O. Microwave power and duration without extrauterine thermal damage in microwave endomyometrial ablation at 2.45 GHz.
J Obstet Gynaecol Res. 2005;31:359e367.
6. Peeters JA, Penninx JP, Mol BW, Bongers MY. Prognostic factors for the successof endometrial ablation in the treatment of menorrhagia with special reference
to previous cesarean section. Eur J Obstet Gynecol Reprod Biol. 2013;167:
100e103.
7. Sambrook AM, Cooper KG, Campbell MK, Cook JA. Clinical outcomes from arandomised comparison of Microwave Endometrial Ablation with Thermal
Balloon endometrial ablation for the treatment of heavy menstrual bleeding.
BJOG. 2009;116:1038e1045.
8. Singh N, Hassanaein M. Comparing satisfaction rates of Microwave and Bipolar
Impedance controlled endometrial ablation. Arch Gynecol Obstet. 2012;285:
1301e1305.
9. Tsuda A. Microwave endometrial ablation for menorrhagia in ofﬁce gynecology. J Microwave Surg. 2012;30:71e75.
10. Nakayama K, Ishibashi T, Ishikawa M, et al. Microwave endometrial ablation ata frequency of 2.45 GHz for menorrhagia: Analysis of treatment results at asingle facility. J Obstet Gynaecol Res. 2014;40:224e229.
11. Kanaoka Y, Yoshida C, Fukuda T, Kajitani K, Ishiko O. Transcervical microwave
myolysis for uterine myomas assisted by transvaginal ultrasonic guidance.
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Gynecology and Minimally Invasive Therapy
Volume 4, Issue 3, 76–80
DOI: http://dx.doi.org/10.1016/j.gmit.2015.03.002

Original article
Clinical practice and short-term efficacy of 2.45-GHz microwave endometrial ablation
to treat menorrhagia

過多月経に対するマイクロ波子宮内膜焼灼術の実践と短期的治療効果
松本直樹，池田申之，竹中俊文，矢﨑聡，佐藤雄一

日本語要約【目的】過多月経に対するマイクロ波子宮内膜焼灼術（MEA）の実践と短期的治療効果を検証し，さらに治療転帰を予測し得る背景因子を探索した。
【方法】MEA を行った全 22 例を研究対象とした。治療効果を検証するための変数は，客観的な評価に基づくものと患者アンケートによる主観的な評価に基づくものに分けた。患者ア
ンケートは治療後（MEA 後約 6 か月の時点）に行い，治療前（初診時から MEA 施術まで）と治療後の状態を同時に回答させた。回答方法には 0 から 10 までの visual analog scale (VAS)を用いた。治療転帰を治療後に判定し，貧血なし・過多月経改善・ホルモン剤治療不要の全てを満たす状態が得られた場合を著効，前 2 項目を満たすがホルモン剤治療を必要とした場
合を有効，有効に満たない場合を無効とした。治療前と治療後の各変数を比較し治療効果を検証した。さらに著効群と非著効群の背景因子を比較した。
【結果】患者背景に関して，年齢 47 歳（中央値，以下同様），子宮筋腫 68%，子宮腺筋症 32%，
初診時ヘモグロビン値 8.6 g/dL。
術後疼痛 VAS スコア 1.0 ポイント，手術満足度 8.1 ポイント。
ヘモグロビン値，経血量，月経期間，月経痛，帯下過多，体調全般が術後改善した。治療転帰は有効 95％，著効 84％，無効 5％であった。著効群では非著効群より子宮体部腔長が短かった。
【結論】MEA を安全に実践した。短期的治療効果から判定した有効率は 95%と高かった。子
宮体部腔長が短いことが著効の転帰と関連していた。