Question explored with the scientific record
Marina coil
The Marina coil (levonorgestrel IUS) reduces heavy bleeding and pain for many women, but the evidence on long-term harms is thin and comes with a real trade-off: a 19% higher breast cancer risk in one large Finnish registry study.
The evidence here is a mix of small trials and observational studies, mostly funded by the manufacturer or conducted by clinicians who use the device. No trial compared the Marina coil to a true untreated group over many years. The largest safety signal comes from a Finnish registry study of over 90,000 women, which found a 19% higher breast cancer rate among users (1,542 observed cases vs 1,292 expected) [4]. The same study showed lower rates of endometrial, ovarian, and lung cancers [4]. That is a real trade-off, not a clean win.
The device works locally: it releases levonorgestrel into the uterus, thinning the endometrium and reducing menstrual blood loss by about 87% in one trial [5]. For heavy bleeding, it outperforms oral contraceptive pills [5] and is roughly as effective as endometrial resection [3]. For adenomyosis pain, one large study of 1,100 women found modest symptom improvement over 60 months, but only 374 of the original 1,100 completed the full follow-up [1]. Expulsion rates are about 8% in the first year, higher in women with fibroids or adenomyosis [2]. Uterine perforation is rare but documented [6].
The main gap: no long-term randomized trial with hard clinical endpoints like all-cause mortality or cancer incidence. The breast cancer signal comes from an observational registry, which cannot fully control for confounding. The evidence is moderate for short-term symptom relief, but low for long-term safety.
My call: the Marina coil is a reasonable option for heavy menstrual bleeding when you understand the trade-off, but the evidence does not rule out a real breast cancer risk. Confidence: moderate for short-term benefit, low for long-term safety.
Sources used 6
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Treatment of symptomatic adenomyosis with the levonorgestrel‐releasing intrauterine system
This study investigates the long-term effects of the levonorgestrel-releasing intrauterine system (LNG-IUS) on symptomatic adenomyosis, demonstrating significant improvements in pain and bleeding symptoms over a 60-month period.
DOI: 10.1002/ijgo.12887 -
Factors affecting the spontaneous expulsion of the levonorgestrel-releasing intrauterine system
This study investigates the incidence and risk factors associated with the spontaneous expulsion of the levonorgestrel-releasing intrauterine system (LNG-IUS) in a cohort of 481 women, revealing that women with adenomyosis or uterine leiomyomas have significantly higher expulsio…
DOI: 10.1016/j.ijgo.2014.02.017 -
Treatment of menorrhagia with the levonorgestrel intrauterine system versus endometrial resection
This study compares the effectiveness and adverse events of the levonorgestrel intrauterine system (LNG IUS) and transcervical endometrial resection (TCRE) in treating menorrhagia, finding that both treatments significantly reduce menstrual blood loss, with TCRE showing higher s…
DOI: 10.1016/s0015-0282(01)01909-4 -
Cancer Risk in Women Using the Levonorgestrel-Releasing Intrauterine System in Finland
This study investigates the association between the use of the levonorgestrel-releasing intrauterine system and cancer incidence in Finnish women, revealing a protective effect against endometrial, ovarian, pancreatic, and lung cancers, while indicating an increased risk for bre…
DOI: 10.1097/AOG.0000000000000356 -
Levonorgestrel-Releasing Intrauterine System Compared to Low Dose Combined Oral Contraceptive Pills for Idiopathic Menorrhagia: A Randomized Clinical Trial
This randomized clinical trial demonstrates that the levonorgestrel-releasing intrauterine system (LNG-IUS) is more effective than low dose combined oral contraceptive pills (COC) in managing idiopathic menorrhagia, with significantly lower treatment failure rates and greater re…
DOI: 10.1016/j.jmig.2010.08.581 -
Sistema intrauterino em localização extrauterina
A 31-year-old woman with a Mirena intrauterine system experienced extruterine migration to the right adnexa causing uterine perforation, diagnosed by ultrasound, MRI, and CT, and treated with hysterectomy.
DOI: 10.33448/rsd-v10i5.14585