A claim you hear on longevity podcasts
Conflicting. Of 4 studies that test it, 2 agree, 1 partly agrees and 1 disagrees.
The claim checked: Bioidentical hormone therapy does not cause breast cancer, but it can make an existing cancer grow Hear it at 19:03
Few studies test this form of hormone therapy: estradiol, the body's own estrogen, with micronized progesterone. Two of four agree. In 80,377 French women, estrogen with progesterone showed no rise in breast cancer. One disagrees: a pooled analysis of 58 studies found risk about doubled with micronized progesterone too. One is mixed: risk crept up with longer use for some tumour types.
Computed from 4 studies that test this point, each judged by two readers, in full. Sources land on both sides. 10 more studies are waiting for a full read and do not count yet.
“We don't necessarily think that that bioidentical hormone therapy is causing cancer, right? But we do know that it can cause cancer to grow um if there is cancer cells there.”
other primary study · 2008 · landmark
“Estrogen-progesterone was associated with a relative risk of 1.00 (0.83–1.22), and estrogen–dydrogesterone with a relative risk of 1.16 (0.94–1.43).”
Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study. Breast Cancer Res Treat
Who: 80,377 postmenopausal French women in the E3N cohort (mostly teachers insured by MGEN), mean age 53.1 at start of follow-up
PMID 17333341
other primary study · 2013
“We found no indication of an increased risk of breast cancer in EP therapy users of micronized progesterone, a result in line with the finding of the E3N cohort [ 19 , 21 ].”
Risk of breast cancer by type of menopausal hormone therapy: a case-control study among post-menopausal women in France. PLoS One
Who: Menopausal women aged 25-75 in Cote d'Or and Ille-et-Vilaine, France (CECILE population-based case-control study, 2005-2007)
PMID 24223752
trial or observed group · 2008
“In the present analysis, the use of estrogen+progesterone was not significantly associated with the risk of any breast cancer subtype, though we found trends of increasing risks with increasing duration of use for lobular and ER+/PR− carcinomas.”
Use of different postmenopausal hormone therapies and risk of histology- and hormone receptor-defined invasive breast cancer. J Clin Oncol
Who: 80,391 postmenopausal French women in the E3N cohort (born 1925-1950, mostly teachers), mean age 53.1 at start of follow-up
PMID 18323549
pooled analysis · 2019 · landmark
“In general, the RR did not differ substantially by the progestagenic constituent of the combinations, including rarely used hormones, such as micronised [natural] progesterone (RR 2·05, 1·38–3·56), although the RR appeared to be somewhat lower for oestrogen plus dydrogesterone ( appendix p 45 ).”
Type and timing of menopausal hormone therapy and breast cancer risk: individual participant meta-analysis of the worldwide epidemiological evidence. Lancet
Who: Postmenopausal women in 58 epidemiological studies (24 prospective, 34 retrospective); main analyses restricted to prospective studies
PMID 31474332
Two of three studies agree. Pooled from two trials of hormone therapy after breast cancer, the cancer came back 3.41 times as often. In another trial, tibolone, a hormone-like drug, raised the chance of the cancer coming back. One is mixed: in Danish women, vaginal estrogen raised recurrence only in women taking aromatase inhibitors.
Computed from 3 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.
pooled analysis · 2005
“A total of 36 recurrences and nine deaths occurred during this time in these trials; the pooled RR for the two randomized trials was 3.41 (95% CI 1.59–7.33).”
Menopausal hormone therapy after breast cancer: a meta-analysis and critical appraisal of the evidence. Breast Cancer Res
Who: Breast cancer survivors with invasive breast cancer who used oral hormone therapy versus non-users, in 2 randomized trials (England, Sweden) and 8 observational studies
PMID 15987460
controlled trial · 2012
“Treatment of BC survivors with tibolone (a specific tissue estrogenic-activity regulator) led to increases in BMD and BC recurrence.”
Tibolone increases bone mineral density but also relapse in breast cancer survivors: LIBERATE trial bone substudy. Breast Cancer Res
Who: Women under 75 with surgically treated breast cancer (T1-3, N0-2, M0) within 5 years and vasomotor symptoms, in 245 centers in 31 countries (LIBERATE trial); bone substudy subset
PMID 22251615
trial or observed group · 2022 · landmark
“In patients treated with VET and adjuvant AIs, we observed an increased risk of recurrence but not mortality.”
Systemic or Vaginal Hormone Therapy After Early Breast Cancer: A Danish Observational Cohort Study. J Natl Cancer Inst
Who: Postmenopausal Danish women aged 35-95 treated for early-stage ER-positive breast cancer 1997-2004 without chemotherapy (DBCG registry)
PMID 35854422
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