October 30, 2025

expert reaction to study on association between different hormonal contraceptives formulations and breast cancer risk in women under 50

A study published in JAMA Oncology looks at hormonal contraceptive formulations and breast cancer risk in women under 50.

Comment provided by our friends at the Spanish SMC:

Dr Ramón Salazar, Head of Medical Oncology at the Catalan Institute of Oncology (ICO) and associate professor of Medicine at the University of Barcelona, said:

“This large Swedish population study, which includes more than two million women, confirms that the use of hormonal contraceptives is associated with a slight increase in the relative risk of breast cancer, but the magnitude of the absolute risk is very small—around one additional case per 7,000–8,000 users per year. The study is methodologically sound, with long-term follow-up and detailed analysis by type of formulation, although, as with any observational study, it cannot establish causality or completely rule out confounding factors such as family history or lifestyle.

“These results should be interpreted with caution. Hormonal contraceptives are very effective and safe drugs, whose benefits—preventing unwanted pregnancies and reducing the risk of ovarian and endometrial cancer—far outweigh the potential risks in most women. The relevance of this study is that it helps to refine the personalised choice of method by identifying formulations with a slightly more favourable risk profile. In clinical practice, the decision should be shared between the patient and the healthcare professional, always taking into account age, family history and individual preferences.

“The Swedish study distinguishes between different types of progestogens and shows that the risk is not the same for all formulations. Preparations containing desogestrel, both in pills and implants, are associated with a slightly higher relative risk, while those containing levonorgestrel or drospirenone show a more neutral profile. Furthermore, the risk increases with duration of use and tends to disappear after discontinuation of treatment. In practical terms, these data support more informed prescribing: in women with personal or family risk factors, a combined or levonorgestrel formulation may be preferred, without sacrificing the overall benefits of hormonal contraception”.

‘Hormonal Contraceptive Formulations and Breast Cancer Risk in Adolescents and Premenopausal Women’ by Fatemeh Hadizadeh et al. was published in JAMA Oncology at 15:00 UK Time Thursday 30 October 2025. 

DOI: 10.1001/jamaoncol.2025.4480

Declared interests

Dr Ramón Salazar : Financial interests declared to the European Society for Medical Oncology (ESMO) as of 1 June 2025:

Esteve, Invited Speaker, Personal, <€5,000

Novartis, Invited Speaker, Personal, <€5,000

SACE Medhealth, Other, Personal, €10,001-€50,000, Commercial Medical Education Company owned by wife until december 2023

Takeda Pharmaceuticals, Advisory Board, Personal, <€5,000

TTD, Other, Personal, No financial interest, Member of executive committee

WNT Pharma, Coordinating PI, Personal and Institutional, Financial interest”