In women with hormone-sensitive breast cancer who want to become mothers, pausing endocrine therapy to try to get pregnant for up to two years does not increase the risk of short-term relapse. This is supported by the results of the Positive clinical trial, published in The New England Journal of Medicine, and coordinated in Spain by the Solti Group, for clinical research in cancer, and by the Spanish Breast Cancer Research Group (Geicam).

After three and a half years of follow-up, the results, which since they were advanced in the last international congress San Antonio Breast Cancer Symposium 2022 (SABCS), show a risk of relapse in these patients of 8.9%, compared to 9.2% in patients who did not pause therapy in search of pregnancy.

Positive is the first prospective study designed to respond to women who are diagnosed with breast cancer at an early age and without having completed their desire to become mothers. It is estimated that between 40% and 60% of patients diagnosed with breast cancer at age 40 or earlier are concerned about their future fertility.

Breast cancer becoming more common in young women

"We know that breast cancer is increasingly common in young women and, therefore, coincides with the desire to be a mother of many of them. For this reason, fertility and pregnancy are important concerns for both cancer patients and researchers," says Manuel Ruiz Borrego, co-coordinator of the Positive study in Spain, member of the Board of Directors of Geicam and head of the Breast Cancer Unit at the Virgen del Rocío Hospital in Seville.

This new study "opens the possibility of a safe pregnancy for those patients with breast cancer who want it, once they have undergone at least 18 months of adjuvant endocrine therapy," says Cristina Saura, coordinator of the study in Spain, member of the board of directors of Solti and head of the Breast Cancer Unit at Vall d'Hebron Hospital and VHIO.

Until now the recommendation was to start looking for pregnancy after a minimum of 5 years after having overcome breast cancer, and provided that there had been no relapses. According to the expert, the results of Positive "may change current clinical guidelines", but warns that "the long-term follow-up of these patients will be essential to corroborate these data".

The president of Geicam, Miguel Martín, who is also head of the Medical Oncology Service of the Gregorio Marañón Hospital, warns that "this study gives peace of mind to doctors and patients who previously decided to interrupt endocrine therapy, after at least two years, to allow a pregnancy".

"It was already known that pregnancy did not worsen the prognosis of women with breast cancer. Many oncologists also discussed with patients the possibility of temporarily interrupting endocrine treatment to allow a very desired pregnancy and we did so, but now there is prospective evidence that supports that option, "says the oncologist.

This has been the Spanish participation in the study

To examine the impact of pausing endocrine therapy to seek pregnancy, the Positive study included 518 women aged 42 years or younger, from twenty countries, with hormone receptor (RH)-positive breast cancer who wanted to become pregnant.

Of these, 72 patients came from 18 Spanish hospitals and were recruited through the Solti and Geicam research groups.Before pausing their treatment, the patients had completed between 18 and 30 months of adjuvant endocrine therapy. In addition, trial participants were urged to resume endocrine treatment after an attempted pregnancy or a two-year hiatus from hormone treatment to try.

The current data emerge after a follow-up of 3 and a half years. However, the researchers will continue to follow the study participants for 10 years.

Interestingly, the results show rates of conception and delivery that are on par with or higher than those of the general population; Of 497 women who were followed to see if they had become pregnant, 317 gave birth to at least one child and a total of 365 children were born, due to multiple or consecutive pregnancies.

Breast cancer and pregnancy

Positive is part of a line of research that seeks to answer the questions about reproductive health of patients with breast cancer. It is also investigated whether there is a causal relationship between pregnancy and the appearance of breast cancer.

Thus, the Pregnancy and Breast Cancer study (Embarcam), led by Geicam, will allow us to have a photo of the so-called gestational breast cancer, diagnosed during pregnancy or the following year, with the aim of anticipating this situation and designing strategies aimed at achieving safe pregnancies.

In this line we want to determine the usefulness of breast milk for the early detection of breast cancer. "With the study of specific cases we have concluded that breast milk would serve to detect cancer mutations earlier than through blood, because the concentration of DNA is much higher in breast milk," says Saura.

"To confirm these data, we plan to launch MMaterna, an international study whose objective will be to analyze the case of women who become pregnant when they are over 40 years old or being healthy carriers of a genetic mutation that increases their risk of breast cancer to see if we are able to diagnose breast cancer earlier in the postpartum period through breast milk than through breast milk samples. blood or conventional radiological studies", he highlights.

  • Breast cancer
  • cancer
  • Pregnancy

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