Analysis of the CANTO cohort published in the journal Annals of Oncology will upset received wisdom on the effects that hormone therapy and chemotherapy have on the quality of life in women with breast cancer.
Contrary to the commonly held view, 2 years after diagnosis, hormone therapy, a highly effective breast cancer treatment worsens quality of life to a greater extent and for a longer time, especially in menopausal patients.
The deleterious effects of chemotherapy are more transient.
Given that current international guidelines recommend the prescription of hormone therapy for 5 to 10 years, it is important to offer treatment to women who develop severe symptoms due to hormone antagonist medication and to identify those who might benefit from less prolonged or intensive treatment strategies.
"This analysis of the CANTO cohort shows for the first time that anti-hormonal treatments do not have lesser effects than chemotherapy on women's quality of life. Quite the contrary, as the diminution in quality of life which is noted at diagnosis is still present two years later, whereas the impact of chemotherapy is more temporary," explained Dr Inès Vaz-Luis, a specialist breast cancer oncologist and researcher at Gustave Roussy.
In this study, researchers measured quality of life in 4,262 patients with localised breast cancer (stage I to III) at the time of diagnosis and at one and two years thereafter.
Primary treatment for these patients was surgical and, for some of them, administration of chemo-therapy and/or radiotherapy.
About 75-80% of them then took hormone therapy for at least 5 years.
Quality of life was measured using a tool which assesses general quality of life in patients with all types of cancer (EORTC QLQ-C30) combined with a tool more specifically designed for use in breast cancer (QLQ-BR23).
For the population studied as a whole there was an overall deterioration in the quality of life at two years from diagnosis.
This deterioration was greater in patients who had received hormone therapy, especially after the menopause.
By contrast, chemotherapy had a bigger effect on quality of life in non-menopausal patients, especially in terms of worsening of cognitive functions.
"It is important in the future that we are able to predict which women are going to develop severe symptoms with anti-hormonal treatment so that we can support them," added Dr Vaz-Luis.
While it has been shown that hormone therapy provides a real benefit in reducing the relapse rate of hormone-dependent cancers which represent 75% of all breast cancers, the deterioration in quality of life may also have a negative effect on patient adherence to treatment.
It is, therefore, important to offer them symptomatic treatment, in particular for menopausal symptoms, musculoskeletal pain, depression, severe fatigue and cognitive dysfunction; and to combine this with supportive measures such as physical exercise and cognitive behaviour therapy.
"It will also be important in the future to differentiate prior to treatment patients who are at high risk of relapse from those at lower risk in order to tailor hormone treatment. This may be done to avoid escalation of anti-hormonal treatment in certain patients," concluded Dr Vaz-Luis.
Dr Vanz-Luis also emphasised that: "Hormone therapy is extremely effective in treating breast cancer, resulting in a reduction by approximately 50% in the risk of relapse, and that the finding of adverse effects does not in any way put into question the excellent risk/benefit ratio of this treatment."