In this real-life French multicenter cohort, we found that only 4.3% of older women aged 70yo or more with MBC were included in a clinical trial in the first-line setting, compared to 10.5% for their younger counterparts. When considering all lines of treatment, 7.1% of older women with MBC were enrolled in a clinical trial.
Several studies [6-12] are consistent with our results showing that older patients were less frequently enrolled in clinical trials, but none of them was specifically dedicated to metastatic breast cancer patients. Moreover, some of these studies were focused on the age of the patients included in clinical trials compared to the median age of disease incidence [6-8, 12]. Other studies were centered on patients treated for gastro intestinal cancer [9], included a small number of patients [10], or used a threshold of 65 years old [11].
In a prospective multicentric French cohort study (Sujets AGés dans les Essais Cliniques - SAGE), evaluating enrollment of patients with colorectal cancer, the inclusion rate with a threshold of 70 yo or more was 9.5% [9]. In the SEER data-base including all tumor types [12], 20% of older patients aged 70 yo or more were enrolled in a clinical trial, far more than our population. As stated by the authors, this high level of enrollment was related to numerous adjuvant endocrine therapy programs, which can lead to more enrollment consistent with the better general condition of this population. The inclusion rate excluding those studies was 12%. Similarly, in Lackman’s study [11], enrollment rate was up to 14%, probably due to the high of proportion of non metastatic patients (66%), and to a lower age threshold of 65 yo.
This low rate of enrollment in MBC was also observed in the OMEGA study, with several barriers to enrollment, such as patients’ refusal of chemotherapy or randomization, comorbidities and oncologist’s preferences [19]. Other barriers to enrollment have also been described [11-12,20] such as availability of trials, older age, ECOG PS, but also the representations of patients and practitioners on the potential benefits and risks expected from the protocol on an individual basis.
In our study, variables associated with participation in a clinical trial in the first-line setting in older patients were younger age (< 80 yo), good ECOG PS (0-1), HER2+ disease, and investigational treatment (chemotherapy/targeted therapy/immunotherapy trials). This is consistent with the SAGE and Lackman’s studies [9, 11]. In the SAGE study, older age (> 80 years old) was significantly associated with non-invitation to participate in a clinical trial (HR= 0.14; 95%CI 0.02–0.60).
The type of disease (HR+ etc.), and the trials available at that time, with their inclusion and exclusion criteria, are important confounding factors, which should lead to some caution in the analysis of these results. The fact that patients were less included in endocrine therapy alone trials is probably due to the few trials enrolling at that time. Conversely, patients harboring HER2+ disease were more often enrolled in clinical trials due to a larger range of clinical trials in this indication. Poor ECOG PS (>1) is an usual exclusion criteria in trials, explaining our results with an OR of 0.15 in this patients’ population.
We also found a better overall survival in older MBC patients included during the first-line setting, and a better relative survival, even after adjustments for confounding factors in a multivariable analysis. This can be interpreted in two ways: one is that patients included in clinical trials have a better natural prognosis and are selected for trials because of their better general condition. The other could be that having access to innovative treatments may increase life expectancy among these patients. Our data do not allow to identify the respective weight of these two potential complementary factors linked to a longer observed survival, because of the retrospective setting, and lack of certain data (unavailable ECOG PS values in almost 50% and unavailable comorbidities, geriatric assessments and causes of death). Of note, a better overall survival when included in a clinical trial was also observed in the Korean MBC Database in a general MBC population [21].
Unfortunately, as mentioned, no geriatric data was available to better characterize older patients, such as cognitive status, depression, or functional autonomy, which could highly change the probability of enrollment in a clinical trial. The number of referrals, patient’s eligibility and finally numbers of patients enrolled were not available in this database preventing from any conclusions regarding patient’s selection. Finally, due to its retrospective nature, data regarding study type (chemotherapy, supportive care or radiotherapy for example) or study phase, was lacking in up to 40% in chemotherapy studies. The QUALISAGE study (NCT03230305), closed to enrollment, will probably help to answer these questions.
Finally, in our study, more patients were included during the 2012-2016 period compared to the 2007-2011 period. This improvement was also observed in younger patients in the first line setting. However, the inclusion rate of older patients increased over time when all treatment lines were taken into account, unlike younger patients. This encouraging result combined with the smaller increase of inclusion rate among younger people in the first line setting, suggest an improved awareness. Efforts are still needed for a better representation and reliable guidelines [22-23].