Despite certain concerns about a cognitive decline after treatment against cancer, most survivors of breast cancer do not present an increased risk of developing Alzheimer’s disease. Some may even have a slightly lower risk than their counterparts without cancer, according to a vast retrospective study conducted in Korea.
However, this potentially protective effect seems to diminish over time, researchers reported in an article published online in the journal JAMA Network Open.
A risk of Alzheimer’s overall reduced in survivors
Overall, “this is a reassuring new for cancer survivors,” said the Pr Tim Ahlespsychologist at the Memorial Sloan Kettering Cancer Center in New York, who did not participate in the study, in Medscape Medical News.
“I often have this question of my patients,” said Professor Ahles. According to these results, “nothing indicates that history of breast cancer or its treatment increase the risk of developing Alzheimer’s disease”.
Breast cancer survivors frequently report cognitive disorders related to cancer – difficulties in concentration or memory – during and after treatment. However, the data available on the link between breast cancer and risk of Alzheimer’s disease is mixed.
A vast study conducted in Sweden, for example, revealed a 35 % increase in Alzheimer’s risk in women who have been diagnosed with breast cancer after 65 years, but not among younger women. Conversely, a population study in Taiwan has found no global increase in the risk of dementia compared to a control group without cancer, while noting a lower risk in patients treated with tamoxifen.
To clarify this contradictory data, the authors of the Korean study have evaluated the risk of Alzheimer’s disease in a vast cohort of patients, taking into account the type of treatment, age and major risk factors.
Using the database of the National Korean Health Insurance Service, the researchers have paired 70,701 patients who underwent breast cancer surgery between 2010 and 2016 to 180,360 women without cancer.
The impact of associated risk treatments and risk factors
The average age of survivors was 53.1 years. About 72 % received radiotherapy. The most used chemotherapies were cyclophosphamide (57 %) and anthracycline (50 %), while the most frequent hormonal treatments were tamoxifen (47 %) and aromatase inhibitors (30 %).
The main criterion of the study was the impact of new Alzheimer’s disease diagnostics, defined by at least a prescription of drugs specific to this pathology (Donépézil, Rivastigmine, Galantamine or Memantine).
After a median follow-up of about 7 years, 1,229 cases of Alzheimer’s disease were recorded in survivors of breast cancer, against 3,430 cases in witness women-or incidence rates of 2.45 and 2.63 for 1,000 people-years, respectively.
This corresponds to a risk of 8 % lower Alzheimer’s disease in breast cancer survivors compared to witnesses (relative risk of sub-distribution [RRS] : 0.92; 95 % CI: 0.86-0.98), especially among women over 65 years of age (RRS: 0.92; 95 % CI: 0.85-0.99).
Among the various treatments, only radiotherapy was associated with a significant reduction in the risk of Alzheimer [RRc] : 0,77).
Other factors, on the other hand, were linked to a significantly higher risk: smoking (RRC: 2.04), diabetes (RRC: 1.58) and chronic renal failure (RRC: 3.11). On the other hand, alcohol consumption, level of physical activity and hypertension did not seem to influence the risk of Alzheimer’s disease.
A temporary protective effect, but reassuring results
However, the protective effect observed seems temporary. The risk reduction was no longer significant after 1 year (RRS: 0.94; CI: 0.87-1.01), 3 years (RRS: 0.97; CI: 0.90–1.05), nor 5 years (RRS: 0.98; CI: 0.89-1.08).
Despite this, the results remain generally reassuring for survivors.
“Concerns about”chemo brain”And the long -term cognitive effects of breast cancer treatment are frequent. But our results suggest that this treatment does not directly lead to Alzheimer’s disease,” write the authors, led by the Dr Su-Min Jeongfrom the National University of Seoul.
Professor Ahles shares this conclusion: “This study shows that there is no solid evidence that cancer treatment increases the risk of developing Alzheimer’s disease. “He adds:” When patients ask me the question, I can now answer them by citing this study as reassuring proof. »»
He specifies, however, that the study does not assess the case of people with genetic predisposition to Alzheimer’s disease, for which treatment could potentially accelerate the appearance of symptoms.
“Does cancer treatment increase the probability or precipitates the appearance of the disease in these people?” This study does not allow us to say, ”he concludes.
Dr. Jeong and Professor Ahles did not report any link of interest in relation to the subject.
Article translated and adapted from the American edition of Medscape.com
Follow the news of Medscape French edition on Bluesky
