A new study of breast cancer patients in Japan has revealed that decades of smoking are associated with an increased risk of early death in pre-menopausal women diagnosed with breast cancer. This finding strengthens the case for smoking cessation, particularly as breast cancer in premenopausal women has significantly worse prognosis than it has in postmenopausal women.
Smoking is injurious to health. It harms almost every organ of the body and is also responsible for many types of cancers and health problems. While lung cancer is a well-documented health hazard linked to smoking, the habit also raises the risk of death from chronic obstructive pulmonary disease (COPD), heart disease, stroke and other cancers, including breast cancer.
AdvertisementBreast cancer is the most commonly occurring cancer in women worldwide. Previous studies have suggested that smoking significantly increases the risk of developing breast cancer in premenopausal women. However, very few studies have investigated the relationship between active smoking and risk of death among breast cancer patients Also, the results of these studies were found to be inconsistent.
Some studies have suggested that women who are active smokers have a higher risk of death from any cause after being diagnosed with breast cancer while others have shown no association between active smoking and overall survival in breast cancer patients. Trying to establish this relationship is of particular importance because smoking might be one of the modifiable lifestyle factors that might improve the prognosis of breast cancer patients.
For the study, the research team followed 848 female breast cancer patients aged 21 years or over at the Miyagi Cancer Centre Hospital (MCCH) between January 1997 and December 2007. The researchers assessed the patients' active or passive smoking status and menopausal status with the help of a self-administered questionnaire. The patient follow-up continued till December 31, 2010.
A total of 302 women died during the 607 year follow-up period. The researchers observed that premenopausal women with breast cancer who smoked for more than 21.5 years had a 3.1 times higher risk of dying from any cause and a 3.4 times higher risk of dying from breast cancer. Among premenopausal patients, current smokers tended to have the shortest survival rate. Shorter survival was also noted among women who started smoking early (≤20 years) and those who smoked heavily (>21 cigarettes per day). The findings clearly indicated a decrease in survival rate with an increase in the duration of smoking.
This increased risk was especially relevant to pre-menopausal women with estrogen receptor (ER+) or progesterone receptor (PR+) tumor. This relationship might be related to estrogen-like substances found in active tobacco smoke that might accelerate the progression of hormone receptor-positive tumors. Detailed analysis of the study data suggests that premenopausal ER+ or PR+ cancer patients with a longer history of smoking tended to have more advanced tumors compared to women who had never smoked or had only smoked for a short duration.
The study did not suggest any significant association between smoking status and survival among postmenopausal breast cancer patients.
One possible reason for this higher risk of death among premenopausal women could be that lifestyle habits related to smoking might have influenced the prognosis of breast cancer. Smoking women were found to be less educated, physically inactive and they consumed fewer green vegetables and fruits. However, further studies are needed to clarify the association between survival and smoking-related lifestyles.
Long-term smoking might also affect the immune system and cause immunological deterioration.
Such delirious effects of smoking on hormones and the immune system, in addition to the above mentioned lifestyle factors could contribute to the increased risk of all-cause and breast cancer-specific death among premenopausal women with ER+ or PR+ breast cancer.
The study did not find any association between exposure to passive smoking and survival of breast cancer patients.
While further large-scale studies are needed to confirm these results, smoking cessation could contribute to a significant reduction in breast cancer mortality. Breast cancer patients should be informed about the importance of smoking cessation in a clinical setting. Moreover, considering the higher risk of death among premenopausal women with a longer duration of smoking, smoking control measures targeting young girls is urgently needed.
The study has been published in Cancer Science.