Survivors of breast cancer are forced to ask themselves whether the diagnosis means that they are more likely to develop a second unrelated cancer in later years. The risks are realistic, but new research suggests that it is relatively small and depends on the patient's age, treatment type, and lifestyle factors at the time of diagnosis. Large-scale research published in BMJ Although the risk of second cancer is slightly higher than the general population, it provides particularly important insights showing that it is important enough to ensure close follow-up and customized survival care.
BMJ We followed 476,373 women in the UK who were diagnosed with early invasive breast cancer between 1993 and 2016, all of whom had surgery. After 20 years of follow-up, 64,747 women were diagnosed with their second primary cancer. Twenty years after diagnosis, the absolute risk of a second non-brain cancer was 13.6%, about 2.1% higher than expected compared to women in the general population. For contralateral or contralateral breast cancer, the risk is 5.6%, indicating a 3.1% increase in population estimates. Young women were at a higher relative risk than older women, with women diagnosed at age 40 having an approximately 6% chance of developing a second cancer by age 60. Adjuvant therapies such as chemotherapy and radiation therapy were found to slightly promote increased risk alone.
Other recent studies support these findings while adding important contexts. A large Korean cohort study using propensity score matching compared patients who received radiation therapy and who found that there was no significant difference in overall risk of secondary malignant neoplasms, even when the group was divided by age, latency period, and number of radiation therapy. This result indicates that although radiation has historically been linked to the development of a particular second cancer, it may not be a major source of risk, particularly when it comes to the use of modern treatments, as previously envisaged.
Meanwhile, a study conducted in the US Integrated Healthcare Delivery System involving more than 16,000 breast cancer survivors reported that treatment type is a determinant of second cancer risk. The researchers found that the risk of soft tissue sarcoma increased after radiation therapy, and the risk of myelodysplastic syndrome increased after chemotherapy. However, the risk of new breast cancer was lower in the group with endocrine therapy. This points to the complex relationship between cancer treatment and long-term impacts and the important role of personalized risk counseling.
Lifestyle and modifiable factors can also affect the risk of secondary cancer. A systematic review and meta-analysis concluded that excess weight is the main cause of the second major cancer in breast cancer survivors, producing important risk factors for obesity and overweight. This gives pharmacists the opportunity to provide weight management counseling as part of survivor care, along with other healthcare professionals.
Furthermore, the occurrence of a second primary cancer has a long-term effect on mortality. A recent study found that breast cancer survivors who developed a second malignant tumor had a 27% increase in the risk of cancer-related death and an 18% increase in the risk of all-cause death compared to those who did not develop another cancer.
For pharmacists, these findings have several practical implications. Cancer survivors should recommend that the overall likelihood of a second cancer is not only slightly above average, but still a concern. Endocrine therapy should be strictly attached when prescribed, not only to reduce recurrence, but also to reduce the risk of second breast cancer. Pharmacists should actively support adherence, monitor negative impacts, and provide education on the importance of long-term therapy. Lifestyle counseling is equally important. In particular, weight control, smoking cessation and alcohol consumption are all factors in both recurrence and risk of secondary cancer.
In conclusion, women who survived early invasive breast cancer are at a lower, but in fact, at increased risk of developing a second primary cancer, both in the opposite breast and elsewhere in their body. The absolute excess risk over the course of 20 years is limited. It is usually only 2% to 3% higher than baseline for non-brain cancer, and slightly higher for contralateral breast cancer. Young survivors and those exposed to specific treatments have different risk profiles and lifestyle factors that can be altered also affect outcomes. Scientific research in the fields of genetics, therapeutic exposure and preventive measures continue to present risk stratification and enhance the quality of survival care.