Q&A: Is Breast Cancer Survival Improving?

A new study suggests that survival of women with recurrent breast cancer has been improving over the past two decades, but it also cautions that more research is needed.

Answering questions about the study results is lead author Sharon H. Giordano, M.D., assistant professor in the Department of Breast Medical Oncology at M. D. Anderson.

What was the goal of the study?

The goal of this study was to determine whether survival had improved for women with recurrent breast cancer (cancer that returned after the initial diagnosis).

How was that information obtained?

Researchers analyzed data from 834 M. D. Anderson patients who had recurrent breast cancer that developed between November 1974 and December 2000.

The major study objective was to evaluate the association between the year that recurrence was detected and subsequent survival. Patients were divided into five groups based on year of breast cancer recurrence, and survival was compared across the five groups.

What were the findings?

Although our findings are suggestive, but not conclusive, our data suggests that the prognosis of patients with recurrent breast cancer has improved from 1974 to 2000.

Our analysis shows there was a statistically significant improvement in survival rates across the five groups, with the more recent patients living longer following diagnosis of recurrence.

Following are the five-year survival rates of patients whose breast cancer recurrence was diagnosed during the specified periods:

• 10% for 1974-1979
• 14% for 1980-1984
• 22% for 1985-1989
• 29% for 1990-1994
• 44% for 1995-2000

The more recent recurrence groups had more favorable prognostic variables, and in turn longer survival, due in part to drug and treatment advances. The more favorable variables included:

• Smaller initial tumor size
• Lower stage of disease
• Fewer lymph nodes involved
• Longer disease-free interval
• Estrogen receptor positive tumors (tumors that use estrogen to fuel their growth)
• Tumors that do not involve the main organs

It is estimated that there has been a reduction in risk of 1% to 2% for each increasing year, although the change was not highly significant statistically. This statistic is consistent with SEER data (Findings from The National Cancer Institute's Surveillance, Epidemiology and End Results cancer registry database.)

What are current breast cancer statistics?

In 2004, approximately 217,440 new cases of breast cancer will be diagnosed in the United States, and 40,580 women can be expected to die from metastatic disease, according to the American Cancer Society.

How conclusive are the results?

Given the inherent difficulty of determining changes of survival over time, we would encourage these results to be interpreted cautiously.

Although the strengths of this study include a large patient population, extensive follow-up (median 9.3 years) and uniform initial staging and follow-up testing, the study is limited by the problems inherent in analyzing survival data over time.

For instance, improvements in radiographic techniques and more precise imaging can change stage distribution. Tiny metastatic lesions, which could have been detected with modern imaging in the 1990s, could have been missed in a patient diagnosed in the 1970s. Therefore, some of the patients diagnosed in the 1970s could have been misclassified as having early stage disease. This would result in an apparent poorer prognosis among patients diagnosed in the 1970s.

In addition, the improvements in radiographic imaging may have resulted in earlier diagnosis of recurrent disease. This would give a misleading appearance of improved survival.

What may be responsible for increased survival?

There has been a marked increase over time in the number of drugs available to treat breast cancer. A major increase occurred in the 1990s with drugs such as taxanes, vinorelbine, capecitabine, Herceptin, aromatase inhibitors and pamidronate.

Therapeutic advances also have clearly been making an impact on the survival of women with early breast cancer. For example, two early trials begun in the 1970s involving adjuvant chemotherapy (chemotherapy before surgery) demonstrated that adjuvant chemotherapy resulted in improved disease-free survival.

How will this study help future research?

Despite advances in therapies for breast cancer, improvement in survival for patients with recurrent or metastatic breast cancer (cancer that has spread) has been difficult to establish.

Overall, breast cancer mortality rates have been declining. From 1995 to 1999, breast cancer death rates decreased by 3.2% annually. However, it remains unclear whether the decrease in the death rate is due to a higher proportion of patients being diagnosed with early stage disease or to improvements in treatment.

We present this data to encourage further research to clarify whether advances in therapy have led to improved survival for women with recurrent breast cancer.