The impact of new chemotherapeutic and hormonal agents on the survival of women with metastatic breast cancer (MBC) in a population based cohort.
Reviewer: Walter Sall, MD
Last Modified: June 1, 2003
Presenter's Affiliation: British Columbia Cancer Agency
Type of Session: Scientific
- Metastatic Breast Cancer is an extremely prevalent diagnosis. Median OS for these patients has historically been 12-24 months. No studies have shown population based data indicating improved survival with newer chemotherapeutic agents over the past 15 years.
- This study aimed to determine whether new agents including taxanes, vinorelbine, aromatase inhibitors, capecitabine and trastuzumab have improved overall survival (OS) for metastatic breast cancer patients in British Columbia, Canada.
Materials and Methods
- The British Columbia Cancer Agency maintains a comprehensive breast cancer registry and oversees the treatment of all breast cancer patients in the province.
- Patients diagnosed with metastatic breast cancer during four time cohorts were analyzed for OS: 1991-92 was the baseline cohort, 1994-95 corresponded to the introduction of paclitaxel and vinorelbine, 1997-98 corresponded to the introduction of taxotere and non-steroidal aromatase inhibitors and 1999-2001 corresponded to the introduction of capecitabine and trastuzumab.
- Patients 75 or younger were eligible.
- 2151 patients were analyzed for OS.
- Patient characteristics, prognostic factors and use of hormonal therapies was not significantly different between cohorts. Significantly more patients in the later cohorts had previously received chemotherapy.
- Median survival for cohorts 1,2,3 and 4 respectively were: 435 days, 449 days, 562 days and 661 days. OS for cohort 3 vs. cohorts 1 and 2 combined was significantly improved (p<0.05). OS for cohort 4 vs. cohort 3 was significantly improved (P=0.05).
- Multivariable analysis shows age, grade, ER status and cohort all to be independent prognostic factors.
- This is the first population based study to show improvement in the survival of metastatic breast cancer patients with the passage of time.
- The implication is that preliminary data showing improved survival with these newer agents translates to population wide benefit.
- Unfortunately, no causal relationship between the use of newer therapeutic agents and the improved survival can be proved due to the inherent limitations of a retrospective study.
Though not statistically significant, a trend towards longer disease free interval, younger age and greater ER (+) status existed for the more recent cohorts. In addition to these positive prognostic factors, more recent patients had the benefit of advances in imaging technology, perhaps leading to the introduction of lead time bias. These factors may have led to the improvement in OS for more recent patients, in addition to any benefit from newer therapeutic agents.
Despite these limitations, these data provide compelling preliminary evidence that newer agents may indeed be modifying the natural history of metastatic breast cancer. Prospective trials are needed to investigate this possibility further.
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