Background: An adjuvant locoregional radiotherapy after radical surgery results in a survival advantage for breast cancer patients. The advantage starts with a delay and reaches about 10% 15 years after diagnosis. What could explain such a delayed efficacy?
Methods: A population-based cohort from 1996 to 1998 and the Munich Cancer Registry with courses of breast cancer disease since 1977 are the empirical basis. The analysis concerns survival rates and survival times in respect to metastases, local and lymph node recurrencies. A metastatic model is derived from the data.
Results: A cohort of 9,347 patients with a mean follow-up of 6.5 years and 2,587 courses with metastases and/or local recurrencies were registered. The overall survival after 15 years was for pT1 57.6%, pT2 37.9%, pT3 24.4% and for pT4 10.5%. Five years after metastasization 20.1 to 12.4% survived, 10 years 6% independent on pT. Ten years after local recurrencies the survival was dependent on pT of the primary tumor: pT1 36.3%, pT2 21.0%, pT3 13.1% und pT4 4.6%. A local recurrency is a prognostic factor for metastasization of the primary tumor, but local recurrencies can also cause metastases. The mean survival time after metastasization of the primary pT1 tumor is estimated about 61 months, after metastasization by local recurrencies about 99 months with a mean time to local recurrencies of 38 months. Further results of the metastatic model are: the development of metastasization is homogeneous and independent on pT-category, the metastatic initiation starts up to 5 years before diagnosis, metastatic-free survival time and progression survival time are independent and an impact of lymph node recurrencies on survival could not be detected.
Conclusions: The reduction of local recurrencies by high-quality primary therapy with radiotherapy and also the early detection of local recurrencies may reduce secondary metastasization and therefore improve survival. The metastasization model also explains the limitation of the therapeutical strategies and the almost mandatory chance of early detection programs of breast cancer.