T h e gross rates of growth of 171 soft tissue metastatic lesions of breast cancer in 54 patients seen at Ellis Fischel State Cancer Hospital were studied. The frequency distributions of these rates are lognormal and are analyzed statistically as such. Both the linear diametric growth rate (LR) and the exponential growth rate, expressed as volumetric doubling times (DT), of 66 untreated lesions were presented as baselines for further study (LR: mean 0.21 mm/day, 95% range of 0.04-1.05; DT: mean 17.1 days, 95% range 3.4-86.1). Rates of growth of simultaneous metastatic lesions of both the same and different sites (e.g., axilla, chest wall, supraclavicular, and other regions) in the same patients were compared. T h e mean ratios of growth of the paired lesions were close to "one"; however, in 95% of the cases the rates can be differentiated by a factor of one-fifth to seven. I n lesions that responded to radiation therapy, hormones, or chemotherapy, the ratios of rate of shrinkage after therapy to the rate of growth before therapy also had means of approximately "one" (95% range of ratios: 0.2-4.2). There is considerable variability of the data presented due to limited numbers of selected lesions that could be measured, the errors of data gathering, and assumptions made during calculations.
HE QUANTIFICATION OF THE RATES AND PAT-
T terns of tumor growth is important to the understanding of the biology and natural history of malignancy. T h e concept of tumor growth rate has many clinical applications. These include estimating the time of tumor induction3,B and the high risk period for recurrence after cancer tlierapy,ll planning the time interval necessary to conduct repeated cancer detection examination,17Je predicting host survival,l6J* and correlating the pathologic and clinical findin,p4J0J4
T h e important value of tumor growth rate in clinical medicine is that it can be used as a guideline to evaluate the effectiveness of therapeutic measures. This was well illustrated in the cases of Wilms' tumor1 and neuroblastoma.8 T h e growth rate data of pulmonary metastases were used to show that resection of secondary testicular cancer in From the Cancer Research Center, and the Department of Surgery of the Ellis Fischel State Cancer Hospital and the