Disease oriented end results.A tool for pathological-clinical analysis

Survival rates in lung cancer patients with and without bronchial asthma

Bronchial asthma itself or the treatment of asthma may modify the immunological response to cancer. The survival of lung cancer patients with a preceding diagnosis of bronchial asthma was compared with that of non-asthmatic lung cancer patients in Finland during 1970-1989. This was accomplished by linking two nation-wide data registers, the medication reimbursement register and the cancer registry. For 921 out of the 926 asthmatic patients with lung cancer diagnosed after the diagnosis of bronchial asthma, a non-asthmatic referent patient, matching with respect to sex, anatomical site, and histological type of tumour, as well as to age and year of lung cancer diagnosis, was successfully found in the files of the Cancer Registry. Another referent group was formed by using the stage of lung cancer at diagnosis as an extra matching criterion; this search was successful for 895 asthmatic lung cancer patients. The corrected 5-year survival rate of asthmatic lung cancer patients was 8.4% and that of the referent patients, not matched for stage, 9.6%. When stage was included as matching criterion the corresponding rates were 8.5% and 8.1% respectively. None of these differences were significant. The prognosis of asthmatic and non-asthmatic lung cancer patients thus seemed to be similar.

Social class as a prognostic factor in breast cancer survival

The effect of social class on survival of female breast cancer patients was studied by linking the patient files of the Finnish Cancer Registry (FCR) with the information on patient's social status, obtained from the 1970 Population Census of Finland. The material consisted of 10,181 patients 25 to 69 years of age at diagnosis, whose cancer was diagnosed between 1971 and 1980. The classification of social class was based on occupation. The effects of social class, age, period of diagnosis, and stage of disease on survival were evaluated using the Cox proportional hazards model; mortality from causes of death other than breast cancer was taken into account using the exact causes of death. Those in the lowest social class had about 1.3 times higher relative excess risk of dying than those in the highest social class. The older the patients, the greater was the difference in survival by social class. Differences in stage distribution explained only a minor proportion of the variation in survival by social class. The Finnish legislation guarantees everyone fairly equal accessibility to health care. The results suggest that more determined efforts should be undertaken to reduce inequity in survival.

Hematopoiesis and aging. V. A decline in hematocrit occurs in all aging female B6D2F1 mice

Longitudinal studies of hematocrits were done in aging B6D2F1 female mice at 54, 64, 91, 105 and 115 weeks of age. A modest decline in hematocrit was observed in 41/42 mice; we have previously shown that the decreased hematocrit of aged as compared to young mice is due to an expansion of plasma volume. Mice which died spontaneously after 91 weeks had lower hematocrits at 91 weeks and 105 weeks than did those which survived to 115 weeks. At each time interval, a sub-group of mice was killed and uptake of 59Fe into blood, foreleg, spleen and liver was studied and total nucleated cells per humerus was determined. The results were generally compatible with the thesis that aging mice maintain normal rates of erythropoiesis under basal conditions. Thus, it would appear that a decrease in hematocrit can be considered an expected part of the aging process in this mouse.

Long-term survival of 458 young breast cancer patients

The authors report the long-term survival of 458 young breast cancer patients with follow-up times ranging from 20 to 51 years. Patients with distant metastases at diagnosis were not included in the study. An excess breast cancer mortality was observed for at least 40 years after diagnosis. At 40 years, the actuarial breast cancer survival for all patients was 32% +/- 3% (standard error). For patients with localized and regional disease, it was 53% +/- 6% and 19% +/- 3%, respectively. A persistent excess mortality after 40 years, however, could not be ruled out because too few patients remained at risk. It is concluded that a cured fraction of patients defined as a group subject only to normal mortality risks, in practice, can only be identified in young patients with a low expected mortality, since older patients give only minor contributions to long-term survival results. In an unselected series of breast cancer patients, an excess breast cancer mortality will probably persist during a period that is longer than the life expectancy of the average patient. A parametric survival model, the log-normal model, was found to provide a good fit to the observed survival data. The cured fraction of patients predicted by the model was similar to the actuarial breast cancer survival at 40 years. These results suggest that the model could be used as a tool for analyzing observed survival patterns in breast cancer. It might thus provide an alternative to the conventional 5- to 10-year rates. The good fit of the model also suggests that late recurrences represent one end of a continuous, broad spectrum of behavior in disseminated breast cancer.

Assessing possible late treatment effects in stopping a clinical trial early: a case study. Diabetic Retinopathy Study report No. 9

Suppose a fixed-sample trial in a disease with a long response time shows a statistically significant benefit of the experimental treatment before patients have completed the planned follow-up period. The question may then arise--and did arise in the Diabetic Retinopathy Study (DRS)--whether the observed early benefit of treatment may be offset at some time in the future by the subsequent development of harmful treatment effects. If this question raises serious concerns, then the investigators are faced with a dilemma. If the trial is stopped because of the observed early treatment benefit and the treatment is administered to the untreated control group as well as to patients outside the study, and if the treatment is later found to have deleterious effects, then it may ultimately do more harm than good to patients. Moreover, the fact that the treatment is harmful may never become known. If, on the other hand, the trial is not stopped and the treatment proves to have no deleterious effects, then the control group and patients outside the study would be harmed because the treatment was withheld. We show how, in the DRS, this very problem was formulated and resolved. First a severe, delayed harmful treatment effect was postulated. Projections based on this postulation showed that the early gains were so great that they were unlikely to be offset--ever. Based in part on these projections, the following decisions were made: (a) the study protocol would be changed so as to allow treatment of the untreated control group, and (b) patients would continue to be followed in order to make possible the detection of late, harmful treatment effects, should they develop.

Is breast cancer a curable disease? A study of 14,731 women with breast cancer from the Cancer Registry of Norway

The question whether breast cancer is curable remains controversial. Late recurrences and death from the disease are not infrequent. Long term follow-up of a large patient population is necessary to study this issue. The authors report a study of 14,731 cases of breast cancer reported to the Cancer Registry of Norway with follow-up times ranging from 5 to 18 years. A model in which the logarithms of the survival times were assumed to be normally distributed, the lognormal model, fitted the data well for individual stages, age groups, and periods of treatment. The cured fraction, i.e., consisting of those only subject to normal mortality risks, was estimated from the model to 35 +/- 1% standard error. In Stages 1, 2, 3, and 4 it was 54 +/- 3%, 27 +/- 1%, 19 +/- 2%, and 2 +/- 1%, respectively. It is concluded, however, that the estimated cure rate in Stages 3 and 4 should be regarded with caution in view of the methodological problems involved in the analysis and the small number of patients with long follow-up. The estimated cured fraction in both the individual stages and in the entire material was significantly higher in patients younger than 55 years of age than in older patients. The median survival of non-cured patients was estimated to be 3.6 years for the entire material. In Stage 1, 2, 3, and 4 it was 7.6 years, 3.4 years, 2.1 years, and 0.7 years, respectively. The lognormal model seems to be a good approximation of breast cancer survival. The model is consistent both with late excess mortality and with the presence of a cured fraction. It is noteworthy that an excess mortality was observed during the whole follow-up period. Extrapolations from the model should therefore be cautiously judged until supported by observed data.

Estimation of risks due to environmental carcinogenesis

Several Federal agencies share responsibility for enforcing laws designed to control human exposures to carcinogens. This enforcement activity often has immense effects on other factors of our environment. Absolute safety is not possible, but increased protection is obtainable. Improvements are urgently needed in our ability not only to detect but also to quantify relative risk. Resources should be directed for maximum overall effect. Relative risk must be quantified if we are to reasonably compare risk and benefit. Examples of the inexactness of current toxicological, epidemiological, and mathematical models for estimating risk due to exposures to DDT, aflatoxinb1, DES, and benzidine are presented. The impact of different laws and regulations applicable to the control of these agents is compared. Reference is made to major programs in toxicological methods for risk estimation.

[Morphology versus prognosis in renal cell carcinoma a statistical approach]

In a group of 102 selected cases of renal cell carcinoma which at various periods after nephrectomy terminated fatally, age, sex, and 23 gross and/or histologic tumor characteristics were examined, subclassified, and evaluated. An attempt was made to correlate these parameters statistically to postoperative survival time. A newly developed and programmed statistical method, i.c. "dichotomic variance analysis", proved to be superior to both multiple regression and cluster analysis. Using infiltrative-destructive tumor growth, polymorphy, and chromatin density of tumor cell nuclei, extension of renal vein invasion, age and sex, as the only 6 required out of 25 distinguished tumor parameters, this statistical multivariate method comprised 7 distinctive groups of different mean geometrical postoperative survival time, obviously corresponding to 7 tumor types of increasing degree of malignancy. By step-wise dichotomic splitting of tumor groups it therefore was possible to delinate schematically some of the complex connections between the criteria or variables of prognostic significance. Conceivable sources of errors possibly influencing reproducibility and practical applicability of the presented dichotomic variance analysis in evaluating prognostic criteria in renal cell carcinoma are discussed.