Kaplan-Meier, marginal or conditional probability curves in summarizing competing risks failure time data?

In the context of competing risks the Kaplan-Meier estimator is often unsuitable for summarizing failure time data. We discuss some alternative descriptive methods including marginal probability and conditional probability estimators. Two-sample test statistics are also presented.

Mortality of workers employed in shoe manufacturing

A retrospective cohort mortality study was conducted among 7814 white shoe manufacturing workers followed from 1940 through 1982. The workers were potentially exposed to solvents (including toluene) and solvent-based adhesives. Benzene may have been present as an impurity of toluene. Mortality due to leukemia and aleukemia was not statistically significantly elevated. Statistically significant excess mortality due to cancer of the trachea, bronchus and lung was observed in the total cohort [standardized mortality ratio (SMR) 147, 95% confidence interval (95% CI) 120-180] and showed a statistically significant trend in standardized relative risk with increasing potential latency, but not with increasing duration of employment. Chronic nonmalignant respiratory disease was significantly elevated among the men (SMR 158, 95% CI 114-217) but was less than expected among the women (SMR 79), a finding suggesting a possible contribution of smoking to the mortality from respiratory cancer. However, adjustment for the potential effects of smoking did not completely eliminate the increased risk for lung cancer.

Changing results of HLA-identical sibling bone marrow transplantation in patients with haematological malignancy during the period 1981-1990

During the years 1981-90 inclusive 227 patients with haematological malignancy received an HLA-identical sibling first transplant at St Vincent's Hospital, Sydney. Recipients with acute leukaemia in first remission or chronic myeloid leukaemia in first chronic phase were analysed as good risk, and those beyond these stages, as poor risk patients. Good risk patients transplanted in the years 1986-90 (n = 52) showed improved actuarial survival (74%) compared to those (n = 58) transplanted during 1981-85 (37%, p = 0.01). There was a suggestion that leukaemia-free survival was also improved in those transplanted during the later time period (62% versus 36%, p = 0.07). In contrast, poor risk patients transplanted during 1986-90 (n = 55) appeared to have worse leukaemia-free survival (15%) compared to those transplanted during 1981-85 (n = 62) (22%, p = 0.09). The incidence of acute graft-versus-host disease (GVHD) grades I-IV in all patients was 94% in those transplanted during 1981-85 (n = 120) and 86% in those transplanted during 1986-90 (n = 107) (p = 0.002). The incidence of acute GVHD grades II-IV was 37% during 1981-83, 20% during 1984-86, and 28% during 1987-90 (p = 0.1). The decrease in incidence and severity of acute GVHD correlated with the introduction of the cyclosporin/short methotrexate regimen in our practice. The incidence of cytomegalovirus (CMV) pneumonitis was 18% in 1981-85, and 11% in 1986-90 (p = 0.09). In 1989 and 1990 no cases of CMV pneumonitis occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of total body irradiation as based on the comparison of preparation regimens for allogeneic bone marrow transplantation for acute leukemia in first complete remission

The role of total body irradiation (TBI) for allogeneic bone marrow transplantation (BMT) for acute leukemia in first complete remission was reevaluated in this study. From Japanese BMT Registry, data of 123 acute leukemia patients in first complete remission who underwent allogeneic bone marrow transplantation in 22 hospitals between 1988 and 1990 were available for the present comparative study of preparation regimens with or without total body irradiation. Two-year survivals were 77% and 51% in the TBI containing regimen group and in the non-TBI regimen group, respectively (p = 0.0010). Corresponding two-year relapse rates were 16% and 37%, respectively (p = 0.0197). Corresponding probabilities of developing interstitial pneumonitis were 21% and 24%, respectively (p = 0.8127). The analysis of causes of death indicated that non-TBI regimen increased the incidence of septicemia and lethal organ failures, such as liver, heart, lung and other multiple sites. It was emphasized that an additional role of total body irradiation was to disperse the treatment-related toxicity in allogeneic bone marrow transplantation for acute leukemia.

Cancer mortality in ethylene oxide workers

A cohort of 1971 chemical workers licensed to handle ethylene oxide was followed up retrospectively from 1940 to 1984 and the vital status of each subject was ascertained. No quantitative information on exposure was available and therefore cohort members were considered as presumably exposed to ethylene oxide. The cohort comprised 637 subjects allowed to handle only ethylene oxide and 1334 subjects who obtained a licence valid for ethylene oxide as well as other toxic gases. Potential confounding arising from the exposure to these other chemical agents was taken into consideration. Causes of death were found from death certificates and comparisons of mortality were made with the general population of the region where cohort members were resident. Seventy six deaths were reported whereas 98.8 were expected; the difference was statistically significant. The number of malignancies for any site exceeded the expected number (standardised mortality ratio (SMR) = 130; 43 observed deaths; 95% confidence interval (95% CI) 94-175) and approached statistical significance. For all considered cancer sites the SMRs were higher than 100 but the excess was only significant (p < 0.05, two sided test) for lymphosarcoma and reticulosarcoma (International Classification of Diseases--9th revision (ICD-9) = 200; SMR = 682; four observed deaths; 95% CI 186-1745). The excess of cases for all cancers of haematopoietic tissue (ICD-9 = 200-208) also approached statistical significance (SMR = 250; six observed deaths; 95% CI 91-544). Focusing the analysis on the subcohort of the ethylene oxide only licensed workers, who are likely to have experienced a more severe exposure to this gas, it became evident that all but one of the observed cases of haematopoietic tissue cancers in the cohort were confined to this subgroup, enhancing the relevant SMR to 700 (95% CI 237-1637) and the SMR of lymphosarcoma and reticulosarcoma to 1693 (95% CI 349-4953).

Minimally differentiated acute leukemia

We have studied 35 adult patients with morphologically undifferentiated peroxidase-negative acute leukemia that failed to meet the criteria for acute lymphoblastic leukemia and compared them to patients with FAB M1-M7 seen by the same physicians. The diagnosis of minimally differentiated acute leukemia (MD-AL) was associated with a higher incidence of prior hematologic disease, lower WBC, fewer blood blasts, lower marrow cellularity and a tendency towards older age. Of all patients treated with AML since January 1983, those with MD-AL were less likely to get a complete remission than those with other subtypes (35 vs 64%, p = 0.03). Treatment failure was usually due to resistant disease. Analysis of outcome as a function of drugs used during induction therapy showed an advantage for regimens containing vincristine and prednisone. The leukemic blast cells of nine patients were immunophenotyped for myeloid, lymphoid and megakaryoblast/platelet antigens. Although there were too few for a full statistical analysis as was applied to the larger group of 35 patients with MD-AL, these patients had a lower bone marrow cellularity as compared to FAB M1-M7 and a low remission rate. Eight of these were found to have positive myeloid markers and met the criteria for FAB M0. We conclude that patients with MD-AL form a distinct group with characteristic presenting features and a low response rate. Outcome data suggest that vincristine and prednisone should be included in experimental induction programs.

Cohort and nested case-control studies of hematopoietic cancers and brain cancer among electric utility workers

Recent studies have raised concern about the potential health effects of occupational exposures to power frequency electric and magnetic fields. We evaluated cancer mortality for leukemia, brain cancer, and lymphoma from 1960 to 1988 in a cohort of 36,221 electric utility workers using cohort analyses and three nested case-control studies. From a volunteer sample of the current workforce that represented a variety of different occupations and work locations, we collected 776 days of magnetic field measurements. We derived exposure information from company job history information and developed exposure scores by linking job history data to measured magnetic fields. In job title analyses, we compared "electrical workers" with other field and craft occupations, office, and technical support staff. Age-specific cancer rates for electrical and reference workers were similar. "Electrical workers" had rate ratios or odds ratios ranging from 0.7 to 1.4. Most ratios were close to 1.0. Lymphomas were slightly elevated compared with leukemias and brain cancers (ratios of 0.9-1.4 vs 0.7-1.2, respectively). Odds ratios for magnetic field exposure indices, based on scores for the mean, median, 99th percentile, and fractions exceeding 10 milligauss and 50 milligauss, were all close to or less than 1.0. The interval estimates indicate no strong association but are somewhat limited by imprecision.

Exposure to butadiene and lymphatic and hematopoietic cancer

Several follow-up studies have assessed lymphatic and hematopoietic cancer (LHC) among workers with potential exposure to 1,3-butadiene. These investigations of the styrene-butadiene rubber and butadiene manufacturing industries include 17,448 subjects with an average of 22 years of follow-up. When the results of the studies are combined, the total number of observed leukemia deaths is 36, compared with 34.2 expected. The standardized mortality ratio is 1.05, with a 95% confidence interval of 0.74-1.46. These null data are compatible with, at most, a weak positive association of butadiene with leukemia. There is little evidence of an association with other forms of LHC among styrene-butadiene rubber workers (55 observed/50.1 expected deaths). Only one study has evaluated directly the relation between estimates of butadiene exposure and leukemia, and this investigation reports a positive association. The result, however, cannot be interpreted as causal, because there is no satisfactory explanation for the marked discrepancy between this case-control study and a null follow-up study based on the same subjects. Overall, the epidemiologic evidence does not provide persuasive evidence that butadiene exposure causes LHC.

A retrospective analysis of bleeding complications in 438 patients with acute leukaemia during the years 1972-1991

The incidence and mortality of bleeding complications have been investigated in 438 patients with acute leukaemia consolidated either by chemotherapy (n = 241) or by bone marrow transplantation (n = 197). Bleeding signs on admission were found in 38% of the chemotherapy-treated group. Haemorrhagic deaths during the 1st month were seen in 10%. The majority of the major bleedings were localized intracranial, but gastrointestinal haemorrhages were also common. The platelet count was significantly lower (40 x 10(9)/l versus 69 x 10(9)/l, p < 0.001) and the leukocyte count significantly higher (31.2 x 10(9)/l versus 11.6 x 10(9)/l, p < 0.001) in the group with bleeding complications than in those without. The haemorrhagic mortality in patients consolidated with chemotherapy compared with transplant patients was similar, 23% and 19%. The majority of the lethal haemorrhages in the latter group were observed in patients undergoing allogenic bone marrow transplantation after engraftment. Septicaemia, graft-versus-host and venous occlusive disease were contributing factors.

Autologous bone marrow transplantation for adult acute leukemia

In this review we have considered the role of ABMT for the acute leukemias. It is apparent from data around the world that ABMT is a curative therapy for patients with both AML and ALL after primary treatment failure. Other than allogeneic BMT, ABMT may be the only curative therapy following relapse, especially in AML. The role of ABMT in first CR is less well defined. There are few data to support the widespread use of ABMT in first CR for ALL. Moreover, the improved survival of adults with ALL with current intense multiagent regimens will probably obviate the need to continue clinical trials of ABMT for ALL in first CR. For patients with AML in first CR, however, it seems that ABMT may well lead to improved rates of DFS compared with chemotherapy alone. Almost every published report describes better DFS for patients who underwent ABMT compared with historical or contemporary controls who were treated with chemotherapy. One note of caution is that as chemotherapy evolves, the increment in survival currently observed from ABMT may diminish, thus rendering ABMT less obviously necessary. On the other hand, from an economic standpoint, ABMT could prove to be cost-effective, because a short, intense treatment that is effective may prove to be less costly than the current extended period of chemotherapy. Because ABMT is becoming safer, it would seem reasonable to continue its use in patients with AML at high risk for relapse (secondary AML, adverse cytogenetics, and so on) while awaiting the outcome of the randomized clinical trials currently underway that are seeking to define the role of ABMT for the general population of patients with AML after initial remission is achieved. Meanwhile, further definition of the relative value of the various purging regimens, preparative regimens, and adjunctive therapy (i.e., IL-2, mAb) warrants study.

[Chemotherapy and bone marrow transplantation for acute leukemia]

Chemotherapy (CT) and bone marrow transplantation (BMT) have made remarkable progress in recent years. The comparison of both treatment modalities has become an important issue. The methods of comparison, however, should be varied according to the subjects and purposes of comparison. For a general comparison of both CT and BMT, the registry data of both treatments, seems adequate. For the comparison of a CT regimen with a BMT regimen, a randomized control study seems most adequate. in order to get an overview. For the selection of treatment for a certain patient, comparison of CT and BMT data from the center in which the patient will be treated seems most important. As the latter comparison we have studied the rate of early death, the rate of long-term survival and medical costs in leukemia patients diagnosed and followed for 5 years, at the Center for Adult Diseases Osaka. The early death rate was similar in both groups of patients. The long-term survival rate was 78% in BMT and 28% in CT patients. Cost effectiveness was also favorable in BMT patients. Data on CT and BMT in each center should be prepared for the selection of treatment for patients at each center.

[Information system on cancer mortality and district characteristics of the Rhineland TUV]

On account of the lack of a comprehensive cancer registry with national coverage for the Federal Republic of Germany, the long-term and interregional evaluation of cancer mortality data is of particular relevance. Therefore, the TUV Rheinland instructed by the Federal Ministry for the Environment, Nature Protection, and Reactor Safety maintains an "Information System on Cancer Mortality and District Characteristics (IKK)" using official cause of death and resident population statistics. Mortality data for a variety of different cancer sites are documented with local and temporal separation for the area of the Federal Republic of Germany (before the German unification) and for a period of 20 years. The IKK data can be employed as a meaningful tool for epidemiological investigations relating to the correlation of cancer mortality and environmental agents. In the present paper the principles of the IKK are described and some examples of results are presented.

Significance of chromosomal changes in patients of different age groups with acute leukemia

Chromosome abnormalities have been observed in about 50% of patients with acute leukemia. There have been several published reports which emphasized the chromosomal changes in relation to the age of the patient and the morphologic type of acute leukemia. All observations suggest that there are both age related similarities and differences. The karyotype is an important independent prognostic factor in acute leukemia; however, age alone (especially above age 70) is the single most important factor for a poor prognosis.

Marrow transplantation from unrelated donors for treatment of hematologic malignancies: effect of mismatching for one HLA locus

One hundred twelve patients less than 36 years old received marrow grafts from unrelated donors as treatment for hematologic malignancy. Seventy donor/recipient pairs were phenotypically identical for HLA-A, -B, and -D, while 42 had a "minor" disparity at one HLA locus. There was an increase in the risk of acute graft-versus-host disease (GVHD) in patients receiving HLA-partially matched grafts compared with those receiving HLA-matched grafts (51% v 36% probability of grades III-IV acute GVHD). However, in this cohort of patients, there was no significant difference in survival (at 1.5 years, 46% v 51% for good-risk patients, 44% v 30% for poor-risk patients). This finding suggests that some degree of HLA disparity can be tolerated in young patients transplanted from unrelated donors for malignant disease, thus making transplantation an option available to larger numbers of patients.

Childhood cancer mortality in the European Community, 1950-1989

A descriptive study on childhood cancer mortality was carried out in the European Community (EC) covering the period 1950-1989. An annual total of 3392 cancer deaths were seen among children in the EC during the period 1979-1988, yielding an age-standardised cancer mortality rate of 50 per 10(6). Leukaemia was the most prevalent cause of death among children with cancer (39%). Excess mortality was observed among boys for cancers at all sites combined and for cancers at specific sites, exclusive of malignant tumours of the kidney. This excess is presumed to be due mainly to sex differences in incidence. Markedly higher mortality rates of childhood cancer were seen in southern countries of the EC than in central and northern countries. This difference appeared to be due mainly to differences in cancer incidence among the countries and to a lesser degree to differences in treatment and survival. An overall decline in mortality from childhood cancer in the EC occurred from the early 1960s. In spite of the improvements in survival, however, childhood cancer remains a major cause of death in the EC, affecting about 15% of children between the ages of 1 and 14.

Autologous bone marrow transplantation with alkyl-lysophospholipid-purged marrow

Autologous bone marrow transplantation (ABMT) appears to offer clinical benefit to leukemia patients, but the major reason for failure is relapse. This may be related to the presence of residual leukemic cells in the harvested marrow. To circumvent this problem, various procedures have been developed to purge ex vivo residual leukemic cells from the marrow. The alkyl-lysophospholipids are a new group of anticancer drugs that target membranes as their major site of action. They are unique in that they are relatively selectively toxic to neoplastic cells and spare normal marrow stem cells and progenitor cells. The most active compound is edelfosine. Twenty-nine patients with acute leukemia in second or subsequent remission or early relapse or in first remission, either with a history of treated extramedullary relapse, or requiring more than one induction program to achieve remission, underwent ablative therapy followed by infusion of autologous marrow which had been purged by a 4-hour exposure to edelfosine prior to cryopreservation. Thirty-one percent of the patients are alive and free of leukemia for a median of 630 days (range 185-1,613). These results in this high-risk group of patients warrant further investigation.

Does in vitro bone marrow purging improve the outcome after autologous bone marrow transplantation?

High-dose therapy with bone marrow rescue is now regarded as an effective treatment for a variety of malignancies. In an attempt to circumvent the scarcity of HLA-matched donors, autologous marrow has been successfully used as the source of cells for hematopoietic reconstitution. There has been considerable controversy as to whether any malignant cells present in the graft could contribute to relapse of disease post-transplant. In this paper we review clinical results obtained by using autologous transplantation and present evidence on how ex vivo tumor purging may contribute to the outcome.

Childhood cancer among Swedish twins

The risk of childhood cancer was evaluated among 35,582 twins born in Sweden between 1952 and 1967. Cancers were identified through linkage with national cancer and mortality registries. Overall, 59 childhood cancers and 41 deaths from cancer occurred before the age of 16. For both sexes combined, the cancer incidence was similar to that in the general population of primarily single-born children (number observed/number expected [O/E] = 1.0, 95 percent confidence interval [CI] = 0.7-1.2). For males under age five, cancer incidence was reduced significantly (O/E = 0.3, CI = 0.1-0.7). There was a substantial increase in all-cause mortality among twins (O/E = 3.7), attributable to a high mortality during the first year of life. Excluding this first year, the O/E for death (all causes) was 1.1 (CI = 1.0-1.3). For cancer mortality of both sexes, the O/E was 0.9 (CI = 0.6-1.2), with no significant reduction of risk in any sex-age group. We conclude that with the possible exception of males aged 0-4 years, the childhood cancer risk of twins appears similar to that of singletons.

Cancer mortality in African and Caribbean migrants to England and Wales

Cancer mortality during 1970-85 of immigrants from East and West Africa and the Caribbean to England and Wales is described. Overall cancer mortality was raised in West African males (RR 1.38, 95% CI 1.25-1.54), and non-significantly raised in West African females (RR 1.14, 0.96-1.37) compared to mortality in the England and Wales-born population. Much of the increased risk was due to very high rates of liver cancer in males (RR 31.6, 23.8-41.9), but rates were also raised for a wide range of other cancers in each sex. Only lung and brain cancer had significantly decreased mortality. In East Africans, overall cancer mortality was low in males (RR 0.63, 0.56-0.70), and in females (RR 0.80, 0.72-0.89). Mortality was significantly low for cancers of the stomach, pancreas and testis, and Hodgkin's disease in males, for cervical cancer in females, and for lung cancer and melanoma in both sexes. Cancer sites with significantly raised mortality included oropharyngeal cancer, leukaemia, and multiple myeloma in both sexes. In Caribbean immigrants overall cancer rates were significantly low in males (RR 0.71, 0.68-0.74) and in females (RR 0.76, 0.73-0.80). Mortality was significantly low for many cancers including colorectal, lung, testis and brain cancers. Mortality was significantly raised only for cancer of the prostate in males, of the placenta in females, and of the liver, non-Hodgkin's lymphoma and multiple myeloma in both sexes. Overall, mortality was high from prostatic cancer and liver cancer, and was low from brain cancer, in predominantly ethnic African immigrant groups. Both East and West African immigrants had raised rates of leukaemia. All of the migrant groups had high rates of multiple myeloma and low rates of testicular, ovarian and lung cancer. Genetic and environmental factors that may contribute to these patterns are discussed.

Comparison of the survivals between bone marrow transplantation and chemotherapy for acute leukemia in first remission--a Japanese single institution study

The outcome of sixty-four patients with acute leukemia in first remission who had been treated with either bone marrow transplantation (BMT) or conventional chemotherapy was retrospectively evaluated (a median follow-up of 37 months). Among them, 26 patients (age range; 14-42 years) received allogeneic BMT from HLA-identical siblings and 38 patients (age range; 13-43 years) who had no HLA-identical donors undertook the continued combination chemotherapy. Kaplan-Meier product-limit estimate of actuarial survival of acute myelogenous leukemia (AML) patients was 48.9% for the BMT group and 15.7% for the chemotherapy group (p = not significant, NS). For acute lymphoblastic leukemia (ALL) patients, the survival following BMT was 80.2% and was significantly higher than that of the chemotherapy group of 33.3% (p < 0.05). The disease-free survival of AML and ALL for the BMT group was 34.3% and 36.5%, respectively, which was higher than that of the chemotherapy group (16.7% and 23.4%, respectively (p = NS)). These findings in our Japanese single institution study suggested that BMT may be the treatment of choice for adult patients with acute leukemia in first remission if they had suitable donors and that more effective therapeutic regimens were necessary for patients without compatible donors in order to obtain the longer remission duration.