Reporting of occupational cancer in Denmark

SVANE LYNGE E. Reporting of occupational cancer in Denmark. Scand J Work Environ Health 1990;16:401-5. Many patients with occupational diseases fail to obtain com pensation because their disease is not recognizedas occupational and reported to the authorities. The present study examined the reporting of pleural mesotheliomas and sinonasal adenocarcinomas - cancers with well-known associations with occupational exposures to asbestos and wood dust - in Denmark in 1983-1987. The estimated underreporting was around 50 11/0. Examination of the medical records of pa tients who had not been reported in 1986-1987 revealed that in most cases the medical records did not contain sufficiently detailed information about occupational exposures. It was recommended that a formal screening interview be carried out whenevera diagnosis is made of a potential occupational cancer. Medical associations may playa major role by issuing guidelines addressing occupational diseases within the fields of their expertise.

Previous studies have demonstrated that many patients with an occupational disease fail to obtain compensation because their disease is not reported and compensation is not claimed for. Apparently, this type of situation occur s even for patients with occupational malignancies (1-3).
Reporting of all known and suspected occupational diseases to the Danish Labour Inspection Service is compulsory for Danish physicians. The report to this service also acts as a claim for worker's compensation from the National Board of Industrial Injuries.
Some rare cancers occur almost exclusively among persons who have had certain occupational exposures. Classic example s are mesothelioma, which is closely linked to asbestos exposure, and sinonasal adenocarcinoma, which is closelylinked to prolonged wood dust exposure. We are convinced that these relations are well known to all Danish physicians, and especially to all specialists concerned with the diagnosis of mesothelioma and sinonasal adenocarcinoma.
According to the nationwide cancer registration data, a total of 48 pleural mesotheliomas and 10 sinonasal adenocarcinomas were diagnosed in Denmark in 1985. However, only 22 pleural mesotheliomas and six sino nasal cancers were reported to the Danish Labour Inspection Service in 1985. Although these numbers might not be strictly comparable, they indicate some underreporting of occupational cancers to the Labour Inspection Service.
In order to make the comparison between the data of the Danish Labour Inspection Service and the Danish Cancer Registry more exact, we undertook a linkage stud y utilizing the personal identification number given to all Danes since 1968. The linkage was supplemented with data from the medical records for a subset of the patients.
The aim of the present study was to examine the degree of possible underreporting of mesothelioma and sinonasal adenocarcinoma to the Danish Labour Inspection Service. We further wanted to study factors affecting the reporting of these diseases, and specifically to test whether the medical records contained sufficiently detailed information about occupational exposures to allow the responsible chief physician to fulfill his obligation to report occupational diseases.

Material and methods
All cases of pleural mesothelioma and sinonasal adenocarcinoma diagnosed in the period [1983][1984][1985][1986][1987] and reported to the Danish Cancer Registry before April 1989were identified. The Danish Cancer Registry has received notifications for all malignant neoplasms diagnosed in Denmark since 1943. Two patients were excluded from the study because the reported diagnosis proved to be wrong (both were lung cancers). Thereafter, 268 cases remained in the study. The distribution by sex and diagnosis is shown in table 1.
The following two institutions receive reports on occupational diseases in Denmark: (i) the Danish Labour Inspection Service (DLlS), where the data are used for priority setting and, in some instances, to initiate factory inspections and (ii) the National Board of Industrial Injuries (NBII), which decides upon compensation s on behalf of the private insurance companies from which the compensations are paid. The Register of Reported Occupational Diseases is kept by the Danis; Labour Inspection Service. This service passes on reports to the National Board of Industrial Injuries, and, vice versa , the National Board of Industrial Injuries passes on compensation claims to the Danish Labour Inspection Service. Throughout this paper "reporting to the DLIS/NBII," denotes that the case has been reported to the authorities and compensation claimed for. By means of the unique personal identification number the 268 persons identi fied in the Danish Cancer Register were sought in the computerized Register of Reported Occupational Diseases. At the time of the linkage, this register contained all cases reported during the period 1983-1987. In addition, the cases identified in the Danish Cancer Register were sought in the data base of the National Board of Industrial Injuries, which contained cases reported until September 1989.
After the linkage, the medical records of the patients with pleural mesothelioma and sino nasal adenocarcinoma diagnosed in 1986-1987 who had not been reported to the DLIS/NBII were requested from the hospital departments which had reported the cases to the Danish Cancer Registry. When it was necessary to elucidate the medical history further , the medical records from other departments in which the patients had been treated were requested too . Data about the diagnosis and about the exposure, as recorded in the medical records, were extracted. The exposure data were classified into the following five categories: category I: cases in which a positive history of exposure 402 to asbestos or wood dust was evident from the medical record of the patient, but no reporting had taken place; category 2: cases in which no data were found in the medical records about exposures, even though the diagnosis was made before death, so that it would have been possible to ask the patient about potential exposures; category 3: cases in-which the exposure history as reported in the medical records was negative, but the information was so scarce that exposure had not been ruled out with reasonable reliability -typically the information in the record had the form "Never exposed to asbestos" without further comments; category 4: cases in which no data were found in the medical records about exposure and the final diagnosis was not arrived at until after death -typically the diagnosis was lung cancer, until autopsy with histological examination revealed that the tumor was a mesothelioma; and category 5: cases in which the medical record contained a reasonably exhaustive, negative exposure history.

Results
Among the 268 cases of pleural mesothelioma and sinonasal adenocarcinoma, 92 (34 010) had been reported to the DLIS /NBII. Only three reported cases involved women . Seventy-eight cases (85 %) involved men with pleural mesothelioma (table 1).
Reporting differed between the age groups -50 % of the middle-aged patients were reported, but only about 25 % of the patients in the younger and older age groups (table 2). Table 3 show s that the frequency of reporting to the DtIS/NBil was highest for cases diagnosed in 1985 and 1986. A slight decline was seen from 1985 to 1986.
Among the 81 cases of pleural mesothelioma and sinonasal adenocarcinoma diagnosed in 1986-1987, 31 men and 20 women had not been reported to the DLIS /NBII. The evaluation of the medical records of these 51 patients is shown in table 4. In 10 cases the medical record contained a reliable, negative expo sure history. In 18 cases the diagnosis had not been sus-  1983  17  47  36  22  69  32  1984  12  42  29  12  60  20  1985  25  39  64  28  58  48  1986  21  42  50  25  64  39  1987  3  8  37  5 17 29 Total 78 178 92 268 pected before death, and no exposure history existed in the medical records. All of these were cases of pleural mesothelioma. In 16 cases no exposure history had been recorded although the patient was alive at the time of the diagnosis, and in four cases an exposure history of a poor quality was recorded. Finally, in three cases of pleural mesothelioma, the medical record gave clear evidence of occupational exposure to asbestos, but the case was not reported. One such case was a 53-year-old mechanic who had worked for 12 years in a shipyard, 20 years before the diagnosis. The medical record specifically mentioned that low-dose asbestos exposure had taken place. The second case was a 78-year-old carpenter who had worked in a shipyard for many years. The third case was a 83-year-old bricklayer, the medical record of whom described exposure to asbestos for about two years, 50 years before the diagnosis. Table 5 shows the decisions made by the National Board of Industrial Injuries concerning compensation for the 92 cases reported in 1983-1987. Only seven were dismissed because there was no evidence of exposure. Five were dismissed because the persons had been self-employed when they were exposed (and therefore were not entitled to compensation, which is only given to employees), and 11 cases were shelved for various administrative reasons (eg, there were no surviving relatives who would be entitled to receive the compensation). In 65 cases of mesothelioma and four cases of sinonasal adenocarcinoma (altogether 75 0/0 of those reported) the claim for compensation was admitted by the National Board of Industrial Injuries. All 69 cases involved men.

Discussion
It has long been known that occupational exposures to asbestos and wood dust playa major role in the causation of pleural mesothelioma and sinonasal adenocarcinoma. In the hospitals, the legal obligation to report on occupational diseases lies formally with the chief physician, and if he/she is to be able to fulfill this obligation, a thorough exposure history must be recorded whenever a diagnosis is made of mesothelioma or sinonasal adenocarcinoma. Our study clearly demonstrates that such a history is not always recorded.
Expected number of occupationally exposed cases Many patients fail to receive compensation because of the lack of an exposure history; exactly how many in our material is difficult to say, since we do not have individual data about occupational exposure from sources other than the medical records. An estimate of the number of occupationally exposed cases can be made fairly easily for sinonasal adenocarcinoma on the basis of the study by Andersen et al (4) which covered Jutland (ie, one-third of the Danish population, over the period [1965][1966][1967][1968][1969][1970][1971][1972][1973][1974]. Seventy percent of the sinonasal adenocarcinoma cases (both sexes combined) occurred among persons who had worked for many years in wood-working occupations.
Regarding mesothelioma , an equivalent Danish case survey does not exist. Assuming that the incidence rate among women in rural areas could be taken as the base-line incidence for unexposed persons, Olsen & Andersson (5) calculated that 70 % of pleural mesotheliomas occurring in Denmark around 1980 were excess cases due to occupational asbestos exposure (equivalent to 80 % of the cases among the men and 45 % of the cases among the women).
The frequencies reported in the literature on asbestos exposure among mesothelioma cases range from II % (6) to 100 % (7). Most studies have included strongly selected populations, inadequate exposure ascertainment, or very long time periods. The existing population-based studies of mesothelioma cases have given slightly lower figures than those calculated by Olsen & Andersson (5). For example, in the United States, Peto et al (8) found that 76 % (69 of 91) of the men and 12 % (3 of 25) of the women diagnosed with mesothelioma in Los Angeles County in 1974-1978 had been exposed to asbestos in the work environment, and Vianna & Polan (9) also found 12 % (6 of 52) exposed cases among women in New York State. The incidence rate for mesothelioma in Denmark around 1980 was among the highest ever recorded on a national basis (10); this level probably explains why the frequency of occupational exposure calculated by Olsen & Andersson (5) was higher than the frequencies found in surveys from other countries.
In table I Andersen's (4) and Olsen & Andersson's (5) figures have been used to make a rough estimate of the number of cases which should have been reported to the DLIS/NBII. Ninety-two patients were reported, and around 190 should have been "expected," so at least 98 patients are missing. For the subset of patients who were diagnosed in 1986-1987, we calculated in the same way that around three cases of sinonasal adenocarcinoma and 16 cases of pleural mesothelioma among the men and around five cases of pleural mesothelioma among the women are missing.
This estimate of around 50 % underreporting cannot be very precise, and it should also be kept in mind that pleural mesotheliomas are difficult to diagnose, as reflected in the high proportion of postmortem diagnoses in our material (18 out of 44 mesotheliomas in [1986][1987]. This problem probably contributed to the underreporting.