Appendix C


Clarification of Cancer Groupings Used in Reporting Results, with Correspondence to National Institute for Occupational Safety and Health Cause-of-Death Codes and International Classification of Diseases Codes for Cancers

In response to a request from the Department of Veterans Affairs, the committee responsible for Update 2006 prepared Table C-1 to demonstrate how conclusions provided for the full range of cancer types and to clarify into which groupings any specific cancer diagnosis falls. The committee for Update 2010 reframed its overview of lymphohematopoietic neoplasms according to the World Health Organization (WHO) classification system (WHO, 2008), which partitions these disorders first according to the lymphoid or myeloid lineage of the transformed cells rather than as lymphomas or leukemias; this emphasizes the close etiologic relationship of chronic lymphocytic leukemia and hairy-cell leukemia with Hodgkin and non-Hodgkin lymphomas and with the neoplasm multiple myeloma and its related condition AL amyloidosis.

The major portion of evidence compiled for review in the Veterans and Agent Orange (VAO) series comes from cohort studies, primarily of mortality but some of incidence. Other data have been generated by case-control studies, which follow the only design amenable to studying very infrequent or very specific health outcomes. How researchers are able to group, analyze, and report their findings is influenced by the distribution of cases that they observe, so the data that VAO committees have had available for review reflect mortality experience at a level of specificity concordant with statistical analysis.

The International Classification of Diseases (ICD) system is used by physicians and researchers around the world to group related diseases and procedures so that morbidity and mortality information can be classified for statistical purposes in a standard form that is amenable to data storage and retrieval. It is a comprehensive hierarchic system that permits great detail but can be collapsed into broad categories. Codes mentioned in VAO reports are stated in terms of

TABLE C-1 Mapping of Groupings of Malignant Neoplasms That Are the Subjects of Conclusions in the Veterans and Agent Orange Series with ICD-9 Codes

aBoldface cancer (sub)site: most comprehensive grouping for which a conclusion has been drawn.

ICD, Revision 9 (ICD-9). ICD-7, ICD-8, and ICD-9 were in effect for deaths that occurred in 1960–1967, 1968–1978, and 1979–1998, respectively; the differences among them are fairly subtle. Although ICD-10, which went into effect for coding causes of deaths that occurred from 1999 on, appears radically different from the earlier versions, it corresponds in large part to basically the same disease entities (see Table C-2). Most published epidemiologic studies considered in the VAO series have been related to health outcomes that occurred and were encoded before ICD-10 went into effect.

Since 1983, the National Institute for Occupational Safety and Health (NIOSH) has maintained software for generating standardized expectations, as derived from US mortality data assembled by the National Center for Health Statistics, for ICD-encoded mortality datasets. An article by Robinson et al. (2006) discusses revisions to that standard software to incorporate deaths coded according to ICD-10 and includes conversions and equivalences among ICD-7, ICD-8, ICD-9, and ICD-10 for 119 exhaustive categories of cause of death. Codes for malignant neoplasms span the ICD-9 range 140.0–208.9, NIOSH’s major categories 02–10, or NIOSH’s more specific minor categories 004–040.

The NIOSH death codes for neoplasms provide comprehensive scaffolding for organizing the committee’s reviews and conclusions by cancer type that is somewhat simpler than ICD classifications but maps completely to the ICD system as it has evolved. Because the NIOSH system has been used to mediate analysis of many sets of cohort data, its groupings correspond quite closely to the published research findings available for review by VAO committees. In general cohort studies, one is unlikely to encounter results on more specific groupings than NIOSH’s minor categories.

As discussed in Chapter 2, the VAO committees have not framed its conclusions strictly in terms of ICD codes, but the ICD system has been a valuable tool for the work of VAO committees. There can be coding errors on hospital records or death certificates, but when researchers present their results labeled with ICD codes, there can be little ambiguity about what they intended. When their most definitive indication is something like “respiratory cancers,” however, there can be uncertainty about where the evidence should be considered. In such cases, the committee has done its best to follow the hierarchy laid out in Table C-1.

As indicated above, many of the studies reviewed by the committee use or were written up at a time when ICD-9 was in place. Accordingly, ICD references in this report use that scheme. ICD-10 began to be implemented in the United States in 1999. It differs from ICD-9 in level of detail (about 8,000 categories vs about 5,000 in ICD-9) and nomenclature (alphanumeric vs the numeric codes of ICD-9); additions and modifications were also made with regard to some coding rules and the rules for selecting an underlying cause of death (Anderson et al., 2001). Table C-2 lists the ICD-9 and ICD-10 codes for the various forms of malignant neoplasm addressed in this report. In situ neoplasms, benign neoplasms,

TABLE C-2 Surveillance, Epidemiology, and End Results (SEER) Program Malignant Neoplasm Site Groupings for ICD-9 and ICD-10

aCancers of the peripheral nerves and the autonomic nervous system are classified as “soft tissue” in ICD. Adapted from Ries et al. (2003), Table A-4.

neoplasms of uncertain behavior, and neoplasms of unspecified behavior have separate codes in both schemes.

REFERENCES

Anderson RN, Minino AM, Hoyert DL, Rosenberg HM. 2001. Comparability of cause of death between ICD-9 and ICD-10: preliminary estimates. National Vital Statistics Reports 49(2):1–32.

Ries LAG, Eisner MP, Kosary CL, Hankey BF, Miller BA, Clegg L, Mariotto A, Fay MP, Feuer EJ, Edwards BK (eds). 2003. SEER Cancer Statistics Review, 1975–2000. Bethesda, MD: National Cancer Institute.

Robinson CF, Schnorr TM, Cassinelli RT, Calvert GM, Steenland K, Gersic CM, Schubauer-Berigan MK. 2006. Tenth revision U.S. mortality rates for use with the NIOSH Life Table Analysis System. Journal of Occupational and Environmental Medicine 48(7):662–667.

WHO (World Health Organization). 2008. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissue (4th edition). Lyon, France: World Health Organization.