Cancers as rare diseases: Terminological, theoretical, and methodological biases.

OBJECTIVE: Was cancer a rare disease in the past? Our objective is to consider the various terminological, theoretical, and methodological biases that may affect perceptions of the rarity of cancer in the past.

MATERIALS AND METHODS: We discuss relevant malignant neoplastic biomedical and paleopathological literature and evaluate skeletal data. We selected 108 archaeological sites (n = 151 cancer cases) with published malignant neoplasms and that were amenable to calculating cancer crude prevalence. Furthermore, datasets from four medieval/postmedieval Portuguese and 12 postmedieval UK sites were used to compare age-adjusted rates for metastatic bone disease and tuberculosis.

RESULTS: In the literature review, mean cancer crude prevalence (1.2 %; 95 % CI = 0.96-1.4) exceeded the threshold for a rare disease (RD). Age-standardized rates of MBD and TB were not markedly different in the sites surveyed.

CONCLUSIONS: Methodological, theoretical and historical factors contribute to assumptions that cancers were rare diseases. The assumption that cancers are extremely rare in the paleopathological literature was not fully supported. Cancer is a heterogeneous concept, and it is important to view it as such. If a disease is considered rare, we may fail to recognize it or dismiss it as unimportant in the past.

SIGNIFICANCE: We present a re-evaluation of the idea that cancer is a rare disease. We present a more nuanced way of comparing rates of pathological conditions in archaeological contexts.

LIMITATIONS: Variation in the amount of useable information in published literature on malignant neoplasms.

SUGGESTIONS FOR FURTHER RESEARCH: More large-scale studies of cancer in the past alongside comparative studies of cancer prevalence with other assumed rare diseases.