Antiquity of cancer

When they excavated a Scythian burial mound in the Russian region of Tuva about 10 years ago, archaeologists struck gold. Crouched on the floor of a dark inner chamber were two skeletons, a man and a woman, surrounded by royal garb from 27 centuries ago: headdresses and capes adorned with gold horses, panthers and other sacred beasts.

But for paleopathologists – scholars of ancient disease – the richest treasure was the abundance of tumours that had riddled almost every bone of the man’s body. The diagnosis: the oldest known case of metastasizing prostate cancer.

Malignant cells from the prostate gland had migrated according to a familiar pattern and left identifiable scars. Proteins extracted from the bone tested positive for PSA, prostate specific antigen. Thought of as a modern disease, cancer has always been with us.
Where scientists disagree is on how much it has been amplified. Archaeologists have made about 200 possible cancer sightings dating to prehistoric times.

A recent report by two Egyptologists in the journal Nature Reviews: Cancer concluded that there is “a striking rarity of malignancies” in ancient human remains. “The rarity of cancer in antiquity suggests that such factors are limited to societies affected by modern lifestyle issues such as tobacco use and pollution resulting from industrialisation,” wrote the authors, A Rosalie David of the University of Manchester in England and Michael R Zimmerman of Villanova University in Pennsylvania.


Not a new disease at all

“There is no reason to think that cancer is a new disease,” said Robert A Weinberg, a cancer researcher at the Whitehead Institute for Biomedical Research in Cambridge, Mass. “In former times, it was less common because people were struck down in midlife by other things.” Another consideration, he said, is medical technology revolution: “We now diagnose many cancers – breast and prostate – that in former times would have remained undetected and been carried to the grave when the person died of other, unrelated causes.”

Tumours can remain hidden inside bones, and those that dig their way outward can cause the bone to crumble and disappear. Only a fraction of the human bone pile has been picked, with no way to know what lies hidden below. Anne L Grauer, president of the Paleopathology Association and an anthropologist at Loyola University of Chicago, estimates that there are roughly 100,000 skeletons in the world’s osteological collections, and a majority have not been X-rayed or studied with more modern techniques.

Analysis by the Population Reference Bureau says the cumulative total of everyone who had lived and died by AD 1 was already approaching 50 billion, and had nearly doubled by 1750. “For a long time archaeologists only collected skulls,” said Heather J H Edgar, curator of human osteology at the Maxwell Museum of Anthropology at the University of New Mexico.

“For the most part, there’s no way to know what the rest of those people’s skeletons might have said about their health.” So how are scientists to evaluate  the significance of the handful of fossilised examples of osteosarcoma, a rare bone cancer that mostly affects young people? (What may be the oldest case was found in 1932 by anthropologist Louis Leakey in a prehistoric relative of man.) Today the incidence of osteosarcoma among people younger than 20 is about five cases per million per year.

“You would need to screen 10,000 individuals to find a case,” said Mel Greaves, a professor of cell biology at the Institute of Cancer Research in England, and the author of Cancer: The Evolutionary Legacy (Oxford, 2000).

There is a further complication: Over 99 per cent of cancers originate not in bone but in softer organs, which quickly decay. Unless they spread to bone, they will most likely go unrecorded.

Ancient mummies would seem to be an exception. But here, too, the pickings have been slim. Only on rare occasions can pathologists get their hands on a comparatively recent mummy like Ferrante I of Aragon, king of Naples, who died in 1494. When his body was autopsied five centuries later, adenocarcinoma, which begins in glandular tissues, was found to have spread to the muscles of his small pelvis.

Over the years, hundreds of Egyptian and South American mummies have turned up a few other cases. A rare tumour called a rhabdomyosarcoma was found on the face of a Chilean child who lived sometime between AD 300 and 600. Zimmerman, co-author of the recent review, discovered a rectal carcinoma in a mummy dated between AD 200 and 400, and he confirmed the diagnosis with a microscopic analysis of the tissue – a first, he said, in Egyptian paleopathology.

Although average life span was lower in ancient Egypt than it is today, Zimmerman argues that many individuals, especially the wealthy, lived long enough to get other degenerative diseases. So why not cancer? Other experts have suggested that most tumours would have been destroyed by the invasive rituals of Egyptian mummification. But in a study published in 1977, Zimmerman showed it was possible for the evidence to survive.

Preserved by mummification

In an experiment, he took the liver from a modern patient who had succumbed to metastatic colon cancer, dried it out in an oven and then rehydrated it – demonstrating, he said, that “the features of cancer are well preserved by mummification and that mummified tumours are actually better preserved than normal tissue.”

But as with skeletons, the problem remains: Given the small sample size, just how much cancer should scientists expect to see? Tony Waldron, a paleopathologist at University College London, analysed British mortality reports from 1901 to 1905 – a period late enough to ensure reasonably good records and early enough to avoid skewing the data with, for example, the spike in lung cancer caused in later decades by the popularity of cigarettes.

He estimated that in an “archaeological assemblage” one might expect cancer in less than two per cent of male skeletons and 4 to 7 per cent of female skeletons. Andreas G Nerlich and colleagues in Munich tried out the prediction on 905 skeletons from two ancient Egyptian necropolises. They diagnosed five cancers – in line with Waldron’s expectations. As many as 13 cancers were found among 2,547 remains buried in Germany between AD 1400 and 1800.

New York Times News Service