Cancer research summaries

There is some evidence to support the theory that cancers might be transmissible through blood. Even if a tumour is too small to be detected, it will shed millions of cells into the circulation every day that may have the potential to establish new malignancies within the donor or blood recipient. Reports of transmission of cancer cells from needles or surgical instruments demonstrate that tumours cells have the capability to be transplanted to, and develop in, healthy recipients. And there is some data to show that transfused patients are at increased risk of cancers, particularly non-Hodgkin lymphoma.

To test some of these ideas, Gustaf Edgren and colleagues set out to investigate whether there is a history of increased cancer diagnoses among individuals that receive blood transfusions from people who donate blood while unaware of their cancers. Using registry data from Sweden and Denmark , the authors created a database from which they identified a group of “exposed” individuals, who had received donated blood from a person who was diagnosed with cancer less than 5 years after giving blood.

The study population comprised all individuals with no history of malignant disease who had received at least one unit of whole blood, erythrocytes, plasma or platelets between 1968 and 2002. All blood donors who contributed to these transfusions were traced through population and health registers and donors who were subsequently diagnosed with a malignancy within 5 years of the blood donation were deemed to harbour a sub-clinical malignancy at the time of donation. The resulting group of exposed individuals numbered 12 012; 342 082 people who received blood from non-precancerous donors were classed as unexposed.

Recipients of blood from people with a known history of cancer were excluded from the analysis as were those for whom 5 years of follow up was not available. All recipients were followed for cancer occurrence using the Swedish and Danish cancer registries. Any recipients diagnosed with cancer within 6 months of transfusion were excluded.

The researchers identified 978 cases of cancer among all the blood recipients but after statistical analysis they found no excess risk of cancer overall among individuals who had received one or more blood products from a precancerous blood donor. The relative risk was not substantially affected by sex age, calendar period, or number of transfusions. What is more, there was no excess risk when patients who received blood from people with cancers at sites that are thought to have the highest risk of metastasising through blood---the lung, liver, skeleton, and central nervous system---were combined.

An additional finding was that the cancer incidence among the 9377 recipients of blood from donors with a previous diagnosis of cancer who were excluded from the main analysis did not differ from that among recipients of blood from non-cancerous donors. “Since we found no increased cancer risk associated with transfusions from an admittedly limited number of donors with a previous history of cancer, it would seem that long-term cancer survivors might be a fairly safe donor group,” concluded the authors.

Risk of cancer after blood transfusion from donors with subclinical cancer: a retrospective cohort study Gustaf Edgren, Henrik Hjalgrim, Marie Reilly, Trung Nam Tran , Klaus Rostgaard, Agneta Shanwell, Kjell Titlestad, Johanna Adami, Agneta Wikman, Casper Jersild, Gloria Gridley, Louise Wideroff, Olof Nyren, Mads Melbye

The Lancet 2007; 369:1724-30

Cancer Research Summaries are overviews of important cancer research findings that have been reported in leading cancer publications. The Cancer Research Summaries are provided by the Cancer Media Service (CMS) in collaboration with Nature Clinical Practice Oncology.

CMS is a resource for journalists operated by the European School of Oncology (ESO). The CMS aims to improve the quality of cancer journalism by helping to put news about cancer in context and explaining the science behind the stories.

The CMS also offers workshops and briefing sessions for journalists interested in learning more about cancer. DON’T MISS our media forum: Cancer: Time for a Reality Check and our award for promoting journalism: The Best Cancer Reporter Award.