A study from Sweden’s Karolinska Institute has indicated that cancerous tumours in overweight women are likely to be larger and harder to detect at early stage through conventional methods.

The study examined 2,012 women who had developed breast cancer between 2001 and 2008, each of whom had been receiving mammograms every 18 months to two years. This is in contrast to the UK where women between the ages of 50-70 are invited to be screened every three years. While those at higher risk are offered screenings on a more frequent basis, being overweight is not taken into account in setting these intervals, despite the condition being known to increase breast cancer risk.

The research team examined the size of patient tumours at the time of diagnosis as well as body mass index (BMI), with a score of over 25 being defined as obese. It was found that being obese and having denser tissue in the breast were both associated with a greater likelihood of having a large tumour at the time of diagnosis. However, with large tumours detected within 12 months of the previous mammogram, only BMI alone was found to be a factor.

"Our study suggests that when a clinician presents the pros and cons of breast cancer screening to the patient, having high BMI should be an important 'pro' argument," argued Dr Fredrik Strand, lead author of the study and Radiologist at Karolinska University Hospital. "In addition, our findings suggest that women with high BMI should consider shorter time intervals between screenings."

However, he noted that he feels that there is more work to be done in the area, and that their study will need to be supported by wider findings to have any impact on the way women approach screening for breast cancer: "I don't think our findings alone will change any recommendations. If more studies would come to the same conclusion, then perhaps there should be a discussion about the frequency of screening of overweight and obese women."