I’ve just presented some data from the Southampton-based POSH study which is a prospective cohort study of young women who were diagnosed with breast cancer at the age of 40 years or under. Over 3,000 women were recruited to the study between 2001 and 2008 and the data we’ve collected is allowing us to look at the effect of various host factors on the course of the disease. The data I was presenting today was looking at the effect of obesity on the outcome of breast cancer in this young patient group.
What we’ve shown is that significant numbers of the patient cohort were either overweight or obese and sadly if you look at both their risk of disease recurrence and their overall survival, both of these things were significantly worse in overweight and obese patients than patients who had a weight within what’s deemed the normal range. We looked at a number of factors to see if we could understand why that is; what we can see is that patients who are overweight or obese are more likely to have larger tumours on presentation, they’re more likely to already have developed into their local lymph nodes but also they’re more likely to have more aggressive tumours, grade 3 tumours, they’re more likely to have oestrogen receptor negative tumours or triple negative tumours, which is generally considered the most aggressive type of breast cancer. What we can’t say yet from our data is exactly why these patients are doing so much worse. It could all be explained by the fact they’ve got more aggressive tumours from a biological point of view but that isn’t the whole story because when you actually do multi-variant analysis to adjust for those factors we still see that patients, particularly with oestrogen receptor positive tumours, are doing worse if they’re overweight or obese.
There’s a lot of interest nowadays in the idea that obesity is associated with high levels in the plasma of some cytokines which may predispose patients to have a more inflammatory environment for the tumour to grow in and that may influence the way the tumour behaves. We’ve also got concerns about the way patients who are overweight and obese that their treatment may not be specifically designed for them. In particular there has been a lot of discussion in the literature recently about how we should dose chemotherapy in patients who are overweight and obese and so we did a pilot study looking at just a small number of locally treated patients to look in detail at their chemotherapy prescriptions. What was particularly interesting was that patients who were obese were suffering with far more delays in their chemotherapy due to a number of different reasons and we wonder, therefore, if this is impacting on the effectiveness of the treatment.
So, in summary, what we’re seeing is that a significant number of young breast cancer patients do fall into the overweight or obese bracket and we know that number is likely to increase if predictions hold true over the next twenty or so years. We know that they’re doing significantly worse in terms of their outcome and we really need to look at both the mechanisms and the treatment options for these patients in order to make sure that they do just as well as normal weight patients in the future.
Do clinicians need to be aware of these issues?
There are two main aspects to the research we need to do in the future. One is to fully understand the mechanisms involved, what the link is between patients being overweight or obese, why and how that should affect the type of breast tumours that they develop. We also need to look at these treatment aspects in both hormonal therapy, to look at the effectiveness, tolerance and adherence to hormonal therapy in different patient groups but also these issues about how we should be dosing chemotherapy in this patient group as well.