Thread by @thefatdoctoruk

OK, now onto recurrence rate (which is what the video is about but I wanted to cover general risk first as it is important to discuss both). Let's check out the evidence. We'll start with Protani et al 2010

https://twitter.com/thefatdoctoruk/status/1619057964698206208

Whilst this study DID show a significant difference in both overall AND disease specific survival rates the study itself concluded "no study has elucidated the causal mechanism and there is currently no evidence that weight loss after diagnosis improves survival".

It goes on to say "Consequently, there is currently no reason to place the additional burden of weight loss on women already burdened with a diagnosis of cancer."
link.springer.com/article/10.100…

Niraula et al showed that there is no evidence that the association of ob*sity with breast cancer outcome differs by hormone receptor or menopausal status. Just to clear up the myth that this is estrogen related.
pubmed.ncbi.nlm.nih.gov/22562122/

Then there's the largest met analysis (Chan et al 2014). It showed a 41% increased risk from all cause mortality and 35% from breast cancer mortality in ppl with a high BMI before diagnosis. This drops to 23% and 25% respectively in ppl with a high BMI <12 months after surgery.

So if you're fat before your initial surgery you're more likely to die from a recurrence of cancer than if you become fat after surgery. This doesn't surprise me as fat ppl are under investigated, experience treatment delays, are stigmatised and have poorer healthcare access

Limitations of study
1. Heterogeneity of 30-60% in studies of ob*se ppl.
2. No information on how advanced cancer was at time of diagnosis in different groups and if this skewed data
3. No information on whether weight changes were intentional, iatrogenic or neither.

4.Did not conduct analyses by race/ethnicity and treatment types as only limited studies had published results yet we know that both will have massive impact on data.
5. Ppl with high BMI are often underdosed at chemo stage which may also explain results
annalsofoncology.org/article/S0923-…

Finally, Goodwin et al 2012. Showed that distant disease free survival (DDFS) was 5% higher for BMI 26-28, 40% higher for BMI 28-55 and 14% higher for BMI 16-22 COMPARED to people with a BMI of 22-25. This was for UNIVARIABLE analysis. But watch...
ascopubs.org/doi/10.1200/JC…

Multivariable: 6% higher for BMI 26-28, 15% higher for BMI 28-55 and 5% LOWER for BMI 16-22 COMPARED to people with a BMI of 22-25.

So that 40% statistic people love to quote is only using univariable analysis. Drops to 15% with multivariable but we always miss that bit out.

So here's my summary:
1. There is definitely a high risk of recurrence and mortality in higher weight ppl with breast cancer but WE DON'T KNOW WHY
2. There is no mechanism of action to explain this risk based on adiposity alone (can't blame estrogen because its ALL types)

3. This increased risk could well be due to doctor bias or delayed examinations/investigations, inequalities in healthcare and the constant stress of weight stigma.
4. There is no evidence that weight loss after treatment for breast cancer decreases risk/improves outcomes.

5. There is no information on whether weight loss after surgery INCREASES RISK/WORSENS OUTCOMES.

Since the diagnosis of breast cancer is such a highly emotive and stressful time for ppl, I believe it is NEGLIGENT to bring up weight loss when we have so little information

Because there's every chance by doing so we are:
1. Stigmatising patients further
2. Exacerbating the already high levels of anti-fat bias in medical professionals who work with cancer patients.
3. Causing unnecessary stress for ppl at a time when they are already burdened

@threadreaderapp unroll