Re: Rethinking neoadjuvant chemotherapy for breast cancer
Some of the responses to the paper by Vaidya et al, (Rethinking neoadjuvant chemotherapy for breast cancer BMJ 2018; 360), suggest a flaw in critical thinking. We have all learnt the difference between a prognostic factors (Prof) and a predictive factors (Pref) in the management of cancer and the confusion we are witnessing is whether pCR is a Prof or a Pref. There is no question that after 4 months of neo-adjuvant therapy (NACT), pCR is a powerful Prof but how can it be a Pref at the time of diagnosis unless one has the power to foresee the future?
The only way forward is to collect tissue from the two arms of a RCT powered to detect an OS difference, comparing NACT with a new drug vs conventional adjuvant therapy, store it at -40o and wait for the results to mature and then look for the ability of molecular signatures associated with the cases that demonstrated a pCR in the NACT arm of the study, to predict overall survival. However, the ethical dilemma is raised by the EBCTCG which shows no difference in overall survival, suggesting that we are dealing with a zero-sum game; for everyone who benefits another one will be disadvantaged.
The best analogy I can come up with involves meteorology. If you got out of doors in this country when the skies are clear without an umbrella, there’s a 50/50 chance of getting wet.
If you wait for the appearance of cumulus nimbus clouds to appear and then take a brolly with you, you’ll keep out the rain but at the cost of wasting the best part of the day. However, science has given us weather forecasting that allows us to decide in advance whether to encumber ourselves with an umbrella when setting out on a cloudless morning.
Competing interests: No competing interests