CTC level (if any) is really a surrogate end point

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CTC level (if any) is really a surrogate end point. The real endpoints are new metastases or resolution of metastases present prior to tx

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I disagree. In the mTBNC naive patients they will be enrolled before there is widespread tumor growth or metastasis. IN this case the CTC (as a surrogate endpoint) will be the primary item that the FDA reviews, as the metastasis and tumor shrinkage will be less prevalent.

With stage 4 non mTBNC patients the tumor shrinkage appears that it will be more significant which may make it the first item to be measured, but the reason the FDA allows CTC levels to be a surrogate endpoint is because it is an indicator of metastasis.

I am not downplaying the importance of tumors shrinking, but we should not down play the importance of stopping (and measuring) metastasis.

Put another way, no new lesions is not necessarily an indicator that the likelihood of metastasis is low. 0 CTC is.