ASCO, page-8

"Authors are strongly encouraged to provide updated data in the abstract, as the novelty of the data will be taken into account during the abstract selection process. No new or updated data may be added to an abstract after it has been formally submitted unless it was formally submitted as a placeholder for a late-breaking data submission abstract.

" Abstracts submitted to ASCO Meetings are considered final and confidential from the time of submission."

^"2 Most abstracts will be publicly available online on Meeting Library approximately two weeks before the Annual Meeting, with plenary and late-breaking abstracts becoming publicly available during the Annual Meeting outside of market
hours."
https://am.asco.org/abstracts