Background: The management of locally advanced rectal cancer (RC) is an evolving clinical field where the multidisciplinary approach can reach its best and liquid biopsy for obtaining tumor-derived component such as circulating tumor DNA (ctDNA) might provide complementary informations. Methods: A systematic review of studies available in literature of liquid biopsy in non-metastatic RC has been performed according to PRISMA criteria to assess the role of ctDNA as a diagnostic, predictive and prognostic biomarker in this setting. Results: Twenty-five publications have been retrieved, of which 8 fulltext articles, 7 abstracts and 10 clinical trials. Results have been categorized into three groups: diagnostic, predictive and prognostic. Few but promising data are available about the use of liquid biopsy for early diagnosis of RC, with the main limitation of sensitivity due to low concentrations of ctDNA in this setting. In terms of prediction of response to chemoradiation, still inconclusive data are available about the utility of a pre-treatment liquid biopsy, whereas some studies report a positive correlation with a dynamic (pre/post-treatment) monitoring. The presence of minimal residual disease by ctDNA was consistently associated with worse prognosis across studies. Conclusions: The use of liquid biopsy for monitoring response to chemoradiation and assess the risk of disease recurrence are the most advanced potential applications for liquid biopsy in RC, with implications also in the context of non-operative management strategies.

Daunorubicinon (I) wird mit Chlorameisenester/Pyridin zum Triester (II) acyliert, anschließend zum Triester (III) mit Aluminiumbromid demethyliert und schließlich mit Alkylhalogeniden/Silberoxid zu den Triestern (IV) alkyliert.

Durch Ein=′ führung der tert.‐Butylgruppe in 9‐Stellung kann das Tetracyclin (I) regiospezifisch in 7‐Stellung nitriert und über mehrere Zwischenstufen in Minocyclin (VI) übergeführt werden.

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