The ICH E3 Guideline provides limited guidance on the synopsis. In the ICH M4E Guideline, additional guidance on the synopsis of a CSR is given including its use as a stand-alone document and its length. While E3 asks for a usual maximum length of 3 pages, M4E extends this page limit for more complex and important studies, e.g., to 10 pages. How should both Guidelines be read together?

The guidance given in the ICH E3 Guideline, which was developed before
M4E, should be combined with the suggestions made in the M4E
Guideline. Since the synopsis will be used as a stand-alone document
within a Common Technical Document, it should be written so that it can
be understood and interpreted on its own, i.e., without the other sections
of a CSR. In addition to a brief description of the study design and
critical methodological information, the synopsis should provide efficacy
and safety results, as well as other critical information including data on
the study population, disposition of subjects, important protocol
deviations, and treatment compliance. Cross-references to other sections
of the CSR should be avoided. As explained in M4E, complex or large
and important studies may require a synopsis longer than 3 pages. The
10-page example given in M4E is not an absolute requirement or limit
but should not need to be exceeded considerably. The use of a tabular
format for the synopsis is not mandatory.