You can log ICAP response headers to an access log using the following substitution variables introduced in SGOS 6.5.9.2 and SGOS 6.6.4.1:
x-icap-reqmod-header(<header_name>)
x-icap-respmod-header(<header_name>)
For example, to log the Apparent Data Types (as determined by ProxyAV/CAS) for a RESPMOD request, add the following substitution to the access log format definition:
x-icap-respmod-header(X-Apparent-Data-Types)