How to cache rewritten URL with mod_cache, mod_rewrite and mod_proxy?

Question

I'm using Apache Web server in a Docker container as a Cache Reverse Proxy. The version is

Server version: Apache/2.4.10 (Debian)
Server built:   Nov 28 2015 14:05:48

The following modules are activated:

/usr/sbin/a2enmod proxy proxy_http
/usr/sbin/a2enmod rewrite
/usr/sbin/a2enmod cache
/usr/sbin/a2enmod cache_disk

mod_cache is configured in etc/apache2/mods-enabled/cache_disk.conf with

 <IfModule mod_cache_disk.c>
    CacheRoot /var/cache/apache2/mod_cache_disk
    CacheEnable disk /
     CacheDirLevels 2
     CacheDirLength 1
 </IfModule>

In /etc/apache2/sites-enabled/000-default.conf, the reverse proxy behavior is configured with rewriting the URL:

<VirtualHost *:80>

        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/html

        LogLevel debug rewrite:trace3

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined

        RewriteEngine On
        RewriteRule ^(.*)test$ http://192.168.99.100:8080$1geo [P]

        ProxyPass / http://192.168.99.100:8080/
        ProxyPassReverse / http://192.168.99.100:8080/

</VirtualHost>

My goal is to cache rewritten URLs. In this case /samplecache/test should be treated the same as /samplecache/geo and only cached once because the response is the same. But it seems that mod_cache always takes the request URL not the rewritten URL, i.e. the calls

curl -v http://192.168.99.100:8090/samplecache/test
curl -v http://192.168.99.100:8090/samplecache/geo

deliver the same result from the backend but they are cached twice. I can see in in the error.log that /sample/test is tacken as cache key instead of the rewritten /samplecache/geo:

[Sun May 01 16:17:05.351716 2016] [cache:debug] [pid 9:tid 139956735403776] mod_cache.c(1332): [client 192.168.99.1:52687] AH00769: cache: Caching url: /samplecache/test
[Sun May 01 16:17:05.352121 2016] [cache_disk:debug] [pid 9:tid 139956735403776] mod_cache_disk.c(1350): [client 192.168.99.1:52687] AH00737: commit_entity: Headers and body for URL http://192.168.99.100:8090/samplecache/test? cached.

How can I use a rewritten URL as cache key, so that it is only cached once.