Please help to optimize query

to avoid USING TEMPORARY and USING FILESORT

[gcan]

Is there any way to avoid Filesorts and Using Temporary in this query?

Indexed columns are:

stats_profileviewers.viewer_id, 
stats_profileviewers.profile_id, 
stats_profileviewers.vtime, 
users_table.id 
portalsession.user 

SELECT 
stats_profileviewers.viewer_id, 
stats_profileviewers.vtime, 
users_table.nick, 
users_table.gender, 
portalsession.user 
FROM stats_profileviewers 
join users_table on stats_profileviewers.viewer_id = users_table.id 
left join portalsession on stats_profileviewers.viewer_id = portalsession.user 
WHERE stats_profileviewers.profile_id='28603' 
order by stats_profileviewers.vtime DESC limit 0, 20;  

+----+-------------+----------------------+--------+----------------------+------------+---------+-----------------------------------------+------+---------------------------------+ 
¦ id ¦ select_type ¦ table ¦ type ¦ possible_keys ¦ key ¦ key_len ¦ ref   ¦ rows ¦ Extra  ¦ 
+----+-------------+----------------------+--------+----------------------+------------+---------+-----------------------------------------+------+---------------------------------+ 
¦ 1 ¦ SIMPLE ¦ stats_profileviewers ¦ ref ¦ profile_id,viewer_id ¦ profile_id ¦ 4 ¦ const   ¦ 6 ¦ Using temporary; Using filesort ¦ 
¦ 1 ¦ SIMPLE ¦ portalsession ¦ index ¦ PRIMARY ¦ PRIMARY ¦ 17 ¦ NULL   ¦ 278 ¦ Using index  ¦ 
¦ 1 ¦ SIMPLE ¦ users_table ¦ eq_ref ¦ PRIMARY ¦ PRIMARY ¦ 4 ¦ databas2.stats_profileviewers.viewer_id ¦ 1 ¦   ¦ 
+----+-------------+----------------------+--------+----------------------+------------+---------+-----------------------------------------+------+---------------------------------+ 
3 rows in set (0.00 sec)  

Thanks.