Saudagar directed by Subhash Ghai starred Dilip Kumar and Raaj Kumar, in the leading roles. It also marked the debut for Manisha Koirala and Vivek Mushran.
"She is very brave and extremely strong. She has taken things very positively," he added.
Manisha, 42, underwent surgery Dec 10.
Asked him how long will she stay in New York, Ghosh said: "She will be there for at least three more months. Now her treatment is going on and she is responding well. Her parents are with her."
Manisha was first admitted to Mumbai's Jaslok Hospital Nov 28 after she reportedly fell unconscious. However, the reason behind her illness was not made clear.
Later, it was reported that she flew to the US for cancer treatment.
She debuted in Bollywood with 1991 hit movie "Saudagar" and later featured in films like "1942 A Love Story", "Bombay", "Dil Se" and "Lajja".