Washington, April 21 (IANS) It's just been a couple of days since he won the Pulitzer, but Indian American cancer specialist Siddhartha Mukherjee has no time to celebrate. He is already back at work, seeing patients and even doing some writing - though he says it will be a while before he gets a topic for another book.

"You know, I have gone back to work really - full clinic, clinical responsibilities, back to seeing patients. I am doing some writing on this as well," Mukherjee told IANS in an interview on phone from New York where he practices. "So, very good to return to work."

The Delhi-born wrote the book "The Emperor of All Maladies: A Biography of Cancer" that made it to the Time magazine's top 10 non-fiction books of 2010 and The New York Times' top five list. On Monday afternoon, he learnt that he had won the Pulitzer for it in the general non-fiction category.

"Well, I am not sure," said Mukherjee, 41, an assistant professor of medicine at Columbia University, when asked if he was planning another bestseller, as his writing style was erratic.

"I am thinking of writing next. But it's too early days for me. It's a lot of time before I can put together a topic that I might take up for a book next."

He says he's balancing his work as a cancer researcher and a physician, "I try writing in very short bursts, often 15-20 minutes, often half an hour and then followed by long periods in the shadows during which I do research and think."

"Then I write again in very short bursts usually in the evenings," Mukherjee said, explaining his writing process. "That's how the book got conceived and written."

The celebrity author may not be writing another book soon. But his prize winning "Emperor of All Maladies" may well be turned into a documentary.

"I haven't planned to turn it into a documentary. But there have been some very very eminent documentarians and very serious documentarians, who have decided to work with me on this," Mukherjee said.

"And I am going to be following their lead," he said. But "it's still in the works".

Mukherjee, who had his schooling at New Delhi's St. Columba's School, where he was five years junior to Bollywood star Shah Rukh Khan, says he thought of writing the book after one of his patients who had stomach cancer told him she was willing to go on fighting but she needed to know what she was battling.

He began writing the book as he couldn't point her to one thing that could explain cancer. "Essentially, it was a long process. I wrote it in little bits and pieces and it took about seven years," Mukherjee told IANS.

On his other writings, Mukherjee said: "I am a scientist and I am a physician. So I write papers. I was writing papers even when I was writing this book. So certainly, I do lots of different kinds of writing."

"I feel very honoured" at getting "one of the world's great honours", said Mukherjee, who is married to the artist Sarah Sze, herself an accomplished sculptor and a recipient of the 2003 MacArthur Fellows "genius grant".

When he first learnt about it Monday afternoon, "I did not believe it, so I called my wife to check if there was an error."