It takes a deft, empathetic touch—and sometimes some firsthand experience—to make a so-called “Disease of the Week” movie work. And The Girl with 9 Wigs, a German dramedy which premiered at the Seattle International Film Festival June 5, works.

Based on the autobiographical novel by Sophie van der Stap, the movie follows Sophie Ritter, a 21-year-old college student suddenly diagnosed with a rare and aggressive form of cancer. As she undergoes chemotherapy, Sophie blogs about the experience, and finds refuge from the treatment’s ravaging physical effects by donning several different wigs. The hairpieces serve as more than just cosmetic decoration: They enable her to find strength, and to hold onto her humanity, on the road to her recovery.

Don’t let the formulaic trailer fool you. The Girl with 9 Wigs transcends the familiarity of its subject matter with touches that make it well worth seeing. Van der Stap played a key role as an advisor to the film, and her compassionate, bluntly humorous literary voice informs the entire movie. This is no garden-variety cancer martyr/victim: Onscreen, Sophie’s a fully-realized human being — replete with an impulsive streak that betrays her youth, and a libido moving at full gallop despite her affliction. A film of this nature stands on the strength of its lead, and actress Lisa Tomaschewsky comes through with an utterly natural, star-making performance as Sophie.

The day after the film’s  SIFF debut, I meet Tomaschewsky and van der Stap in the lobby of the W Hotel for our interview. A lot of heads turn as they navigate down the stairs to the hotel’s sun-saturated foyer. Part of that magnetism is superficial (Tomaschewsky spent years working as a fashion model, and van der Stap looks like she could be one herself), but there’s no denying that they each possess an intangible presence beneath the surface. Audrey Hepburn-gamine and shy, Tomaschewsky regards the rush of hotel guests and SIFF staff with non-judgmental but observant eyes. Van der Stap, meantime, carries herself with the unpretentious assurance and strength of someone who’s seen challenges well beyond her 29 years.

Both women bonded famously during the filming of The Girl with 9 Wigs, and that camaraderie surfaces frequently as they speak with me about the movie that brought them together. They good-naturedly rib each other, with van der Stap taking the role of protective, lovingly-wisecracking older sister while Tomaschewsky expounds on a budding acting career with undisguised enthusiasm. And like the film they’re helping to promote, their recollections reflect a healthy balance of humor and insight.

This is the North American premiere of The Girl with 9 Wigs. How do you feel about the movie playing in America?

Lisa Tomaschewsky: Actually, I didn’t expect that it was going to show in the States, so for me it’s something very special. It’s my first big film role. There are some moments where I still can’t believe it. I just started acting two years ago!

Sophie, did you ever think that your story would become the basis of a feature film?

Sophie van der Stap: Not when I started writing it, no. I didn’t even think it was going to be a book. Now in hindsight, I can see [that] it has some ingredients that work. It’s a very honest and direct story that wasn’t written for an audience. It was written for me.

Before your cancer, you started out studying political science. When did you begin writing?

SV: I discovered it in the hospital. And I think that it has something to do with the whole process of having to let go of your life. It’s a bit ironic. You don’t think you have that much time anymore, but you have plenty of time, because you don’t have a life anymore. So the writing came, and that helped me escape the mental battle. How do I use the time I still have left? It was a great way as well to build a bridge to the world, to be a little bit less alone in my experiences and my feelings.

It’s very interesting how the usage of the wigs became so therapeutic for you.

SV: What actually happens, I think, is you take a pace of your own through the whole process. Everything is decided for you, but you discover you can still be there in your own way, and for me that was the wigs and the writing; just finding something good in a bad situation that’s been given to you. I discovered that, with the help of my wigs, I could say, “OK, Cancer, you’re here, but I’m still here as well.” The wigs became sort of my ‘cancer breaks.’ The reality of cancer is just too ugly to face 24 hours a day, so I needed to find my escapism.

Lisa, did you know about Sophie’s story prior to landing the part?

LT: I heard about the story some years ago, but I didn’t connect immediately connect it to the first details that I [received]. When I heard it was based on a true story, then I remembered, “Oh, there’s a book out called The Girl with 9 Wigs.” For me, it was a wonderful chance to leave the fashion world and be a part of the acting world.

Sophie, your real story actually took place in Amsterdam. The movie takes place in Germany…

SV: …For financial considerations [laughs]!

Aside from relocating the story to Germany, how accurate was the film?

SV: In a way, we had to fictionalize stuff, of course. There are many more characters in the book. I also had 54 weeks of chemo, and we had to change that because today the treatment is shorter. But what’s very accurate is the heart of the story, how we dealt with it. So 90 percent of the jokes and the conversations [in the movie] are in the book. The relationships to the people in the hospital and my parents — those are exactly the way they were in real life, and in the book.

Lisa, what was it like preparing for the role, physically as well as mentally?

LT: Well, I had to gain weight for the role. I’m naturally very skinny, so it’s not that easy for me…

SV: Oh, shut up…[Both laugh]

LT: That was the first step. Then I met Sophie for the first time, in Hamburg, when we first started shooting. For me it was love at first sight. She had this special aura. She still has it.

I’d read a lot about Sophie on the web, and I read her book three times. You think that you know somebody, just because you’ve read their writing. But when that person is standing in front of you, and you are playing them, there’s a line you have to cross. So I started talking with her about my feelings about cancer. My grandma died of breast cancer, so talking about it’s not so easy for me. But after making the movie, I’m not that afraid of cancer anymore. [Sophie] was so helpful, and we’ve had a great time together.

SV: Of course, Lisa had to shave her head. When she wasn’t on the film set, she would find herself in a whole new reality, being bald and wearing the wigs.

Lisa, did you work closely with Marc Rothemund, the director, on the creation of the character?

LT: Yeah. I had my little image of Sophie in my head, and Marc had almost the exact same image, so that was perfect. But of course, sometimes he said, “This is not the right way: Try something different.” It was a big education, because it was my first big part. I found that actually, if I listened to him, and trusted him, it definitely worked.

SV: Marc discovered her. It was a risk for him to use a girl who wasn’t known yet, and there were many girls who were interested in this part. But Marc said, “I want Lisa. I see something in her.” What I liked very much was to see that she brought a lot of herself to the part. I got to know her, and I saw she brought a lot of herself to the role — especially the humor.

Did you improvise a lot on the set?

LT: When I read the script for the first time, I had so many questions. Marc was like, “Lisa, stop asking questions!” I was like, “It’s my first role. I have to know where I’m coming from, where I have to go…” I did put some of my humor in it. For example, when I walk down the corridor and start doing this little ride on the IV holder, that was my idea. Or when I’m doing the radiation, I thought, OK, when you see me topless, everyone’s focused on it. So it was my idea to put faces on the tape on my nipples. One was a little smiley-face; one was a little Dracula [laughs].

Lisa, do you plan on continuing with modeling as well as acting?

LT: I quit modeling. That was the reason I took a chance cutting off my hair: I cut off everything that was important for a model. Also, I can’t be creative modeling. With acting, I have everything. I can be creative, and it’s not all about the beauty. I’m happy in this world, and I think I’ve made the right decision.