Patrick Dempsey on His Mom's Legacy After Losing Her to Cancer: 'This Is the Purpose for Living' (Exclusive)

Patrick Dempsey has been dedicated to helping people affected by cancer ever since his late mother Amanda's diagnosis in 1997.

On Wednesday, the actor spoke exclusively with PEOPLE about his dedication to cancer patients in honor of his mother, at a presentation hosted by SurvivorNet.

"She's a real inspiration behind it because there was nothing in the community that would be supporting her like we do," The Dempsey Center founder, 57, tells PEOPLE at the PHM HealthFront in New York City. "This is the purpose for living, building this out and building awareness."

The Maine native is now celebrating 15 years since opening the doors of their first location in 2008.

"We're treating the person, we're not treating the cancer. So we treat everybody. We treat the whole family," Dempsey explains of the personalized and comprehensive cancer care provided at no cost.

"So whatever we can do, we simply ask, you know, 'what can we do to make your life better?' And then wait for the response and then try to go from there," he says.

SurvivorNet CEO and co-founder Steve Alperin praised Dempsey's contribution to cancer care, also noting the importance of people sharing personal stories, which is the health media site's focus.

"The story of triumph, the story of loss, the story of perseverance, helps someone be more receptive to clinical information," Alperin tells PEOPLE, noting that teaming up with someone like the Grey's Anatomy alum has the power to reach and affect more people.

"People need information. There are a lot of mental health gaps. And he's been dealing with cancer since 1998," Alperin tells PEOPLE of Dempsey's background as a caregiver and "hands-on" work ethic.

"SurvivorNet, The Dempsey Center. We fill in gaps. 50 percent of people diagnosed with cancer say they don't understand their options. I try to make a business to help people help themselves."

Adds Publicis Health Media president Andrea Palmer to PEOPLE, "The reason we built this is because to me, health really has a bit of a higher order. And the things that we're doing from a partnership perspective, from brand leadership, from how we connect our brands and our clients with the community, really does a lot of impact."

Among The Dempsey Center's impactful services intended to treat the "body and soul," including "yoga, nutrition, reiki, acupuncture, and support groups," Dempsey continues to PEOPLE, "We have a kids' program called The Healing Tree. That's just for the children, and for them and how they've been impacted with their peer group."

"And that's the important thing is to be in control of your own destiny — to empower someone with compassion, empathy, and clarity is really important," the father of three adds. "So this impact that we've had with cancer made a big difference in a positive way."

Fortunately, Amanda, who fought a 17-year battle with ovarian cancer, was able to witness what her son and daughters were building until her death in 2014 at 79 years old. And Amanda was even able to participate, which Dempsey says gave her a purpose to continue her fight.

As for what Amanda was best at? "Really the one-on-ones," Dempsey says fondly. "She didn't like to be on stage and be the center of attention. But she was really good if she would meet someone who was recently diagnosed, she would go off and talk to them one-on-one. And that was her real strength. And I think for her it gave her a better understanding of why she survived for so long."

"Many people that she went through treatment with didn't make it," he continues. "And why did she? So she — and we find this to be true with a lot of our survivors who come back in and do the mentor program, that they're giving back with their experience. And that was what she took away from it. And she was very proud. Of the family and the community."

Stating that she should never have survived that long and how grateful he is that she did, Dempsey says he feels he had enough time with his mom, "where we always had a good conversation, cleared the air, and when she left it was, it was time for her to go and she was ready."

As for whether or not he feels he had enough closure. "I do," he responds.

"There were a couple surgeries, we weren't sure that she was gonna make it. And we had some of our best conversations where everything was on the table. She was very open and very clear and forthright with what she was feeling. And so for me, yes, but not all of my siblings. My siblings did not have that closure and are still paying the price of that," he says.

"It can rip people apart," he adds, which is why a prime focus at The Dempsey Center is to get families "on the same page."

"Being able to communicate, be able to open up and to let go of those emotions or be able to communicate the fears or anxieties in a safe environment. Then everybody can kind of understand, oh, 'now I know where you're coming from.'"

For Dempsey, the grieving process thankfully made him become a better husband and father. He has been married to celebrity makeup artist and beauty CEO Jillian Dempsey for 24 years. They share a daughter Talula, 21, and twin sons Darby and Sullivan, 16.

"You really do prioritize your family and your children," he says. "The family unit I think is really important and makes me appreciate that more."

As for his personal bond with his wife, Jillian, "we have a great relationship we're at the best place we've ever been in our relationship," Dempsey says. "We really take time to support each other in our endeavors. And I think that's the key. Longevity. I think we're gonna be 24 years this year, and you know, it's really taking the time to support each other and to hear each other. So it's nice."

Though he is primarily focused on his family, his career, and helping others, Dempsey says he still is able to make time for racing and will be making an announcement on an upcoming racing program in June.

"It's very exciting," the Disenchanted star says of his longtime passion. "It's a partnership between Tag Heuer and Porsche."

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Then on September 23, The Dempsey Center has The Dempsey Challenge lined up, which is an annual run, walk and bike ride near the Lewiston, Maine location. "And that allows us to raise money so that all of our services are absolutely no cost."