Four months. It may not seem like a long time to many people, but for those with cancer, it's 120 days they might not have.

A breakthrough treatment for prostate cancer patients is changing that for some, but people who've gone through the process have mixed emotions about it.  

Ray Schmidlin and Robert Obin are two men with prostate cancer who know the disease will kill them.  

"I expect to die of prostate cancer. It's a matter of when," says Schmidlin.  

Both Schmidlin and Obin have been treated with Provenge, a therapeutic vaccine using their own blood to slow down the cancer. Certain cells are harvested, altered and infused back into the body to help the immune system attack the cancer.

Studies show Provenge can improve a patient's median survival rate by four months, and it reduced patients' risk of death by 22 percent. Obin believes it's the reason he's still around.  

"It's not going to cure me, but that will help me to give me, I don't know, more days?" says Obin.

Schmidlin says the immunotherapy took a toll on him. The active grandfather tells us he was strapped down for several hours at a time during six weeks of treatment. 

"And that was pretty stressful, because you couldn't, you couldn't move," says Schmidlin. 

He's not sure the discomfort and confinement was worth it. 

"If I'm going to live 60 months, I don't want to spend the money and the time to live 64 months," explains Schmidlin.

"I think it's a controversial topic," says Jorge A. Garcia, M.D., a director advanced prostate cancer program at the Cleveland Clinic. 

Garcia is Schmidlin's physician and says there are misconceptions about Provenge.  

"The patient automatically believes if I get the treatment, I'm going to live four months more, and that's inaccurate," says Garcia.

He goes on to say some live longer but some don't make it to four months, and it's not for all prostate cancer patients.

Provenge is designed for those who show few or no symptoms, but have a form of the disease that has spread and is resistant to hormonal therapy.  

"I think that there's a selective group of patients who should actually consider getting it," says Garcia. 

He also says it doesn't lower PSA levels, shrink tumors, or reduce symptoms like bone pain.  

"But yet, you're likely to live longer,"adds Garcia.

While Garcia believes Provenge is a breakthrough, he says it's important for patients to know it may or may not be the right option for them.