Grandma woke Sam Johnson at 10 minutes to 8.

"Sam!" she called upstairs.

He rolled out of bed, stepped into his moccasins, and in seven minutes was out the door on the way to his last chemotherapy treatment.

Sam, 18, was a high school freshman in December 2003 when his nose and gums started bleeding and a bruise on his arm swelled like a baseball. The diagnosis: acute lymphoblastic leukemia. Sam was one of 3,200 American children diagnosed each year.

The chemotherapy regimen lasted 3½ years, the standard protocol for boys - all of Sam's time in high school. He graduates in June.

His life has been a seemingly endless stretch of vomit, sickness, spinal injections, and thousands upon thousands of pills. His father joked that Sam vomited so much from the medicines that "he knew where every waste can in the school was after a while."

Sam lost his hair. He was rushed from his home in Haddonfield to the emergency room by ambulance when allergic reactions to drugs constricted his airway. He had blood transfusions. He missed so much school that tutors came to the house.

"A ton of bad stuff," said Sam.

But Friday was his last day of chemo.

He arrived at the Children's Hospital of Philadelphia specialty-care center in Voorhees by 8:30 a.m. His grandmother, Helen Hamilton, 83, drove him. His parents, Doug and Anne Johnson, were off celebrating their 25th anniversary - postponed since last summer because of his treatments.

"We felt kind of safe going, knowing it was so close to the end," his father wrote in an e-mail. "But, other than one other long weekend, we have not been away from Sam during the three-year ordeal. To see him get done now is the most incredibly great event that could ever happen to us."

They will be home next week for a big blowout party, to celebrate and thank everyone. A young leukemia patient Sam befriended in chemotherapy will be the DJ.

The staff at the Voorhees center is extremely fond of Sam. Sometimes the lab technicians, who check his blood counts, call him "the King," since he was elected homecoming king last fall at Haddonfield Memorial High School.

Nurse Denise Desrochers injected the IV needle into Sam's right hand, right above his knuckles. He didn't flinch.

"So where did you decide?" she asked, referring to his college choice.

"I still don't know," he said.

Sam is choosing between University of Delaware and Loyola University in Baltimore.

Once the IV was in, but before getting the drugs, Sam went to Barbara Greenbaum's office for an exam. She is his oncologist. He sat on the table and kicked off his shoes.

He said he'd been feeling well, no pain. Then he grimaced.

"I just got a whiff of my moccasins," he said.

According to Greenbaum, in 1975, only 49 percent of children with leukemia would be cancer-free after five years. Now the success rate is 83 percent and climbing, she said. And survivors who go five years without cancer have only the most remote chance of its coming back.

"My anticipation for Sam is growing up, going to college, getting married, having kids - hopefully in that order. That is my expectation."

Along with his last chemo treatment, Sam would be getting a bone-marrow biopsy - a needle into his pelvis bone, drawing marrow fragments so staff could be certain there was no evidence of leukemia. That final procedure had been scheduled for the following week, when Sam's parents would be home, but Greenbaum decided to combine the two that morning.

"Will I be able to go to my dance tonight?" asked Sam. His jacket and tie were already laid out on the bed.

"Yes," said the doctor. "Just go home and sleep."

The last chemo, a syringe full of vincristine, took only seconds to inject into his IV. It was 9:30 a.m. No act could have been more anticlimactic.

Then the nurse, preparing for the marrow biopsy, injected morphine.

Sam's grandmother, with him since his diagnosis, holding his hand and hugging him through many of the treatments, decided the room was too crowded with journalists, a hospital media person, nurse, lab technician and doctor.

"I'm going to slip out," she said to Sam. "I love you."

"I love you too, Grandma," he said.

Sam lay on his side, his knees curled up, his hip exposed.

"You're going to feel a little bit of an 'Ow,' " the doctor said.

"Ow. Ow. Ow. Ow," said Sam.

But these were mellow ows.

"So, are you taking any AP exams?" the nurse asked.

"Biology and government," he replied.

The exams would be the Monday after his end-of-chemotherapy party. Sam wasn't worried about his score, because he planned to take intro biology in college. He'd need good grades for medical school.

"Since all this happened to me," he told the nurse, "I've decided to become a doctor."

"Oh, that hurts so much . . .

"Breathe," she said. "Big breaths. You're doing such a good job."

The room got very silent.

"Feels like an elephant stepping on your back," the nurse said. "Your bones are so hard."

"I drink my milk," Sam said. "Oh, God, that hurts so much."

He sort of laughed as he moaned - good-natured in his misery. The nurse later said the good-naturedness was from the sedative. And Sam wouldn't remember much of the procedure.

Soon enough, Sam was on his back, drinking apple juice.

And that was pretty much it.

He lay down for another half-hour, until the staff was certain he was steady on his feet. His grandmother would drive.

"He's free," said the nurse. "A free man."

"I should have brought sparklers," said his grandma.

From the waiting room, Sam text-messaged about 30 friends at school:

"Last chemo clinic is over!!!"

He would keep taking pills for a week, then come back monthly for checkups for two years.

Sam had planned to go home and sleep, and skip the day of school. But now he wanted to celebrate. His grandmother went to Acme and bought a cake, inscribing it "Congratulations, Sam." He brought it into last-period AP government.

After he handed teacher Jeff Boogaard the cake, he asked meekly, "Can I have an extension on my homework today?"

"With the media here, do you expect me to say no?" Boogaard replied and laughed. "Of course."

Everyone high-fived and ate marble sheet cake.

Then it was home to rest up before the dance.

Contact staff writer Michael Vitez at 215-854-5639 or mvitez@phillynews.com.