DO YOU READ HARRY POTTER?” This was one of the first things my oncologist said to me.

Just a few days after my daughter’s second birthday, sudden, excruciating abdominal cramps sent me to the hospital. A CT scan, an ultrasound and exploratory surgery revealed no answers, and the pain went away. But at my doctor’s urging, I went for a colonoscopy.

After the procedure, a nurse directed me to a semi-private corner instead of the exit, where I found my husband waiting in an armchair. It didn’t dawn on me that anything was amiss until someone quietly placed a box of tissues between us.

The doctor got straight to the point: There was a huge tumor in my colon. He kept talking, explaining something about genetic disorders. I had to interrupt him as the sentences began to pile up, uncomprehended.

“Are you saying I have cancer?” I asked, clutching my husband’s hand.

“We can’t officially say that until we get the biopsy results, but I know what colon cancer looks like,” he said, looking at me, then down at the floor. In a hopeless attempt to soften the blow, he added: “I’m sorry. You seem like nice people.”

I felt knocked down by the force of shock; dizzy, sick, scared. Then, indignant. The news seemed as ridiculous and unfair as something from a cartoon—a piano falling out of the sky on my head.

What were my odds of survival? Would I need chemotherapy? No one could answer for several more weeks—until after a surgeon removed the entire tumor, and half my colon. When the surgical pathology report finally did arrive, well, that’s when the conversation turned to children’s books.

“I wish I had a sorting hat,” my oncologist was saying. He was referring to a magical hat in the Harry Potter books that helped point the way forward for young wizards. “I need something that would tell me, okay, this patient’s in the 5% that would benefit from chemo.”

My lymph nodes were unaffected, which was great news. But the tumor was so deeply invasive that some of the cancer cells had perforated the wall of the colon. They could still be lurking inside me. In practical terms, this meant that I was either cured or I was at risk for a more dangerous cancer down the road. He explained that there was roughly a 20% chance of recurrence, but chemo could reduce that to about 15%. It would be a big treatment for a small risk. Unfortunately, the choice was mine to make.

Decisiveness had never been my forte. I used to love “choose your own adventure” books, where the reader gets directed between alternate chapters and endings depending on a choice at a crucial moment. (“Does our heroine open the door? Turn to page 57 if yes, page 60 if no.”) But I loved them precisely because I didn’t have to choose just one plot. By flipping back and forth through the pages, I could unfold a whole series of parallel universes.

I decided to see a second oncologist, who pulled out his laptop to show me how ambiguous the clinical guidelines were for treating my stage 2B colon cancer. Stage 1 and 2A cancers typically don’t require anything more than surgery, while stages 3 and 4 involve aggressive chemo regimens. But I was right in the middle. For stage 2B, the flowchart points to all possible options: Infusions. Pills. Clinical trials. Or nothing at all.

Life, unfortunately, lets you turn pages in only one direction. And it was time to choose.

I ended up returning to the first oncologist, and together we decided on six months of oral chemo. For me, the decision finally came down to a look at my daughter’s face. A few percentage points of risk reduction doesn’t sound like much—until you stack it up against the chance of not being here for her in the long run.

If I make it to three years of clean CT scans after this, my oncologist says I should throw a small party. After five years, a huge party. That’s one prescription I look forward to filling.