After writing obituaries for a decade, I received a phone call on Tuesday, Nov. 12, that began routinely enough.

Name of subject?

“Pat Koch Thaler” — the sister of the former New York City mayor Edward I. Koch, his sounding board and a former dean at New York University.

Day of death? “Saturday.”

The 9th, right?

The answer spooked me: “No, the 16th. And she wants to speak with you first.”

I have interviewed the subjects of dozens of obituaries before their deaths. But I’d never been contacted on behalf of someone who was about to take her own life, much less wanted to talk about it.

After 22 years of fending off cancer, Ms. Thaler had run out of miracles. Twice the disease had gone into remission, only to return. One kidney had been removed. She had been bombarded by radiation, chemotherapy and ablation. Finally, the tumors had been declared inoperable.

“My mother died in agony,” Ms. Thaler recalled. Her mother was 62, misdiagnosed and undergoing aan operation to remove her gall bladder when surgeons found her body was riddled with cancer.