But now, five years after her terminal brain cancer diagnosis, the acclaimed actress who starred in the Mary Tyler Moore Show is still going strong.
Harper, 78, admitted she is amazed at her own longevity while battling leptomeningeal carcinomatosis (LC), a rare complication of cancer affecting the brain and spinal cord.
Even her oncologist is surprised, and the only thing he can put it down to is the fairly new chemotherapy drug he gave her in a last-ditch attempt to give her a bit more time.
'It's a miracle she's still here,' Dr Jeremy Rudnick, her oncologist, told People.
'Valerie developed this disease at a time when we keep coming up with stronger and better targeting drugs for her particular cancer.
LC only affects five percent of cancer patients. It is the name for an unusual complication, in which the disease spreads to membranes in the spinal cord, rather than to other organs or brain tissue.
It means that the cancer cells are floating in cerebrospinal fluid, which can rapidly spread throughout the entire nervous system and is incredibly difficult to stop or control.
LC typically evolves from breast cancer, melanoma and lung cancer - which Harper, who also starred in the spin-off show Rhoda, battled and beat in 2009.
The most common symptom is mental confusion and a headache that feels like intense pressure. Some patients also experience a numb chin, issues walking and seizures.
Without treatment, patients are given about six weeks to live after being diagnosed with LC. Treatment usually gives patients three months at most.
'I still have cancer, but I'm okay and most of my days are good,' Harper said.
She said her husband of 30 years Tony Cacciotti, a producer and actor and personal trainer, is her full-time carer.
Treatments for LC are limited, and delivering drugs to the central nervous system is complicated.
Most patients will get a hole drilled in their skull, so that chemotherapy can be delivered intrathecally.
Harper was on an unidentified chemotherapy drug but switched to an experimental drug earlier this year after experiencing seizures.