JOHN RENNIE

Two years ago, for roughly the 15,000th time, I patted our dog Newman on the head. That time my fingers found an unexpected depression half the size of a ping-pong ball above and behind his right eye.

Thinking he had somehow bashed in his skull, my wife Jennifer and I rushed Newman to a nearby veterinarian, who quickly set us straight. His skull was fine. Rather, the bulky muscles of Newman’s forehead and jaw had withered, revealing the bony contours beneath.

The most likely cause was a brain tumor. With that suggestion, we plunged into a two-year lesson in the treatment of canine cancer.

See a video tribute to Newton.

The National Canine Cancer Foundation estimates that one out of every three dogs gets cancer, in part, because modern pets’ longer life spans allow more time for malignancies to develop. The breeding practices that created pugs, Afghans and every other variety also littered the species’ DNA with predispositions to health problems. Newman was neither particularly old nor overbred: he was a nine-year-old, 40-pound black mystery breed with hints of terrier and shepherd whom Jennifer had found at a rescue shelter. He might simply have fallen victim to one of those unfortunate spontaneous mutations that cause cancer, for which no satisfying explanation exists.

An MRI scan confirmed that a neural sheath tumor wrapped around Newman’s fifth cranial nerve had choked off signals to his facial muscles and caused them to atrophy. With such brain tumors, chemotherapy is problematic because the brain protectively isolates itself from most compounds that enter the bloodstream—the so-called blood-brain barrier. Our vets therefore suggested that the best course might be a sophisticated (and, alas, expensive) therapy in which robot-guided beams of gamma rays would zero in on the tumor with minimal harm to surrounding brain cells.

See the MRI scan of Newton’s tumor.

But first, the vets prudently X-rayed the rest of Newman’s body to see whether tumors might be hiding in other tissues, too. Lesions that turned up on his lungs represented an even more urgent threat than the brain tumor did. The prescribed treatment swung back around to chemo: we would try to poison the lung tumors and hope for incidental benefits in the brain.

Newman’s chemotherapy consisted of two drugs given as pills on alternate days: cyclophosphamide with breakfast on Tuesdays, Thursdays and Saturdays, and Palladia™ (toceranib phosphate, FDA approved in 2009 as the first cancer drug specifically for dogs) with dinner on Mondays, Wednesdays and Fridays. Every evening he took omeprazole to protect his stomach lining from the corrosive chemotherapeutics. Other drugs stood by as needed for pain, for nausea, for diarrhea. There were also bags of plastic gloves for handling the chemo agents, and a pill splitter for chopping the tablets down to appropriate doses. I gathered Newman’s array of supplies into a green, soft-sided lunch box to keep everything together, and committed the dosages and schedules to memory.

For dogs, chemotherapy is often less grueling than for humans—many dogs suffer few or no side effects. The reason, however, is that they do not receive comparable doses of the toxic drugs. Justifying months of chemical hell is easier with people who might gain decades of added life. The tradeoff, of course, is that the dogs’ chemo is less potent.

During his previous eight years with us, our canine Rasputin had survived eating a box of chocolates, New York City garbage, some kind of wire clip that snagged in his intestines and a mouthful of rat poison. So it was no surprise that Newman took chemotherapy in stride. He continued to lead me on daily walks that went for miles, and his vigor and sociable nature held up well, pushing far past the early benchmarks for his mortality. Periodic checkups confirmed that the tumors in his lungs were stable or shrinking. It was easy to forget that he was sick at all.

But Newman was also undeniably (if ever so incrementally) slowing down, whether because of the brain tumor, the drugs or his own advancing age. He was sleeping more and walking less. Jumping and running involved more obvious effort. Once voracious, he became a picky eater, and every shift in his diet threw off his digestion.

Early in 2011, Newman’s problems began to escalate. His vision and hearing took a tumble. Chewing seemed more taxing for him; he gave up gnawing on his favorite rawhides. At night, he seemed unable to get comfortable, even when we gave him pain pills. He would wander restlessly around our apartment, or ask to be taken for aimless walks through the neighborhood. Even inside our home, he would sometime stop as though confused about where he was.

With his life becoming a burden to him and no hope for improvement in sight, Jennifer and I knew we had no choice. In August we took Newman out to the Pocono Mountains, where he had always enjoyed nosing through the tall grasses and leaves, to make his last hours happy. In a quiet room in the veterinarian’s office, Newman went to sleep cuddled in my wife’s arms as he had countless times before, and his good heart came to a stop.