WHO AMONG us has not indulged the provocative day dream, "What would I do if I knew I had 10 years to live . . . starting today? How would I change my life? What would I do with the time left to me?"

For Paul Tsongas, senator from Massachusetts, 42 years old, husband, father of three young children, that abstraction became a reality one day in the fall of 1983. A lump discoverd in his groin casually dismissed as "a hernia" proved to be an enlarged lymph node, a sentinel of a systemic cancer. Without notice, the safe presumptions of a sparkling political career and a warm, close family life were dismissed to be replaced by punishing doubts about the future of life itself. The diagnosis was that of an indolent nodular lymphoma, giving the senor the likelihood of a number of years free of debility and compromise but, also, the certain knowledge of eventual death -- 10 years, more or less.

In the months that followed, Paul Tsongas struggled to answer the questions posed by a future with a distant but suddenly visible wall built into it. One generous decision he made was to share his experience by writing about it. Now, barely a year later, he has given us Heading Home, the human, simple and eloquent record of the time that followed his diagnosis.

Externalities aside, Tsongas quickly saw himself as a different person. "I was no longer the senator from Massachusetts. I was a frightened human being who loved his wife and children, and desperately wanted to live." At other times he saw more easily beyond his immediate emotions. "But now I had spent three months thinking about and negotiating with the reality that we are all going to die. We all had a date, and on the next day the sun would still be shining somewhere, the rain would stil be falling somewhere, the moon and stars would still be in their places. The earth was timeless, not those who inhabited it. What had to be done, had to be done now."

What was it that Paul Tsongas had to do? Nearing the end of his first term in the Senate, Tsongas was an accomplished legislator, a neoliberal leader, and a revered political opponent few would challenge in his home state. A second term was a given and the presidency itself was a long-term possibility. Without question, there were powerful reasons for Tsongas to downplay his illness personally and publicly and continue his career as a statesman and politician.

And yet, even in the best of times, Tsongas was an atypical member of the political fraternity, not given to socializing, preferring time spent with family and close friends. His children were young (ages 2, 6 and 9) and a focal point of his life as was his wife, Niki, who functioned as his friend, confidant and counselor. Finances were tight and before his diagnosis the Tsongases had decided to move the family back to Lowell, Massachusetts. Regardless, the divided life of a senator would continue to keep him separated from Niki and the children for significant amounts of time.

THE dilemma of Heading Home is, given 10 years to live, what counts? What really counts? Career or family? . . . Public life, private life? Paul and Niki Tsongas agonized over that choice, vacillated a bit and then finally opted for family and privacy. In January 1984, the senator announced his retirement from politics for reasons of illness and began his transition back to private citizen.

Heading Home describes one man's heroic coping, leading him to abandon a position that many of us covet but will never achieve. Paul Tsongas' accommodation to his cancer on a personal level, however, stands in contrast to the reticence he displays in dealing with it publicly. His retirement announcement was crafted carefully to avoid any mention or implication of cancer. Tsongas states clearly and honestly that the notion of being "the senator with cancer" is loathsome to him. It was his hope to leave the Senate as an athlete being carried high, not as a "cancer victim." But the story surfaced anyway, and he was obliged to negotiate a second set of disclosures and media events that detailed his cancer. The cover of the book itself proclaims that "The Senator from Massachusetts tells how the discovery of his illness (sic) dramatically changed his priorities . . . " leaving the reader to wonder what "his illness" is.

To be sure, the notion of cancer is still a dreaded one often equated with automatic death. As Paul Tsongas is demonstrating for us, though, this surmise is inaccurate. People can suvive with cancer. People can survive beyond cancer. This, it seems to me, is one of the important and dramatic messages of Heading Home. I wish the senator had felt able to celebrate it a bit more.

Paul Tsongas has decided what to do with the rest of his life. The attention and power of the Senate exerted a strong pull on him. But, had he opted for another term, he "would not have helped Ashley on his science project or accompanied Katina on her Brownie weekend camping trip or had Molly fall asleep in my arms in the hammock." Those are unusual, brave and beautiful priorities in our world. Paul Tsongas has enriched and educated us with his candor. One hopes he will continue his chronicle of life in future volumes.