The guest of honor couldn't make it to the American Cancer Society's Salute to Volunteers Luncheon yesterday, and the news that Marvella Bayh had been hospilized again touched the affair with a tangible sadness.

Her husband, Sen. Birch Bayh (D-Ind.), represented her, and said that "last night and this morning she had a bad reaction to certain treatment and she just couldn't be here." There was an audible gasp from the crowd of about 900 Washington-area volunteers when it was announced that Mrs. Bayh would not be present to accept the Hubert H. Humphrey Inspirational Award that was to honor the woman "whose spirit and courage in her personal fight against cancer are a lasting inspiration to cancer patients and to all Americans.

Mrs. Bayh discovered she had cancer more than seven years ago. After an initial mastectomy, the cancer appeared to be arrested, but in February 1978 she was told it had spread to her bones. Doctors said it was widespread, inoperable, and that she might have five or six years more to live.

Friends said yesterday that she had planned to attend the luncheon, and had her hair done Tuesday in expectation of going. She has been taking treatment as an outpatient, but has not been hospitalized for some time. In addition to working with writer Mary Lynn Kotz on her autobiography. "Marvella - A Personal Journey." she is a full-time lobbyist for the Washington office of the American Cancer Society.

"This is a bittersweet day for the Bayh family," said Sen. Bayh to the lunch crowd. "My son Evan and I deeply appreciate that you would choose our wife and mother for this award." Bayh appeared near tears; at one point he paused to regain his composure as the crowd sat in respectful silence for several moments.

There were tears earlier as well, when Tracey Andrus, 23-year-old daughter of Interior Secretary Cecil D. Andrus, told of her discovery of and apparent recovery from Hodgkin's desease four years ago.

As her parents listened, each occasionally wiped their eyes discreetly, Miss Andrus told how "the summer of 1975 seemed a long way in the past, but it could have been the end of my future."

She told how she discovered a lump on her neck one Friday night during a summer vacation, and in the interval before she could see her doctor "I spent the next two days thinking about life and about my life . . . funny how dear something becomes when it is threatened."

When she left Stanford University Medical Center after 2 1/2 months of radiation therapy, she said, she "looked at the fountain outside the building, tears streaming down my face . . . I looked at the sky . . . I got in my car and drove away . . . I am again making long distance plans for my future."

She said that without research funded by the American Cancer Society "I might not be here today," because the doctor who discovered the treatment that conquered her cancer was supported in part by Society funds.

Thank you very much, you're beautiful," she said as she ended her speech to enthusiastic applause. Miss Andrus will graduate in June with a degree in marketing from Boise State University, and works 40 hours a week in a ski shop. Yesterday she also visited the White House to receive a citation from President Carter.

The National Citation of the Society's D.C. chapter was presented yesterday to Washington Post cartoonist Herbert . Block "for lending his art and wit to signal the dangers of smoking" in numerous editorial cartoon over the years.

Block, who is known more familiar as Herblock, stopped smoking 20 years ago after being a five-pack-a-day man for years.

"I've never seen so much nonsmoking in my life," he said to the crowd after accepting his award. "Some of you must be dying to get out of here."

Herblock, 69, has worked for The Post since 1945. Among the numerous awards he has been given are three Pulitzer Prizes.

The award to Mrs. Bayh was presented by the late Sen. Humphrey's sister, Frances Humphrey Howard, who said what her brother and Mrs. Bayh had in common is "the knowledge that the purpose of life is to be helpful to others . . . but the most important thing we can say about her is that she's our friend. She's our friend and she counts."

Sen. Bayh, who spent the morning with his wife at the hospital, said "both she and I are determined that she will be here to pay tribute to the honoree next year."

Then he put on his glasses and read a short speech his wife had planned to give. She talked about courage, and the importance of love and hope in her battle against cancer. "If I have courage, it's in knowing that I alone am not strong enough, and I need love from God and from others."