A woman using the pseudonym Wendy Grace (she asked that ABC News not use her real name) and her mother in Minnesota face such a situation now. Her mother was diagnosed with breast cancer five years ago, but was treated with successful surgery. While she began a regimen of tamoxifen to avoid recurrence, she stopped that after two years -- three years short of the time she was supposed to take the drug -- and turned to an alternative diet instead.
"She said it made her feel funny and so she stopped taking it, which I think was a huge mistake," said Grace. "[She] and I don't have a close relationship as much as we used to because of it. I'm afraid she's not going to be around for her grandchildren because of her decisions."
She said the situation has also caused friction between her parents, since her father also opposes her mother's choice of treatments.
"My father can't even sit down and have a normal meal with her," said Grace, because of the diets her mother has taken on, and for which she spends hundreds of dollars on every month. "It's caused a lot of stress and tension between my mother and my father."
While Grace's mother's decision to forgo conventional treatment may be more unusual, her desire for an alternative treatment is not.
"I would argue the majority of patients are seeking out complementary treatments alongside their conventional treatments," said Lorenzo Cohen, director of the Integrative Medicine Program at M.D. Anderson Cancer Center in Houston. "What's very uncommon is that a patient receives alternative treatment in place of conventional treatments."
Cohen noted there are times when alternative therapies would be less likely to be discouraged.
"There are certain situations ... when there is nothing out there in the conventional world that will help them, if they want to take something of unproven benefit, we try to do it in an educated manner," he said.
He noted that doctors will try to ensure that those treatments do not harm the patient's health or quality of life, however.
And in cases where the patient's condition is curable, doctors are likely to be more assertive.
"If there is a useful conventional treatment that is out there, then our responsibility is to try to have a discussion to encourage them to use treatments that we know are going to help them," said Cohen. "They can do that alongside some of the nonconventional treatments. That's something that can be done safely as long as we have information about the nonconventional treatment."
What's very uncommon is that a patient receives alternative treatment in place of conventional treatment," Cohen explained.
In some cases, doctors believe, the desire for an alternative therapy may be more a fear of chemotherapy than the belief in the alternatives.
"[There's] just a real aversion to taking something people see as toxic and dangerous," said Dr. Mary Hardy, medical director of the Simms/Mann -- UCLA Center for Integrative Medicine, part of UCLA's Jonsson Comprehensive Cancer Center. "You can't argue that these are really strong medicines. Sometimes people have a very negative bias against chemotherapy, sometimes warranted, sometimes not."