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."
Hardy said many patients may be opposed to chemotherapy if they know someone who had taken the last generation of chemotherapy drugs, which tended to have harsher side effects than current treatments. And others have different reasons.
"For a lot of people it's just denial -- 'I'm just not that sick,'" said Hardy. "You have to pick through which of the issues is driving this decision to address the issue that's really there," she said. "If you don't address those issues, you can't do any treatment planning."
She noted that in some cases the fear may be driven by the length of the treatment, which might explain why some people avoid chemotherapy or follow-up treatment, but are willing to undergo surgery.
Dr. David Gorski, a surgical oncologist at Wayne State University, said that while medical oncologists may have to convince patients to use conventional medical treatments, the patients rarely decline surgery.
"I can only recall maybe once or twice in the past 10 years where somebody refused surgery," he said. "I don't know what it is about surgery, but I can almost always persuade patients at least to let me take the tumor out."
But while some patients may shun conventional therapies, doctors say some can be convinced to use them if their fears are understood.
Anne Coscarelli, director of the Simms/Mann -- UCLA Center for Integrative Oncology, said she recalls this type of patient, a mother of young children, who was worried about the possible "unnatural" changes to her body.
"I listened to her about what she was saying," Coscarelli said. "After listening to her, I was able to reframe it."
Coscarelli recalls she told the mother, "Your natural body actually created something, and that's the cancer. I wonder if doing something that disrupts the natural order of your body might actually be a better choice for you."
She said the patient took the therapy.
In Grace's case, her concern about her mother's alternatives is that they are unproven and seem dangerous. Many of her mother's diets have been to remove folic acid from her body.
Grace also worries that her mother's diet has led to a cognitive decline. Her mother recently had to transfer to a less demanding job.
"Cognitive decline has been reported and is not rare [in breast cancer cases] -- but every patient doesn't have the same level of difficulty," said Hardy. "Folic acid is needed for cognitive function. I am not sure why she is on a low folic acid diet -- that part doesn't really make sense to me."
Grace said if her mother followed her advice, she would do things differently.
"The first thing is to get in contact with her cancer doctor and have her see a nutritionist he suggests," she said. "He's got a medical degree for a reason. This chiropractor -- he's always suggesting off the wall stuff that I don't even think he should have a profession."
Gorski noted that while Grace's mother has forgone treatment, it might not mean her cancer will recur -- particularly since she took tamoxifen for the first two years.
"She's already gotten some of the benefit from it. She may already have gotten most of the benefit for it," he said, explaining that patients who stick with tamoxifen reduce the risk of recurrence by about 50 percent. "I wouldn't advise it, I'd advise her to finish the whole course, but she's probably reduced her risk of recurrence some already."
Gorski said he believes that many unproven alternative treatments exist in breast cancer because the course of the disease can be very different in different people.
"The aggressiveness of breast cancer can be incredibly variable, ranging from very rapid growth to percolating along for years on end," he said.
He also said that the mother's cancer has already been removed, with the tamoxifen serving as an adjuvant therapy -- designed to prevent recurrence rather than cure the disease -- and so, the outlook may be positive even with unproven treatments.
As a physician who hears requests from breast cancer patients for alternative therapies, Dr. Marisa Weiss, founder of breastcancer.org, said the key is understanding patient concerns and not losing dialogue, even if the patient chooses an unproven route.
"Basically, I would say to them, clearly you've made this choice to do alternative medicine, and I believe I've told you everything I can based on these studies and experience. I can't force you to do it, but let's choose a time to re-evaluate," said Weiss.
She said while a patient might ignore a doctor's advice, keeping the dialogue preserves the relationship in the event the patient changes their mind and chooses to go with conventional therapy.
Coscarelli notes that something similar holds true for families of patients who shun conventional medicine.
"I think it's sometimes really hard to allow people to make their own decisions when you disagree with them," she said, noting that she has seen these conflicts in her work, between relatives and spouses.
"There's a lot of appraisal that goes on for individuals, said Coscarelli. "This daughter and mother have a real conflict in belief systems, and ultimately the mother gets to make the decision about her own body. The important thing would be to not let the decision deteriorate their relationship. There's a limit to what the daughter can do."
She recommended that someone in Grace's situation can try and provide education, probably by having her mother speak with someone who is "bilingual," versed in both Western and alternative medicine methods.
But ultimately, the decision will be out of Grace's hands.
"Ultimately, this mom's going to determine her own treatment, and the daughter's going to need to be able to accept that," said Coscarelli.