People receiving treatment for serious cancers may harbor false hopes for a full recovery, according to a recent study.

81 percent of people with advanced colorectal cancer, and 69 percent of people with advanced lung cancer believe chemotherapy treatment can cure them, say researchers from the Dana-Farber Cancer Institute.

After surveying more than 1,200 people with end-stage cancer, study authors found only a small number of people who didn't subscribe to the myth of chemotherapy as a cure-all.

Chemotherapy can give a person with advanced cancer a few more weeks or months of life and it may offer them some pain relief. But, the likelihood of long-term survival—let alone a cure—in the later stages of these diseases is exceedingly rare.

According to figures from the American Cancer Society, only about six percent of people with late-stage colon or rectal cancer live for at least five more years. For lung cancer, that number is about four percent.

Chemotherapy isn't always ineffective—it can be an extremely helpful treatment. When a person's cancer is caught in the earlier stages, chemotherapy often succeeds in sending the disease into remission.

Optimism can be a valuable tool for coping with a difficult diagnosis, but misplaced faith in the power of medical intervention may prevent a senior from choosing the treatment path that's best for them.

Chemotherapy is just one of several different types of cancer treatment. Other options include: surgery to remove malignant organs and tissues, radiation therapy, targeted therapy, immunotherapy and hyperthermia.

Those with terminal cancer may also decide to forgo additional treatment for their condition, and elect to only receive palliative or hospice care.

In an editorial accompanying the Dana Farber study, Thomas Smith, M.D., professor of oncology and director of Palliative Medicine at Johns Hopkins, voiced his concerns that doctors often shy away from discussions about end-of-life planning and palliative care because doing so could steal a patient's hope.

"What they don't realize is that hope is impossible to extinguish," he says. Smith feels that, no matter what the prognosis is, "Palliative care discussions can help patients focus on better quality of life."

An elder's ability to benefit from these different treatment routes will depend on a variety of factors, such as the type of cancer they have and how advanced it is, as well as their age and overall health.

Having so many different options means it's critical that cancer-stricken seniors and their caregivers fully understand the variety of individual factors involved in a treatment decision—including how effective a particular therapy is likely to be.

Browse Our Free Senior Care Guides

"If patients do not know whether a treatment offers a realistic possibility of cure, their ability to make informed treatment decisions that are consistent with their preferences may be compromised," says lead study author, Jane Weeks, M.D., in a press release, "This misunderstanding may pose obstacles to optimal end-of-life planning."

It's important for caregivers and seniors to engage in honest, open discussions with their doctor regarding personal preferences and care goals before starting any type of treatment plan.

For more information on how to have these kinds of conversations, and why they are important, see:

Knowing a Senior's Goals and Values Makes Health Decisions Easier

How to Talk to Your Doctor: A Guide for Caregivers and Elders