“Your cancer has come back.”

These are words no one treated for cancer wants to hear, yet they are words I have said far too often in my own career. In this case, I had said this to a patient I had cared for ever since her initial diagnosis. At that time, she had stage III breast cancer. After her surgery, she took the chemotherapy I recommended and then the endocrine therapy. Things seemed to be going so well.

I looked into her eyes, expecting to see fear and sadness. Instead, she met my gaze with curious resignation, wanting to know more and what we were going to do.

“Although it’s back, it isn’t involving any major organs; it’s metastasized to your bones. The goal will be to treat your cancer, but not diminish your quality of life. It’s not curable, but it’s definitely treatable. You can live with this — for years.”

She appeared more hopeful after this and responded, “Sounds like a plan!”

That was three years ago. She remained on the same treatment, tolerated the side effects, and the cancer had indeed stayed where it was: no signs of progression.

She came to see me recently in follow-up; she looked wonderful and felt well. Her exam and her labs were excellent. “You look great,” I said to her. “Why don’t we see each other again in three months, unless, of course, something comes up or you get worried.” She looked troubled. “Is there something you want to ask me?” I said.

“Yes,” she replied. “ My primary care doctor recommended a colonoscopy. He said I should be screened for colon cancer, and that sort of freaked me out. I don’t think I could handle being diagnosed with another cancer. And if I don’t have to, I really don’t want to have this test. What do you think?”

I was unsure. She has metastatic breast cancer and our goal continues to be maximizing her quality of life and stabilizing her cancer, knowing that cure was not possible, even with more aggressive treatment. Our approach represents a “less is more” program to cancer care. I see her infrequently, monitor her symptoms, and order occasional blood work or scans. Although I know a colonoscopy is not a major procedure, it requires anesthesia, prep time, and can be uncomfortable. In addition, there are co-pays to consider, and then the big what-if: what if something is found, would she need more tests, more procedures, even surgery? It all seemed to contradict our approach to the disease she already has — and always will.

Yet — I know early detection saves lives, and this is true with colonoscopy, and this was the dilemma she now faced. Was not going through with a colonoscopy smart? Yes she has metastatic breast cancer, but I keep telling her, her prognosis is good. Shouldn’t finding early colon cancer be a priority in her own life? And then, what if she didn’t undergo screening and died of colon cancer, not her breast cancer? Certainly, screening would have made sense after the fact. Perhaps most troubling to her (and to me) was this: would advising against a colonoscopy be a tacit signal that I had given up on her, and perhaps, she on herself?

U.S. health care guidelines recommend routine health maintenance to increase early diagnosis of disease and prevent suffering. In general, prevention measures should be offered to patients who are otherwise well because they are also most likely to benefit, in terms of maintenance of current quality of life, productivity, and well-being. However, it remains unclear how (or if) we should offer the same recommendations to patients living with advanced or metastatic cancer.

The magnitude of this issue is likely significant. The American Cancer Society estimates that approximately 14 million Americans with a history of cancer alive in the United States alone. However, not all of those with a history of cancer are cancer-free. Estimates are that the proportion of patients living with metastatic disease is not small. For patients with breast cancer, the Metastatic Breast Cancer Network estimates that up to 150,000 of the approximately 2.9 million survivors are estimated to be living with metastatic disease today.

So, how do we approach preventative medicine in these patients? The answer is made even more complicated by the recognition that patients with metastatic disease constitute a heterogeneous group, both biologically and prognostically. Some may have a biologically slow-growing cancer and may live for years. For others, cancer is a biologically more aggressive entity, and time will be measured in weeks or months.

Thus far, the limited data come from studies that have evaluated the frequency of primary screening in those approaching a more terminal phase of their illness. For example, in a 2010 study from the Surveillance, Epidemiology and End-Results (SEER) cancer registry was used to identify over 87,000 patients 65 years and older diagnosed with late-stage colorectal, breast, gastroesophageal, and advanced stage pancreatic cancers. Among women, the rate of screening mammography was 9% and Pap tests was 5.8%. Almost 20% of all patients underwent cholesterol screening, and 2% underwent endoscopy. While these data suggest that screening continues to be performed in patients with metastatic or advanced disease, its relevance to the larger population of patients living with cancer as a more chronic condition is not clear, particularly because their study selected an older patient population with a relatively poor prognosis.

The situation my patient faced is not uncommon, which is illustrated by Katherine O’Brien. Katherine was in her forties when she was diagnosed with stage IV breast cancer, metastatic to her bones, and now five years later she lives with the knowledge that her cancer is incurable. She recalls recently having a discussion about whether to undergo a colonoscopy, a discussion prompted by her primary care doctor. “I privately told myself, I know I have metastatic breast cancer, so why would I bother with yet another test?” O’Brien says empathy guides some oncologists’ counsel. “Some say it’s almost a kindness to the patient: ‘You have to do all these tests and doctors’ appointments, I’m not going to add this on top of them.’”

So, did she have it? “Well, I was having issues, and I wanted to figure out what was happening, so yeah, I chose to do it.”

But she notes these dilemmas extend to other screening considerations. “I had a unilateral mastectomy and I am going through scans every four to five months, and I’ve decided I’m not doing mammograms too. But I have to say, when I get those annual reminders that I am due for a mammogram it irritates me, and it’s an issue for women with metastatic breast cancer. There’s a bitterness because I’d love to have the chance NOT to have metastatic breast cancer, but I do. Early detection is not going to help me. It’s literally a reminder of something I don’t have (my breast) and a future I won’t have (because of metastatic breast cancer).”

For some patients, life with cancer as a more chronic condition is becoming a reality. Still, the possibility that their lives will end due to their index cancer is also never far away. What role should primary prevention play in their care? Beyond the detection of new disease, we must consider whether our actions now will indeed impact outcomes — whether they be psychological, physical, or fiscal. But where is the evidence for good decision-making?

We need higher-quality data to help balance our patients’ individual goals and preferences. Therefore, I am partnering with Consano.org to evaluate this question more fully. We’ll be working together to crowdfund this question so that those directly impacted can also participate in conducting the research itself. It will give me a new way to conduct and collaborate with advocates and patients directly.

Until then, we need to acknowledge that there is no best practice on the role of primary prevention for patients living with advanced or metastatic disease. For my patient, we decided not to proceed. It was not a data-driven decision, but a leap of faith — that life would only hand her one lemon at a time.

Don S. Dizon is an oncologist who blogs at ASCO Connection, where this post originally appeared.