How Does Cancer Actually Kill You?

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Cancer does not always cause death, but it is estimated that more than 600,000 people will die of cancer in the United States in 2021.

Cancer prognosis can depend greatly on the stage of cancer, with terminal cancer being one that cannot be cured or treated. It’s sometimes also called end-stage cancer. Any type of cancer can become terminal cancer.

When cancer is found early, it is easier to treat and more likely to end with a full recovery. Many times a cancer detected early can be cured by a surgical procedure and possibly some follow-up chemotherapy.

Asian woman in 60s embracing her mid-30s daughter who is fighting cancer and is wearing a headcovering. They are seated on a couch and have contemplative expressions.

FatCamera / Getty Images 

How Cancer Causes Death

Even though cancer can lead to death, it's not necessarily cancer that causes someone to die. Causes of cancer deaths can include:

  • Organ failure due to the size and stress of a tumor
  • Complications during surgery
  • Organ rupture due to tumor size
  • Infection due to the immune system's ability to fight off illness while on cancer treatment

Since all the organs in our body connect one way or another, all it takes is for one to begin shutting down, and the rest may start to follow suit. In the end, the person with cancer passes away.

Depending on the type of cancer, the cause of death can vary. Here are some more details on how cancer can cause death.

Bones

Malignant hypercalcemia is one of the more common disorders found in patients with advanced-stage cancer, affecting up to 44% of patients.

As cancer advances, some of the cancer cells find a way into the bloodstream. When this happens, these cancer cells can easily travel throughout the entire body. Many patients with advanced-stage cancers will experience malignant hypercalcemia because a high amount of blood flow runs through our bone marrow every day. This high level of blood flow gives cancer cells easy access to our bones.

Once the cancer cell finds a place in the bone marrow to set up camp, it multiplies and invades the healthy bone marrow.

Malignant hypercalcemia symptoms can be vague, but a quick blood test to check calcium levels will help your medical team diagnose and treat this condition.

However, hypercalcemia does not also result in significant spread of cancer to the bones. Another primary mechanism of hypercalcemia in patients with advanced cancer is paraneoplastic syndrome, which is related to the production of the parathyroid hormone related peptide (PTHrp). In this case, hypercalcemia does not cause significant spread to the bones.

Brain

Brain herniation is a common occurrence for those who have cancer. Brain herniation is possible both with cancer originating in the brain or cancer which has spread to the brain.

Brain herniation happens when the brain runs out of room inside the skull and tries to find a way to make room by finding folds or openings with available space.

While a brain herniation can happen for many reasons, it's more than likely due to cancer growth inside the brain when someone has cancer.

The most common brain herniation symptoms are:

  • Severe headaches
  • High blood pressure
  • Irregular pulse
  • Heart attack
  • Slipping into a coma
  • Loss of reflexes like blinking, swallowing, pupils reacting to light

Breast

Two of the leading causes of death for those with breast cancer are:

Both of these conditions come from blood clots.

Since one of the many things tumors do is secrete a substance that increases your blood's ability to clot, your risk for life-threatening blood clots increases. One study found women with breast cancer have three to four times the increased risk of a deadly blood clot than women without cancer.

The danger with blood clots isn't merely their existence; it's what happens when these clots dislodge from where they form.

Since blood flows throughout your entire body and isn't assigned to stay in one small area, these clots may start in your calf. However, they may end up getting stuck in another part of your body, like your brain or lungs. When the blood clot gets lodged in one of these areas, blood flow gets cut off, and the result can be deadly.

Symptoms of a blood clot include:

  • Pain
  • Swelling
  • Tightness
  • Redness
  • Warmth in your leg

If you experience any of these symptoms, it's essential to contact your healthcare provider immediately. 

Blood clots can occur in many other types of advanced cancers. They are not exclusively an issue for people with breast cancer.

Cervical/Vaginal

Like breast cancer, cervical cancer also increases the risk for blood clots.

There's also a risk for a tumor in this area to block the ureter, causing a backup of urine—similar to having a kink in a garden hose.

This blockage also plays into the risk for a condition called uremia. Uremia happens when kidneys stop filtering waste from the body properly, and therefore, it backs up into the bloodstream. When this happens, your body is typically in the final stages of kidney failure.

Uremia cannot be reversed without dialysis or a kidney transplant.

Gastrointestinal Tract

With cancer or tumors inside the abdominal region, there's a risk of them growing so large they obstruct the flow of waste through vital organs such as the intestines Or, these tumors can grow through the wall of the bowel or stomach, causing a hole that allows the contents to spill into the intestinal cavity, which can cause severe infection.

In both cases, there is a significant risk for infection, especially for those with colorectal cancer. 

Lungs

For those with cancer, there is an increased chance of respiratory failure. In fact, respiratory failure is one of the main reasons someone is admitted to an intensive care unit (ICU) and is one of the leading causes of death for those with cancer.

Since cancer treatments often impair the body's immune system, infections are easier to acquire.

While there are many causes for respiratory failure, when it comes to someone with cancer, pneumonia is the most common reason. 

How End-Stage Is Diagnosed

Diagnosing anything as end-stage involves more than a simple glance at the information in the chart. In general, there are two different scores—or risk assessments—considered in an end-stage diagnosis. These include:

  • Karnofsky Performance Scale: This gives a score between 0 and 100, identifying whether the body is functioning normally or if the normal function is impaired. A person without any medical concerns will receive a 100. When a provider signals a score below 30—which identifies their patient as requiring special assistance—insurance will begin to cover at-home nursing or hospice care.
  • Palliative Prognosis Score: This looks less at the objective state a person is in and is more about the statistics. They'll be looking for symptoms such as lack of hunger along with the presence of white blood cells and lymphocytes. The Palliative Prognosis Score goal is to measure the patient's physical status while participating in a palliative care program.

Both the Karnofsky Performance and Palliative Prognosis Scores help guide the medical staff and family through options for:

  • Treatments
  • Care goals
  • Discussing end-of-life arrangements

While these scores might help narrow down an expected time frame, they are simply estimates. What might be three months on paper could quickly become two weeks, while one month may turn into six months.

While science can provide us a lot of information on when to expect death, it is still nothing more than an estimate.

What to Expect

When facing the final weeks and days of cancer, each person's experience is different. Since each experience is different, it's difficult to give an exact checklist of signs, symptoms, or experiences to expect.

Some people find comfort in sharing their feelings and what they are experiencing with those close to them. Others find it too difficult to discuss and would rather avoid the topic altogether. Since this is such a personal decision, it's helpful when people are upfront about their wish to discuss or avoid this topic. When those around know what someone wants, it's easier for them to provide support through this transition.

Many people find comfort in knowing they will likely become unconscious before they die. Therefore, they will not be aware of what is going on—very similar to falling asleep and not hearing the alarm go off.

One of the key signs of death approaching is an increase in sleeping and feeling weak.

There will be moments where they have their eyes closed and don't seem to be responding. Even though their eyes are closed doesn't mean they can't hear you. Many studies show hearing might be the last sense to be lost.

It's important to continue talking to your loved ones, give them comforting words, and remember to tell them when you leave or enter the room.

There are also breathing changes, along with a loss of bowel and bladder control coming from the body, allowing muscles that don't usually relax to relax. If they are at home receiving care through hospice, the hospice nurse has ways to protect the bed and also keep your loved one clean and comfortable.

As the body begins the natural process of dying, there are a lot of physical changes. While it can be distressing to watch these changes happen, it doesn't mean your loved one is in distress or pain.

Many times, when someone is dying, the people around them have reasonable concerns about their loved one's comfort. While the nurses and healthcare providers will do their best to make them comfortable, it's a good idea to let them know if your loved one seems more restless than usual, as this can be a sign of discomfort. The medical provider can consider changing the treatment plan.

Eventually, a time will come when the dying person will not want to eat or drink.

Trying to force them to eat or drink will only create distress and make the transition harder. You can try giving them small pieces of ice or small sips of fluids if they are thirsty or their mouth is dry. Some people also seem to find comfort in having lip balm put on their dry lips or having a swab of water around their lips. 

When someone is dying, the heart's pumping becomes weaker, so the circulation is reduced to extremities like hands, arms, legs, and feet. This causes the dying person to feel cold to the touch.

You can keep them warm with thick socks or blankets—but not a heated blanket. Heated blankets can cause them to overheat or burn them if faulty. Since they often can't express their thoughts clearly, they likely cannot tell you if the blanket is getting too hot.

As someone with cancer gets closer to death, they will often say things that make no sense or are completely out of character for them.

They may start yelling or pushing you away, which can be difficult on you and anyone on the receiving end of this unusual behavior. Remember, this behavior isn't about you. It is merely part of the process. They are unaware they are acting out of character because the body's chemistry is out of balance.

As someone gets closer to the end, the more unbalanced the chemicals in the body become. This is usually a few hours or days before death. At this point, breathing becomes irregular, sometimes noisy, and they are unable to wake up at all.

A Word From Verywell

Cancer is a difficult diagnosis to process for both the patient and their family. If you're going through this challenging time, remember to create some time for self-care. Reach out to a counselor, therapist, or mental health professional to help you cope with the anxiety, depression, stress, and grief you will experience.

Helping a loved one through the end of life can take a toll on your well-being, even in the most ideal of situations. Asking for help from a palliative care program, hiring an at-home nurse, or getting hospice involved is always a good idea. Having a professional available to answer questions and assure you everything is as OK as possible is helpful. 

It's also helpful to surround yourself with a group of friends or loved ones who can be your personal support team through this time. These are people who will help you laugh when you need some comic relief, but they also let you cry on their shoulder during the tough times. They are the ones who will remind you to eat, offer to run errands, and sit in silence with you so that you know you're not alone. Having a few good people around you during this time will help ease the stress and allow you to go through the grief process.

Ultimately, it's important to remember you don't have to keep it all together all the time. You don't need to have all the answers, and you don't need to handle this situation correctly. When things get bumpy, allow yourself some grace and remind yourself you're doing the best you can.

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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. The American Cancer Society. Facts & figures 2021 report. Updated January 12, 2021.

  2. Kim SH, Shin DW, Kim SY, et al. Terminal versus advanced cancer: do the general population and health care professionals share a common language? Cancer Res Treat. 2016;48(2):759-767. doi:10.4143/crt.2015.124

  3. Mirrakhimov AE. Hypercalcemia of malignancy: an update on pathogenesis and managementN Am J Med Sci. 2015;7(11):483-493. doi:10.4103/1947-2714.170600

  4. Walker AJ, West J, Card TR, Crooks C, Kirwan CC, Grainge MJ. When are breast cancer patients at highest risk of venous thromboembolism? A cohort study using English health care data. Blood. 2016;127(7):849-857. doi:10.1182/blood-2015-01-625582

  5. Riihimäki M, Thomsen H, Sundquist K, Hemminki K. Colorectal cancer patients: what do they die of? Frontline Gastroenterol. 2012;3(3):143-149. doi:10.1136/flgastro-2012-100141

  6. Sears SP, Carr G, Bime C. Acute and chronic respiratory failure in cancer patients. Oncologic Critical Care. Published online July 9, 2019:445-475. doi:10.1007/978-3-319-74588-6_43