Cancer has a reputation as a deadly disease. Taken as a whole, about half of patients receiving treatment for invasive cancer (excluding carcinoma in situ and non-melanoma skin cancers) die from cancer or its treatment. However, the survival rates vary dramatically by type of cancer, with the range running from basically all patients surviving to almost no patients surviving.

Patients who receive a long-term remission or permanent cure may have physical and emotional complications from the disease and its treatment. Surgery may have amputated body parts or removed internal organs, or the cancer may have damaged delicate structures, like the part of the ear that is responsible for the sense of balance; in some cases, this requires extensive physical rehabilitation or occupational therapy so that the patient can walk or engage in other activities of daily living. Chemo brain is a usually short-term cognitive impairment associated with some treatments. Cancer-related fatigue usually resolves shortly after the end of treatment, but may be lifelong. Cancer-related pain may require ongoing treatment. Younger patients may be unable to have children. Some patients may be anxious or psychologically traumatized as a result of their experience of the diagnosis or treatment.

Survivors generally need to have regular medical screenings to ensure that the cancer has not returned, to manage any ongoing cancer-related conditions, and to screen for new cancers. Cancer survivors, even when permanently cured of the first cancer, have approximately double the normal risk of developing another primary cancer. Some advocates have promoted "survivor care plans"—written documents detailing the diagnosis, all previous treatment, and all recommended cancer screening and other care requirements for the future—as a way of organizing the extensive medical information that survivors and their future healthcare providers need.

Progressive and disseminated malignant disease harms the cancer patient's quality of life, and some cancer treatments, including common forms of chemotherapy, have severe side effects. In the advanced stages of cancer, many patients need extensive care, affecting family members and friends. Palliative care aims to improve the patient's immediate quality of life, regardless of whether further treatment is undertaken.Hospice programs assist patients similarly, especially when a terminally ill patient has rejected further treatment aimed at curing the cancer. Both styles of service offer home health nursing and respite care.

Predicting either short-term or long-term survival is difficult and depends on many factors. The most important factors are the particular kind of cancer and the patient's age and overall health. Medically frail patients with many comorbidities have lower survival rates than otherwise healthy patients. A centenarian is unlikely to survive for five years even if the treatment is successful. Patients who report a higher quality of life tend to survive longer.^[97] People with lower quality of life may be affected by major depressive disorder and other complications from cancer treatment and/or disease progression that both impairs their quality of life and reduces their quantity of life. Additionally, patients with worse prognoses may be depressed or report a lower quality of life directly because they correctly perceive that their condition is likely to be fatal.

In the developed world, one in three people will be diagnosed with invasive cancer during their lifetimes. If all people with cancer survived and cancer occurred randomly, the lifetime odds of developing a second primary cancer would be one in nine.^[98] However, cancer survivors have an increased risk of developing a second primary cancer, and the odds are about two in nine.^[98] About half of these second primaries can be attributed to the normal one-in-nine risk associated with random chance.^[98] The increased risk is believed to be primarily due to the same risk factors that produced the first cancer (such as the person's genetic profile, alcohol and tobacco use, obesity, and environmental exposures), and partly due to the treatment for the first cancer, which typically includes mutagenic chemotherapeutic drugs or radiation.^[98] Cancer survivors may also be more likely to comply with recommended screening, and thus may be more likely than average to detect cancers.^[98]

Despite strong social pressure to maintain an upbeat, optimistic attitude or act like a determined "fighter" to "win the battle", personality traits have no connection to survival.^[99]