Cancer is a major public health concern globally. It is the most frequent cause of death in economically developed countries . Among all cancers, lung cancer is the leading cause of cancer deaths worldwide . In the United States, approximately 221,130 new cases of lung cancer (14% of all cancer diagnoses) are expected in 2011 out of which 156,940 deaths (27% of cancer deaths) are estimated due to lung cancer . Given the incurable nature of lung cancer, it is considered a terminal illness with a five-year survival rate of approximately 16% .
Patients diagnosed with terminal illness such as lung cancer confront several decisions related to management of the disease. Opting for treatment (for example, chemotherapy, radiotherapy, or surgery) instead of palliation, or vice versa, is one such critical decision. Depending on the stage of the disease, potential benefits of anticancer therapy intended to palliate specific tumor-related symptoms may be at the expense of treatment-related harms and the inconvenience associated with undergoing treatment. At other times, palliative care (for example, pain medications or low dose radiotherapy)  rather than anticancer therapy may be preferable. Informed decision-making related to the management of a terminal disease thus requires accurate prognosis of the disease with or without treatment.
Briefly, prognosis refers to the likelihood of an individual developing a particular health outcome over a given period of time, based on the individual’s clinical and non-clinical profile . Accurate assessment of prognosis is key to informed decision-making. For example, if a patient is diagnosed with a terminal illness such as lung cancer, a prognostic question of critical concern to the patient, family, and the physician is how long the patient is expected to live. Other important outcomes may include disease progression, health-related quality of life, and treatment-related harms. Reliable prognostication of life expectancy can prevent subjecting patients to costly and unnecessary treatment for an unduly long period before transitioning to hospice care . This in turn can help patients and their families prepare for the impending events and plan for the patient’s remaining lifespan . Accurate prognostic information can also help physicians decide on choice of curative versus palliative treatments. For instance, if evidence shows no effect of curative treatment on disease progression, significant treatment-related harms can be avoided in favor of palliative treatments . It can help investigators avoid optimism bias, the ‘unwarranted belief in the efficacy of new therapies’  or making ‘overly optimistic assumptions regarding treatment benefits when designing RCTs’ . Accurate disease prognosis thus underpins all management decisions related to the disease, including choice of treatment, planning of supportive care, as well as allocation of resources.
Despite the significance of disease prognosis in clinical decision-making, systematic assessment of prognosis in patients with lung cancer without treatment has not been performed. We are aware of only one narrative review on the subject [4, 10]. Accordingly, this systematic review was undertaken to assess the survival of patients with a confirmed diagnosis of lung cancer without active treatment. Specifically, our aim was to estimate overall survival in lung cancer when no anticancer therapy is provided.