Background and objectives: Current estimates of the proportion of cancer patients who will require radiotherapy (RT) are based almost entirely on expert opinion. The objective of this study was to use an evidence-based approach to estimate the proportion of incident cases of lung cancer that will require RT at any point in the evolution of the illness.
Methods: A systematic review of the literature was undertaken to identify indications for RT for lung cancer, and to ascertain the level of evidence that supported each indication. An epidemiologic approach was then used to estimate the incidence of each indication for RT in a typical North American population of lung cancer patients. The effect of sampling error on the estimated appropriate rate of RT was calculated mathematically, and the effect of systematic error, was estimated by sensitivity analysis.
Results: It was shown that 53.6% +/- 3.3% of small-cell lung cancer (SCLC) cases develop one or more indications for RT at some point in the course of the illness, 45.4% +/- 4.3% in their initial treatment, and 8.2% +/- 1.5% later for recurrence of progression. Overall, 64.3% +/- 4.7% of non-small-cell lung cancer (NSCLC) cases require RT, 45.9% +/- 4.3% in their initial treatment, and 18.3% +/- 1.8% later in the course of the illness. The proportion of NSCLC cases that ever require RT is stage dependent; 41.0% +/- 5.5% in Stage I; 54.5% +/- 6.5% in Stage II; 83.5% +/- 10.6% in Stage III; and 65.7% +/- 7.6% in Stage IV. In total, 61.0% +/- 3.9% of all patients with lung cancer will develop one or more indications for RT at some point in the illness, 44.6% +/- 3.6% in their initial treatment, and 16.5% +/- 1.5% later for recurrence or progression.
Conclusion: This method provides a rational starting point for the long-term planning of radiation services, and for the audit of access to RT at the population level. We now plan to extend this study to the other major cancer sites to enable us to estimate the appropriate RT treatment rate for the cancer population as a whole.