A practical approach to pulmonary risk assessment in the radiotherapy of lung cancer

https://doi.org/10.1016/j.semradonc.2004.06.004Get rights and content

The risk of lung injury is a significant limiting factor in the use of thoracic radiotherapy for lung cancer. Given the high mortality and local failure rates in patients with unresectable lung cancer, a goal has been to increase the dose to the tumor as much as possible while trying to limit the damage to normal tissue. Efforts have been made to predict the risks for lung injury pretreatment, based on the planned dose and volume of lung treated, with mixed results. Complicating factors include performance status, underlying medical conditions, possible genetic predisposition to injury, and tumor location-associated changes in lung function. Much as a thoracic surgeon stratifies a patient’s risk for pulmonary morbidity before resection, radiation oncologists should perform an assessment of patient specific factors that will impact on the potential toxicity of a given course of treatment. We present a proposed approach to the evaluation, risk assessment, and follow-up of patients treated with thoracic radiotherapy for lung cancer.

Section snippets

Pretreatment evaluation

Because no two patients are the same; individualized evaluation is critical. A thorough history and physical examination should be performed with particular emphasis to exercise capacity, preexisting cardiopulmonary conditions, smoking history, performance status, active respiratory tract infection, bronchospasm, and fluid overload. CT scanning of the thorax is typically performed as part of the staging process and should also be reviewed for evidence of emphysema, fibrosis, pleural effusion,

Optimization

After the initial evaluation, it is important to treat any reversible processes, such as bronchospasm, infection, ischemic heart disease or pulmonary embolic. There may be circumstances where such treatment could render a medically inoperable patient operable. Lifestyle changes, such as smoking cessation and regular exercise, should be encouraged. In any event, the patient’s ability to tolerate radical RT/CHT is much likely to be greater with an optimized medical condition.

Risk assessment before surgery

Radiation oncologists can learn about pulmonary toxicity risk assessment from surgical data, as lung resection may be considered the ultimate local toxicity. Much of the data are anecdotal and retrospective, accumulated during the last 50 years. Nonetheless, given the number of patients treated, there is a great volume of information and experience.

A model of a typical algorithm for selection of patients suitable for lung resection is shown in Fig 1.20, 21, 22 Assessment of operability is

Risk assessment before RT

Because surgical predictors for postresection functional changes are suboptimal, it should come as no surprise that predictions of RT-toxicity/functional changes are even less accurate. Surgical resection respects anatomic boundaries, while RT fields do not. The areas of lung impacted by RT are not typically defined by anatomic units, as with surgery.

Surgery is, thus, an all-or-nothing modality; a portion of lung is either resected or not. RT-induced lung injury is more complex. Regional

Predictors of RT-induced lung injury

The quality of prediction is likely to be related to the endpoints chosen-ie, radiographic changes, symptoms—therefore it is important to decide what is called “lung injury.” The potential outcomes in patients can be divided into subclinical (ie, asymptomatic, but measurable) versus clinical (symptomatic). Likewise, these parameters can be subdivided into partial organ or whole organ effects (Table 4). Subclinical alterations are more likely to become manifest the longer the patient lives, due

Conclusions

Optimizing radiation therapy efficacy, while minimizing toxicity, is a complex process in the treatment of patients with lung cancer. We have presented an approach to risk assessment in patients with lung cancer based on the data currently available. It is our hope that with prospective observation, added information from clinical trials, the addition of new cytoprotectors and treatment delivery techniques, the proposed assessment algorithm can be improved.

Acknowledgments

Supported in part by NIH grants CA69579. Jane Hoppenworth for assistance with the manuscript preparation.

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