The effects of radiation therapy, chemotherapy and the radioprotector amifostine on the diffusion capacity of patients with non-small cell lung cancer (NSCLC)

Radioprotectants: Adding Quality of Life to Survivorship?

OBJECTIVES

To explore the use of radioprotectants in oncology and their affect on quality of life (QOL).

DATA SOURCES

Textbooks, manuals, and journals in radiation oncology and cancer nursing.

CONCLUSION

Many studies have shown that the use of amifostine has decreased the intensity and severity of treatment-related side effects as well as improving QOL. However, more research is needed in the development of newer agents and refining older agents.

IMPLICATIONS FOR NURSING PRACTICE

With the advent of combined modality treatments, overall response and survival benefit has increased as well as enhanced toxicities affecting one's QOL. Agents such as radioprotectants and advances in supportive care have assisted in minimizing treatment-related side effects. Strides toward providing quality, compassionate care remain the goal of oncology nurses, while enhancing the QOL for cancer patients.

Pulmonary toxicity associated with the treatment of non-small cell lung cancer and the effects of cytoprotective strategies

Concurrent chemoradiation regimens for the treatment of non-small cell lung cancer have resulted in improved treatment outcomes. However, they are also more toxic. Acute esophagitis and pneumonitis are experienced by a large number of treated patients. Cytoprotective agents are used to reduce treatment-related toxicity. The cytoprotectant amifostine has been shown to reduce some of the toxicity associated with concurrent chemoradiation. Clinical studies of its role in reducing esophagitis and radiation pneumonitis are discussed. Lung irradiation also leads to a reduction in lung diffusion capacity (DLCO). The magnitude of this reduction is related to the volume of lung irradiated as well as to the use and timing of chemotherapy. Concurrent chemoradiation regimens result in a larger reduction in DLCO than radiation alone. Small changes in DLCO can be detected with sensitive pulmonary function tests, but are subclinical. Larger reductions in DLCO correlate with significant clinical symptoms. Preliminary data show that amifostine can significantly decrease the treatment-related reduction in DLCO associated with concurrent chemoradiation (42% v 24%; P = .004). Additional studies are being designed to verify these results and to further define the evolving role of cytoprotection in cancer care.

The relationship between local dose and loss of function for irradiated lung

PURPOSE

To determine the relationship between the local radiation dose and the decrease in lung function associated with thoracic irradiation.

PATIENTS AND METHODS

Twenty-six patients treated with thoracic irradiation for lung cancer, for whom three-dimensional CT-based dosimetry was used in treatment planning, were evaluated with before and after treatment pulmonary function tests. Six patients were treated with radiotherapy alone (2.15 Gy daily fractions), and 20 patients with concurrent chemotherapy (cisplatin, etoposide) with hyperfractionated (HF) radiation therapy (1.2 Gy in twice-daily fractions). Eleven patients treated with concurrent HF chemoradiation also received the radioprotector amifostine. The normalized decrease in the diffusing capacity for carbon monoxide (DL(CO)) was used as an objective measure of the change in lung function. The dose-volume histogram (DVH) data were used to estimate the local dose-response relationship for loss of DL(CO). In each subvolume of lung, the loss in normalized DL(CO) was assumed to be a sigmoid function of dose, ranging from no loss at low doses to total loss at high doses. The whole-lung decrease in DL(CO) was modeled as the sum of the local declines in DL(CO) over all subvolumes. Nonlinear regression analysis was used to estimate the parameters of the local dose-response function.

RESULTS

The data are most consistent with a pronounced decrease in DL(CO) when the local dose (for radiotherapy alone or HF concurrent chemoradiation) exceeds 13 Gy (95% CI, 11-15 Gy). In patients who received amifostine in addition to HF radiotherapy with concurrent chemotherapy, this stepwise loss of DL(CO) occurred above 36 Gy (95% CI, 25-48 Gy). Grade 2 or higher pulmonary symptoms were associated with a DL(CO) loss of >30% (p = 0.003).

CONCLUSIONS

The decrease in pulmonary diffusion capacity correlates with the local dose to irradiated lung. Amifostine significantly reduces the loss in DL(CO). A local dose-loss relationship for normalized DL(CO) can be extracted from DVH data. This relationship allows an estimate of the loss of function associated with a radiation treatment plan. Different plans can thus be compared without resort to an empiric DVH reduction algorithm. The very low (13 Gy) threshold for deterioration of DL(CO) suggests that it is better to treat a little normal lung to a high dose than to treat a lot to a low dose.