[Importance of dosimetric factors predicting radiation toxicity in lung cancer treatment].

OBJECTIVE

To evaluate prognostic importance of dosimetric parameters (V20, V30 and V40) in the incidence of lung radiation toxicity caused by external-beam radiation therapy in patients with lung cancer.

MATERIAL AND METHODS

A total of 82 patients with lung cancer were analyzed prospectively. They were treated in the Oncology Institute of Vilnius University from 2002 to 2005. Three-dimensional conformal radiotherapy was administered to all patients; radiation dose was > or =50 Gy, delivered in daily fractions of 2 Gy. All patients received concurrent chemotherapy and part of them - surgery. All patients were evaluated before radiation therapy and after 3-, 6-, and 12-month follow-up. V20, V30, and V40 were calculated from dose-volume histograms using the Eclipse(TM) radiotherapy treatment planing system. Based on radiological findings and clinical symptoms radiation-induced lung injury (radiation pneumonitis and radiation fibrosis) was diagnosed.

RESULTS

Nearly half of patients (48%) developed grade < or =2 pulmonary toxicity according to the Subjective, Objective, Management and Analytic/Late Effects on Normal Tissues (SOMA/LENT) scale. The percentage volume of normal lung tissue receiving >20 Gy dose was 38%, >30 Gy--25%, and >40 Gy--18%. In patients free of radiation toxicity V20 was 30%, V30--22%, and V40--18%, and in patients with radiation-induced pulmonary toxicity V20 was 48%, V30--30%, and V40--18%.

CONCLUSIONS

Dosimetric parameters V20, V30, and V40 are significant predictive factors for radiation-induced pulmonary toxicity. At this time planned V20 and V30 are too high and they should be minimized in order to reduce radiation-induced pulmonary toxicity.