Radiation dose-volume effects in the esophagus

Abstract

Publications relating esophageal radiation toxicity to clinical variables and to quantitative dose and dose-volume measures derived from three-dimensional conformal radiotherapy for non-small-cell lung cancer are reviewed. A variety of clinical and dosimetric parameters have been associated with acute and late toxicity. Suggestions for future studies are presented.

Fig. 1

Correlations between acute esophagitis and Vx values (volume greater than x Gy). p Values correlated with relative or absolute volumes (in cubic centimeters); relative volumes used except as noted for 2006 data from Wei et al. (22). Lower values indicate better correlations with outcomes. As the wide variety of correlation shapes suggests, there does not appear to be any singular “threshold” dose above which a toxic effect is observed.

Fig. 2

Incidence of acute esophagitis according to V_x (volume receiving more than x Gy). x-Axis values estimated according to range of doses reported. Each curve annotated as follows: V_dose (investigator, number of patients, percentage with concurrent chemotherapy [CCT]. Percentage of patients who received sequential chemotherapy in studies by Ahn et al. (11), Belderbos et al. (19), and Kim et al. (20) was 44%, 38%, and 15%, respectively. Data for V₅₀ (Ahn et al. [11]) at 15, 45, and 75 Gy represent reported rates of Grade 2 or greater acute esophagitis plotted in dose bins at <30%, 30–60%, and >60%, respectively. Similarly, for V₇₀ (Ahn et al. [11]), V₅₀ (Rodriguez et al. [23]), and V₆₀ (Kim et al. [20]), each symbol represents rates of acute esophagitis at <10% vs. 11–30% vs. 31–64%, and ≤30% vs. ≥30%, and ≤30 vs. >30%, respectively. Dashed horizontal lines reflect dose ranges ascribed to each data point. Upper x-axis range of greatest data point for V50 (Rodriguez et al. [23]), V₅₀ (Ahn et al. [11]), and V₆₀ (Kim et al. [20]), are indefinite according to data (light-gray dotted bars). Solid and open symbols represent reported rates of Grade 2 or greater acute esoph-agitis and Grade 3 or greater acute esophagitis, respectively. Thicker and thinner solid lines represent higher and lower doses of V_x, respectively (i.e., thicker line for V₇₀ and thinner line for V₂₀).