Duodenal complications in radiotherapy for bile duct cancer: A dose–volume histogram analysis

Abstract 

Purpose

To establish a method of quantitative assessment of the duodenal exposure dose to avoid duodenal morbidity after radiotherapy for bile duct cancer.

Methods and Materials

After external beam radiotherapy (ERTx) and intraluminal high-dose-rate brachytherapy (BRTx), 4 of 10 patients developed Grade 3 or 4 ulcers at the posterior wall of the duodenal bulb (PWDB) (compromised group); the remainder exhibited no duodenal complications (spared group) for 14 (range, 7–59) months after radiotherapy. The radiation exposure to the duodenal volume at risk (V_duod) in ERTx and BRTx was individually analyzed using dose–volume histograms in terms of the mean doses (the average dose of V_duod[D_ave] and the median dose of V_duod [D_median]), dose covering 1% or 5% of V_duod (dose covering 1% of the V_duod [D₁] and dose covering 5% of the V_duod [D₅], respectively), and the V_duod receiving 100% or 150% of the prescribed radiation dose (V₁₀₀ and V₁₅₀, respectively) in ERTx (D_ave, D_median, D₅) and BRTx (D_ave, D₁, D₅, V₁₀₀, V₁₅₀). D_ave and D₅ were converted to biologically effective doses (BEDs), and each corresponding values of ERTx and BRTx were summed presenting as BED_{ave_sum} and BED_{5_sum}.

Results

The PWDB was consistently involved in 100% of the prescription dose area in ERTx. The compromised group had smaller exposure doses without significant difference (SD). In BRTx, the PWDB was exposed to higher doses. The compromised group had larger dose exposures without SD and larger volume exposures (V₁₀₀, V₁₅₀) with SD in BRTx. The BED_{ave_sum} and BED_{5_sum} showed no difference between the groups.

Conclusions

Measuring the duodenal volume exposed to determine doses that exceed the prescription in BRTx may be useful for predicting intractable complications in the combined radiotherapy.

Keywords: Brachytherapy, Bile duct cancer, Dose–volume histogram