Patterns of care and brachytherapy boost utilization for vaginal cancer in the United States

Vaginal cancer is an uncommon malignancy that is usually treated with definitive radiation therapy. Following external beam radiation therapy (EBRT), a brachytherapy boost is delivered to achieve a total dose of 70-85 Gy. We sought to determine the trends of brachytherapy boost utilization in the treatment of vaginal cancer and to identify the factors associated with its utilization.

Using the National Cancer Data Base (NCDB), we identified 1530 patients with vaginal cancer from 2004 to 2011 who were treated with radiation therapy and had a recorded boost modality. The following additional variables were identified: age, year of diagnosis, Charlson/Deyo comorbidity score, stage, histology, race, brachytherapy dose rate, brachytherapy applicator technique, treatment facility volume, and utilization of chemotherapy. Multivariable logistic regression analysis was performed to identify factors independently associated with brachytherapy boost.

Seventy-seven percent of the 1530 women received brachytherapy boost and 23% received EBRT boost. The rate of brachytherapy boost utilization decreased from 87.7% in 2004 to 68.6% in 2011 (P < .001). Of all the nonbrachytherapy boost modalities, intensity modulated radiation therapy (IMRT) demonstrated the greatest increase (4.5% to 23.5%). For those who had brachytherapy boost, the rate of high-dose-rate increased from 76.3% to 90.8% (P = .02). Multivariate analysis revealed that high facility volume was associated with increased odds of brachytherapy boost (odds ratio [OR], 2.3; range, 1.5-3.4). Higher stage and advanced age were associated with decreased odds of brachytherapy boost (OR, 0.2; range, 0.1-0.3 and OR, 0.5; range, 0.3-0.8). Utilization of chemotherapy, histology, race, and comorbidity index were not significantly associated with brachytherapy boost utilization.

Using the NCDB, we identified a concerning decline in the utilization of brachytherapy boost for those with vaginal cancer and a corresponding increase in IMRT boost technique. The strongest factor predicting for brachytherapy boost utilization is treatment at a high volume facility.