Primary cancer location predicts predominant level of brachial plexopathy

Changes in radiation therapy practice and cancer incidence bring into question prior evidence suggesting that radiation therapy predominantly injures the brachial plexus upper trunk, while tumor invasion typically injures the lower trunk.

We reviewed electrodiagnostic brachial plexopathy reports in cancer survivors for predominant trunk involvement, injury mechanism (tumor invasion vs radiation), and primary cancer location.

Fifty-six cases of cancer-associated brachial plexopathy were identified. There was no relationship between injury mechanism and brachial plexus injury level. However, primary cancer location superior/inferior to the clavicle increased the odds of predominantly upper/lower trunk involvement by a factor of 60.0 (95% confidence interval: 7.9, 1401, respectively).

Cancers superior/inferior to the clavicle increase the likelihood of predominantly upper/lower trunk plexopathy, respectively, regardless plexus injury mechanism. These findings contrast with older work, possibly due to more precise radiation therapy techniques and increased incidence of radiosensitive head and neck cancers.