Variation in "supraclavicular" lymph node depth is partly determined by treatment position

The so-called "supraclavicular" region bears the confluence of deep jugular, upper mediastinal and axillary lymph node groups and therefore it is often part of the target volume in common malignancies like lung cancer, breast cancer and head and neck cancer. For treating this area, several authors recommend an anterior portal with the dose prescribed to a tissue depth of 3 cm, which does not fit our institution's experience.

In 119 consecutive patients a computed tomography for planning purposes was performed. We used the subclavian blood vessels between clavicula and first rib as an estimate of the confluence of the mentioned lymph node regions and determined their tissue depth (which does not describe the deepest part of the lymph vessels).

Mean and median of the tissue depth were 5 cm in a range from 2 to 9 cm. Only in less than 20% of the measurements we found the vessels located 3 cm or less under the surface which would correspond to a depth of the lymph node target volume 4 to 5 cm. Increasing body mass resulted in deeper location of the vessels. The position of the patient's arms influenced the tissue depth even more. Arms risen above the head resulted in 55% of the measurements in tissue depths of 6 cm or deeper compared to 6% in patients treated with arms beside the body.

Standardized treatment prescriptions do not cope adequately with individual anatomy. Treatment position especially of the arms influences location of the "supraclavicular" lymph node region in thoracic treatment. Target volume delineation by computed tomography seems the most accurate solution, although it is the most expensive one. Patient immobilization is crucial for accuracy of treatment delivery.