Regional radiotherapy to axilla and supraclavicular fossa for adjuvant breast treatment: a comparison of four techniques.

PURPOSE

The three techniques commonly used to treat the axilla and supraclavicular nodes in adjuvant radiotherapy all have significant disadvantages, including underdosing the deeper nodes, excessively irradiating normal tissues, or producing undesirable hot spots. We assessed whether an anterior field with posterior boost field to the axilla with customized compensation of the anterior beam (APcomp-PAboost) would minimize these drawbacks.

METHODS AND MATERIALS

The axillary and supraclavicular nodal volumes, planning target volume (PTV), irradiated volume, and brachial plexus were contoured for 10 patients. The plans for each technique-single anterior field (AP); anterior to posterior parallel pair (AP-PA); anterior field with posterior boost (AP-PAboost); and APcomp-PAboost-were then generated for each patient using CadPlan and compared.

RESULTS

The AP plan gave poor PTV coverage in 60% of cases. The AP-PA provided good PTV coverage and minimal hot spots, but resulted in consistent unnecessary RT to the medial posterior neck. The skin and tissue of the medial posterior neck and chest wall (i.e., the tissue overlying the posterior half of the ribs and posterior to the latissimus dorsi muscle, which forms the posterior wall of the axilla) was incidentally included in the radiation fields of the AP-PA and the exit of the AP beam. No nodal tissue is present in this region, and, therefore, this tissue was unnecessarily irradiated to higher doses with the AP-PA technique. The AP-PAboost provided adequate PTV coverage and a limited dose to the medial posterior neck, but produced hot spots in excess of 120% in 90% of cases. The APcomp-PAboost provided good PTV coverage, a limited dose to the medial posterior neck, and hot spots to <120% in all cases.

CONCLUSION

In most cases, the APcomp-PAboost technique offered the best compromise, but the AP-PA technique may be preferred if a less intense hot spot is sought.