Postmastectomy radiotherapy with integrated scar boost using helical tomotherapy.

Area of Science:

• Medical Physics
• Radiation Oncology
• Oncology

Background:

• Postmastectomy radiation therapy requires precise dose delivery to chest wall and nodal regions.
• Simultaneous integrated boost (SIB) techniques are used to escalate dose to specific areas like the scar.
• Accurate dosimetry and setup reproducibility are critical for effective treatment and minimizing side effects.

Purpose of the Study:

• To evaluate the dosimetry of helical tomotherapy with a strip bolus for postmastectomy patients receiving SIB to the scar region.
• To compare dose distribution, setup accuracy, and reproducibility with and without a strip bolus.

Main Methods:

• Six postmastectomy patients were treated with helical tomotherapy using a 5-mm-thick strip bolus covering the scar planning target volume (PTV) plus a 2-cm margin.
• Two treatment plans (with and without bolus) were generated for each patient.
• Dose-volume histograms, in vivo dosimetry using thermoluminescence dosimeters (TLD), and megavoltage computed tomography (MVCT) verification were used for evaluation.

Main Results:

• The strip bolus reduced air cavities and improved dose uniformity to the scar PTV (106.6% hotspot with bolus vs. 111.4% without).
• In vivo dosimetry confirmed accurate dose delivery beneath the bolus.
• MVCT verification showed daily setup and dose delivery within 2% accuracy compared to planned doses.
• Higher setup reproducibility was observed with the strip bolus setup.

Conclusions:

• Using a strip bolus over the postmastectomy scar region with helical tomotherapy is feasible and beneficial.
• This technique enhances dose uniformity to the scar PTV, improves setup reproducibility, and ensures accurate dose delivery.
• Strip bolus application represents a valuable method for optimizing SIB dosimetry in postmastectomy radiation therapy.