Accelerated partial breast irradiation using 3D conformal radiation therapy (3D-CRT)

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Early-stage breast cancer treatment often involves lumpectomy followed by radiation therapy.
• Partial-breast irradiation (PBI) aims to reduce treatment time and toxicity compared to whole-breast irradiation.
• Three-dimensional conformal radiation therapy (3D-CRT) is a precise radiation delivery technique.

Purpose of the Study:

• To present and assess the clinical feasibility of a novel 3D-CRT technique for treating the lumpectomy cavity plus a 1.5-cm margin in early-stage breast cancer patients.
• To determine an appropriate planning target volume (PTV) margin accounting for breathing motion and patient setup uncertainty.

Main Methods:

• A 3D-CRT technique for PBI was developed using archived CT scans.
• Clinical feasibility was assessed in 9 prospectively enrolled patients.
• Doses of 34 Gy or 38.5 Gy were delivered in 10 fractions over 5 days.
• The impact of breathing motion and setup uncertainty on clinical target volume (CTV) coverage was evaluated.

Main Results:

• A 5 mm "breathing-only" margin ensured 98%-100% CTV coverage by the 95% isodose line during breathing extremes.
• A total CTV-to-PTV margin of 10 mm was sufficient to cover organ motion and setup errors.
• Patient tolerance was excellent with minimal acute toxicity, including no skin changes and only mild hyperpigmentation/erythema at follow-up.

Conclusions:

• Accelerated partial-breast irradiation using 3D-CRT is technically feasible for early-stage breast cancer.
• A 10 mm CTV-to-PTV margin appears adequate for most patients.
• Further studies with more patients and longer follow-up are needed to validate the margin and assess long-term outcomes.