KEY POINTS
- This single-centre retrospective study included 16 patients with favorable early-stage breast cancer treated after breast-conserving surgery. All received 30 Gy in 5 non-consecutive fractions using helical tomotherapy with daily megavoltage computed tomography guidance; median follow-up was 17.7 months.
- Mean planning target volume V95% was 98.0% ± 2.7%, although the predefined coverage target was met in 13 of 16 plans (81.3%). Mean heart dose was 0.82 Gy, and mean ipsilateral lung dose was 2.91 Gy; all patients met laterality-specific cardiac constraints.
- Mean ipsilateral breast V15 Gy was 46.2% ± 12.9%, with the <50% constraint achieved in 11 of 16 plans (68.8%). High-dose spillage outside the planning target volume was minimal.
- The planning target volume-to-whole-breast volume ratio was associated with ipsilateral breast V15 Gy (β=30.06, R²=0.336, p=0.019). A cutoff of approximately 0.33 showed 100% sensitivity and 54.5% specificity, with an area under the curve of 0.636, for identifying V15 Gy ≥50%.
- Grade 1 dermatitis occurred in 10 patients (62.5%), with no grade 2 or higher dermatitis or other grade 2 or higher acute toxicity. No local recurrence or disease-related death was reported during the available follow-up.
CLINICAL TAKEAWAY
Helical tomotherapy appears capable of delivering five-fraction partial breast irradiation with favorable target coverage and low cardiac and pulmonary exposure in carefully selected patients. The planning target volume-to-breast ratio may help flag plans in which ipsilateral breast constraints will be difficult to meet, but the threshold requires validation; these findings are preliminary, not practice-changing.