Helical Tomotherapy versus Conventional Technique for Post Mastectomy Left Sided Breast Cancer; Dosimetric Study.

PURPOSE: To evaluate the feasibility of using Helical Tomotherapy (HT) for post mastectomy left-sided breast cancer.

METHODS AND MATERIALS: Treatment plans were generated for 5 post mastectomy left sided breast cancer patients treated at king Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia, comparing three-dimensional technique with the HT planning. The prescribed dose was 50 Gy in 25 fractions; the planning target volume (chest wall and nodal volumes) was contoured according to RTOG atlas and the heart, lungs, spinal cord and contralateral breast were contoured as Organs at Risks (OARs).

RESULTS: Both plans achieved the planning criteria, however the HT plan increased the minimal dose to the PTV (78% vs. 45.4%, p=0.043), improving the dose conformity (0.76 vs. 0.38, p=0.034) and dose homogeneity (1.05 vs. 1.2, p=0.08), while a three-dimensional technique has better V20 of lung (15.8% vs. 22.6%, p=0.04), Mean Lung Dose (7.6Gy vs. 13.8Gy, p=0.043), contralateral breast dose (0.1 vs. 12.7, p=0.043) and comparable Mean Heart Dose (4.4Gy vs. 5.3Gy, p=0.136).

CONCLUSION: Both plans achieved comparable target coverage and OARs sparing, however HT plans provided better dose conformity and homogeneity than did the three-dimensional plans at the cost of less sparing of the heart, left lung and contralateral breast for treatment of left-sided post mastectomy breast cancer.