Uncomplicated Tumour Control Probability (UTCP) in post-operative radiotherapy of left breast cancer- three dimensional conformal versus Intensity Modulated Radiation Therapy (IMRT )

Objective: To analyze the effect of intra- and interfractional motion during breast intensity modulated radiation therapy (IMRT) by calculating dose distribution based on four-dimensional computed tomography (4DCT). Methods: 20 patients diagnosed with left breast cancer were enrolled. Three-dimensional CT (3DCT) along with 10 phases of 4DCT were collected for each patient, with target volumes independently delineated on both 3DCT and all phases of 4DCT. IMRT plans were generated based on 3DCT (43.2 Gy in 16 fractions). The plan parameters for each segment were split into phases based on time duration estimates for each respiratory phase, with phase-specific dose distributions calculated and summated (4D-calculated dose). The procedure is repeated for 16 fractionations by randomly allocating starting phase using random-number generation to simulate interfractional discrepancy caused by different starting phase. Comparisons of plan quality between the original and 4D-calculated doses were analyzed. Results: There was a significant distortion in 4D-calculated dose induced by respiratory motion in terms of conformity and homogeneity index compared to those of the original 3D plan. Mean doses of the heart and the ipsilateral lung were significantly higher in the 4D-calculated doses compared to those of the original 3D plan (0.34 Gy, p = 0.010 and 0.59 Gy, p < 0.001), respectively). The mean internal mammary lymph node (IMN) dose was significantly greater in the 4D-calculated plan, compared to the original 3D plan (1.42 Gy, p < 0.001). Conclusions: IMN doses should be optimized during the dose-calculation for the free-breathing left breast IMRT. Advances in knowledge: The interplay effect between respiratory motion and multileaf collimator modulation caused discrepancies in dose distribution, particularly in IMN.

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Intensity-Modulated Radiation Therapy in Breast Cancer Patients Following the Release of a Choosing Wisely Recommendation

JNCI Journal of the National Cancer Institute ◽

10.1093/jnci/djz198 ◽

2019 ◽

Vol 112 (3) ◽

pp. 314-317

Author(s):

Mylin A Torres ◽

Keerthi Gogineni ◽

David H Howard

Keyword(s):

Breast Cancer ◽

Radiation Therapy ◽

Cancer Patients ◽

Three Dimensional ◽

Intensity Modulated Radiation Therapy ◽

Conformal Radiotherapy ◽

Breast Conserving Surgery ◽

Breast Cancer Patients ◽

Intensity Modulated ◽

Percentage Points

Abstract In 2013, the American Society for Radiation Oncology recommended against the routine use of intensity-modulated radiation therapy (IMRT) in breast cancer patients. We evaluated trends in the use of IMRT before and after the release of the recommendation. Using Surveillance, Epidemiology, and End Results Medicare data, we identified 13 457 breast cancer patients diagnosed between 2012 and 2015 who received breast-conserving surgery and postsurgery, whole-breast, IMRT, or three-dimensional conformal radiotherapy. We find that the use of IMRT decreased by 4.6 (95% confidence interval [CI] = 3.6 to 5.6; two-sided P < .001) percentage points in hospital-based clinics. In freestanding radiotherapy clinics, which had baseline rates of IMRT use that were more than 20 percentage points higher than in hospital-based clinics, use of IMRT declined by 6.1 (95% CI = 3.5 to 8.7; two-sided P < .001) percentage points. Use of IMRT declined following the release of the recommendation, but a large share of patients treated in freestanding clinics continue to receive IMRT.

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