Correlation of Conventional and Conformal Plan Parameters for Predicting Radiation Pneumonitis in Patients Treated with Breast Cancer

Abstract

PurposeThe purpose of this study is to evaluate the correlation between the conventional plan parameters and dosimetric parameters obtained from conformal radiotherapy (RT) planning, and between these parameters and radiation pneumontitis (RP) incidence.MethodsClinical and dosimetric data of 122 patients that were treated with mastectomy and adjuvant 3D conformal RT (39% received 2-field RT [2-FRT], and in addition, 61% received 4-field RT [4-FRT]) were retrospectively analyzed. Central lung depth (CLD), maximum lung depth (MLD), and lung length were measured by the conventional plan. Lung dose-volume histograms (DVH) were created with conformal planning, and the lung volumes receiving 5 to 50 Gy (V5Gy to V50Gy) were calculated. Minimum (Dmin), maximum (Dmax), and mean doses (Dmean) for the ipsilateral lung and bilateral lungs were measured by DVH. Correlations between 3D dosimetric data and 2D radiographic parameters were analyzed.ResultsThe conventional plan parameters did not significantly differ between 2-FRT and 4-FRT. The conformal plan Dmin, Dmax, and Dmean values were higher in 4-FRT versus 2-FRT. CLD and MLD were correlated with DVH parameter V5Gy to V45Gy values for ipsilateral, as well as bilateral lungs for 2-FRT. MLD and ipsilateral Dmean via 2-FRT planning had the strongest positive correlation (r=0.76, p<0.01). Moderate correlations existed between CLD and ipsilateral and bilateral lung V5Gy-45Gy, and between MLD and bilateral lung V5Gy-45Gy values in 2-FRT. Only four patients developed symptomatic RP, 4 with 4-FRT and one with 2-FRT.ConclusionThe conformal plan parameters were strongly correlated with dose-volume parameters for breast 2-FRT. With only 4 cases of Grade 3 RP observed, our study is limited in its ability to provide definitive guidance, however assuming that CLD is an indicator for RP, V20Gy could be used as a predictor for RP and for 2-FRT. A well-defined parameters are still required to predict RP in 4-FRT.

The Relationship between Lung and Heart Two-Dimensional Parameters and Three-Dimensional Dose-Volume Data in Adjuvant Radiotherapy for Breast Cancer

“…The characteristics of the patient population in the present study were similar to previous studies. Similar to our study, patients in previous studies had different types of surgery (BCS or mastectomy) for left- or right-sided breast cancer ( 16 , 17 , 21 ). Possible causes for these discrepancies can be associated with patient-specific anatomy, variation in the shape of the anterior chest wall, variation in the patient’s position, and patient motion related to breathing.…”

“…Teh et al found a strong correlation between CLD and ipsilateral lung V 10-40Gy in patients treated with 2FRT (n = 51), whereas no statistically significant correlation between CLD and ipsilateral lung V 10-40Gy was observed in patients treated with 3FRT (n = 38) ( 16 ). In another similar study, Onal et al have also reported that although there is a correlation between ipsilateral lung volume irradiated and the CLD during two-field tangential breast radiotherapy, this correlation is reduced once supraclavicular fields are added for nodal irradiation ( 21 ). By contrast, with 3FRT, the results of our study show that there is a moderate correlation between CLD and ipsilateral lung V 5-10Gy , as well as a good correlation of CLD and ipsilateral lung V 20Gy , as observable in Table 5 .…”

“…Previous studies have demonstrated a correlation of a simple 2D parameter such as CLD with lung 3D dose-volume data ( 16 , 17 , 21 ). Teh et al found a strong correlation between CLD and ipsilateral lung V 10-40Gy in patients treated with 2FRT (n = 51), whereas no statistically significant correlation between CLD and ipsilateral lung V 10-40Gy was observed in patients treated with 3FRT (n = 38) ( 16 ).…”

Occurrence of pneumonitis following radiotherapy of breast cancer – A prospective study

“…In the past, telecobalt therapy [ 11 ] caused pneumonitis in up to 35% of all treated breast cancer patients, whereas incidences reported for modern CT(computer tomography)-based photon therapy range from 1% [ 12 ] and 4% [ 13 ], 12% [ 14 , 15 ] to 21% [ 16 ]. However, the correlation between normal tissue complication probabilities (NTCPs) and dosimetry parameters, such as extent of co-irradiated lung tissue [ 17 ], central lung distance [ 18 ], and mean lung dose [ 19 , 20 ], is still discussed.…”

Effects of Setup Errors on Dose Distribution for Tangential Wedge Field and Field-in-Field Techniques During Breast Irradiation

“…3,4 Thus, for whole-breast irradiation, standard tangential RT is gradually being replaced by IMRT forward or inverse planning techniques. 5 The field-in-field (FIF) technique, also named as forward IMRT planning, is a simple preferred method that can be performed at any center that has a multileaf collimator (MLC). 6,7 Although the FIF technique achieves a more homogenous dose distribution compared with standard tangential field RT, IMRT plans can be more susceptible to set-up errors and breast shape changes because IMRT plans contain nonglancing segments.…”