The dose distribution within the target was more homogenous, and the doses for healthy tissue were less in the FIF plan compared to the tangential wedge plans.

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Background: To evaluate the impact of four different rectum contouring techniques and rectal toxicities in patients with treated with 3D conformal radiotherapy (3DCRT).

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Background/Aim: To compare simultaneousintegrated boost (SIB) versus sequential-boost (SB) delivered in the context of whole-breast irradiation (WBI) via volumetricmodulated arc therapy (VMAT) and helical-tomotherapy (HT). Materials and Methods: Planning target-volume (PTV) dosimetric parameters and organs at risk (OAR) were analyzed for SB plan (50 Gy plus 16 Gy boost) and SIB plan (50.4 Gy WBI and 64.4 Gy tumor bed boost) in VMAT and HT techniques. Results: Conformity and homogeneity for targetvolume doses were better in HT plans compared to VMAT plans. There were no significant differences in ipsilateral lung doses between VMAT and HT plans for SB/SIB techniques, except for a significantly higher lung V5 value with VMAT-SB, and lung V13 value with HT-SIB technique. HT provided a statistically significant decrease in contralateral lung mean V5. Conclusion: The SIB technique showed better target-volume dose distribution in both HT and VMAT plans, and better sparing heart in HT compared to the SB technique. Breast cancer (BC) is the most common cancer and is a major cause of cancer-related death in women (1). Currently, adjuvant radiotherapy (RT), especially whole-breast irradiation (WBI) after breast-conserving surgery (BCS), is accepted as standard-of-care for early BC patients as this multimodal treatment increases local control and improves overall survival in early BC (2, 3). Additional tumor-bed boost after WBI has also been shown to reduce local recurrence (4); however, a long-term follow-up study found that inhomogeneous radiation in tumor-bed boosts, and use of photon beam boosts led to poorer cosmetic outcomes in patients (5). Therefore, in the past few decades, a lot of attention has focused on the development of new techniques to achieve a homogeneous dose distribution, better local control, and improve cosmetic outcomes for WBI after BCS. Breast RT techniques range from conventional tangential field RT, field-in-field conformal RT (CRT), intensity modulated RT (IMRT), volumetric arc therapy (VMAT) to helical tomotherapy (6-11). For tumor-bed boost, relatively simple electron or hybrid techniques (i.e., a combination of different techniques for WBI and boosts), have been used. Recent dosimetric studies have demonstrated that multi-field 3D-CRT, IMRT, or VMAT are superior to electron therapy with respect to the target-volume coverage and sparing normal tissues (12-15). Moreover, simultaneous-integrated boost (SIB), which is a technique wherein a boost is delivered to the tumor bed concurrently with WBI, has been reported to be technically and dosimetrically feasible (11-13, 15-17). The rationale underlying the SIB technique is to escalate radiation doses in the area at highest risk without prolonging treatment duration. This dose escalation provides improved patient comfort while shortening the duration of RT, and also exploits the higher sensitivity of breast tumor cells to larger single doses. However, more advanced techniques are required to increase the uniformity of the radiation dose to improve p...

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.

ABSTRACT. In this study, we investigated the shrinking effect of concurrent threedimensional conformal radiotherapy (3D-CRT) and androgen deprivation (AD) on prostate volume, and its possible impact on the dose received by the rectum and bladder during the course of 3D-CRT. The difference between the prostatic volumes determined on pre-treatment planning CT (PL-CT) and post-treatment CT (PT-CT) following a 3D-CRT course was assessed in 52 patients with localised prostate carcinoma. The changes in mean prostate volume when compared with PL-CT and PT-CT-based measurements were assessed. The pre-and post-treatment mean prostate volumes for the whole study population were 49.7 cm 3 and 41.0 cm 3 (p50.02), respectively. The study cohort was divided into two groups depending on the duration of neoadjuvant androgen deprivation (NAD): 23 patients (44.7%) were designated as ''short NAD'' (#3 months; SNAD) and the remaining 29 (55.3%) as ''long NAD'' (.3 months; LNAD). Patients on SNAD experienced a significantly greater reduction in prostate volume compared with those on LNAD (14.1% vs 5.1%; p50.03). A significant increase in rectum V 40-60 values in PT-CT compared with PL-CT was demonstrated. LNAD patients had significantly higher rectal V 50-70 values at PT-CT compared with the SNAD group. There was a significant decline in V 30 -V 75 bladder values in PT-CT compared with PL-CT in the SNAD group. In conclusion, a higher prostate volume reduction during 3D-CRT was demonstrated when RT planning was performed within 3 months of NAD. However, this reduction and daily organ motion may lead to an unpredictable increase in rectal doses. Neoadjuvant androgen deprivation (NAD) before RT has been demonstrated to shrink the prostate volume effectively [11,12], and thus has became a widely accepted and essential part of locally advanced prostate cancer management. On average, the prostate gland shrinks about 20-50% of its initial volume within 3 months of NAD [11][12][13][14][15] and, although the rate slows down, this shrinking effect continues beyond this period [16][17][18][19] The cytoreduction in the prostate provided by NAD may lower the complication rates observed at higher RT doses by reducing the target volumes, depending on the reduced doses received by normal tissues [15,20].A relatively long treatment interval (7-8 weeks) is usually mandated for three-dimensional conformal radiotherapy (3D-CRT) of prostate carcinoma, and the shrinkage of the prostate gland continues during this period. In this setting, it is reasonable to assume, theoretically, that there is a possibility of a larger than planned volume of surrounding critical organs that may shift into the intermediate or high-dose regions during the RT course, which may unpredictably increase the dose received by the rectum and bladder [11,12,21]. Based on the above assumption, we planned to evaluate prostate shrinkage during 3D-CRT in relation to NAD duration, and to investigate the possible impact of this volume reduction on the dose received by the rectum and blad...