Verificação dos desvios de setup e cálculo de margem de PTV em tumores de próstata com 3DCRT

Mestrado em Radioterapia

Estudo dos desvios detectados pelas imagens portais no cancro da próstata em radioterapia conformacional (3DCRT)

Mestrado em Radioterapia

Helical tomotherapy versus 3D conformal radiotherapy in dosimetric planning for patients with localized prostate cancer

Radiotherapy is one of the therapeutics selected for localized prostate cancer, in cases where the tumour is confined to the prostate, penetrates the prostatic capsule or has reached the seminal vesicles (T1 to T3 stages). The radiation therapy can be administered through various modalities, being historically used the 3D conformal radiotherapy (3DCRT). Other modality of radiation administration is the intensity modulated radiotherapy (IMRT), that allows an increase of the total dose through modulation of the treatment beams, enabling a reduction in toxicity. One way to administer IMRT is through helical tomotherapy (TH). With this study we intent to analyze the advantages of helical tomotherapy when compared with 3DCRT, by evaluating the doses in the organs at risk (OAR) and planning target volumes (PTV).

Planeamento dosimétrico de tumores de pulmão

Qual a técnica de irradiação a utilizar? RT convencional, 3DCRT, IMRT, SBRT. Esta selecção depende muito dos equipamentos disponíveis, mas idealmente deve ser sempre acompanhada de técnicas de IGRT.

Comparação dosimétrica de dois sistemas de planeamento de tratamento em radioterapia conformacional 3D

Dissertação de mestrado em Biofísica e Bionanossistemas

Evaluation of organ-specific peripheral doses after 2-dimensional, 3-dimensional and hybrid intensity modulated radiation therapy for breast cancer based on Monte Carlo and convolution/superposition algorithms: implications for secondary cancer risk assessment.

To make a comprehensive evaluation of organ-specific out-of-field doses using Monte Carlo (MC) simulations for different breast cancer irradiation techniques and to compare results with a commercial treatment planning system (TPS). Three breast radiotherapy techniques using 6MV tangential photon beams were compared: (a) 2DRT (open rectangular fields), (b) 3DCRT (conformal wedged fields), and (c) hybrid IMRT (open conformal+modulated fields). Over 35 organs were contoured in a whole-body CT scan and organ-specific dose distributions were determined with MC and the TPS. Large differences in out-of-field doses were observed between MC and TPS calculations, even for organs close to the target volume such as the heart, the lungs and the contralateral breast (up to 70% difference). MC simulations showed that a large fraction of the out-of-field dose comes from the out-of-field head scatter fluence (>40%) which is not adequately modeled by the TPS. Based on MC simulations, the 3DCRT technique using external wedges yielded significantly higher doses (up to a factor 4-5 in the pelvis) than the 2DRT and the hybrid IMRT techniques which yielded similar out-of-field doses. In sharp contrast to popular belief, the IMRT technique investigated here does not increase the out-of-field dose compared to conventional techniques and may offer the most optimal plan. The 3DCRT technique with external wedges yields the largest out-of-field doses. For accurate out-of-field dose assessment, a commercial TPS should not be used, even for organs near the target volume (contralateral breast, lungs, heart).

Combined radiohormonotherapy in node positive lymph node prostate cancer

Purpose: Pelvic radiation therapy (RT) represents a therapeutic option in the treatment of node-positive prostate cancer but it remains controversial, because of its high rate toxicities. New radiation technique such as IMRT may reduce these complications. In this study, we aimed to assess the rate of toxicities according to CTC-NCI.v3 in such patients treated with either 3DCRT or IMRT (Tomotherapy).Methods and Materials: From January 2008 to December 2010, data were analyzed from 30 consecutive patients including 29 node-positive prostate cancer undergoing definitive or adjuvant RT (IMRT and/or 3DCRT) after radical prostatectomy and lymphadenectomy combined to hormonal therapy. Median age was 66 years (range : 52-83). Median preoperative PSA value was 12 ng/ml (range: 2.72-165). According to the pT-classification, there were 4 pT2, 7 pT3a, 10 pT3b, and 1 pT4 patients. Pathologic positive lymph nodes were found in 23 patients. Radiologic positive lymph nodes were found in 5 patients. Two patients were node negative. Gleason score was ranging between 7 to 10. Twelve patients were treated by Tomotherapy including 4 with simultaneous integrated boost (SIB). Eighteen patients were treated by Tomotherapy including 2 with SIB to the whole pelvis and 3DCRT boost to the prostate. V50% for bladder and rectum were recorded. Acute and late toxicities were assessed according to CTC-NCI.v3 classification.Results: With a median follow-up of 17 months, only one patient presented nodal and metastatic failure. Urinary incontinence was graded 1 after surgery for 6 patients and grade 2 in two. Sexual impuissance was noted in 3 patients. Acute toxicities during RT were proctitis grade 0 in 23 patients (76.5%), grade 1 in 7 (23.5%). Nocturia grade 1 in 9 patients. Interruption of treatment was seen in only case because of grade 3 urinary incontinence. Late effects included erectile dysfunction in 5 patients (83%) and one patient had grade 3proctitis requiring colostomy 3 months after RT. Median Dose-Volume Histogram according to radiation techniques V50% bladder V50% rectum Tomotherapy (IMRT) 36.25 Gy 39 Gy Tomotherapy + 3DCRT 41.26 Gy 39.18 GyConclusion: Based on our above-mentioned findings, there is no a significant difference in morbidity in patients treated with Tomotherapy or Tomotherapy with 3DCRT boost.

Acute toxicity of curative radiotherapy for intermediate risk localized prostate cancer in the EORTC trial 22991

Introduction: EORTC trial 22991 randomly assessed the addition of concomitant and adjuvant short-term hormonal therapy to curative conformal/intensity-modulated radiotherapy (RT) for intermediate risk localized prostate cancer. We report the acute toxicity (assessed weekly during RT) for the organs at risk (genito-urinary (GU) and gastro-intestinal (GI)) in relation to radiation parameters. Material and Methods: Eligibility criteria were age _80 years, PSA _ 50 ng/ml, N0M0 and either tumour stage cT2a (1997 UICC TNM) or cT1b-c combined with PSA_10 ng/ml and/or Gleason score _7. We report toxicity for all eligible patients who received the planned RT with documented acute toxicity (CTCAEv.2) and RT-quality assurance parameters. The RT dose (70 Gy, 74 Gy or 78 Gy) and technique (3DCRT vs IRMT) were per institution choice, the randomization was stratified for institution. Statistical significance was set at 0.05. (ClinicalTrials.gov: NCT00021450) Results: Of 819 randomized patients, 28 were excluded from the analysis (3 with <60 Gy RT, 25 with missing information). Of the 791 analysed patients, 652 (82.4%) were treated with 3D-CRT, 139 with IMRT. In the 3DCRT group, 195 patients (29.9%) were treated with a total prescribed dose of 70 Gy; 376 (57.7%) with 74 Gy and 81 (12.4%) with 78 Gy. In the IMRT group, 28 (20.1%) were treated to a total dose of 74 Gy and 111 (79.9%) with 78 Gy. Overall, only 7 of 791 patients (0.9%) had grade 3 GI toxicity during RT: diarrhea (N = 6), rectal bleeding (N = 1) and proctitis (N = 1). Fifty patients (6.3%) had grade 3 GU toxicity: urinary frequency (N = 38, 4.6%), dysuria (N = 14, 1.7%), urinary retention (N = 11, 1.3%), urinary incontinence (N = 2) and hematuria (N = 1). No grade 4 toxicity was reported. Hormonal treatment did not influence the risk of side effects (p>0.05). The risk of grade _2 GI toxicity significantly correlated to D50%-rectum (p = 0.004) with a cut-of value of 44 Gy. The risk of grade _2 GU toxicity was moderately affected by Dmax-bladder (p = 0.051). Overall, only 14 patients (1.8%) had residual grade 3 toxicities one month after RT. Conclusion: 3D-CRT and IMRT up to 78 Gy is well tolerated. Dmaxbladder and D50%-rectum were related to the risk of grade_2 GU and GI toxicity, respectively. IMRT lowered D50% rectum and Dmax-bladder. An irradiated volume >400 cc for 3D-RT and a dose of 78 Gy, even for IMRT, negatively affected those parameters and increased the risk for toxicity.