Dosimetric evaluation of VMAT and helical tomotherapy techniques comparing conventional volumes with clinical target volumes based on new ESTRO ACROP post-mastectomy with immediate implant reconstruction contouring guidelines.

BACKGROUND: The ESTRO-ACROP Consensus Guideline (EACG) recommends implant excluded clinical target volume (CTVp) definitions for post-mastectomy radiation therapy after implant-based immediate breast reconstruction (IBR). The purpose of this study is to investigate the effectiveness of Helical Tomotherapy (HTp) and Volumetric Modulated Arc Therapy (VMATp) treatment techniques in terms of CTVp coverage and reduced organ at risk (OAR), normal tissue and implant doses when CTVp was used for treatment planning as the target structure instead of conventional CTV. METHODS: Eight left-sided and eight right-sided breast cancer patients who underwent IBR after mastectomy were included in this study. Planning CT data sets were acquired during free breathing and patients were treated with HT technique targeted to conventional CTV. Retrospectively, CTVp was delineated based on EACG by the same radiation oncologist, and treatment plans with HTp and VMATp techniques were generated based on CTVp. For each patient, relevant dosimetric parameters were obtained from three different treatment plans. RESULTS: There was no statistically significant difference on target coverage in terms of, PTVp-D95, PTVp-Vpres, homogeneity index (p > 0.05) between HTp and VMATp plans. But, the conformity numbers were significantly higher (HTp vs VMATp, 0.69 ± 0.15 vs 0.79 ± 0.12) for VMATp (Z = - 2.17, p = 0.030). While HTp significantly lowered Dmax and Dmean for LAD (LAD-Dmax: χ2 = 12.25, p = 0.002 and LAD-Dmean: χ2 = 12.30, p = 0.002), neither HTp nor VMATp could reduce maximum and mean dose to heart (p > 0.05). Furthermore, heart volume receiving 5 Gy was significantly higher for VMATp when compared to HTp (21.2 ± 9.8 vs 42.7 ± 24.8, p: 0.004). Both techniques succeeded in reducing the mean dose to implant (HTp vs HT, p < 0.001; VMATp vs HT, p < 0.001; VMATp vs HTp, p = 0.005). CONCLUSION: Both HTp and VMATp techniques succeeded to obtain conformal and homogeneous dose distributions within CTVp while reducing the mean implant dose. HTp was found to be superior to VMATp with regards to lowering all OAR doses except for CB.

Limited field adaptive radiotherapy for glioblastoma: changes in target volume and organ at risk doses.

OBJECTIVE: This study aimed to investigate the tumor volume changes occurring during limited-field radiotherapy (RT) for glioblastoma patients and whether a volume-adapted boost planning approach provided any benefit on tumor coverage and normal tissue sparing. MATERIALS AND METHODS: Twenty-four patients underwent simulation with magnetic resonance (MR) and computed tomography (CT) scans prior to RT (MR_initial, CT_initial) and boost treatment (MR_adapt, CT_adapt). For the boost phase, MR_initial and MR_adapt images were used to delineate GTV2 and GTV2_adapt, respectively. An initial boost plan (Plan_initial) created on CT_initial for PTV2 was then reoptimized on CT_adapt by keeping the same optimization and normalization values. Plan_adapt was generated on CT_adapt for PTV2_adapt volume. Dose volume histogram parameters for target volumes and organs-at-risk were compared using these boost plans generated on CT_adapt. Plan_initial and Plan_adaptive boost plans were summed with the first phase plan and the effect on the total dose was investigated. RESULTS: Target volume expansion was noted in 21% of patients while 79% had shrinkage. The average difference for the initial and adaptive gross tumor volume (GTV), clinical target volume (CTV), and planning target volume (PTV) volumes were statistically significant. Maximum dose differences for brainstem and optic chiasm were significant. Healthy brain tissue V10 and ipsilateral optic nerve maximum doses were found to decrease significantly in Plan_adaptive. CONCLUSION: Results of this study confirm occurrence of target volume changes during RT for glioblastoma patients. An adaptive plan can provide better normal tissue sparing for patients with lesion shrinkage and avoid undercoverage of treatment volumes in case of target volume expansion especially when limited-fields are used.

Prognostic factors in medically inoperable early stage lung cancer patients treated with stereotactic ablative radiation therapy (SABR): Turkish Radiation Oncology Society Multicentric Study.

OBJECTIVE: We identified factors influencing outcomes in patients with medically inoperable early stage lung cancer (MIESLC) treated with stereotactic ablative radiation therapy (SABR) at 14 centers in Turkey. MATERIALS AND METHODS: We retrospectively analyzed 431 patients with stage I-II MIESLC treated with SABR from 2009 through 2017. Age; sex; performance score; imaging technique; tumor histology and size; disease stage radiation dose, fraction and biologically effective dose with an α/ß ratio of 10 (BED10 ); tumor location and treatment center were evaluated for associations with overall survival (OS), local control (LC) and toxicity. RESULTS: Median follow-up time was 27 months (range 1-115); median SABR dose was 54 Gy (range 30-70) given in a median three fractions (range 1-10); median BED10 was 151 Gy (range 48-180). Tumors were peripheral in 285 patients (66.1%), central in 69 (16%) and <1 cm from mediastinal structures in 77 (17.9%). Response was evaluated with PET/CT in most cases at a median 3 months after SABR. Response rates were: 48% complete, 36.7% partial, 7.9% stable and 7.4% progression. LC rates were 97.1% at 1 year, 92.6% at 2 years and 91.2% at 3 years; corresponding OS rates were 92.6%, 80.6% and 72.7%. On multivariate analysis, BED10 > 100 Gy (P = .011), adenocarcinoma (P = .025) and complete response on first evaluation (P = .007) predicted favorable LC. BED10 > 120 Gy (hazard ratio [HR] 1.9, 95% confidence interval [CI] 1.1-3.2, P = .019) and tumor size (<2 cm HR 1.9, 95% CI 1.3-3, P = .003) predicted favorable OS. No grade 4-5 acute side effects were observed; late effects were grade ≤3 pneumonitis (18 [4.2%]), chest wall pain (11 [2.5%]) and rib fracture (1 [0.2%]). CONCLUSION: SABR produced encouraging results, with satisfactory LC and OS and minimal toxicity. BED10 > 120 Gy was needed for better LC and OS for large, non-adenocarcinoma tumors.

Critical appraisal of RapidArc radiosurgery with flattening filter free photon beams for benign brain lesions in comparison to GammaKnife: a treatment planning study.

BACKGROUND: To evaluate the role of RapidArc (RA) for stereotactic radiosurgery (SRS) of benign brain lesions in comparison to GammaKnife (GK) based technique. METHODS: Twelve patients with vestibular schwannoma (VS, n = 6) or cavernous sinus meningioma (CSM, n = 6) were planned for both SRS using volumetric modulated arc therapy (VMAT) by RA. 104 MV flattening filter free photon beams with a maximum dose rate of 2400 MU/min were selected. Data were compared against plans optimised for GK. A single dose of 12.5 Gy was prescribed. The primary objective was to assess treatment plan quality. Secondary aim was to appraise treatment efficiency. RESULTS: For VS, comparing best GK vs. RA plans, homogeneity was 51.7 ± 3.5 vs. 6.4 ± 1.5%; Paddick conformity Index (PCI) resulted 0.81 ± 0.03 vs. 0.84 ± 0.04. Gradient index (PGI) was 2.7 ± 0.2 vs. 3.8 ± 0.6. Mean target dose was 17.1 ± 0.9 vs. 12.9 ± 0.1 Gy. For the brain stem, D(1cm3) was 5.1 ± 2.0 Gy vs 4.8 ± 1.6 Gy. For the ipsilateral cochlea, D(0.1cm3) was 1.7 ± 1.0 Gy vs. 1.8 ± 0.5 Gy. For CSM, homogeneity was 52.3 ± 2.4 vs. 12.4 ± 0.6; PCI: 0.86 ± 0.05 vs. 0.88 ± 0.05; PGI: 2.6 ± 0.1 vs. 3.8 ± 0.5; D(1cm3) to brain stem was 5.4 ± 2.8 Gy vs. 5.2 ± 2.8 Gy; D(0.1cm3) to ipsi-lateral optic nerve was 4.2 ± 2.1 vs. 2.1 ± 1.5 Gy; D(0.1cm3) to optic chiasm was 5.9 ± 3.1 vs. 4.5 ± 2.1 Gy. Treatment time was 53.7 ± 5.8 (64.9 ± 24.3) minutes for GK and 4.8 ± 1.3 (5.0 ± 0.7) minutes for RA for schwannomas (meningiomas). CONCLUSIONS: SRS with RA and FFF beams revealed to be adequate and comparable to GK in terms of target coverage, homogeneity, organs at risk sparing with some gain in terms of treatment efficiency.

Definitive radiotherapy in locally advanced non-small cell lung cancer: dose and fractionation.

Definitive radiotherapy plays a major role in the treatment of locally advanced non-small cell lung cancer (LA NSCLC). After the impact of RT dose for lung cancer was established, a number of trials were structured with the aim of better local control and overall survival by either dose escalation or shortening the total treatment time through conventional/altered fractionation, even in combination with chemotherapy (CT) and other targeted agents. In spite of the increased number of these studies, the optimal dose or fractionation still remains to be determined. Another aspect questioned is the incorporation of these higher doses and shorter treatment times with chemotherapy or targeted agents. This review summarises the results of significant trials on dose and altered fractionation in the treatment of LA-NSCLC with an emphasis on possible future perspectives.

Neoadjuvant hyperfractionated-accelerated radiotherapy with concomitant chemotherapy in esophageal cancer: phase II study.

PURPOSE: Concomitant use of chemotherapy and a radiation dose schedule that is more efficient compared to conventional radiotherapy may provide better outcomes in patients with esophageal cancer. This study aimed to assess the efficacy and tolerability of neoadjuvant cisplatin-based chemotherapy and hyperfractionated accelerated radiotherapy regimen in this group of patients. METHODS AND MATERIALS: A total of 20 newly diagnosed treatment-naïve esophageal cancer patients were included in the study. Neoadjuvant cisplatin and 5-FU were given with 28-day intervals in a total of three courses. Along with the third course of chemotherapy, hyperfractionated accelerated radiotherapy (HART) was given with the following dose schedule: 5760 cGy/36 fr/16 day. RESULTS: All patients could receive the planned RT dose of 5760 cGy. Odynophagia was the most frequent grade III acute toxicity (50%). None of the acute toxicity reactions required treatment discontinuation. Grade III or higher subacute/late toxicity occurred in 10 patients (75%) including 5 deaths, mostly esophageal. Radiologically, 8 patients (40%) had complete response, 8 (40%) had partial response, and 3 (15%) had stable disease, with only 1 patient (5%) having progressive disease. Seven patients underwent surgery. Overall, 8 patients (40%) had local control. The 5 years overall survival rate was 38.1%. CONCLUSIONS: Neoadjuvant hyperfractionated accelerated radiotherapy plus chemotherapy may help to target local disease control and increase survival in patients with esophageal cancer. Further studies to improve neoadjuvant and radical chemoradiotherapy dose schedules are warranted for maximum tumor control rates with minimal toxicity.