Stereotactic MR-guided adaptive radiotherapy (SMART) for primary rectal cancer: evaluation of early toxicity and pathological response.

Background: The purpose of this study is to measure the effects of stereotactic MR-guided adaptive radiotherapy (SMART) for rectal cancer patients in terms of early toxicity and pathological response. Materials and methods: For this prospective pilot study, patients diagnosed with locally advanced rectal cancer (LARC) with positive lymph node clinical staging underwent SMART on rectal lesion and mesorectum using hybrid MR-Linac (MRIdian ViewRay). Dose prescription at 80% isodose for the rectal lesion and mesorectum was 40 Gy (8 Gy/fr) and 25 Gy (5 Gy/fr), respectively, delivered on 5 days (3 fr/week). Response assessment by MRI was performed 3 weeks after SMART, then patients fit for surgery underwent total mesorectal excision. Primary endpoint was evaluation of adverse effect of radiotherapy. Secondary endpoint was pathological complete response rate. Early toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE v5.0). Results: From October 2020 to January 2022, twenty patients underwent rectal SMART. No grade 3-5 toxicity was recorded. Twelve patients were eligible for total mesorectal excision (TME). Mean interval between the completion of SMART and surgery was 4 weeks. Pathological downstaging occurred in all patients; rate of pathological complete response (pCR) was 17%. pCR occurred with a prolonged time to surgery (> 7 weeks). Conclusion: To our knowledge, this is the first study to use stereotactic radiotherapy for primary rectal cancer. SMART for rectal cancer is well tolerated and effective in terms of tumor regression, especially if followed by delayed surgery.

Magnetic resonance guided SBRT reirradiation in locally recurrent prostate cancer: a multicentric retrospective analysis.

AIMS: Reirradiation of prostate cancer (PC) local recurrences represents an emerging challenge for current radiotherapy. In this context, stereotactic body radiation therapy (SBRT) allows the delivery of high doses, with curative intent. Magnetic Resonance guided Radiation Therapy (MRgRT) has shown promising results in terms of safety, feasibility and efficacy of delivering SBRT thanks to the enhanced soft tissue contrast and the online adaptive workflow. This multicentric retrospective analysis evaluates the feasibility and efficacy of PC reirradiation, using a 0.35 T hybrid MR delivery unit. METHODS: Patients affected by local recurrences of PC and treated in five institutions between 2019 and 2022 were retrospectively collected. All patients had undergone previous Radiation Therapy (RT) in definitive or adjuvant setting. Re-treatment MRgSBRT was delivered with a total dose ranging from 25 to 40 Gy in 5 fractions. Toxicity according to CTCAE v 5.0 and treatment response were assessed at the end of the treatment and at follow-up. RESULTS: Eighteen patients were included in this analysis. All patients had previously undergone external beam radiation therapy (EBRT) up to a total dose of 59.36 to 80 Gy. Median cumulative biologically effective dose (BED) of SBRT re-treatment was 213,3 Gy (103,1-560), considering an α/ß of 1.5. Complete response was achieved in 4 patients (22.2%). No grade ≥ 2 acute genitourinary (GU) toxicity events were recorded, while gastrointestinal (GI) acute toxicity events occurred in 4 patients (22.2%). CONCLUSION: The low rates of acute toxicity of this experience encourages considering MRgSBRT a feasibile therapeutic approach for the treatment of clinically relapsed PC. Accurate gating of target volumes, the online adaptive planning workflow and the high definition of MRI treatment images allow delivering high doses to the PTV while efficiently sparing organs at risk (OARs).

Shoulder girdle impairment in breast cancer survivors: the role of range of motion as predictive factor for dose distribution and clinical outcome.

BACKGROUND: Pain and functional impairment of the ipsilateral shoulder girdle in patients who underwent surgery and radiotherapy for breast cancer (BC) is a late complication reported in the literature. We analyze a correlation with dosimetric parameters and propose an algorithm for sparing strategies. METHODS: A total of 111 patients treated for BC were included in this observational analysis during follow-up protocol visits. Exclusion criteria were the presence of moderate or severe arthrosis history and/or rheumatologic diseases. All the patients had complete physical and multidimensional examinations during joint (physiatrist and radiotherapy oncology) follow-up visits. A scapula-humeral articulation (SHA) standardized contouring was performed retrospectively on Eclipse® treatment plans. A possible correlation between patients' characteristics, radiotherapy, and dosimetry analysis and functional impairment was investigated at statistical analysis. Results of analysis were summarized into a proposal of algorithm for sparing SHA. RESULTS: A total of 111 patients were selected during follow-up visits. Mean age of patients was 60 years (range 41-85 years). A total of 103 patients (93%) underwent conservative surgery, with 110 patients (99%) undergoing axilla surgery as well. Fifty-two patients (46.8%) presented a reduction of range of motion (ROM) abduction on the treated side at the observational analysis. Mean ROM abduction reduction was 13°06' (range 0°-100°). Disability of the Arm, Shoulder and Hand questionnaire (DASH) score results were excellent in 79 patients (71.2%), discrete in 15 patients (13.5%), good in 15 patients (13.5%), and sufficient in 2 patients (1.8%). Median EQD2 Dmax at SHA was 18 Gy (range 0.22-51.9 Gy) and median EQD2 mean dose at SHA was 2 Gy (range 0.04-24.32 Gy). Univariate analysis showed a linear correlation between DASH score and ROM of abduction of treated side (ρ=-0.7), ROM of abduction and ROM of flexion in ipsilateral arm (ρ=0.8), or ROM of abduction and ROM of flexion in contralateral arm (ρ=0.8). A statistically significant difference in ROM abduction between the 2 arms was found at χ2 test (P<0.05 at χ2 confidence interval = 95%). Cox linear regression analysis showed ROM abduction on treated arm as a predictive factor of DASH score (P<0.0001). Age (P<0.05), DASH score (P=0.006), and ROM abduction on treated arm (P=0.005) were found as independent predictive factors of mean dose at multivariate analysis. A mean dose higher than 7 Gy and ROM abduction reduction more than 30° were related to DASH score level reduction. CONCLUSIONS: This hypothesis-generating study introduces an algorithm to be validated for management of sparing SHA and improving quality of survivorship. ROM evaluation after surgery, early physiotherapy, standard contouring, and planning adaptation represent possible indications to preserve shoulder impairment. Further prospective studies are needed to discriminate impairment of surgery and radiotherapy in order to personalized therapeutic plan programs.