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We aimed to identify a five-fraction schedule of adjuvant radiotherapy (radiation therapy) delivered in 1 week that is non-inferior in terms of local cancer control and is as safe as an international standard 15-fraction regimen after primary surgery for early breast cancer. Here, we present 5-year results of the FAST-Forward trial. FAST-Forward is a multicentre, phase 3, randomised, non-inferiority trial done at 97 hospitals (47 radiotherapy centres and 50 referring hospitals) in the UK. Patients aged at least 18 years with invasive carcinoma of the breast (pT1–3, pN0–1, M0) after breast conservation surgery or mastectomy were eligible. We randomly allocated patients to either 40 Gy in 15 fractions (over 3 weeks), 27 Gy in five fractions (over 1 week), or 26 Gy in five fractions (over 1 week) to the whole breast or chest wall. Allocation was not masked because of the nature of the intervention. The primary endpoint was ipsilateral breast tumour relapse; assuming a 2% 5-year incidence for 40 Gy, non-inferiority was predefined as ≤1·6% excess for five-fraction schedules (critical hazard ratio [HR] of 1·81). Normal tissue effects were assessed by clinicians, patients, and from photographs. This trial is registered at isrctn.com, ISRCTN19906132. Between Nov 24, 2011, and June 19, 2014, we recruited and obtained consent from 4096 patients from 97 UK centres, of whom 1361 were assigned to the 40 Gy schedule, 1367 to the 27 Gy schedule, and 1368 to the 26 Gy schedule. At a median follow-up of 71·5 months (IQR 71·3 to 71·7), the primary endpoint event occurred in 79 patients (31 in the 40 Gy group, 27 in the 27 Gy group, and 21 in the 26 Gy group); HRs versus 40 Gy in 15 fractions were 0·86 (95% CI 0·51 to 1·44) for 27 Gy in five fractions and 0·67 (0·38 to 1·16) for 26 Gy in five fractions. 5-year incidence of ipsilateral breast tumour relapse after 40 Gy was 2·1% (1·4 to 3·1); estimated absolute differences versus 40 Gy in 15 fractions were −0·3% (−1·0 to 0·9) for 27 Gy in five fractions (probability of incorrectly accepting an inferior five-fraction schedule: p=0·0022 vs 40 Gy in 15 fractions) and −0·7% (−1·3 to 0·3) for 26 Gy in five fractions (p=0·00019 vs 40 Gy in 15 fractions). At 5 years, any moderate or marked clinician-assessed normal tissue effects in the breast or chest wall was reported for 98 of 986 (9·9%) 40 Gy patients, 155 (15·4%) of 1005 27 Gy patients, and 121 of 1020 (11·9%) 26 Gy patients. Across all clinician assessments from 1–5 years, odds ratios versus 40 Gy in 15 fractions were 1·55 (95% CI 1·32 to 1·83, p<0·0001) for 27 Gy in five fractions and 1·12 (0·94 to 1·34, p=0·20) for 26 Gy in five fractions. Patient and photographic assessments showed higher normal tissue effect risk for 27 Gy versus 40 Gy but not for 26 Gy versus 40 Gy. 26 Gy in five fractions over 1 week is non-inferior to the standard of 40 Gy in 15 fractions over 3 weeks for local tumour control, and is as safe in terms of normal tissue effects up to 5 years for patients prescribed adjuvant local radiotherapy after primary surgery for early-stage breast cancer. National Institute for Health Research Health Technology Assessment Programme.

Background Microvascular invasion (MVI) is considered to be one of the important prognostic factors that affect postoperative recurrence in patients with hepatocellular carcinoma (HCC) with variable results across their treatment options. This study was carried out to investigate efficacy of postoperative adjuvant RT in HCC patients with MVI. Methods This was single center, prospective study carried out in HCC patients with MVI, aged 35–72 years. All patients were non-randomly allocated to receive standard postoperative treatment of HBV/HCV and nutritional therapy or RT in addition to standard postoperative treatment (1:1). The primary endpoints assessed were relapse-free survival and overall survival. The prognostic factors associated with survival outcomes were also analyzed. The safety events were graded according to NCI-CTCAE v4.03 criteria. Results Of the 115 patients eligible for study, 59 patients were included in analysis. Univariate analysis revealed that MVI classification ( P  = 0.009), post-operative treatment strategies ( P  = 0.009) were prognostic factors for worst RFS; tumor size ( P  = 0.011), MVI classification ( P  = 0.005) and post-operative treatment ( P  = 0.015) were associated for OS. The 1-, 2-, 3-year RFS rates were 86.2, 70.5 and 63.4% for patients in RT group, and 46.4, 36.1, and 36.1% in control group. For OS, corresponding rates were 96.6, 80.7, and 80.7% for patients in RT group and 79.7, 58.3, and 50.0% in control group. Subgroup classification of HCC patients according to low risk MVI showed significantly longer RFS ( P  = 0.035) and OS ( P  = 0.004) in RT group than control group, while for high risk MVI, RT depicted longer OS than control group with no significance ( P  = 0.106). Toxicities were usually observed in acute stage with no grade 4 toxicities. Conclusion Postoperative adjuvant RT following hepatectomy offers better RFS for HCC patients with MVI than with standard postoperative therapy. Also, it will be useful to control microscopic lesions in both M1 (low risk) and M2 (high risk) subgroups of HCC patients with MVI. Trial registration Trial Registration number: ChiCTR1800017371 . Date of Registration: 2018-07-26. Registration Status: Retrospectively registered.

BackgroundPORTEC-2 was a randomised trial for women with high-intermediate risk (HIR) endometrial cancer, comparing pelvic external beam radiotherapy (EBRT) with vaginal brachytherapy (VBT). We evaluated long-term outcomes combined with the results of pathology review and molecular analysis.Methods427 women with HIR endometrial cancer were randomised between 2002–2006 to VBT or EBRT. Primary endpoint was vaginal recurrence (VR). Pathology review was done in 97.4%, combined with molecular analysis.ResultsMedian follow-up was 116 months; 10-year VR was 3.4% versus 2.4% for VBT vs. EBRT (p = 0.55). Ten-year pelvic recurrence (PR) was more frequent in the VBT group (6.3% vs. 0.9%, p = 0.004), mostly combined with distant metastases (DM). Ten-year isolated PR was 2.5% vs. 0.5%, p = 0.10, and DM 10.4 vs. 8.9% (p = 0.45). Overall survival for VBT vs. EBRT was 69.5% vs. 67.6% at 10 years (p = 0.72). L1CAM and p53-mutant expression and substantial lymph-vascular space invasion were risk factors for PR and DM. EBRT reduced PR in cases with these risk factors.ConclusionLong-term results of the PORTEC-2 trial confirm VBT as standard adjuvant treatment for HIR endometrial cancer. Molecular risk assessment has the potential to guide adjuvant therapy. EBRT provided better pelvic control in patients with unfavourable risk factors.

Unlike for extremity sarcomas, the efficacy of radiotherapy for retroperitoneal sarcoma is not established. The aim of this study was to evaluate the impact of preoperative radiotherapy plus surgery versus surgery alone on abdominal recurrence-free survival. EORTC-62092 is an open-label, randomised, phase 3 study done in 31 research institutions, hospitals, and cancer centres in 13 countries in Europe and North America. Adults (aged ≥18 years) with histologically documented, localised, primary retroperitoneal sarcoma that was operable and suitable for radiotherapy, who had not been previously treated and had a WHO performance status and American Society of Anesthesiologists score of 2 or lower, were centrally randomly assigned (1:1), using an interactive web response system and a minimisation algorithm, to receive either surgery alone or preoperative radiotherapy followed by surgery. Randomisation was stratified by hospital and performance status. Radiotherapy was delivered as 50·4 Gy (in 28 daily fractions of 1·8 Gy) in either 3D conformal radiotherapy or intensity modulated radiotherapy, and the objective of surgery was a macroscopically complete resection of the tumour mass with en-bloc organ resection as necessary. The primary endpoint was abdominal recurrence-free survival, as assessed by the investigator, and was analysed in the intention-to-treat population. Safety was analysed in all patients who started their allocated treatment. This trial is registered with ClinicalTrials.gov, NCT01344018. Between Jan 18, 2012 and April 10, 2017, 266 patients were enrolled, of whom 133 were randomly assigned to each group. The median follow-up was 43·1 months (IQR 28·8–59·2). 128 (96%) patients from the surgery alone group had surgery, and 119 (89%) patients in the radiotherapy and surgery group had both radiotherapy and surgery. Median abdominal recurrence-free survival was 4·5 years (95% CI 3·9 to not estimable) in the radiotherapy plus surgery group and 5·0 years (3·4 to not estimable) in the surgery only group (hazard ratio 1·01, 95% CI 0·71–1·44; log rank p=0·95). The most common grade 3–4 adverse events were lymphopenia (98 [77%] of 127 patients in the radiotherapy plus surgery group vs one [1%] of 128 patients in the surgery alone group), anaemia (15 [12%] vs ten [8%]), and hypoalbuminaemia (15 [12%] vs five [4%]). Serious adverse events were reported in 30 (24%) of 127 patients in the radiotherapy plus surgery group, and in 13 (10%) of 128 patients in the surgery alone group. One (1%) of 127 patients in the radiotherapy plus surgery group died due to treatment-related serious adverse events (gastropleural fistula), and no patients in the surgery alone group died due to treatment-related serious adverse events. Preoperative radiotherapy should not be considered as standard of care treatment for retroperitoneal sarcoma. European Organisation for Research and Treatment of Cancer, and European Clinical Trials in Rare Sarcomas.

Standard adjuvant chemoradiotherapy (60–66 Gy) following surgery for HPV-associated oropharyngeal squamous cell carcinoma has excellent oncological control but high treatment morbidity. We aimed to compare toxicity of a 30–36 Gy regimen of de-escalated adjuvant radiotherapy and standard of care treatment. We did this phase 3, open-label, randomised controlled trial in two academic sites in the USA. Eligible participants were adults aged 18 years or older, with American Joint Committee on Cancer 7th edition pathological stage III–IV HPV-associated oropharyngeal squamous cell carcinoma and had more than 70% p16-immunoreactivity on immunohistochemistry evaluation of the surgical specimen. All patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 1 or less and at least one intermediate pathological risk factor. Patients were stratified by the presence of extranodal extension and smoking status (<10 packs per year vs ≥10 packs per year) Eligible patients were randomly assigned (2:1) using a minimisation method with a random element to receive de-escalated adjuvant radiotherapy (30–36 Gy in 1·5–1·8 Gy fractions twice per day over 2 weeks plus intravenous docetaxel 15 mg/m2 on days 1 and 8 of treatment) or standard of care (60 Gy in 2 Gy fractions once daily over 6 weeks plus intravenous cisplatin 40 mg/m2 once a week). The primary endpoint was cumulative, chronic grade 3 or higher toxicity rate 3–24 months after radiotherapy. Primary analysis was done in patients who received treatment and had no missing data. This trial is registered with ClinicalTrials.gov, NCT02908477, and is complete. Between Oct 11, 2016, and Aug 20, 2020, 254 patients with newly diagnosed oropharyngeal squamous cell carcinoma were assessed for inclusion. Nine did not meet inclusion criteria and 17 declined to participate. 228 patients were enrolled, with 194 proceeding to protocol treatment and analysis (130 in the de-escalated adjuvant radiotherapy group and 64 in the standard of care group). Median patient age was 59·4 years (range 37·9–81·6). 173 (89%) of 194 patients were male and 21 (11%) were female. 183 (95%) of 194 patients were White, four (2%) were Hispanic, three (2%) were Asian, and one (1%) was Native American. Median follow-up was 37·3 months (IQR 27·6–49·2). Seven patients were excluded from analysis of the primary late toxicity endpoint (five patients in the de-escalated adjuvant radiotherapy group and two patients in the standard of care group). The cumulative chronic grade 3 or higher toxicity rate at 3–24 months was 3% (four of 125 patients) in the de-escalated adjuvant radiotherapy group and 11% (seven of 62 patients) in the standard of care group (p=0·042) with a cumulative chronic percutaneous endoscopic gastric (PEG) tube rate of 2% (two of 125 patients) in the de-escalated adjuvant radiotherapy group and 8% (five of 62 patients) in the standard of care group (p=0·039). The most common grade 3 or higher toxic effects in the de-escalated adjuvant radiotherapy group were dysphagia (two [2%] of 125 patients), oesophagitis (one patient [1%]) and hearing impairment (one patient [1%]). The most common grade 3 or higher toxic effects in the standard of care group were dysphagia (five [8%] of 61 patients), oesophagitis (one patient [2%]), fatigue (one patient [2%]), pain (one patient [2%]), and osteonecrosis of the jaw (one patient [2%]). De-escalated adjuvant radiotherapy was a more tolerable treatment in terms of chronic toxicities, demonstrating less cumulative grade 3 or higher toxicity compared with standard of care. Further clinical trials exploring indications for the DART regimen are warranted. The Department of Radiation Oncology, Mayo Clinic, Minnesota and Arizona, the Braillier Family Research Fund, and the Matteson Family Research Fund.

The optimal schedule of radiation treatment after breast-conserving surgery for invasive breast cancer is unknown. In this study, two groups of patients received either hypofractionated radiation or a standard schedule of radiation treatment. Ten years later, the two groups had similar risks of local recurrence and a similar appearance of the breast. Two groups of patients received either hypofractionated radiation or a standard schedule of radiation treatment. Ten years later, the two groups had similar risks of local recurrence and a similar appearance of the breast. In women with breast cancer who undergo breast-conserving surgery, whole-breast irradiation reduces the risk of local recurrence and can prevent the need for mastectomy. 1 – 4 An update of a meta-analysis conducted by the Early Breast Cancer Trialists' Collaborative Group showed that breast irradiation after breast-conserving surgery reduces mortality from breast cancer. 5 However, up to 30% of women in North America who undergo breast-conserving surgery do not undergo breast irradiation, in part because of the inconvenience of the therapy and its cost. 6 In the original trials that evaluated whole-breast irradiation after breast-conserving surgery, 50.0 Gy of radiation was commonly given in . . .

Adjuvant radiotherapy has been shown to halve the risk of biochemical progression for patients with high-risk disease after radical prostatectomy. Early salvage radiotherapy could result in similar biochemical control with lower treatment toxicity. We aimed to compare biochemical progression between patients given adjuvant radiotherapy and those given salvage radiotherapy. We did a phase 3, randomised, controlled, non-inferiority trial across 32 oncology centres in Australia and New Zealand. Eligible patients were aged at least 18 years and had undergone a radical prostatectomy for adenocarcinoma of the prostate with pathological staging showing high-risk features defined as positive surgical margins, extraprostatic extension, or seminal vesicle invasion; had an Eastern Cooperative Oncology Group performance status of 0–1, and had a postoperative prostate-specific antigen (PSA) concentration of 0·10 ng/mL or less. Patients were randomly assigned (1:1) using a minimisation technique via an internet-based, independently generated allocation to either adjuvant radiotherapy within 6 months of radical prostatectomy or early salvage radiotherapy triggered by a PSA of 0·20 ng/mL or more. Allocation sequence was concealed from investigators and patients, but treatment assignment for individual randomisations was not masked. Patients were stratified by radiotherapy centre, preoperative PSA, Gleason score, surgical margin status, and seminal vesicle invasion status. Radiotherapy in both groups was 64 Gy in 32 fractions to the prostate bed without androgen deprivation therapy with real-time review of plan quality on all cases before treatment. The primary endpoint was freedom from biochemical progression. Salvage radiotherapy would be deemed non-inferior to adjuvant radiotherapy if freedom from biochemical progression at 5 years was within 10% of that for adjuvant radiotherapy with a hazard ratio (HR) for salvage radiotherapy versus adjuvant radiotherapy of 1·48. The primary analysis was done on an intention-to-treat basis. This study is registered with ClinicalTrials.gov, NCT00860652. Between March 27, 2009, and Dec 31, 2015, 333 patients were randomly assigned (166 to adjuvant radiotherapy; 167 to salvage radiotherapy). Median follow-up was 6·1 years (IQR 4·3–7·5). An independent data monitoring committee recommended premature closure of enrolment because of unexpectedly low event rates. 84 (50%) patients in the salvage radiotherapy group had radiotherapy triggered by a PSA of 0·20 ng/mL or more. 5-year freedom from biochemical progression was 86% (95% CI 81–92) in the adjuvant radiotherapy group versus 87% (82–93) in the salvage radiotherapy group (stratified HR 1·12, 95% CI 0·65–1·90; pnon-inferiority=0·15). The grade 2 or worse genitourinary toxicity rate was lower in the salvage radiotherapy group (90 [54%] of 167) than in the adjuvant radiotherapy group (116 [70%] of 166). The grade 2 or worse gastrointestinal toxicity rate was similar between the salvage radiotherapy group (16 [10%]) and the adjuvant radiotherapy group (24 [14%]). Salvage radiotherapy did not meet trial specified criteria for non-inferiority. However, these data support the use of salvage radiotherapy as it results in similar biochemical control to adjuvant radiotherapy, spares around half of men from pelvic radiation, and is associated with significantly lower genitourinary toxicity. New Zealand Health Research Council, Australian National Health Medical Research Council, Cancer Council Victoria, Cancer Council NSW, Auckland Hospital Charitable Trust, Trans-Tasman Radiation Oncology Group Seed Funding, Cancer Research Trust New Zealand, Royal Australian and New Zealand College of Radiologists, Cancer Institute NSW, Prostate Cancer Foundation Australia, and Cancer Australia.

Adjuvant radiotherapy reduces the risk of biochemical progression in prostate cancer patients after radical prostatectomy. We aimed to compare adjuvant versus early salvage radiotherapy after radical prostatectomy, combined with short-term hormonal therapy, in terms of oncological outcomes and tolerance. GETUG-AFU 17 was a randomised, open-label, multicentre, phase 3 trial done at 46 French hospitals. Men aged at least 18 years who had an Eastern Cooperative Oncology Group performance status of 1 or less, localised adenocarcinoma of the prostate treated with radical prostatectomy, who had pathologically-staged pT3a, pT3b, or pT4a (with bladder neck invasion), pNx (without pelvic lymph nodes dissection), or pN0 (with negative lymph nodes dissection) disease, and who had positive surgical margins were eligible for inclusion in the study. Eligible patients were randomly assigned (1:1) to either immediate adjuvant radiotherapy or delayed salvage radiotherapy at the time of biochemical relapse. Random assignment, by minimisation, was done using web-based software and stratified by Gleason score, pT stage, and centre. All patients received 6 months of triptorelin (intramuscular injection every 3 months). The primary endpoint was event-free survival. Efficacy and safety analyses were done on the intention-to-treat population. The trial is registered with ClinicalTrials.gov, NCT00667069. Between March 7, 2008, and June 23, 2016, 424 patients were enrolled. We planned to enrol 718 patients, with 359 in each study group. However, on May 20, 2016, the independent data monitoring committee recommended early termination of enrolment because of unexpectedly low event rates. At database lock on Dec 19, 2019, the overall median follow-up time from random assignment was 75 months (IQR 50–100), 74 months (47–100) in the adjuvant radiotherapy group and 78 months (52–101) in the salvage radiotherapy group. In the salvage radiotherapy group, 115 (54%) of 212 patients initiated study treatment after biochemical relapse. 205 (97%) of 212 patients started treatment in the adjuvant group. 5-year event-free survival was 92% (95% CI 86–95) in the adjuvant radiotherapy group and 90% (85–94) in the salvage radiotherapy group (HR 0·81, 95% CI 0·48–1·36; log-rank p=0·42). Acute grade 3 or worse toxic effects occurred in six (3%) of 212 patients in the adjuvant radiotherapy group and in four (2%) of 212 patients in the salvage radiotherapy group. Late grade 2 or worse genitourinary toxicities were reported in 125 (59%) of 212 patients in the adjuvant radiotherapy group and 46 (22%) of 212 patients in the salvage radiotherapy group. Late genitourinary adverse events of grade 2 or worse were reported in 58 (27%) of 212 patients in the adjuvant radiotherapy group versus 14 (7%) of 212 patients in the salvage radiotherapy group (p<0·0001). Late erectile dysfunction was grade 2 or worse in 60 (28%) of 212 in the adjuvant radiotherapy group and 17 (8%) of 212 in the salvage radiotherapy group (p<0·0001). Although our analysis lacked statistical power, we found no benefit for event-free survival in patients assigned to adjuvant radiotherapy compared with patients assigned to salvage radiotherapy. Adjuvant radiotherapy increased the risk of genitourinary toxicity and erectile dysfunction. A policy of early salvage radiotherapy could spare men from overtreatment with radiotherapy and the associated adverse events. French Health Ministry and Ipsen.

About 15% of patients with endometrial cancer have high-risk features and are at increased risk of distant metastases and endometrial cancer-related death. We designed the PORTEC-3 trial to investigate the benefit of adjuvant chemoradiotherapy compared with radiotherapy alone for women with high-risk endometrial cancer. PORTEC-3 was a multicentre, open-label, randomised, international trial. Women with high-risk endometrial cancer were randomly allocated (1:1) to radiotherapy alone (48·6 Gy) in 1·8 Gy fractions five times a week or chemoradiotherapy (two cycles concurrent cisplatin 50 mg/m2 and four adjuvant cycles of carboplatin area under the curve [AUC] 5 and paclitaxel 175 mg/m2) using a biased coin minimisation procedure with stratification for participating centre, lymphadenectomy, stage of cancer, and histological type. The primary endpoints of the PORTEC-3 trial were overall survival and failure-free survival analysed in the intention-to-treat population. This analysis focuses on 2-year toxicity and health-related quality of life as secondary endpoints; analysis was done according to treatment received. Health-related quality of life was assessed with the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) the cervix cancer module and chemotherapy and neuropathy subscales of the ovarian cancer module at baseline, after radiotherapy and at 6, 12, 24, 36, and 60 months after randomisation. Adverse events were graded with Common Terminology Criteria for Adverse Events version 3.0. The study was closed on Dec 20, 2013, after achieving complete accrual, and follow-up remains ongoing for the primary outcomes analysis. This trial is registered with ISRCTN.com, number ISRCTN14387080, and with ClinicalTrials.gov, number NCT00411138. Between Sept 15, 2006, and Dec 20, 2013, 686 women were randomly allocated in the PORTEC-3 trial. Of these, 660 met eligibility criteria, and 570 (86%) were evaluable for health-related quality of life. Median follow-up was 42·3 months (IQR 25·8–55·1). At completion of radiotherapy and at 6 months, EORTC QLQ-C30 functioning scales were significantly lower (worse functioning) and health-related quality of life symptom scores higher (worse symptoms) for the chemoradiotherapy group compared with radiotherapy alone, improving with time. At 12 and 24 months, global health or quality of life was similar between groups, whereas physical functioning scores remained slightly lower in patients who received chemoradiotherapy compared with patients who received radiotherapy alone. At 24 months, 48 (25%) of 194 patients in the chemoradiotherapy group reported severe tingling or numbness compared with 11 (6%) of 170 patients in the radiotherapy alone group (p<0·0001). Grade 2 or worse adverse events were found during treatment in 309 (94%) of 327 patients in the chemoradiotherapy group versus 145 (44%) of 326 patients in the radiotherapy alone group, and grade 3 or worse events were found in 198 (61%) of 327 patients in the chemoradiotherapy group versus 42 (13%) of 326 patients in the radiotherapy alone group (p<0·0001), with most of the grade 3 adverse events being haematological (45%). At 12 and 24 months, no significant differences in grade 3 or worse adverse events were found between groups; only grade 2 or higher sensory neuropathy adverse events persisted at 24 months (25 [10%] of 240 patients in the chemoradiotherapy group vs one [<1%] of 247 patients in the radiotherapy alone group; p<0·0001). Despite the increased physician and patient-reported toxicities, this schedule of adjuvant chemotherapy given during and after radiotherapy in patients with high-risk endometrial cancer is feasible, with rapid recovery after treatment, but with persistence of patient-reported sensory neurological symptoms in 25% of patients. We await the analysis of primary endpoints before final conclusions are made. Dutch Cancer Society, Cancer Research UK, National Health and Medical Research Council, Project Grant, Cancer Australia Grant, Italian Medicines Agency, and Canadian Cancer Society Research Institute.

Background Human papillomavirus-positive oropharyngeal squamous cell carcinoma is increasing in incidence worldwide. Current treatments are associated with high survival rates but often result in significant long-term toxicities. In particular, long-term dysphagia has a negative impact on patient quality of life and health. The aim of PATHOS is to determine whether reducing the intensity of adjuvant treatment after minimally invasive transoral surgery in this favourable prognosis disease will result in better long-term swallowing function whilst maintaining excellent disease-specific survival outcomes. Methods/Design The study is a multicentre phase II/III randomised controlled trial for patients with biopsy-proven Human papillomavirus-positive oropharyngeal squamous cell cancer staged T1-T3 N0-N2b with a primary tumour that is resectable via a transoral approach. Following transoral surgery and neck dissection, patients are allocated into three groups based on pathological risk factors for recurrence. Patients in the low-risk pathology group will receive no adjuvant treatment, as in standard practice. Patients in the intermediate-risk pathology group will be randomised to receive either standard dose post-operative radiotherapy (control) or reduced dose radiotherapy. Patients in the high-risk pathology group will be randomised to receive either post-operative chemoradiotherapy (control) or radiotherapy alone. The primary outcome of the phase II study is patient reported swallowing function measured using the MD Anderson Dysphagia Inventory score at 12 months post-treatment. If the phase II study is successful, PATHOS will proceed to a phase III non-inferiority trial with overall survival as the primary endpoint. Discussion PATHOS is a prospective, randomised trial for Human papillomavirus-positive oropharyngeal cancer, which represents a different disease entity compared with other head and neck cancers. The trial aims to demonstrate that long-term dysphagia can be lessened by reducing the intensity of adjuvant treatment without having a negative impact on clinical outcome. The study will standardise transoral surgery and post-operative intensity-modulated radiotherapy protocols in the UK and develop a gold-standard swallowing assessment panel. An associated planned translational research programme, underpinned by tumour specimens and sequential blood collected as part of PATHOS, will facilitate further empirical understanding of this new disease and its response to treatment. Trial registration This study is registered with ClinicalTrials.gov identifier NCT02215265 .