Practice-changing clinical trials in radiation oncology for gastrointestinal malignancies in 2021-2023

Gastrointestinal cancers are one of the most frequent cancers and a leading cause of cancer deaths worldwide. We provide an overview of the most important practice-changing trials that were either published or presented at the international scientific meetings in 2021-2023. Highlights included reports on three phase III trials (CONCORDE/PRODIGE 26, ARTDECO, and a study by Xu et al.) that evaluated dose escalation in the definitive setting for locally advanced oesophageal cancers, as well as two phase III trials that evaluated the role of chemotherapy (neo-AEGIS) and targeted therapy (NRG/RTOG 1010) in the neoadjuvant setting for adenocarcinoma oesophageal cancers or gastroesophageal junction cancer. CheckMate 577 evaluated nivolumab in patients who had residual pathological disease after neoadjuvant chemoradiation followed by complete resection. The use of radiation therapy for borderline and locally advanced pancreatic cancer is also discussed (SMART and CONKO-007 trials). Stereotactic body radiation therapy followed by sorafenib was compared to sorafenib alone in patients with hepatocellular carcinoma in the NRG/RTOG 1112 study. New options in the management of rectal cancer are emerging such as total neoadjuvant treatment (PRODIGE 23, RAPIDO, PROSPECT), organ preservation (OPRA, OPERA), and the role of immunotherapy in patients with DNA mismatch-repair deficient/microsatellite instability. Finally, preliminary results of the ACT 4 trial that evaluated de-escalation in anal cancer are presented.

[Organ preservation in oropharyngeal cancers treatment: What arguments for radiotherapy?]

Management of oropharyngeal cancer depends on several factors. Immediate surgery or radiotherapy may be considered. If the patient is operable, the choice depends on the extent of the disease, the contributing factors, and the expected functional results. For HPV-positive cancers, studies show comparable efficacy between surgery and radiotherapy. For early-stage cancers, unimodal treatment should be preferred. For HPV-negative cancers, the results of retrospective and observational studies are in favor of surgery. These studies have some limitations. In observational and/or retrospective studies, reclassification biases and the applicability of propensity scores weaken the validity of studies showing differences in management. Tumor and patient comparability are others majors interpretation biases. It is precipitate to conclude that surgery is superior for HPV-negative oropharyngeal cancers. Toxicity, therefore, becomes a criterion of choice for treatment. Unimodal management by surgery allows limited toxicity for the early stages. Surgery has less impact on salivation. Radiotherapy is rather less deleterious for swallowing in the early stages. For the advanced stages of HPV-induced tumors, the non-superiority of surgery should lead to the choice of radiochemotherapy. For oropharyngeal cancers, the possible benefit of surgery in HPV-negative oropharyngeal cancers must be confirmed in randomized studies. For the early stages of oropharyngeal cancer with unimodal treatment, management could be decided by shared decision making.

[Organ preservation for rectal cancer: What are the arguments in favor of radiotherapy?]

Standard care for rectal cancers relies on both tumor (location relative to the sphincter, T and N stage, sphincter involvement) and patients characteristics. Radical surgery (total mesorectal excision) following short-course radiotherapy (RT) or standard chemo-radiotherapy, associated with induction or consolidation chemotherapy (total neoadjuvant treatment), remains the cornerstone of locally advanced rectal cancer (T3cd, T4 and/or N+) treatment. Nevertheless, for early stages, this radical resection could be avoided in favor of conservative approaches combining RT (external, contact, brachytherapy) with or without chemotherapy (concurrent, induction or consolidative), or even be limited, for good responders, to a local excision with view of organ-preservation strategies. This conservative approach could also be offered selectively to patients with complete clinical response after the induction sequence, irrespective of initial tumor characteristics. The Watch and Wait strategy relies on clinical, endoscopic and radiological evaluations, as well as sustained surveillance. Ongoing studies aim to improve response rates, either with chemotherapy intensification, or RT boost dose escalation with brachytherapy or contact-therapy.

[Rectal Cancer: Organ preservation and neoadjuvant treatment escalation]

Standard treatment consisting of chemoradiotherapy followed by radical surgery with total mesorectal excision, results in good oncologic local control but high morbidity and poor functional results. Since chemoradiotherapy results in 15% pathological complete response, even reaching up to 30% in case of association with neoadjuvant chemotherapy, radical surgery has been recently debated for good responders. Therefore, a de-escalation strategy, by omitting radical surgery in good responders, has recently been developed with two different options: a watch and wait strategy, requiring an accurate clinical and radiological definition of complete response and a local excision strategy including patients with sub-complete response. Ongoing trials focus on response optimization by chemotherapy intensification or radiotherapy dose escalation. However, many questions are still to be answered regarding definition of complete response, follow-up strategy, morbidity of salvage surgery in case of recurrence as well as long-term oncological and functionnal results.

[Rectal cancer: Towards personalized medicine]

The standard of care for patients with locally advanced rectal cancer has recently changed and is now based on the concept of total neoadjuvant therapy with the association of radiotherapy and systemic chemotherapy before radical surgery. The addition of noeadjuvant systemic chemotherapy before or after radiotherapy during preoperative course significantly decreased the risk of distant metastases and prolonged disease-free survival after surgery. The risk of recurrence varies among patients and the standard management associating chemotherapy, radiotherapy and surgery may expose many patients to overtreatment and can negatively affect quality of life. In this setting, several ongoing trials evaluate the possibility of less aggressive individually tailored approach based on omission of one of three treatments. In particular, NORAD and PROSPECT trials evaluate whether irradiation could be safely omitted in patients who are good responders to induction chemotherapy and have locally advanced primarily resectable tumor with large predictive circumferential resection margin. In the other hand, the total neoadjuvant therapy had significantly improved the pathological complete response rate, up to 30%, leading the concept of non-operative management and organ-preserving strategies. The phase III GRECCAR 12 study has therefore evaluated the potential benefit of intensification of neoadjuvant chemotherapy whereas OPERA and MORPHEUS trials assessed radiotherapy dose escalation by contact X-ray or brachytherapy for organ-preserving strategies. To date, total neoadjuvant therapy following by radical surgery remains the standard of care but probably less aggressive approach with omission of radiotherapy or surgery will become a new standard in selected patients in next future.

[Organ preservation by chemoradiation for bladder cancer]

When localized, the reference treatment of urothelial, muscle-invasive bladder tumours relies on radical cystectomy with reconstruction by enterocystoplasty if possible or Bricker bypass. Trimodal therapy combining transurethral resection of the tumour followed by concomitant chemotherapy may be considered as a therapeutic alternative to radical cystectomy in well-selected patients with unifocal tumours, stage T2, non-diverticular location, without in situ carcinoma or hydronephrosis and with macroscopically complete transurethral resection. The functional prognosis of the bladder and quality of life should be discussed with the patient as well as the need for salvage surgery for persistent tumour at a 45-Gy dose level, the latter being a highly unfavourable prognosis factor. On the other hand, this trimodal treatment is the reference in case of surgical contraindication. This article details the methods and results of the main series available in the literature in terms of local control, survival, bladder preservation rates and complications, as well as study prospects.

[Organ preserving strategies for rectal cancer treatment]

For rectal cancers, the current standard of care consists of chemoradiation followed by radical surgery with total mesorectal excision. Oncologic results are good, especially regarding local recurrence rates, but at the cost of high morbidity rates and poor anorectal, urinary and sexual function results. Since chemoradiation yields 15 to 25% pathological complete response, the role of radical surgery is questioned for patients presenting with good response after chemoradiation and two organ preservation strategies have been offered: watch and wait strategy and local excision strategy. The aim of this review is to give the results of organ preservation after chemoradiotherapy series and to highlight different questions regarding initial patient's selection, complete clinical response definition, risk of mesorectal nodal involvement, follow-up modalities as well as oncologic and functional results.