Against the motion
SP-1008
Abstract
This house believes that short-course radiotherapy is the ideal schedule as part of total neoadjuvant therapy programs for rectal cancer Against the motion
Authors: Maria Antonietta Gambacorta1
1Fondazione Policlinico universitario A. Gemelli-IRCCS, Radiation Oncology, Rome, Italy
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Abstract Text
The treatment of locally advanced rectal cancer is radiotherapy+/chemotherapy followed by surgery. The goal of preoperative treatment is improvement of local control.
The aim of long course radiochemotherapy (LC-CRT) is also tumor shrinkage. This leads to a reduction in CRM+ and a pCR rate of 15-20%. The latter observation has led to the initiation of organ preservation research projects, not only in LARC but also in early cancers, where CR can be achieved in up to 40% of patients.
Dose escalation, the interval between the end of preoperative treatment and response assessment, and chemotherapy intensification are all factors contributing to the improvement of tumor response.
LC-CRT is the type of treatment that best fits these modes of improving cancer outcomes.
Dose: LC-CRT is the treatment that can best exploit the advantages of IMRT-IGRT, allowing dose differentiation on the elective CTV and GTV, dose escalation schedules on the GTV and dose adaptation to smaller volumes during treatment. These features make LC-CRT a local treatment that can be tailored to tumor presentation and treatment goals, compared to SCRT which is a ‘one fits all’ treatment that, regardless of tumor presentation, does not allow dose differentiation, escalation or adaptation.
Interval: several studies on LC-CRT have shown that prolonging the interval between CRT and surgery leads to an increase in tumor response with pCR rates of up to 30%, 95% of which occur 10 weeks after the end of CRT. Delaying surgery after SCRT resulted in a better tumor response rate with pCR of 11%, which is still lower than those obtained with preoperative LC-CRT.
CT intensification: the addition of consolidation CT to LC-CRT demonstrated an increased complete response rate and improved DFS. Although the RAPIDO trial demonstrated better pCR DFS of LCRT and FOLFOX compared to adjuvant LC-CRT +/- CT, the two arms are unbalanced in both treatment intensity and the interval between RT and surgery. Despite these differences, local control still favored LC-CRT. More robust results are expected from ongoing studies comparing LCRT regimens with SCRT and consolidation CT versus LC-CRT and consolidation CT with the same interval between preoperative RT and surgery.