Dose-Effect Relationship in Chemoradiotherapy for Locally Advanced Rectal Cancer: A Randomized Trial Comparing Two Radiation Doses

What is most relevant in preoperative rectal cancer chemoradiotherapy – the chemotherapy, the radiation dose or the timing to surgery?

“…A similarly designed study randomized patients to CRT without or with a brachytherapy boost (10 Gy in 2 fractions). The primary endpoint, pCR rates did not differ (18% in both) but more tumor regressions were seen [26]. In spite of this, again no differences in other outcomes were seen [27].…”

“…This has also been done by the group in Sao Paolo, Brazil pioneering organ preservation, to see more cCRs [36]. To add a brachytherapy boost to the center of the tumor, as explored by a Danish group, may also increase pCR rates (although this was not seen in the randomized trial [26]), but this will neither improve outcome after surgery. Although it may result in more cCRs and thus more organ preservation.…”

MRI volumetry for prediction of tumour response to neoadjuvant chemotherapy followed by chemoradiotherapy in locally advanced rectal cancer

“…In addition, a studyspecific MRI was performed after NACT and the first three RT fractions, MRI NACT . The median time from MRI PRE to the start of NACT was 5 days (range, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], and the median time from MRI CRT to surgery was 20 days (range, 7-98). 41 of the study patients were imaged using a 1.5-T GE Signa® LS scanner (GE Healthcare, Milwaukee, WI) with a phased-array torso coil.…”

“…8,9 In LARC, MRI-based tumour volume changes have been investigated as a parameter of treatment response after the full course of CRT. [10][11][12][13][14] Recognizing the dose-volume relationship, 15 it is anticipated that small tumour volume at the time of CRT is correlated to good treatment response. To our knowledge, the potential of MRI volumetry after NACT alone has been explored only in two studies; a pilot study of 16 patients 16 and a recent study of 40 patients; 17 the latter also assessing the performance of fluorine-18 fludeoxyglucose positron emission tomography ( 18 F-FDG-PET).…”

Radiation Techniques for Increasing Local Control in the Non-Surgical Management of Rectal Cancer

“…Radiation dose does seem to play a role, with higher doses resulting in higher pCR rates. Studies by our own group demonstrated the existence of a dose-response relationship for pathological tumour regression [19] and provided a quantitative estimate for the effect of dose [20•]. A meta-analysis of studies utilizing high-dose pre-operative radiotherapy also concluded that the use of radiation dose ≥60 Gy results in high rates of pCR.…”