Neo-adjuvant radiotherapy in rectal cancer

Table 4 Main differences between and potential advantages of short-course and long-course preoperative radiotherapy in intermediate (bad) rectal cancers¹

	Short-course	Long-course
Total (physical) radiation dose	25 Gy	45-50.4 Gy
Fraction size/number of fractions	5 Gy/5	1.8-2 Gy/23-28
Radiation duration	1 wk	4.5-5.5 wk
BED2, acute effects	37.5 Gy	37.5-44.4 Gy
BED2, late effects	66.7	72-84 Gy
Overall treatment time	About 10 d	10-14 wk
Demands of radiation resources	Planning + 5 fractions	Planning + 23-28 fractions
Concomitant chemotherapy3	No	Yes
Acute toxicity	Minimal	More
Late toxicity	Present, considered limited in the “bad” group	Present, but not extensively studied. Anticipated to be higher than after short-course
Down-sizing/down-staging	No4	Yes5

¹In locally advanced (ugly) tumours, long-course CRT is the preferred option although short-course RT with a delay to surgery is an option if CRT is not tolerated because of high age or co-morbidity;

²Biologically effective dose according to the time-corrected linear quadratic model. Major uncertainties exist in the relative biological efficacy of the fractionation schedules concerning the acute, antitumour effects. The parameters selected for the acute effects were those used in the meta-analyses from 2001[7], even if they can be criticized and probably are incorrect. For late effects, an α/β of 3 Gy with no time correction is used. The anticipated antitumour effects do not thus differ substantially and late toxicity is at least not higher with short-course RT;

³Improved local control with long-course RT, increased acute toxicity and probably also late toxicity. Should not be given with short-course RT;

⁴Seen after short-course RT with delayed surgery;

⁵Not relevant in these intermediate tumours (unless organ-preservation is aimed at), however, relevant in locally advanced (ugly) tumours. BED: Biologically effective dose.