The utility of short-course radiotherapy in a watch-and-wait strategy for rectal cancer – the need to measure the interval to tumour response assessment from the radiation start

Figures & data

Table 1. Patient and tumour characteristics in relation to the schedule of neoadjuvant radiotherapy.

	The percentages of patients (number of patients)
	5 × 5 Gy N = 199	5 × 5 Gy +  chemotherapy N = 197	Chemoradiation N = 94	p-value
Diagnosis				0.04
Rectal cancer	99% (196)	99% (194)	94% (88)
Anal canal adenocarcinoma	2% (3)	2% (3)	6% (6)
Age in years				<0.001
<60	20% (39)	32% (62)	26% (24)
60-66	19% (38)	31% (60)	31% (29)
67-74	22% (44)	27% (54)	26% (24)
≥75	39% (78)	11% (21)	18% (17)
Participating institution				<0.001
1	55% (109)	84% (166)	31% (29)
2	7% (13)	3% (6)	0
3	13% (26)	5% (9)	1% (1)
4	16% (31)	6% (12)	36% (34)
5	5% (9)	1% (1)	6% (6)
6	6% (11)	2% (3)	26% (24)
Distance between tumour and the anal verge in cm				0.025
0-2	17% (33)	19% (38)	30% (28)
3-4	32% (63)	31% (61)	38% (36)
5	25% (49)	21% (41)	11% (10)
6-8	27% (53)	29% (57)	21% (20)
Unknown (number)	1
cT category				<0.001
cT1	1% (1)	1% (1)	2% (2)
cT2	19% (38)	8% (16)	22% (21)
cT3	74% (148)	68% (134)	57% (54)
cT4	6% (12)	23% (46)	18% (17)
cN category
N0	54% (106)	28% (55)	35% (33)
N+	47% (92)	72% (142)	65% (61)
Unknown (number)	1
Tumour length in cm				<0.001
1-3	16% (32)	12% (23)	22% (21)
4	30% (59)	17% (34)	22% (21)
5-6	35% (69)	38% (75)	36% (34)
≥7	19% (37)	33% (64)	19% (18)
unknown (number)	2	1
% of circumferential extent				<0.001
≤40	22% (44)	17% (33)	34% (32)
50	33% (66)	26% (51)	22% (21)
60-90	23% (45)	20% (40)	31% (29)
100	22% (43)	37% (72)	13% (12)
unknown	2	1
Mesorectal fascia threatened				<0.001
No	76% (129)	24% (45)	54% (43)
Yes	24% (41)	76% (146)	46% (37)
unknown	29	6	14
Tumour mobility				<0.001
Movable	89% (163)	71% (136)	92% (81)
Fixed	11% (21)	29% (55)	8% (7)
Unknown (number)	15	6	6
Interval in weeks between start of RT and the first response evaluation				<0.001
<9.1	34% (68)	23% (45)	4% (4)
9.1 − 11.4	27% (54)	35% (69)	5% (5)
10.4 − 12.0	23% (45)	31% (60)	18% (17)
>12.0	16% (32)	12% (23)	72% (68)
Study				<0.001
Study A	17% (33)	2% (4)	31% (29)
Study B	83% (166)	98% (193)	69% (65)

Table 2. Clinical complete response (cCR) in relation to the radiotherapy schedule and categories of tumour grouped by the chance of achieving cCR.

	% of patients with cCR (number of patients with cCR/ total number of patients in a subgroup) N = 490	95% confidence interval
Entire cohort
5 × 5 Gy	14% (27/199)	9%−19%
5 × 5 Gy + chemotherapy	13% (25/197)	8%−18%
Chemoradiation	22% (21/94)	14%−30%
Subgroup analyses^a
High chance for cCR
5 × 5 Gy	26% (18/69)	16%−37%
5 × 5 Gy + chemotherapy	38% (17/45)	24%−52%
Chemoradiation	45% (17/38)	29%−61%
Intermediate chance for cCR
5 × 5 Gy	10% (7/68)	3%−17%
5 × 5 Gy + chemotherapy	10% (5/51)	2%−18%
Chemoradiation	9% (3/32)	0%−19%
Low chance for cCR
5 × 5 Gy	3% (2/60)	0%−7%
5 × 5 Gy + chemotherapy	2% (2/100)	0%−5%
Chemoradiation	4% (1/24)	0%−12%

^aThe high chance for cCR was assigned to cancers involving ≤50% of the circumferential extent and ≤4 cm of the length. The low chance for cCR was assigned to circular cancers or with ≥7 cm tumour length. The intermediate-chance category includes all other cancers [6]. Three patients were excluded from the subgroups analyses because of the lack of data with respect to the tumour length or circumferential extent. The crude rate of distant metastases in patients who entered the watch-and-wait program and were assigned to the high chance category was 13% (7 of 52), intermediate-chance category 0% (0 of 15) and low chance category 1 of 4. The corresponding figures for the rate of all causes of deaths were 17% (9 of 52), 13% (2 of 15) and 1 of 4, and for the rates of deaths related to rectal cancer 8% (4 of 52), 0% (0 of 52) and 0 of 4.

Jankowski M, Pietrzak L, Rupiński M, Polish Colorectal Study Group, et al. Watch-and-wait strategy in rectal cancer: is there a tumour size limit? Results from two pooled prospective studies. Radiother Oncol. 2021;160:229–235.

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Data availability statement

The database has been deposited in a repository and is available upon request.