Outcome of different radiotherapy strategies after breast conserving surgery in patients with ductal carcinoma in situ (DCIS)

Figures & data

Figure 1. Flow chart describing available tumor material from the randomized SweDCIS trial, for evaluation of 10-year absolute total local recurrence risk according to five different radiotherapy strategies.

Table 1. Treatment of invasive or in situ recurrences in 74 women after initial breast conserving surgery for primary DCIS, with or without adjuvant radiotherapy.

	BCS without adjuvant RT		BCS with adjuvant RT
Recurrence type Treatment	In situ n = 25	Invasive n = 29	In situ n = 8	Invasive n = 12
Radiotherapy^a	5 (20%)	16 (55%)	1 (12%)	1 (8%)
BCS^b	8 (32%)	8 (28%)	3 (38%)	3 (25%)
Mastectomy^b	17 (68%)	20 (69%)	5 (62%)	9 (75%)
Reconstruction^c	6 (24%)	5 (17%)	3 (38%)	2 (17%)
Chemotherapy^d	1 (4%)	4 (14%)	1 (12%)	4 (33%)

^a± boost.

^b± axillary staging.

^cAny reconstruction.

^dAny chemotherapy regime.

DCIS: ductal breast carcinoma in situ; BCS: breast conserving surgery.

Table 2. Costs for different treatments according to diagnostic related grouping in Sweden 2020 and converted to US dollars.

Treatment cost	US dollars
Radiotherapy breast (boost or no boost)	$4900
Breast Conserving Surgery (Sentinel Lymph Node Biopsy or not)	$6700
Mastectomy	$12,900
Mastectomy + axillary clearance	$19,800
Mastectomy + Implant Reconstruction	$16,500
Delayed Implant Reconstruction	$16,500
Immediate or Delayed Autologous Reconstruction	$41,300
Chemotherapy (any regime)	$6900

Table 3. The calculated 10-year absolute total breast event risks (invasive and in situ) for patients treated with breast conserving surgery with negative margins and with adjuvant radiotherapy given according to different strategies in the SweDCIS randomized study.

		Total breast event risk at 10-years
Strategy	Treatment (numbers)	Absolute risk (CI 95%)
Strategy 1	RT to none	18.2% (12.5%–26.3%)
Strategy 2	RT to all	7.9% (5.0%–12.6%)
Strategy 3	No RT tot DCISionRT Low Risk (n = 264)	12.9% (6.9%–23.5%)
	RT to DCISionRT Elevated Risk (n = 240)	8.3% (4.5%–5.3%)
Strategy 4^a	No RT to RTOG 9804 good-risk (n = 197)	11.6% (5.7%–23.9%)
	RT to RTOG 9804 high-risk (n = 306)	7.1% (3.9%–13.2%)
Strategy 5^b	No RT to SwG low-risk (n = 65)	15.9% (4.8%–52.5%)
	RT to SwG high-risk (n = 439)	7.5% (4.6%–12.5%)

CI 95%: 95% Confidence Interval; DS: Decision Score; RT: Radiotherapy; SwG: Swedish National Guidelines.

^aGood-risk clinicopathologic DCIS criteria modified from RTOG 9804, consisting of screen detected, non-palpable lesions with a size ≤2.5 cm, NG I-II, and negative margins.

^bLow-risk criteria from modified Swedish National Guidelines NG I-II, size <1.5 cm, negative margin, and age ≥52years years.

Table 4. Proportion of women having adjuvant radiotherapy, number of recurrences at 10-years, and mean total cost per RT-strategy per woman undergoing breast conserving surgery for DCIS.

DCIS BCS ± RT	RT%	Recurrences at 10-years (invasive/in situ)	Cost (including adjuvant RT and treatment of recurrence)
Strategy 1, RT to none	0%	18.6% (8.4/10.2)	$3927
Strategy 2, RT to all	100%	7.8% (4.7/3.1)	$6541
Strategy 3, RT per DCISionRT	52%	10.5% (5.3/5.2)	$4781
Strategy 4, RT per RTOG 9804	61%	8.9% (3.5/5.4)	$4851
Strategy 5, RT per SwG	87%	8.6% (3.6/5.0)	$6079

BCS: breast conserving surgery; RT: radiotherapy; SwG: Swedish National Guidelines. $: US dollars.

Table 5. Numbers needed to treat (NNT) and harm for the different radiotherapy strategies in relation to cost and recurrence risk at 10-years compared to RT to none, in the SweDCIS cohort with women undergoing breast conserving surgery for primary DCIS.

Treatment	Adjuvant RT (%)	NNT	Prevented recurrences (%)	Caused harm^a (%)	Incremental cost per woman (US $)	Cost per prevented recurrence (US $)
Strategy 1, RT to none	0	–	–	–	–	–
Strategy 2, RT to all	100	9.3	10.8	8.3	$2,614	$24,201
Strategy 3, DCISionRT	52	6.4	8.1	4.3	$853	$10,534
Strategy 4, RTOG 9804	61	6.3	9.7	5.1	$929	$9,525
Strategy 5, SwG	87	8.7	10.0	7.2	$2,152	$21,521

^aAccording to reference 13.

RT: adjuvant radiotherapy; DCIS: ductal breast carcinoma in situ; SwG: Swedish National Guidelines; $: US dollars; NNT: numbers needed to treat.

McCormick B, Winter K, Hudis C, et al. RTOG 9804: a prospective randomized trial for good-risk ductal carcinoma in situ comparing radiotherapy with observation. J Clin Oncol. 2015;33(7):709–715. doi: 10.1200/JCO.2014.57.9029.

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Data availability statement

All data can be provided by the corresponding author.