How effective is radiotherapy in reducing recurrence risk?

Hi sambo!

In addition to learning from members here, you may also be interested in checking out the article Radiation and Hormonal Therapy After DCIS Surgery Lowers Recurrence Risk from our main site.

Hope this helps.

The Mods

There aren't a lot of studies on the impact of radiation on reducing recurrence risk after a MX for DCIS, because rads is given so rarely in that type of situation.  However, as Annette said, many studies have shown that for those who have a lumpectomy for DCIS, rads cuts the recurrence risk by 50%.  So one could assume that the benefit is the same after a MX.

As for what the risk might be with close margins after a MX for DCIS, here are some studies on that:

Local recurrence of ductal carcinoma in situ after skin-sparing mastectomy   A retrospective review of 223 consecutive patients with DCIS treated by SSM and immediate reconstruction was performed. Age younger than 50 years, tumor size > 40 mm, high tumor grade, tumor necrosis, surgical margins < 1 mm, type of biopsy (excisional versus core), and SSM type were examined as risk factors for recurrence. RESULTS:  Mean followup was 82.3 months (range 4.9 to 123.2 months). Recurrences developed in 11 patients (5.1%), including: local (n = 7; 3.3%), regional (n = 2; 0.9%), and distant (n = 2; 0.9%). All seven local recurrences were detected by physical examination. No patients received adjuvant radiation therapy. Two of 19 patients with surgical margins < 1 mm developed LR (10.5%). Univariate analysis showed high tumor grade (p = .019) to influence LR.

Close or positive margins after mastectomy for DCIS: pattern of relapse and potential indications for radiotherapy   Between 1994 and 2002, the pathology reports of 574 patients who had undergone mastectomy at our institution for pure ductal carcinoma in situ were retrospectively reviewed. Of the 574 patients, 84 were found to have margins of <10 mm. Of the 84 patients, 4 underwent postoperative radiotherapy and were excluded, leaving 80 patients for this analysis. Of the 80 patients, 31 had margins <2 mm and 49 had margins of 2.1-10 mm. High-grade disease was observed in 47 patients; 45 patients had comedonecrosis; and 30 had multifocal disease. Of the 80 patients, 51 were <60 years of age.  RESULTS: With a median follow-up of 61 months, 6 (7.5%) of the 80 patients developed local recurrence. Of the 31 patients with a margin of <or=2 mm, 5 (16%) developed local recurrence vs. only 1 (2%) of 49 patients with a margin of 2.1-10 mm (p = 0.0356). Of the 6 patients with local recurrence, 5 had high-grade disease and/or comedonecrosis. All six recurrences were noted in patients <60 years old.  CONCLUSION:  The findings of this review suggest that patients with pure ductal carcinoma in situ who undergo mastectomy with a margin of <2 mm have a greater-than-expected incidence of local recurrence. Patients with additional unfavorable features such as high-grade disease, comedonecrosis, and age <60 years are particularly at risk of local recurrence. These patients might benefit from postmastectomy radiotherapy.

Impact of margin status on local recurrence after mastectomy for ductal carcinoma in situ  The primary cohort consisted of 142 patients who did not receive postmastectomy radiation therapy (PMRT). For those patients, the median follow-up time was 7.6 years (range, 0.6-13.0 years). Twenty-one patients (15%) had a positive margin, and 23 patients (16%) had a close (≤2 mm) margin. The deep margin was close in 14 patients and positive in 6 patients. The superficial margin was close in 13 patients and positive in 19 patients. One patient experienced an isolated invasive chest wall recurrence, and 1 patient had simultaneous chest wall, regional nodal, and distant metastases. The crude rates of chest wall recurrence were 2/142 (1.4%) for all patients, 1/21 (4.8%) for those with positive margins, 1/23 (4.3%) for those with close margins, and 0/98 for patients with negative margins. PMRT was given as part of the initial treatment to 3 patients, 1 of whom had an isolated chest wall recurrence.  CONCLUSIONS: Mastectomy for pure DCIS resulted in a low rate of local or distant recurrences. Even with positive or close mastectomy margins, the rates of chest wall recurrences were so low that PMRT is likely not warranted.

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And here is one study that did look at the effects of rads after a MX for DCIS for 16 high risk patients (positive or close margins, or huge area of DCIS):

The Role of Adjuvant Radiotherapy after Mastectomy in Ductal Carcinoma in Situ, Breast  Results:  Median age of patients receiving adjuvant radiotherapy was 48 (mean 50, range 31-73). Average lesion size was 6.8cm (median 6cm, range 1.5cm-15cm). Of the 16 patients evaluated 7 had positive or extremely close margins (<1mm), 7 had close margins (1mm), while 2 had free margins (2mm and 5mm). The lesion size of the 2 patients with free margins was 10cm and 15cm.... No patient experienced lymphedema, 2/16 experienced decreased range of motion in shoulder, 2/16 patients experienced chronic mild pain with no analgesic requirement. Two patients had implant reconstruction before radiotherapy and 2 patients had subsequent reconstruction. Both patients with immediate reconstruction experienced failure of the implant while both patients reconstructed after radiotherapy have experienced satisfactory cosmetic outcome. With median follow-up of 4.75 years (mean 4.26years, range 0.33-9.17years), freedom from local recurrence, disease free survival and overall survival is 100%.

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So the 3 studies show recurrence rates of 10.5%, 16% and 4.5%, respectively, for those who had close or positive margins after a MX for DCIS. Margin size and grade, and possibly age (< 60 years of age) seem to be the key factors in determining recurrence risk after a MX. The small study of those who had rads with close or positive margins shows a 0% recurrence risk.

Sambo, thank you!  And I will say that in your shoes, I think I would be leaning towards rads too. 

I was lucky because when I had my MX, my close margin was at the skin, right at the scar line.  Back in my day, rads was rarely given after a MX for DCIS - although I did discuss it with my surgeon once we had the pathology report and saw the close margin - but the easier solution was simply to remove a bit more of the skin at the incision line when my PS did the exchange surgery.  As a result I don't have as smooth an incision line as I otherwise might, but it was important to me to try to ensure that the last of those DCIS cells were removed or killed off.  Going into my surgery, I figured that the one advantage of having the MX was that it would bring my recurrence risk to the lowest level possible and I didn't want to jeopardize that for the sake of a cosmetic result.