How do you approach the discussion of omission vs. inclusion of adjuvant radiation in patients with low to intermediate-grade DCIS?

There are several factors when evaluating patients with low/intermediate grade DCIS and the role of RT:

1. Estrogen negative. While rare, I almost always recommend RT.
2. Willingness to take endocrine therapy. More and more patients are concerned about taking endocrine therapy and I discuss RT in these patients (though trials looking at omitting RT in these patients had mixed numbers receiving endocrine therapy).
3. Technique. I routinely offer these patients partial breast irradiation so the decision is a bit easier as they are going from 3-4 weeks of WBI to 5 fractions (our PBI technique).
4. Outcomes. I discuss the ECOG and RTOG 9804 data and also the fact that the recurrences had not plateaued at 12 years. I discuss the 15% LR recurrence rate if omitting RT and that half of these recurrences are invasive (Solin et al., PMID 26371148). I discuss that in general, RT for DCIS is not associated with a survival advantage but that invasive recurrences are associated with a breast cancer mortality increase (Wapnir et al., PMID 21398619)
5. Margins. I review current guidelines and that ECOG used 3 mm margins and review their pathology in relation.

Our guidance and approach to DCIS at MSKCC is a joint guidance developed by rad onc and surgery. We developed this to try to make our approach uniform across the network. Notably, we acknowledge that outside of the absolute indications, there is a lot of unstructured decision-making based on patient preferences. In short, outside the absolute indications, it is never wrong to omit radiotherapy, nor is it wrong to offer it.

DCIS:

• Indications for adjuvant radiotherapy (presence of any one of these factors is sufficient):

• Presence of any grade 3 component on biopsy or surgery specimens (MSK path review needed for both specimens).
• Size >2.5 cm.
• Age <40.
• Any close margin (<2 mm). Note that if the close margin is the sole indication for adjuvant RT, consider re-excision (discuss with surgeon and patient).

• For all other risk factors and combinations of risk factors, discussion with the patient and the patient’s risk tolerance for subsequent in-breast events needs to be discussed and considered. Observation can be considered for any patient not meeting the criteria above. Radiotherapy can be considered for any patient with DCIS, including low-risk/good-risk DCIS (depending on the risk tolerance of the patient). Approximate risk of total and invasive recurrence in the breast are:

• Factors to consider include:

• Definition of RTOG 9804 “Good Risk” (low or intermediate grade, <2.5 cm with margins >/=3 mm).
• MSK nomogram risk.
• Age 40-50.
• ER status.
• Use of endocrine therapy.
• NOTE on size: Without frank measurement, one block is typically 3mm thick. Approx. DCIS size = # positive slides x 3 mm. 

NOTE: TROG randomized study demonstrated the benefit of boost in non-good-risk DCIS patients. Can omit for good-risk.

I find that most patients can understand the concept of local recurrence risk of “1% per year of follow-up from diagnosis” without radiation. I usually present this information first. I then add that radiation had a significant impact on that local recurrence, with the 10-year rate of failure below 2%. Next, I further explain that between 10 and 15 years of follow-up, the risk of recurrence/new disease increases more rapidly but still at 15 years, the radiation reduces the risk of a local failure compared to no radiation by about one-half.

For women under the age of 50 though, I believe the risk of local failure is higher and I tend to encourage radiation in that age group, even if they have “good risk” DCIS.

Finally, I remind my patients that radiation lowers the risk of local failure, although the patient has an excellent overall survival from this “Stage 0” cancer.

We typically start this discussion with a general review of the pathophysiology and natural history of DCIS. We explain that radiation has not been shown in a prospective randomized trial to impact overall survival; as such, patient preference is paramount to decision-making. Based on the low-risk cohort from ECOG-ACRIN E5194 (Solin et al., PMID 26371148) and RTOG 9804 (McCormick et al., PMID 34406870), we explain that there is an approximately 1%/year risk of local recurrence for low-risk disease, about half of which are invasive cancers. We then discuss the side effects of radiation and attempt to put these in perspective with respect to both incidence and severity.

In addition, we discuss potential treatments that may be necessary should they have a recurrence. Finally, we try to put both the side effects and radiation benefits in the context of their other medical co-morbidities and life expectancy. Typically, these are protracted conversations often influenced by guidance the patient has already received from their surgeon. It is frequently helpful to meet with the patient a second time after they have had a chance to digest the first conversation. 

Collaborated with Dr. @Dr. First Last.

For almost all patients, I explain that there is a local control benefit (2/3 reduction based on RTOG 9804, etc., which ends up being ~10% absolute reduction for most) but probably no survival benefit. My strength of recommendation would depend on age, size, margin, etc. but I always tell patients that the decision is theirs to get radiation or not, as long as they understand the risks and benefits. For those still on the fence, I sometimes order DCISionRT, explaining that the study isn't quite ready for prime time yet.

If radiation, I try to enroll those who qualify for our 1-week partial breast protocol (3 or 5 fxs) done in collaboration with Weill Cornell. Otherwise, the standard is a 3-week course whole breast w/ or w/o SIB. Whenever possible, I keep the heart and lungs completely out of the fields (prone breast or other technique), even if it means missing a small corner of the breast, as long as it's not the corner with the tumor bed.

I wouldn’t. If it’s worth operating, it’s worth irradiating. RT is likely less risky than anesthesia, particularly, for an older patient.

I plead stupidity.

As several of you cite data that many recurrences continue in years 10-15 after treatment and well beyond year 15, how can you accept APBI trials or those with hypofractionation, none of which have reached the minimum follow-up that surgeons demanded in the 1980s for accepting lumpectomy/XRT as an equal treatment to mod rad mastectomy?

I plead ignorance but am willing to learn. Of course, I have read all of Jay Harris's editorials several years ago. But as late local recurrences are seemingly continuing, shouldn't we go back to old-fashioned but proven whole breast XRT and boost at 180/200 cGy/day in the interim? I am willing to learn!