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BREAST CONSERVATION FOR DUCTAL CARCINOMA IN SITU: WHAT IS THE RISK?

MONICA MORROW, M.D.

Lynn Sage Comprehensive Breast Center, Northwestern University Medical School, Chicago, IL 606 11

The increased detection rate of ductal carcinoma in situ (DCIS) by screening mammography presents a clinical dilemma. It is clear that for invasive cancer, survival after breast conservation is equal to survival after mastectomy and local recurrence in the breast does not appear to cause distant metastases, although it may herald their devel- opment (3, 6). The situation with ductal carcinoma in situ is different. At the time of diagnosis, the risk of met- astatic disease is negligible. Failure rates of 2% or less are seen after the treatment of intraductal carcinoma with mastectomy (5, 7) and mastectomy has the additional advantage of identifying occult foci of invasive carcinoma, which are seen in association with DCIS in as many as 20% of cases (7). Post-mastectomy follow-up is primarily directed toward identifying carcinoma in the contralateral breast, and consists of mammography annually and phy- sician visits at 6- to 12-month intervals.

Although mastectomy is safe and effective, it seems somewhat paradoxical that a woman’s reward for screen- ing and early detection is a mastectomy when her coun- terpart with invasive cancer is able to save her breast. This is particularly true because autopsy studies (1) and the results of treatment with e.rtcision alone (2,4) suggest that not all intraductal carcinclma is an obligate precursor of invasive disease.

The critical question in breast-conserving therapy for DCIS is what is the long-:erm risk of breast recurrence, and how likely are these recurrences to be salvaged? The article by Solin et al. (9) begins to answer these questions. In a group of 272 women. treated with excision and ra- diotherapy, a 16% incidence of local recurrence was ob- served at 10 years. However, 40% of the recurrences were seen between 5 and 10 years post-treatment, and an ad- ditional 12% occurred after 10 years, emphasizing the long natural history of DCIS. All of the recurrences in this series were detected when they were technically resectable. As has been demonstrated in other reports (2, 4, 7) 50% of the recurrences were invasive carcinoma, and 5 patients, all with invasive recurrence, have developed metastatic

disease. In addition, 10 patients required systemic therapy at the time of recurrence. After 5 years of follow-up, 86% of patients undergoing mastectomy remain free of distant metastases. However, the median follow-up after salvage mastectomy (3.7 years) is too short to conclude that the risk of further metastases is insignificant.

This study emphasizes several important points. Al- though 14% of the 42 women who recurred developed distant metastases, these patients were drawn from a group of 272 women, making the overall risk of metastatic dis- ease 1.8%, a figure comparable to the risk of failure after mastectomy. A similar low risk of metastatic disease was observed by the NSABP (4) in 399 women with DCIS treated with excision and breast irradiation. Nodal me- tastases were seen in 2 patients and distant metastases developed in a single patient at 5 years of follow-up.

At present, our ability to identify those women with apparently localized DCIS who will recur is limited, and our ability to predict tumors that have the biological po- tential to recur with invasive disease is nonexistent. While we await developments in molecular biology, which will allow us to identify that tumors will progress to metastatic disease, our efforts must be directed toward minimizing local recurrence. The low incidence of local failure re- ported in this series was obtained at institutions with con- siderable expertise in the selection and management of patients treated with a breast-conserving approach. The importance of careful mammographic and pathological evaluation of these patients prior to treatment selection cannot be overemphasized. Diagnostic mammography with spot magnification views to define fully the extent of calcifications should be carried out prior to excision. A specimen radiograph and a postexcision mammogram will aid in assessing the completeness of the resection. The pathological evaluation should include inking the surface of the specimen prior to sectioning and a mea- surement of specimen, as well as tumor size. Because measurement of microscopic DCIS is often difficult, re- porting the number of blocks in which DCIS is present,

Reprint requests to: M. Morrow, M.D.

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Accepted for publication 1 July 1994.

236 I. J. Radiation Oncology 0 Biology 0 Physics Volume 30, Number I, 1994

as well as its extent on a given slide, is often useful. The relationship of the lesion to calcifications, if present, should be noted, and the extent of margin involvement and proximity to margins should be stated. Finally, his- tologic subtype and nuclear grade should be assessed. Us- ing this information, the clinician can roughly estimate the risk of local recurrence, and hence the risk of metas- tases.

to 4-month intervals for the first 5 postoperative years, with visits every 6 months thereafter.

Another issue to consider in the selection of breast- conserving therapy is follow-up. The optimal follow-up schedule for the detection of recurrence at an early stage remains unknown. In this study, 70% of the recurrences detected mammographically were intraductal carcinoma and did not appear to impact on survival. Is mammog- raphy at 6-month intervals during the period of highest risk for recurrence indicated? One-fourth of the recur- rences observed were mammographically occult, indicat- ing that the choice of breast-conserving surgery carries with it a long-term commitment to follow-up not only with mammography, but also by an experienced clinician. In our hands, this consists of physical examinations at 3-

The final answer on the risk of breast-conserving ther- apy for DCIS awaits studies with longer follow-up and greater numbers of patients, as well as the results of clinical trials such as the NSABP B24 study of the effect of ta- moxifen on local failure rates. The currently available data suggest that a woman’s risk of dying of breast cancer with breast-conserving treatment of DCIS is only l-2% at 10 years, but probably does not end at that time point. The risk of undergoing a mastectomy to treat local recurrence is considerably higher, and the risk of requiring careful lifetime follow-up is 100%. Whether these risks are worth assuming can only be decided by an individual patient after a careful review of our current understanding of the biology of intraductal carcinoma. In our experience, ap- proximately two-thirds of women with intraductal car- cinoma are medically eligible for breast-conserving sur- gery, and 80% of those who are eligible chose the proce- dure, suggesting that for the majority of women breast preservation is a worthy risk.

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Fisher, B.; Anderson, S.; Fisher, E. R.; Redmond, C.; Wick- erham, D. L.; Wolmark, N.; Mamounas, E. P.; Deutsch, M.; Margolese, R. Significance of ipsilateral breast tumor recurrence after lumpectomy. Lancet 338:327-33 1; 199 1.

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