Long-term outcomes of ductal carcinoma in situ of the breast: a systematic review, meta-analysis and meta-regression analysis

This overview of long-term (≥10 years) outcomes of 9391 women with 9404 cases of DCIS confirms more extensive local treatment is associated with lower rates of total (DCIS or invasive) or invasive LR. This meta-analysis updates and extends previous work [2], not only with longer follow-up and more studies, but through the additional evaluation of patients who had biopsy-only, adjuvant TAM, and through meta-regression providing adjusted estimates.

Progressively lower estimated proportions of LR are demonstrated with more treatment, from the least radical local treatment (biopsy-only), with the highest LR rate (27.8 %), through BCS (25.5 %) or BCS + RT (13.6 %), to Mx with lowest LR (2.6 %). We found evidence of a reduction in ipsilateral LR (both invasive and DCIS) in those receiving adjuvant RT ± TAM amongst BCS patients. Those who have CS + RT + TAM demonstrate significantly lower invasive LR-rates (4.7 %) than those who receive CS(alone) and only one adjuvant treatment (TAM 11.0 %, RT 7.2 %).

This meta-analysis combines aggregate data from studies to estimate ipsilateral LR and BCDRs in patients with DCIS with more precision than is possible in individual studies. Combining studies increases cases for analysis reducing stochastic variation. Confounding may occur because of differences between studies in treatment categories with respect to age profile, period of diagnosis, and country. Prospective studies are likely to have less measurement bias than retrospective clinical cohort studies. RCTs often have stringent exclusion criteria and often only include a minority of potential cases, whereas observational retrospective studies are more inclusive, providing more generalizable results. Despite the outlined limitations, summarizing published data using meta-analysis may assist clinicians in estimating likely recurrence-rates after various treatments. Outside of RCTs, the remaining studies were likely to have tailored patient treatment according to the clinical situation, with, for example, larger, higher-grade DCIS having more extensive surgery such as a Mx rather than BCS with or without RT. Similar outcomes between different treatment groups treated according to risk does not prove that the treatments are equivalent. This also applies to randomized trials where selected patients with higher risk disease are not offered participation in the trial.

Although this work is based on studies employing various designs and follow-up durations, outcomes data were approximated to 10 years to provide meaningful comparisons. In addition, we investigate outcomes at ≥ 15-years follow-up in the biopsy-only group, finding high rates of LR and breast cancer death; results should be interpreted with knowledge these cases were only identified as having DCIS on retrospective pathology review and may not be entirely representative of outcomes for untreated DCIS. Cases in the biopsy-only group were low-to-intermediate grade DCIS left in situ, and help provide data on the natural history of this disease. Our study highlights even longer periods of follow-up may be necessary to detect survival differences from local therapies, given the average time to ipsilateral invasive breast cancer recurrence for low-intermediate grade DCIS is 131 months and high grade, 76-months [38]. The identified small difference in LR between the biopsy-only and BCS groups could be explained by the possibility positive margins remained after the BCS surgery, the slow natural history of DCIS and that there were only small numbers assessed in the biopsy-only group. Also, DCIS may have been completely excised in the biopsy-only specimens and been less extensive.

Nine hundred and sixty-three DCIS patients treated by Mx are identified with long-term outcomes reported at 10 years–the total LR rate was 2.6 %. This compares with our earlier study with ≤ 10-year follow-up LR rate of 1.4 % (0.7–2.1 %) [2]. Residual subcutaneous and breast tissue containing tumor cells may have been left in situ if suboptimal surgery had been performed, which, in turn, may have raised the LR rate. As results are similar over the years of data collection (1953–2003), with the exception of one paper with small numbers [20], it would appear confounding from differing influences of screening and treatment might not be as great as once thought.

The addition of postoperative irradiation is advantageous for local control for DCIS patients treated with BCS, with adjuvant RT halving LR [2, 3]. Our early meta-analysis recommended the addition of RT to BCS to lower ipsilateral LR risk, particularly in tumors with necrosis, high-grade cytological features, a comedo subtype, or close/positive surgical margins [2]. The DCIS Oxford overview examined data from 3729 women managed with BCS from four RCTs, two of which had 10-year data available [3]. The absolute 10-year risk of any ipsilateral event was reduced from 28 to 13 % with RT; women aged over 50 years had the greatest proportional risk reduction with RT. We include three of these trials in this analysis; our results are in line with those of the Oxford overview. Potentially, this absolute benefit of RT (with minimal toxicity) added to BCS, may be even greater when follow-up time is extended [39]. Long-term SEER data revealed an equivalent left-to-right cardiac mortality ratio when modern RT techniques were used [40, 41]. Scandinavian data detected the rate of major coronary events was proportional to mean heart dose [42]; with improved homogeneity of radiation dosing using 3D and 4D computed tomography planning and intensity-modulated radiation therapy, a decrease in late toxicity is expected [43‐45].

Our analysis highlights the effect of adjuvant treatment in lessening total and invasive LR in BCS patients, compared to no adjuvant treatment; those at lowest risk were those who received both adjuvant treatments (RT and TAM). Initial use of TAM in DCIS was sporadic, often without knowledge of hormone receptor status.

The adjusted invasive LR rate in this review did not appear to be lowered with the addition of TAM (CS(alone) 11.3 % versus CS + TAM(no RT) 11.0 %), whereas the addition of RT to CS reduced invasive LR to 7.2 %, dropping further to 4.7 % with CS + RT + TAM. It is puzzling to understand why TAM did not seem to reduce the invasive LR rate; Cuzick et al. reported significant rate reductions with TAM for ipsilateral LR of DCIS (hazard ratio (HR) 0.71), and contralateral LR of invasive (HR 0.47) and DCIS (HR 0.36), but TAM had no effect on ipsilateral invasive LR rates (HR 0.95) [11]. The results suggest that TAM does very little to prevent invasive recurrence on the same side over and above CS alone. We know clinically that elderly patients with invasive breast cancer treated with TAM rather than a mastectomy eventually progress due to tumour resistance to this cytostatic drug [46]. Given the long follow-up in our study, it is possible any residual tumour cells would have become resistant. On the other hand, the ipsilateral LR rate was reduced when TAM was added to CS + RT. RT not only sterilizes residual cancer cells within the breast, but could additionally have a synergistic effect when combined with TAM; whether this is due to post-RT factors within the altered normal breast tissue, or is a weighting of effect of TAM in the prevention of initiation of new cancer.

Wapnir et al. [12] observed an identical 7.5 % 15-year cumulative invasive LR rate in patients with negative margins ± TAM, but positive margins were predictive of TAM response; TAM morbidity of endometrial cancer risk at 163 months doubled in the CS + RT + TAM group (1.7 %) when compared with the CS + RT(no TAM) group (0.78 %) (P = NS). Recent articles estimate DCIS has a mean estrogen receptor rate of 69–79 % and discuss ER as a predictive biomarker for endocrine manipulation [47‐49]. A Cochrane review meta-analysis examining the addition of TAM to RT for women with breast conservation for DCIS demonstrated a lower risk of ipsilateral (HR,0.75) and contralateral (HR,0.50) breast events [50]. In two large TAM-RCTs, receptor status was not used in the randomisation process, nor in reporting of outcomes [11, 12]. However, NSABP B-24 has since published evidence of a significant reduction in subsequent breast cancer with TAM use, only when tumor cells were estrogen receptor positive, with no benefit identified in estrogen receptor-negative tumors [51].

Invasive local control results suggesting that patients receiving breast conservation for DCIS may benefit from both RT + TAM must be considered in the context of the risks and benefits of such therapies. Treatment should ideally be discussed in a multidisciplinary forum and include an informed patient’s opinion and consent to validate the final decision. Factors that may influence non-use of TAM include: ER-negative DCIS, patients with a high risk of subsequent complications such as deep venous thrombosis, probability of menopausal symptoms and endometrial cancer (especially age >65 years), particularly when LR-risk is low. Factors in favor of TAM-use may include presence of moderate-to-strong breast cancer family history, significant surrounding atypical hyperplasia or lobular carcinoma in situ, and the BCS + RT patient’s perceived benefit of reducing 10-year risk of invasive LR. The risk of metastatic breast cancer following invasive recurrence from DCIS has been reported as 13–40 % [39, 52, 53]. Breast cancer-specific survival in women diagnosed with DCIS is significantly reduced following an invasive LR; both Donker et al. and Wapnir et al. documented respectively a 17-fold and 7-fold increase in the risk of breast cancer death after an invasive LR compared with those who had a DCIS LR or no LR [12, 53].

No significant difference in BCDR was observed at 10 years between the Mx, BCS + RT and BCS groups, possibly due to early detection and management of recurrences. The biopsy-only group had the highest BCDR at 10 years, and although not statistically different from other groups, may be due to a small number of cases. When ≥15-year follow-up data were used, the ≥15-year BCDR in the biopsy-only group was high (17.9 %), potentially a reflection of latent progression of invasive recurrences to metastatic disease and death. The 10-year BCDRs were no different in patients who had CS ± adjuvant therapy after meta-regression analysis. However, it may be data are not yet mature enough to produce statistical significance, considering the association between reduction in invasive LR and improvement in breast cancer survival [54, 55]. The DCIS Oxford overview did not report a breast cancer survival advantage, but only two of four trials had long-term data [3].

In the NSABP B-17/B-24 studies, cumulative probability of breast cancer-related death was 10.4 %, 10 years after the occurrence of ipsilateral invasive breast cancer recurrence [12]. In EORTC data, patients with ipsilateral invasive LR had a significantly worse breast cancer-specific survival at 60 % (HR,17.66) and overall survival (HR,5.17) ten years after LR, compared to those who had ipsilateral DCIS LR or did not experience a recurrence, with breast cancer-specific survival around 95 % (P < 0.001) highlighting that treatment strategy minimizing invasive recurrence is important for some patients [53].

Nomograms can estimate for risk recurrence for women with DCIS. The Van Nuys Prognostic Index and its variations (for Mx and BCS patients) has been evaluated for risk recurrence in independent populations [56], as has the Memorial Sloan-Kettering Cancer Center (MSKCC) DCIS Nomogram (for BCS patients) [57]; the MSKCC data were based on 1681 consecutive women.

Ongoing DCIS management trials include assessment of the role of TAM versus aromatase inhibitors [58] and of the role of trastuzumab in HER2-positive DCIS patients [59]. A validation study of genetic profiling for DCIS recurrence risk is under way [60]. These or other approaches, alone or in combination, may provide an outcome advantage over current management.