DEGRO practical guidelines: radiotherapy of breast cancer II

Current controversies in radiotherapy for breast cancer

Multimodal treatment approaches have substantially improved the outcome of breast cancer patients in the last decades. Radiotherapy is an integral component of multimodal treatment concepts used in curative and palliative intention in numerous clinical situations from precursor lesions such as ductal carcinoma in situ (DCIS) to advanced breast cancer. This review addresses current controversial topics in radiotherapy with special consideration of DCIS, accelerated partial breast irradiation (APBI) and regional nodal irradiation (RNI) and provides an update on the clinical practice guidelines of the Breast Cancer Expert Panel of the German Society of Radiation Oncology (DEGRO).

Trends in use and outcome of postoperative radiotherapy following mastectomy: A population-based study

PURPOSE

The objective of the present population-based study was to evaluate the role and effectiveness of postmastectomy radiation therapy (PMRT) in clinical practice.

METHODS

The study included 16,675 patients diagnosed with invasive breast cancer from 1988 to 2012 and resident within the catchment area of the Munich Cancer Registry. Use of PMRT, local recurrence-free survival (LRFS), cumulative incidence of time to local recurrence, relative survival and conditional overall survival (cOS), were analysed for different time periods (1988-1997 and 1998-2012).

RESULTS

Variables favouring the use of PMRT on multivariate logistic regression analysis included young age, large tumour size, positive resection margin and positive nodal status. Over time, a significant increase of PMRT was registered for patients with ⩾4 positive lymph nodes. Moreover, the present findings track a less frequent use of PMRT in elderly patients. After adjusting for age, tumour characteristics and therapies, the Cox regression analysis for LRFS identified PMRT as an independent predictor for improved local control (HR: 2.145; 95% CI: 1.787-2.574, p<0.0001). Patients with 1-3 involved lymph nodes had a 10-year cumulative incidence of local recurrence of 13.7% following mastectomy, compared to 6.5% following PMRT (p=0.0001). Comparable findings were obtained for patients presenting with ⩾4 positive lymph nodes. All effects were smaller or extinct in elderly patients aged ⩾70years. On multivariate analysis for cOS, no significant advantage for PMRT could be detected (HR: 1.084; 95% CI: 0.986-1.191, p=0.095).

CONCLUSION

The present study was useful in providing an overview on trends in the adoption of PMRT over a 25-year period. An increase in the use of PMRT from 1988 to 2012 was observed, especially in high-risk patients with ⩾4 positive lymph nodes. Patients selected for PMRT had an improved local control and an equivalent relative survival compared to patients who had no indication for PMRT.

Ductal Carcinoma In Situ of the Breast: Evaluating the Role of Radiation Therapy in the Management and Attempts to Identify Low-risk Patients

Ductal carcinoma in situ of the breast has rapidly increased in incidence over the past several decades secondary to an increased use of screening mammography. Local treatment options for women diagnosed with ductal carcinoma in situ include mastectomy or breast-conserving therapy. Although several randomized trials have confirmed a >50% reduction in the risk of local recurrence with the administration of radiation therapy (RT) compared with breast-conserving surgery alone, controversy persists regarding whether or not RT is needed in selected "low-risk" patients. Over the past two decades, two prospective single-arm studies and one randomized trial have been performed and confirm that the omission of RT after surgery is associated with higher rates of local recurrence even after selecting patients with optimal clinical and pathologic features. Importantly, these trials have failed to consistently and reproducibly identify a low-risk cohort of patients (based on clinical and pathologic features) that does not benefit from RT. As a result, adjuvant RT is still advocated in the majority of patients, even in low-risk cases. Future research is moving beyond traditional clinical and pathologic risk factors and instead focusing on approaches such as multigene assays and biomarkers with the hopes of identifying truly low-risk patients who may not require RT. However, recent studies confirm that even low-risk patients identified from multigene assays have higher rates of local recurrence with local excision alone than would be expected with the addition of RT.

Radiotherapy of Ductal Carcinoma In Situ

Ductal carcinoma in situ (DCIS) is a heterogeneous disease in both its biology and clinical course. In the past, recurrence rates after breast-conserving surgery have been as high as 30% after 10 years. The introduction of mammography screening and advances in imaging have led to an increase in the detection of DCIS. The focus of this review is on the role of radiotherapy in the multidisciplinary treatment, including current developments in hypofractionation and boost delivery, and attempts to define low-risk subsets of DCIS for which the need for adjuvant radiation is repeatedly questioned.

Immunostaining of ∆Np63 (using the p40 antibody) is equal to that of p63 and CK5/6 in high-grade ductal carcinoma in situ of the breast

As a result of breast cancer screening programs, high-grade ductal carcinoma in situ (DCIS) of the breast is diagnosed more often. Frequently, a DCIS diagnosis can only be made using immunohistochemical stains to visualize the myoepithelial layer in order to assess microinvasion. Standard markers for myoepithelial cells are CK5/6 and p63. An isoform of the latter, ∆Np63, is recognized by a recently developed antibody, p40. Here, we compare the standard myoepithelial markers CK5/6 and p63 with p40. We immunostained full sections of tissue samples of 35 high-grade DCIS and compared the staining pattern of CK5/6, p63 and p40 in tumour tissue and in normal glands. Staining patterns of myoepithelial cells for p63 and p40 were similar in terms of the percentage of stained nuclei. In all cases, p63 was strongly expressed, while this was the case for p40 in 31 (89%) and moderately in 4 (11%) cases. All but one case (97%) showed a similar percentage of stained myoepithelial cells in comparing CK5/6 and p40 staining. CK5/6 expression was heterogeneous and strong/moderate/weak in 60, 34 and 6 % respectively. Compared to surrounding normal glands, staining of myoepithelial cells for all three markers in the neoplastic lesion was attenuated. In high-grade DCIS, p40 staining is highly specific for myoepithelial cells. Its staining pattern and intensity are equal to p63, which opens up its use for daily practice. Staining with p40 is less heterogeneous than that for CK5/6.

Prognostic and predictive value of p-Akt, EGFR, and p-mTOR in early breast cancer

BACKGROUND AND PURPOSE

There are scarce data available on the prognostic/predictive value of p-Akt and p-mTOR protein expression in patients with high-risk early breast cancer.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded (FFPE) tumor tissue samples from 997 patients participating in two adjuvant phase III trials were assessed for EGFR, PTEN, p-Akt, p-mTOR protein expression, and PIK3CA mutational status. These markers were evaluated for associations with each other and with selected patient and tumor characteristics, immunohistochemical subtypes, disease-free survival (DFS), and overall survival (OS).

RESULTS

p-mTOR protein expression was negatively associated with EGFR and positively associated with PTEN, with p-Akt473, and with the presence of PIK3CA mutations. EGFR expression was positively associated with p-Akt473, p-Akt308, and PIK3CA wild-type tumors. Finally, p-Akt308 was positively associated with p-Akt473 expression. In univariate analysis, EGFR (p = 0.016) and the coexpression of EGFR and p-mTOR (p = 0.015) were associated with poor OS. Among patients with p-Akt308-negative or low-expressing tumors, those treated with hormonal therapy were associated with decreased risk for both relapse and death (p = 0.013 and p < 0.001, respectively). In the subgroup of patients with locoregional relapse, positive EGFR and mTOR protein expression was found to be associated with increased (p = 0.034) and decreased (p < 0.001) risk for earlier relapse, respectively. In multivariate analysis, low levels of p-Akt308 and the coexpression of EGFR and p-mTOR retained their prognostic value.

CONCLUSION

Low protein expression of p-Akt308 was associated with improved DFS and OS among patients treated with hormonal therapy following adjuvant chemotherapy. Coexpression of EGFR and p-mTOR was associated with worse OS.