Dandy-Walker Phenotype with Brainstem Involvement: 2 Distinct Subgroups with Different Prognosis.

BACKGROUND AND PURPOSE: Although cardinal imaging features for the diagnostic criteria of the Dandy-Walker phenotype have been recently defined, there is a large range of unreported malformations among these patients. The brainstem, in particular, deserves careful attention because malformations in this region have potentially important implications for clinical outcomes. In this article, we offer detailed information on the association of brainstem dysgenesis in a large, multicentric cohort of patients with the Dandy-Walker phenotype, defining different subtypes of involvement and their potential clinical impact. MATERIALS AND METHODS: In this established multicenter cohort of 329 patients with the Dandy-Walker phenotype, we include and retrospectively review the MR imaging studies and clinical records of 73 subjects with additional brainstem malformations. Detailed evaluation of the different patterns of brainstem involvement and their potential clinical implications, along with comparisons between posterior fossa measurements for the diagnosis of the Dandy-Walker phenotype, was performed among the different subgroups of patients with brainstem involvement. RESULTS: There were 2 major forms of brainstem involvement in patients with Dandy-Walker phenotype including the following: 1) the mild form with anteroposterior disproportions of the brainstem structures "only" (57/73; 78%), most frequently with pontine hypoplasia (44/57; 77%), and 2) the severe form with patients with tegmental dysplasia with folding, bumps, and/or clefts (16/73; 22%). Patients with severe forms of brainstem malformation had significantly increased rates of massive ventriculomegaly, additional malformations involving the corpus callosum and gray matter, and interhemispheric cysts. Clinically, patients with the severe form had significantly increased rates of bulbar dysfunction, seizures, and mortality. CONCLUSIONS: Additional brainstem malformations in patients with the Dandy-Walker phenotype can be divided into 2 major subgroups: mild and severe. The severe form, though less prevalent, has characteristic imaging features, including tegmental folding, bumps, and clefts, and is directly associated with a more severe clinical presentation and increased mortality.

Refining the Neuroimaging Definition of the Dandy-Walker Phenotype.

BACKGROUND AND PURPOSE: The traditionally described Dandy-Walker malformation comprises a range of cerebellar and posterior fossa abnormalities with variable clinical severity. We aimed to establish updated imaging criteria for Dandy-Walker malformation on the basis of cerebellar development. MATERIALS AND METHODS: In this multicenter study, retrospective MR imaging examinations from fetuses and children previously diagnosed with Dandy-Walker malformation or vermian hypoplasia were re-evaluated, using the choroid plexus/tela choroidea location and the fastigial recess shape to differentiate Dandy-Walker malformation from vermian hypoplasia. Multiple additional measures of the posterior fossa and cerebellum were also obtained and compared between Dandy-Walker malformation and other diagnoses. RESULTS: Four hundred forty-six examinations were analyzed (174 fetal and 272 postnatal). The most common diagnoses were Dandy-Walker malformation (78%), vermian hypoplasia (14%), vermian hypoplasia with Blake pouch cyst (9%), and Blake pouch cyst (4%). Most measures were significant differentiators of Dandy-Walker malformation from non-Dandy-Walker malformation both pre- and postnatally (P < .01); the tegmentovermian and fastigial recess angles were the most significant quantitative measures. Posterior fossa perimeter and vascular injury evidence were not significant differentiators pre- or postnatally (P > .3). The superior posterior fossa angle, torcular location, and vermian height differentiated groups postnatally (P < .01), but not prenatally (P > .07). CONCLUSIONS: As confirmed by objective measures, the modern Dandy-Walker malformation phenotype is best defined by inferior predominant vermian hypoplasia, an enlarged tegmentovermian angle, inferolateral displacement of the tela choroidea/choroid plexus, an obtuse fastigial recess, and an unpaired caudal lobule. Posterior fossa size and torcular location should be eliminated from the diagnostic criteria. This refined phenotype may help guide future study of the numerous etiologies and varied clinical outcomes.

Imaging Characteristics of CNS Neuroblastoma-FOXR2: A Retrospective and Multi-Institutional Description of 25 Cases.

BACKGROUND AND PURPOSE: The 5th edition of the World Health Organization Classification of CNS tumors defines the CNS neuroblastoma FOXR2 in the group of embryonal tumors. Published clinical outcomes tend to suggest a favorable outcome after resection, craniospinal irradiation, and chemotherapy. This multicenter study aimed to describe imaging features of CNS neuroblastoma-FOXR2, which have been poorly characterized thus far. MATERIALS AND METHODS: On the basis of a previously published cohort of tumors molecularly classified as CNS neuroblastoma-FOXR2, patients with available imaging data were identified. The imaging features on preoperative MR imaging and CT data were recorded by 8 experienced pediatric neuroradiologists in consensus review meetings. RESULTS: Twenty-five patients were evaluated (13 girls; median age, 4.5 years). The tumors were often large (mean, 115 [ SD, 83] mL), showed no (24%) or limited (60%) perilesional edema, demonstrated heterogeneous enhancement, were often calcified and/or hemorrhagic (52%), were always T2WI-hyperintense to GM, and commonly had cystic and/or necrotic components (96%). The mean ADC values were low (687.8 [SD 136.3] × 10-6 mm2/s). The tumors were always supratentorial. Metastases were infrequent (20%) and, when present, were of nodular appearance and leptomeningeal. CONCLUSIONS: In our cohort, CNS neuroblastoma FOXR2 tumors showed imaging features suggesting high-grade malignancy and, at the same time, showed characteristics of less aggressive behavior. There are important differential diagnoses, but the results of this study may assist in considering this diagnosis preoperatively.

Stroke Recurrence in Children with Vertebral Artery Dissecting Aneurysm.

BACKGROUND AND PURPOSE: Pediatric vertebral artery dissecting aneurysm is a subtype of vertebral artery dissection that can be challenging to diagnose and may be associated with stroke recurrence. This study examines the presenting features, clinical outcomes, and recurrence risk in a cohort of children with vertebral artery dissection, comparing those with aneurysms with those without. MATERIALS AND METHODS: The medical records of children evaluated for vertebral artery dissection were retrospectively reviewed for neurologic presentation, treatment, stroke recurrence, and angiographic appearance of dissection. Cohort patients were categorized into 2 groups based on the presence or absence of a vertebral artery dissecting aneurysm and compared via the Fisher exact test, Student t test, and log-rank analyses. P < .05 was deemed statistically significant. RESULTS: Thirty-two patients met the inclusion criteria, including 13 with vertebral artery dissecting aneurysms. Five cases of vertebral artery dissecting aneurysm were missed on the initial evaluation and diagnosed retrospectively. All patients received antiplatelet or anticoagulation therapy at the time of diagnosis. Children in the vertebral artery dissecting aneurysm group were more likely to present with stroke (P = .059), present at a younger age (P < .001), and have recurrent stroke (P < .001) compared with the group of children with vertebral artery dissection without an aneurysm. After surgery, no patients with vertebral artery dissecting aneurysm experienced recurrent stroke (P = .02). CONCLUSIONS: Vertebral artery dissecting aneurysm is often missed on the initial diagnostic evaluation of children presenting with stroke. In children with vertebral artery dissection, the presence of an aneurysm is associated with stroke presentation at a younger age and stroke recurrence.

Congenital Nasal Pyriform Aperture Stenosis: Evidence of Premature Fusion of the Midline Palatal Suture.

BACKGROUND AND PURPOSE: Various etiologies have been theorized for the development of congenital nasal pyriform aperture stenosis (CNPAS). Imaging possibly implicates abnormal fusion of the midline palatal suture and deficient lateral growth of the midface in affected neonates. MATERIALS AND METHODS: A single-center, retrospective study was performed at a tertiary care pediatric hospital involving neonates and infants between 0 and 90 days of life. Maxillofacial CT scans of patients were reviewed. Abnormality of the palatal suture and midface transverse dimensions were measured and analyzed in patients with and without CNPAS. RESULTS: A total of 109 patients between 0 and 90 days of life had maxillofacial CT scans. Thirteen patients were classified as having CNPAS, 27 patients had normal scans (control group), and 69 patients were excluded because of the presence of other craniofacial anomalies. All patients with CNPAS had evidence of abnormal fusion of the midline palatal suture. Zero patients without CNPAS had a midline palatal suture abnormality. The mean widths of the pyriform aperture were 5.7 mm (SD, 1.7) in the CNPAS group and 13.1 mm (SD, 2.7) in the control group (P < .0001). The mean distance between the superior portions of the nasolacrimal ducts was 9.1 mm (SD, 2.1) in the CNPAS group, and the mean of the control group was 13.4 mm (SD, 2.2) (P < .0001). CONCLUSIONS: Patients with CNPAS have abnormal fusion of the midline palatal suture and exhibit lateral growth restriction of the midface. This may implicate synostosis of the midline palatal suture and abnormal midface growth.

Cost and Utility of Routine Contrast-Enhanced Neck MRA in a Pediatric MRI Stroke Evaluation Protocol.

BACKGROUND AND PURPOSE: Cervical arterial dissection is one of the frequent causes of pediatric arterial ischemic stroke. Out of concern for missing cervical arterial dissection in patients in whom pediatric stroke is suspected, our tertiary children's hospital added contrast-enhanced 3D neck MR angiography to every pediatric stoke work-up. This research investigated whether the routine use of contrast-enhanced neck MRA in our MR imaging stroke protocol ever detected a cervical arterial abnormality when the DWI, SWI/gradient recalled-echo, or circle of Willis MRA findings from the brain MR imaging were reported as normal. MATERIALS AND METHODS: The institutional PACS data base was searched for stroke protocol MRIs that included DWI, gradient recalled-echo or SWI, circle of Willis MRA, and 3D contrast-enhanced neck MRA in patients younger than 18 years of age with examinations performed between September 2010 and June 2017. RESULTS: In only a single case (0.15%) were the DWI, SWI/gradient recalled-echo, or circle of Willis MRA findings all separately reported as normal and the contrast-enhanced neck MRA findings reported as abnormal. To reach these findings, we screened 681 patients, which would have resulted in an estimated >$200,000 in Medicare charges and $80,000 in of out-of-pocket cost to patients. CONCLUSIONS: In our large series, the addition of a routine contrast-enhanced neck MRA to our pediatric stroke MR imaging protocol was of extremely low yield. We believe the use of neck MRA should reasonably be limited to cases in which abnormalities are initially detected on standard brain sequences or to patients with atypical presentation or recurrent pathology.

Age-Dependent Signal Intensity Changes in the Structurally Normal Pediatric Brain on Unenhanced T1-Weighted MR Imaging.

BACKGROUND AND PURPOSE: Various pathologic and nonpathologic states result in brain parenchymal signal intensity changes on unenhanced T1-weighted MR imaging. However, the absence of quantitative data to characterize typical age-related signal intensity values limits evaluation. We sought to establish a range of age-dependent brain parenchymal signal intensity values on unenhanced T1WI in a sample of individuals (18 years of age or younger) with structurally normal brains. MATERIALS AND METHODS: A single-center retrospective study was performed. Gadolinium-naïve pediatric patients with structurally normal MR brain imaging examination findings were analyzed (n = 114; 50% female; age range, 68 days to 18 years). ROI signal intensity measurements were obtained from the globus pallidus, thalamus, dentate nucleus, pons, and frontal lobe cortex and subcortical white matter. Multivariable linear regression was used to analyze the relationship between signal intensity values and age. RESULTS: Results demonstrated a statistically significant association between signal intensity values and linear age in all neuroanatomic areas tested, except the frontal gray matter, (P < .01). There were no statistically significant differences attributable to patient sex. CONCLUSIONS: Age-dependent signal intensity values were determined on unenhanced T1WI in structurally normal pediatric brains. Increased age correlated with increased signal intensity in all brain locations, except the frontal gray matter, irrespective of sex. The biologic mechanisms underlying our results remain unclear and may be related to chronologic changes in myelin density, synaptic density, and water content. Establishing age-dependent signal intensity parameters in the structurally normal pediatric brain will help clarify developmental aberrations and enhance gadolinium-deposition research by providing an improved understanding of the confounding effect of age.

Asymptomatic Interhypothalamic Adhesions in Children.

With the use of high-resolution MR imaging techniques, we have increasingly observed anomalies of the hypothalamus characterized by a band of tissue spanning the third ventricle between the hypothalami, often without associated clinical sequelae. Historically, hypothalamic anomalies are highly associated with symptoms referable to a hypothalamic hamartoma, midline congenital disorder, hypothalamic-pituitary dysfunction, or seizures, with very few asymptomatic patients reported. The interhypothalamic tissue described in our cohort was observed incidentally through the routine acquisition of high-resolution T1WI. No referable symptoms were identified in most of the study group. In the appropriate patient population in which associated symptoms are absent, the described hypothalamic anomalies may be incidental and should not be misdiagnosed as hypothalamic hamartomas.

MRI findings in children with acute flaccid paralysis and cranial nerve dysfunction occurring during the 2014 enterovirus D68 outbreak.

BACKGROUND AND PURPOSE: Enterovirus D68 was responsible for widespread outbreaks of respiratory illness throughout the United States in August and September 2014. During this time, several patients presented to our institution with acute flaccid paralysis and cranial nerve dysfunction. The purpose of this report is to describe the unique imaging findings of this neurologic syndrome occurring during an enterovirus D68 outbreak. MATERIALS AND METHODS: Patients meeting a specific case definition of acute flaccid paralysis and/or cranial nerve dysfunction and presenting to our institution during the study period were included. All patients underwent routine MR imaging of the brain and/or spinal cord, including multiplanar T1, T2, and contrast-enhanced T1-weighted imaging. RESULTS: Eleven patients met the inclusion criteria and underwent MR imaging of the brain and/or spinal cord. Nine patients presented with brain stem lesions, most commonly involving the pontine tegmentum, with bilateral facial nerve enhancement in 1 patient. Ten patients had longitudinally extensive spinal cord lesions; those imaged acutely demonstrated involvement of the entire central gray matter, and those imaged subacutely showed lesions restricted to the anterior horn cells. Ventral cauda equina nerve roots enhanced in 4 patients, and ventral cervical nerve roots enhanced in 3, both only in the subacute setting. CONCLUSIONS: Patients presenting with acute flaccid paralysis and/or cranial nerve dysfunction during the recent enterovirus D68 outbreak demonstrate unique imaging findings characterized by brain stem and gray matter spinal cord lesions, similar to the neuroimaging findings described in previous outbreaks of viral myelitis such as enterovirus 71 and poliomyelitis.

Excision of the primary tumour in patients with metastatic breast cancer: a clinical dilemma.

BACKGROUND: Approximately 10% of new breast cancer patients will present with overt synchronous metastatic disease. The optimal local management of those patients is controversial. Several series suggest that removal of the primary tumour is associated with a survival benefit, but the retrospective nature of those studies raises considerable methodologic challenges. We evaluated our clinical experience with the management of such patients and, more specifically, the impact of surgery in patients with synchronous metastasis. METHODS: We reviewed patients with primary breast cancer and concurrent distant metastases seen at our centre between 2005 and 2007. Demographic and treatment data were collected. Study endpoints included overall survival and symptomatic local progression rates. RESULTS: The 111 patients identified had a median follow-up of 40 months (range: 0.6-71 months). We allocated the patients to one ot two groups: a nonsurgical group (those who did not have breast surgery, n = 63) and a surgical group (those who did have surgery, n = 48, 29 of whom had surgery before the metastatic diagnosis). When compared with patients in the nonsurgical group, patients in the surgical group were less likely to present with T4 tumours (23% vs. 35%), N3 nodal disease (8% vs. 19%), and visceral metastasis (67% vs. 73%). Patients in the surgical group experienced longer overall survival (49 months vs. 33 months, p = 0.01) and lower rates of symptomatic local progression (14% vs. 44%, p < 0.001). CONCLUSIONS: In our study, improved overall survival and symptomatic local control were demonstrated in the surgically treated patients; however, this group had less aggressive disease at presentation. The optimal local management of patients with metastatic breast cancer remains unknown. An ongoing phase iii trial, E2108, has been designed to assess the effect of breast surgery in metastatic patients responding to first-line systemic therapy. If excision of the primary tumour is associated with a survival benefit, then the preselected subgroup of patients who have responded to initial systemic therapy is the desired population in which to put this hypothesis to the test.

Resection margin status in lumpectomy specimens for duct carcinoma of the breast: correlation with core biopsy and mammographic findings.

BACKGROUND: The strategy for surgical treatment of breast carcinoma proven by biopsy is mainly based on the physical and mammographic examinations. To investigate if the pathological findings in core biopsy are contributory to planning the surgical strategy, we correlated the status of ductal carcinoma in situ (DCIS) in the core needle biopsy of breast, the mammographic changes and the status of resection margins in the subsequent lumpectomy. STUDY DESIGN: Consecutive 130 core needle biopsies with prior mammography and subsequent lumpectomy were reviewed. Biopsies were divided into: group I, DCIS; group II, DCIS and infiltrating carcinoma (IC); and group III, IC. Mammographic findings were categorized into four groups: (a) nonspecific findings; (b) calcification (Ca(++)); Ca(++) and mass, and mass only. The status of margins in correlating lumpectomy specimens was reviewed. Close margin was defined as a free margin at less than 0.1cm from the carcinoma. RESULTS: The rates of positive or close margins in three groups I, II, and III were 13/18, 18/48, and 2/64 (P < 0.001); and in mammography groups of nonspecific finding, Ca(++), Ca(++) mass and mass only were 5/6, 7/15, 8/37, and 13/72 (P < 0.001), respectively. Of the total of 14 cases with positive margins of more than 0.5 cm in length, 8, 4, and 2 cases were from group I, II, and II, respectively. In addition, 13 of 21 cases with nonspecific changes or with only Ca(++) in mammograms belonged to the group I; 10 of these 13 cases were associated with positive margins. Forty-one of 72 cases presenting as a mass only in mammograms belonged to the group III; only 2 of these 41 cases were associated positive margins. CONCLUSIONS: Correlation of the extent of carcinoma with pre-operative histopathological findings was better than with mammography. Core biopsies containing only DCIS, particularly in cases with nonspecific findings or with only Ca(++) in mammograms, represent a group of breast carcinoma that pose the high risk for incomplete resection in lumpectomy. Surgical management of patients having these cores includes wider resection margins than would otherwise be taken. Most core biopsies with only IC were associated with negative margins.

Waiting times from abnormal breast screen to diagnosis in 7 Canadian provinces.

BACKGROUND: Delay to breast cancer diagnosis following an abnormal screening result is associated with anxiety and personal disruption. We assessed the patterns and timeliness of diagnostic follow-up after breast cancer screening for women with abnormal results who attended organized screening programs in 7 provinces. METHODS: Using data from the Canadian Breast Cancer Screening Database, we identified 203,141 women aged 50-69 years who underwent screening in 1996 through provincially organized breast cancer screening programs in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Nova Scotia and Newfoundland. We prospectively followed women with an abnormal screening result through to the completion of the assessment process. We evaluated the waiting times from screening examination to first assessment, from screening examination to first imaging, from screening examination to diagnosis and from first assessment to diagnosis for 13,958 women, stratified according to screening program, mode of detection, whether a biopsy was performed and whether cancer was diagnosed. RESULTS: We observed considerable variations between and within programs in the time to diagnosis. The median time from screening examination to first assessment was 2.6 weeks. The median time from screening examination to diagnosis was 3.7 weeks; this time increased to 6.9 weeks for women undergoing biopsy. Even when no biopsy was performed, 10% of the women waited 9.6 weeks or longer for a diagnosis, as compared with 15.0 weeks or longer for 10% of the women undergoing biopsy. Among the women who had a biopsy, the use of core biopsy was associated with a shorter median time to diagnosis than was open biopsy, and those found to have cancer had shorter waiting times than women with benign biopsy findings. INTERPRETATION: Women undergoing assessment of an abnormal breast cancer screening result waited many weeks for a diagnosis, especially when a biopsy was performed. To ensure that targets for timeliness, adopted nationally in 1999, are realized, improved models of care or dissemination of existing efficient techniques to reach a diagnosis will be needed.

Breast cancer: better care for less cost. Is it possible?

OBJECTIVES: To estimate the potential for cost reduction in the acute care setting and the required investment in the home care setting of implementing an outpatient/early discharge strategy for operable (stages I and II) breast cancer in Canada. METHODS: Data from a community hospital were augmented by expert knowledge and incorporated into the breast cancer submodel of Statistics Canada's Population Health Model. For the estimated 90% of patients for whom this approach was assumed to be appropriate, the resource utilization for outpatient breast-conserving surgery and 2 days of hospitalization for those women undergoing mastectomy was quantified and costed, as were the appropriate home care services. A 5% readmission rate for complications was assumed. Cost per case, total cost burden, investment in home care, savings in acute care, and net savings were calculated. Sensitivity analyses were performed around readmission rates and home care/surgical follow-up costs. All costs were determined in 1995 Canadian dollars. RESULTS: The cost of initial treatment for the 15,399 women diagnosed with stages I and II breast cancer in 1995 in Canada was estimated to be $127.6 million. Hospitalization made up 53% of these costs. Under the outpatient/early discharge strategy, the acute care cost of initial breast cancer management could be reduced by $47.2 million, with an investment in home care of $14.5 million ($453 per patient), resulting in an overall net saving of $33 million. Under this strategy, hospitalization would contribute only 21% to the total care cost. CONCLUSIONS: If Canadian surgeons and healthcare administrators were to work together to put in place processes to support ambulatory breast cancer surgery and if resources were redirected to the provision of home-based post-operative care, there would be potential for a large net healthcare saving and preservation of high-quality patient care.

Mastectomy or lumpectomy? Helping women make informed choices.

PURPOSE: To develop an instrument to help clinicians inform their patients about surgical treatment options for the treatment of breast cancer and to evaluate the impact of the instrument on the clinical encounter. METHODS: We developed an instrument, called the Decision Board, to present information regarding the benefits and risks of breast-conserving therapy (lumpectomy plus radiation therapy) and mastectomy to women with early-stage breast cancer to enable them to express a preference for the type of surgery. Seven surgeons from different communities in Ontario administered the instrument to women with newly diagnosed clinical stage I or II breast cancer over an 18-month period. Patients and surgeons were interviewed regarding acceptability of the instrument. The rates of breast-conserving surgery performed by surgeons before and after the introduction of the instrument were compared. RESULTS: The Decision Board was administered to 175 patients; 98% reported that the Decision Board was easy to understand, and 81% indicated that it helped them make a decision. The average score on a true/false test of comprehension was 11.8 of 14 (84%) (range, 6 to 14). Surgeons found the Decision Board to be helpful in presenting information to patients in 91% of consultations. The rate of breast-conserving surgery decreased when the Decision Board was introduced (88% v 73%, P =.001) CONCLUSION: The Decision Board is a simple method to improve communication and facilitate shared decision making. It was well accepted by patients and surgeons and easily applied in the community.

Surgical management of early stage invasive breast cancer (stage I and II). Provincial Breast Disease Site Group.

GUIDELINE QUESTION: What is the optimal surgical management of early stage invasive breast cancer (stage I and II)? More specifically, what is the relative efficacy (and safety) of breast conservation therapy (lumpectomy with axillary dissection) compared with modified radical mastectomy? OBJECTIVE: To make recommendations about surgical management and techniques in the treatment of early stage invasive breast disease (stage I and II). OUTCOMES: Survival, local recurrence (for lumpectomy patients) and quality of life are the primary outcomes of interest. PERSPECTIVE (VALUES): Evidence was selected and reviewed by 6 members of the Ontario Cancer Treatment Practice Guidelines Initiative, Disease Site Group for Breast Cancer (Breast DSG). Earlier drafts of this evidence-based recommendation have been reviewed, discussed and approved by the Breast DSG, which comprises surgeons, medical oncologists, radiation oncologists, epidemiologists, a pathologist and a medical sociologist. There was no consumer participation in the development of this guideline. QUALITY OF EVIDENCE: There are 7 randomized controlled trials (RCTs) comparing breast conservation therapy with mastectomy in women with early stage breast cancer. BENEFITS: In 6 RCTs, no statistically significant differences were detected in survival rate between the mastectomy and conservative therapy (lumpectomy) groups. In 1 RCT, a statistically significant differences was detected in favour of the mastectomy arm; however, this was an early trial with substantial methodologic weaknesses. HARMS: None. PRACTICE GUIDELINE: Women with early stage invasive breast cancer (stage I and II) who are candidates for breast conservation therapy (see discussion of technical factors) should be offered the choice of either breast conservation therapy (excision of tumour with clear margins and axillary dissection) or modified radical mastectomy. The choice is an individual one for the patient, and thus she should be fully informed of the options, including the risks and benefits of each procedure. She should be informed that breast irradiation is part of the procedure for breast conservation therapy. In addition, she should be aware of the potential need for further surgery if the margins are positive. For further information about the use of radiotherapy in the management of early stage breast cancer, please refer to the Ontario Cancer Treatment Practice Guidelines Initiative's practice guideline Breast Irradiation in Women with Early Stage Invasive Breast Cancer Following Breast Conserving Surgery.