Median Maximum Diameter Research Articles

Delayed chronic type A dissection following CABG: implications for evolving techniques of revascularization.

Postoperative dissection in some patients is related to manipulation of the aorta and accounts for 3% to 5% of deaths after cardiac surgery. Between 1987 and 1999, 109 patients with previous cardiac operations were treated for chronic type A dissection. In 31 of the patients, the etiology was related to aortic manipulation. Twenty-one patients (17 men, 4 women; 67+/-13 years of age) had isolated coronary artery bypass grafting (CABG) as their first operation and were reviewed. The interval between operations was 52.9+/-47.3 months. Reoperation was elective in 11 patients, urgent in 10 patients. Median maximal aortic diameter was 6.8+/-2.1 cm; 9 patients had major aortic insufficiency. The intimal tear was at the partial occlusion clamp site in 12 patients (57.1%), at the cross-clamping site in 4 patients (19.1%), and at the proximal anastomosis in 1 patient (4.8%); 4 patients (19.1%) had multiple tears at several sites. Cystic media necrosis was present in 9.5% of the patients, severe atherosclerosis in 47.6% of the patients, and 42.9% of the patients had both. Nine patients (42.9%) underwent a modified Bentall procedure, 12 patients (57.1%) underwent a supracoronary anastomosis, and all had open distal anastomosis. There were two (9.5%) hospital deaths and three (14.3%) postoperative strokes. Freedom from cardiac or aorta-related mortality was 85.7% at a mean follow-up of 49.3 months. In patients who develop type A dissection of the aorta after previous CABG, the intimal tear most often is at partial occlusion clamp site. This complication is associated with morbidity and mortality. It remains to be seen whether the use of partial occlusion clamps on the pulsating and often diseased aorta during off-pump coronary artery bypass (OPCAB) will increase the risk of delayed iatrogenic dissections.

New Era in Breast Cancer: Impact of Screening on Disease Presentation

Mammographic screening produces markedly smaller breast cancers with fewer axillary lymph nodes and more ductal carcinoma in situ. Over the past 25 years at the New England Deaconess Hospital, the mean maximum diameter of breast cancers has decreased by 10% every 5 years and is now only 2.1 cm. The median maximum diameter in the years from 1989 to 1993 is only 1.5 cm. Axillary lymph node metastases also are declining progressively. This continuing decline in mean and median maximum diameters and incidence of axillary lymph node metastases shows no signs of abating at the present time. Universal mammographic screening of appropriately aged women should be a public health goal to further this trend towards markedly earlier breast cancer detection with much higher survival and new opportunities for modified therapy.

The new era in breast cancer. Invasion, size, and nodal involvement dramatically decreasing as a result of mammographic screening.

To describe the magnitude of changes and opportunities that may arise for simplified surgical procedures for women with breast cancer because of the decreasing size and lymph node involvement in invasive breast cancer and earlier presentation of noninvasive and invasive breast cancer. DESIGN AND MAIN OUTCOME ASSESSMENT: Cases (N=1001) of breast cancer from a tertiary and a community hospital between 1989 and 1993 were analyzed for invasion, size, nodal status, and change over time. Ductal carcinoma in situ constituted 14% and 18% of the cancers at the two hospitals. At the tertiary and community hospitals, the mean maximum diameters were 2.1 and 2.0 cm, respectively, and the median maximum diameters were 1.5 and 1.7 cm, respectively, for invasive breast cancer. Twenty-nine percent and 28%, respectively, were 1 cm or less in diameter. Axillary nodal metastases occurred in only 31% of the invasive cancers (tertiary hospital); only 10% had more than three nodal metastases. In the T1a and T1b cases, nodal metastases occurred in only 10% and 43% of the positive nodes were solitary; only 16% had more than three nodal metastases. The proportion of ductal carcinoma in situ, T1a and T1b, and node-negative cases increased significantly over time. Within the next decade, the proportion of all breast cancers that are ductal carcinoma in situ will approach 33%, and invasive cancers will approach 1 cm in median maximum diameter. Therapy simplification will be logical because of very small size, low risk of recurrence after breast conservation, and excellent prognosis, and might include increased breast conservation, avoidance of axillary nodal dissection, and omission of radiation therapy to conserve breasts. Adjuvant therapy will be based on the prognostic features of the primary cancer and findings from careful histologic examination of the sentinel lymph nodes.

COST-EFFECTIVE PREOPERATIVE EVALUATION, OPERATIVE TREATMENT, AND POSTOPERATIVE FOLLOW-UP IN THE BREAST CANCER PATIENT

Although medical criteria based on retrospective and prospective studies form the basic foundation for the strategies enunciated in this article, efficiency in management and cost effectiveness follow because of the simplification that has been found to be appropriate by analyzing reports over the past decade and using common sense. In addition, the realization of the effectiveness of mammographic screening programs should encourage all surgeons to promote and practice yearly mammographic screening in appropriately aged women. At present, this means women between the ages of 50 and 75, but there is increasing evidence that women between the ages of 40 and 49 may benefit. A compromise would suggest women over 45 years of age as appropriate, recognizing the controversy now raging over the effectiveness of screening in women 40 to 49 years old. Wide appreciation of the major gains in breast cancer detection by use of mammographic screening programs needs to be emphasized. We have predicted that within a decade the median maximum diameter of all invasive breast cancer in the United States will be only 1 cm if mammographic screening programs are widespread. If this occurs, there would be extraordinary gains in reduced patient morbidity and cost savings and undoubtedly changes will occur in the previously unyielding age-adjusted mortality rate. The goal of entirely outpatient management in the vast majority of breast cancer patients can be achieved by such mammographic screening as well as by the adaptation of induction chemotherapy and breast conservation in the majority of advanced primary breast cancer patients that still appear.

Stereotactic radiosurgery using the gamma knife for acoustic neuromas

To assess the efficacy and toxicity of stereotactic radiosurgery using the gamma knife for acoustic neuromas. Between January 1990 and January 1993, 36 patients with acoustic neuromas were treated with stereotactic radiosurgery using the gamma knife. The median maximum tumor diameter was 21 mm (range: 6-32 mm). Tumor volumes encompassed within the prescribed isodose line varied from 266 to 8,667 mm3 (median: 3,135 mm3). Tumors < or = 20 mm in maximum diameter received a dose of 20 Gy to the margin, tumors between 21 and 30 mm received 18 Gy, and tumors > 30 mm received 16 Gy. The dose was prescribed to the 50% isodose line in 31 patients and to the 45%, 55%, 60%, 70%, and 80% isodose line in one patient each. The median number of isocenters per tumor was 5 (range: 1-12). At a median follow-up of 16 months (range: 2.5-36 months), all patients were alive. Thirty-five patients had follow-up imaging studies. Nine tumors (26%) were smaller, and 26 tumors (74%) were unchanged. No tumor had progressed. The 1- and 2-year actuarial incidences of facial neuropathy were 52.2% and 66.5%, respectively. The 1- and 2-year actuarial incidences of trigeminal neuropathy were 33.7% and 58.9%, respectively. The 1- and 2-year actuarial incidence of facial or trigeminal neuropathy (or both) was 60.8% and 81.7%, respectively. Multivariate analysis revealed that the following were associated with the time of onset or worsening of facial weakness or trigeminal neuropathy: (a) patients < age 65 years, (b) dose to the tumor margin, (c) maximum tumor diameter > or = 21 mm, (d) use of the 18 mm collimator, and (e) use of > five isocenters. The 1- and 2-year actuarial rates of preservation of useful hearing (Gardner-Robertson class I or II) were 100% and 41.7% +/- 17.3, respectively. Stereotactic radiosurgery using the gamma knife provides short-term control of acoustic neuromas when a dose of 16 to 20 Gy to the tumor margin is used. Preservation of useful hearing can be accomplished in a significant proportion of patients.

Major hepatic resection for metachronous metastases from colon cancer.

Hepatic resection of metastatic colorectal cancer is being performed with increasing frequency. Reports describe wide variations in survival after resection of solitary of multiple metastases. In 23 consecutive patients having major hepatic resection for metachronous metastases from colorectal cancers, 18 patients had one, two, or three metastases and five had four or more individual metastases; the cure rate of one, two, or three metachronous metastases was comparable to reports of resected solitary simultaneous metastases. The median maximum diameter of metastases in patients both surviving and dead was 7 cm. Features separating surviving from dead patients were resection margins of at least 1 cm and fewer than four metastatic nodules. All patients with four or more hepatic metastases died of disease, 80% with further liver metastases. Only three of 18 (17%) patients with one, two, or three metastases developed further hepatic lesions. This study suggests that the biology of the hepatic metastatic disease is paramount; timing of the hepatic resection is of little importance. Delayed resection of suitable biologic situations does not impair survival opportunities, and early resection of inappropriate biologic situations with more than three hepatic metastases does not improve survival. Therefore, programs of early detection with the use of carcinoembryonic antigen (CEA) screening or "second look" operations will not increase cure rates.

Are Regular Patterns in Desert Shrubs Artefacts of Sampling?

Ebert & McMaster (1981) show that, if shrubs which are within 4.2 m of one another are mistaken for single individuals, a random pattern of dots, representing the desert shrub Larrea tridentata (DC.) Coville at a density of 250 individuals ha-1, could be mistaken for a significantly regular pattern by the variance: mean ratio method. They suggest on this basis that the regular patterns detected in Larrea tridentata by Woodell, Mooney & Hill (1969) do not exist and argue that there is no convincing evidence for a regular pattern in any desert shrub. We comment as follows. (i) In the study of Woodell, Mooney & Hill (1969) individual plants of Larrea tridentata were easily distinguished in the field. Many of the plants were multi-stemmed. In the absence of conflicting evidence, however, Woodell and his co-workers assumed that the stems in each discrete group were, or had been, connected underground. Unless the connections were visible, they assumed that each separate clump of stems constituted an individual. Ebert & McMaster (1981) state that during early growth in Ambrosia (= Franseria) dumosa and Encelia farinosa, clumps are formed by the simultaneous germination of different genets. Evidence for this phenomenon in large clumps of Larrea tridentata is lacking. (ii) The main problem in studies of the distribution of Larrea tridentata individuals is its clonal growth pattern, which at some sites may make the definition of an individual arbitrary. Sternberg (1976) described it: 'The centre of a creosote bush dies and is replaced by new stems which eventually form new crowns peripheral to the original central crown. Over long periods of time with repeated cycles in which old stems die and new ones are formed peripherally, the creosote bush growth pattern results in a ring of satellite clumps around a circular to elliptic sterile centre.' The impact of this morphological pattern on pattern analyses is uncertain, especially at sites where the plants are not even-aged. When the variance: mean ratio method is used to detect non-random patterns, however, the clonal spread of L. tridentata seems likely to bias the ratio away from regularity. This is because when two groups of stems begin to appear distinct they will be close together. Larrea tridentata grows so slowly that most plants at most sites will never reach an age where the groups are widely separated. (iii) At the four sites with significant regular patterns of L. tridentata, the sizes and densities of the plants differed considerably (Table 1). At Inyokern, shrubs with their centres only 0. 5 m apart were easily distinguished. At Yuma, shrubs with their centres 2 m apart were distinguishable. (iv) Ebert & McMaster's (1971) simulation of the pattern analysis has two main deficiencies. First, plants as far apart as 4.2 m would, in some cases, be considered the same individual although the median maximum diameter of the shrubs ranged from 1 1 m to 2.0 m only at the four sites (Table 1). Secondly, Woodell, Mooney & Hill (1969) found a shrub density of 110 ha-1 at Yuma. Ebert & McMaster assumed that the shrub density at all sites was 250 ha-'. At lower densities a smaller proportion of shrubs will be confounded.

Changing patterns of breast cancer.

Over a 40-year period at one hospital, 3,426 operative specimens of primary breast cancer were seen and analyzed for the maximum diameter of the primary cancer and the number of metastatic axillary lymph nodes. Statistically, significant trends toward progressively smaller primary cancers and fewer axillary metastases have been recorded, particularly over the 20 years ending in 1968. Currently, the median maximum diameter of primary breast cancer is 2.5 cm, and the mean maximum diameter is 3.07 cm. Fifty-three percent of all specimens now have negative axillary lymph nodes, and of those with positive axillary lymph nodes, 31% have one metastatic node, 14% have two metastatic nodes, and 13% have three metastatic nodes.