Bilateral mastectomy operations and the role for the cosurgeon technique: A Nationwide analysis of surgical practice patterns

Traditionally, bilateral mastectomy (BM) operations are performed by a single surgeon but a two-attending co-surgeon technique (CST) has been described. A questionnaire was sent to members of the American Society of Breast Surgeons to assess national BM practices and analyze utilization and perceived benefits of the CST. Among surgeons responding, most continue to use the single-surgeon approach for BMs; however, 14.1% utilize the CST and up to 31% are interested in future CST use. Time savings, mentorship, cost savings, and opportunity to learn new techniques were identified as perceived CST advantages.

Surgeon Variability and Factors Predicting for Reoperation Following Breast-Conserving Surgery

BACKGROUND

Reoperation after breast-conserving surgery (BCS) is common and has been partially associated with the lack of consensus on margin definition. We sought to investigate factors associated with reoperations and variation in reoperation rates across breast surgeons at our cancer center.

METHODS

Retrospective analyses of patients with clinical stage I-II breast cancer who underwent BCS between January and December 2014 were conducted prior to the recommendation of 'no ink on tumor' margin. Patient demographics and tumor and surgical data were extracted from medical records. A multivariate regression model was used to identify factors associated with reoperation.

RESULTS

Overall, 490 patients with stage I (n  = 408) and stage II (n  = 89) breast cancer underwent BCS; seven patients had bilateral breast cancer and underwent bilateral BCS procedures. Median invasive tumor size was 1.1 cm, reoperation rate was 22.9% (n  = 114) and varied among surgeons (range 15-40%), and, in 100 (88%) patients, the second procedure was re-excision, followed by unilateral mastectomy (n  = 7, 6%) and bilateral mastectomy (n  = 7, 6%). Intraoperative margin techniques (global cavity or targeted shaves) were utilized in 50.1% of cases, while no specific margin technique was utilized in 49.9% of cases. Median total specimen size was 65.8 cm³ (range 24.5-156.0). In the adjusted model, patients with multifocal disease were more likely to undergo reoperation [odds ratio (OR) 5.78, 95% confidence interval (CI) 2.17-15.42]. In addition, two surgeons were found to have significantly higher reoperation rates (OR 6.41, 95% CI 1.94-21.22; OR 3.41, 95% CI 1.07-10.85).

CONCLUSIONS

Examination of BCS demonstrated variability in reoperation rates and margin practices among our breast surgeons. Future trials should look at surgeon-specific factors that may predict for reoperations.

Bilateral mastectomies: can a co-surgeon technique offer improvements over the single-surgeon method?

PURPOSE

Bilateral mastectomy (BM) is traditionally performed using a single-surgeon (SS) technique (SST); a co-surgeon (CS) technique (CST), where each attending surgeon concurrently performs a unilateral mastectomy, offers an alternative approach. We sought to compare the CST and SST for BM with respect to operative times and complications.

METHODS

Patients undergoing BM without reconstruction at our institution between 2005 and 2015 were identified using operative caselogs and stratified into CS- and SS-cohorts. Operative time (OT; incision to closure) was calculated. Patient age, cancer presence/stage, hormone receptor/BRCA status, breast weight, axillary procedure, and 30-day complications were extracted. Differences in OT, complications, and demographics between cohorts were assessed with t tests and Chi-square tests. A multivariate linear regression model was fit to identify factors independently associated with OT.

RESULTS

Overall, 109 BM cases were identified (CS, n = 58 [53.2%]; SS, n = 51 [46.8%]). Average duration was significantly shorter for the CST by 33 min (21.6% reduction; CS: 120 min vs. SS: 153 min, p < 0.001), with no difference in complication rates (p = 0.65). Demographic characteristics did not differ between cohorts except for total breast weight (TBW) (CS: 1878 g vs. SS: 1452 g, p < 0.05). Adjusting for TBW, CST resulted in a 27.8% reduction in OT (44-min savings, p < 0.001) compared to SST.

CONCLUSIONS

The CST significantly reduces OT for BM procedures compared to the SST without increasing complication rates. While time-savings was < 50% and may not be ideal for every patient, the CST offers an alternative BM approach potentially best-suited for large TBW patients and those undergoing axillary procedures.

Patient Prognostic Score and Associations With Survival Improvement Offered by Radiotherapy After Breast-Conserving Surgery for Ductal Carcinoma In Situ: A Population-Based Longitudinal Cohort Study

PURPOSE

Radiotherapy (RT) after breast-conserving surgery (BCS) is a standard treatment option for the management of ductal carcinoma in situ (DCIS). We sought to determine the survival benefit of RT after BCS on the basis of risk factors for local recurrence.

PATIENTS AND METHODS

A retrospective longitudinal cohort study was performed to identify patients with DCIS diagnosed between 1988 and 2007 and treated with BCS by using SEER data. Patients were divided into the following two groups: BCS+RT (RT group) and BCS alone (non-RT group). We used a patient prognostic scoring model to stratify patients on the basis of risk of local recurrence. We performed a Cox proportional hazards model with propensity score weighting to evaluate breast cancer mortality between the two groups.

RESULTS

We identified 32,144 eligible patients with DCIS, 20,329 (63%) in the RT group and 11,815 (37%) in the non-RT group. Overall, 304 breast cancer-specific deaths occurred over a median follow-up of 96 months, with a cumulative incidence of breast cancer mortality at 10 years in the weighted cohorts of 1.8% (RT group) and 2.1% (non-RT group; hazard ratio, 0.73; 95% CI, 0.62 to 0.88). Significant improvements in survival in the RT group compared with the non-RT group were only observed in patients with higher nuclear grade, younger age, and larger tumor size. The magnitude of the survival difference with RT was significantly correlated with prognostic score (P < .001).

CONCLUSION

In this population-based study, the patient prognostic score for DCIS is associated with the magnitude of improvement in survival offered by RT after BCS, suggesting that decisions for RT could be tailored on the basis of patient factors, tumor biology, and the prognostic score.

Abstract P3-12-02: Patient prognostic score and survival benefit offered by radiotherapy for ductal carcinoma in situ

Background: In general, radiotherapy (RT) follows breast-conserving surgery (BCS) and remains the standard of care for the surgical management of both invasive carcinoma and ductal carcinoma in situ (DCIS). Although it is associated with better local control, the magnitude of survival benefit conferred by RT for DCIS has not yet been established. We sought to evaluate whether a survival benefit exists with the addition of RT for patients with DCIS and to validate a patient prognostic score to predict survival benefit.

Methods: We performed a retrospective longitudinal cohort study by using the Surveillance Epidemiology and End Results database (SEER 17). Between 1988-2007, we identified 32,144 eligible patients who underwent BCS for DCIS. Using age, year of diagnosis, race, tumor size, hormone receptor status, tumor grade, marital status and SEER region, we calculated propensity score weights to balance clinicopathologic factors between patients receiving only surgery and those receiving surgery and RT. This cohort was divided into seven groups according to the previously validated patient prognostic score proposed by Smith et al. Breast cancer mortality (BCM) was assessed using a log-rank test and a multivariable Cox proportional hazards model.

Results: Of 32,144 cases of DCIS, 20,329 cases (63%) were treated with RT (+RT group) and 11,815 cases (37%) were treated with surgery alone (-RT group). There were 304 breast cancer-specific deaths observed over the follow-up period (median 96 months). The weighted cumulative incidence of BCM at ten-years was 1.8% for the +RT group compared to 2.1% for the -RT group (p= 0.003). The effect of RT on survival differed by nuclear grade (p= 0.007), age (p= 0.004), and tumor size (p=0.02). We found that the survival benefit for the +RT group was significantly greater than for the –RT group in subgroups of patients with higher nuclear grade, younger age, and larger tumor size, whereas a statistical reduction of BCM with RT was not observed among patients without these prognostic factors. Moreover, the magnitude of survival benefit was significantly correlated with the patient prognostic score [p&lt;0.0001, Table].

Conclusion: In this population-based cohort study, the patient prognostic score for DCIS accurately estimated the magnitude of survival benefit offered by radiotherapy after BCS, suggesting that decisions for RT could be tailored based on prognostic score and patient preference. Limitations of this study include unmeasured confounders such as a lack of information about patients' comorbidities, margin status and endocrine therapy, and further external validation is needed to confirm our results.

Patient Prognostic Score and Hazard Ratio (HR) Comparing Mortality between Radiotherapy Group and non-Radiotherapy GroupPatient Prognostic ScoreNumber of patients in -RT groupNumber of patients in +RT groupWeighted HR of BCM95% CIWeighted HR of OM95% CI078213881.20.67 - 2.10.910.76 - 1.11267744801.00.70 - 1.50.880.78 - 0.992410570800.690.51 - 0.940.710.63 - 0.793304854170.730.48 - 1.10.680.58 - 0.81496517010.310.16 - 0.580.420.30 - 0.5852232480.290.09 - 0.910.430.21 - 0.9161515N.A. N.A. Abbreviation: RT, Radiotherapy; BCM, Breast Cancer Mortality; OM, Overall Mortality: N.A., not available

Citation Format: Sagara Y, Freedman RA, Vaz-Luis I, Mallory MA, Wong S, Aydogan F, DeSantis S, Barry WT, Golshan M. Patient prognostic score and survival benefit offered by radiotherapy for ductal carcinoma in situ. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-12-02.

Survival Benefit of Breast Surgery for Low-Grade Ductal Carcinoma In Situ: A Population-Based Cohort Study

IMPORTANCE

While the prevalence of ductal carcinoma in situ (DCIS) of the breast has increased substantially following the introduction of breast-screening methods, the clinical significance of early detection and treatment for DCIS remains unclear.

OBJECTIVE

To investigate the survival benefit of breast surgery for low-grade DCIS.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective longitudinal cohort study using the Surveillance, Epidemiology, and End Results (SEER) database from October 9, 2014, to January 15, 2015, at the Dana-Farber/Brigham Women's Cancer Center. Between 1988 and 2011, 57,222 eligible cases of DCIS with known nuclear grade and surgery status were identified.

EXPOSURES

Patients were divided into surgery and nonsurgery groups.

MAIN OUTCOMES AND MEASURES

Propensity score weighting was used to balance patient backgrounds between groups. A log-rank test and multivariable Cox proportional hazards model was used to assess factors related to overall and breast cancer-specific survival.

RESULTS

Of 57,222 cases of DCIS identified in this study, 1169 cases (2.0%) were managed without surgery and 56,053 cases (98.0%) were managed with surgery. With a median follow-up of 72 months from diagnosis, there were 576 breast cancer-specific deaths (1.0%). The weighted 10-year breast cancer-specific survival was 93.4% for the nonsurgery group and 98.5% for the surgery group (log-rank test, P < .001). The degree of survival benefit among those managed surgically differed according to nuclear grade (P = .003). For low-grade DCIS, the weighted 10-year breast cancer-specific survival of the nonsurgery group was 98.8% and that of the surgery group was 98.6% (P = .95). Multivariable analysis showed there was no significant difference in the weighted hazard ratios of breast cancer-specific survival between the surgery and nonsurgery groups for low-grade DCIS. The weighted hazard ratios of intermediate- and high-grade DCIS were significantly different (low grade: hazard ratio, 0.85; 95% CI, 0.21-3.52; intermediate grade: hazard ratio, 0.23; 95% CI, 0.14-0.42; and high grade: hazard ratio, 0.15; 95% CI, 0.11-0.23) and similar results were seen for overall survival.

CONCLUSIONS AND RELEVANCE

The survival benefit of performing breast surgery for low-grade DCIS was lower than that for intermediate- or high-grade DCIS. A prospective clinical trial is warranted to investigate the feasibility of active surveillance for the management of low-grade DCIS.

Does "Two is Better Than One" Apply to Surgeons? Comparing Single-Surgeon Versus Co-surgeon Bilateral Mastectomies

BACKGROUND

Bilateral mastectomies (BM) are traditionally performed by single surgeons (SS); a co-surgeon (CS) technique, where each surgeon concurrently performs a unilateral mastectomy, offers an alternative approach. We examined differences in general surgery time (GST), overall surgery time (OST), and patient complications for BM performed by CS and SS.

METHODS

Patients undergoing BM with tissue expander reconstruction (BMTR) between January 2010 and May 2014 at our center were identified through operative case logs. GST (incision to end of BM procedure), reconstruction duration (RST) (plastic surgery start to end of reconstruction) and OST (OST = GST + RST) was calculated. Patient age, presence/stage of cancer, breast weight, axillary procedure performed, and 30-day postoperative complications were extracted from medical records. Differences in GST and OST between CS and SS cases were assessed with a t test. A multivariate linear regression was fit to identify factors associated with GST.

RESULTS

A total of 116 BMTR cases were performed [CS, n = 67 (57.8 %); SS, n = 49 (42.2 %)]. Demographic characteristics did not differ between groups. GST and OST were significantly shorter for CS cases, 75.8 versus 116.8 min, p < .0001, and 255.2 versus 278.3 min, p = .005, respectively. Presence of a CS significantly reduces BMTR time (β = -38.82, p < .0001). Breast weight (β = 0.0093, p = .03) and axillary dissection (β = 28.69, p = .0003) also impacted GST.

CONCLUSIONS

The CS approach to BMTR reduced both GST and OST; however, the degree of time savings (35.1 and 8.3 %, respectively) was less than hypothesized. A larger study is warranted to better characterize time, cost, and outcomes of the CS-approach for BM.

Does “two is better than one” apply to surgeons? Comparing single-surgeon and cosurgeon bilateral mastectomy outcomes

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Background: Bilateral mastectomies (BM) are generally performed by a single surgeon (SS). A two-attending ‘co-surgeon’ (CS) technique, in which each surgeon concurrently performs a unilateral mastectomy, offers an alternative operative approach. We sought to examine differences in general surgery time (GST), overall surgery time (OST), and patient outcomes for BM performed by CS and SS at our institution. Methods: Patients undergoing BM with tissue expander reconstruction (BMTR) between January 2010 and May 2014 at our institution were identified and divided into SS and CS cases. Operative records were used to calculate GST (incision to end of BM procedure), reconstruction time (plastic surgery start time to end of reconstruction) and OST (OST = GST + reconstructive time). Patient age, presence and stage of cancer, breast weight, axillary procedure [sentinel node biopsy (SNB) or axillary dissection (ALND)], and 30-day postoperative complications were extracted from medical charts. Differences in GST and OST between CS and SS performed cases were assessed using a t-test. A linear regression was performed to identify factors contributing to GST. Results: We identified 116 BMTR cases performed by 8 breast surgeons, [CS, n = 67 (57.8%); SS, n = 49 (42.2%)]. Demographic characteristics did not significantly differ between groups. In the bivariate analyses, GST and OST for CS cases were significantly shorter than for SS, 75.8 vs 116.8 minutes, p < 0.0001, and 255.2 vs 278.3 minutes, p = 0.005, respectively. The linear regression demonstrated a significant decrease in GST when BMTR was performed by CS (β = -38.82, p < 0.0001); total breast weight (β = 0.0093, p = 0.03) and axillary dissection (β = 28.69, p = 0.0003) were found to significantly impact GST. Conclusions: The GST of BMTR is significantly decreased using a CS-approach without impacting complication rates. However, the degree of GST and OST-reduction suggests the addition of a CS does not proportionally impact surgical time as would be expected. A CS-approach may be more beneficial for patients with large total breast weight or those requiring ALND. A larger study is warranted to better characterize time, cost, and outcomes of the CS-approach for BM.

Tumor subtype and race in male breast cancer: A population-based cohort study

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Background: Subtypes of female breast cancer have been shown to vary by race, however data on the significance of molecular profiling and the distribution of subtype according to race/ethnicity for male breast cancer is lacking and warrants research. We sought to investigate the differences in male breast cancer according to tumor subtypes and racial/ethnic profiles using the Surveillance, Epidemiology, and End Results Program (SEER) database. Methods: We used the SEER database (SEER 18 registries) to identify all cases of male breast cancer diagnosed between 2010 and 2012. The cases were classified based on estrogen receptor (ER), progesterone receptor (PR) and HER2 status as follows: ER and/or PR positive and HER2−; ER and/or PR and HER2 +; ER−, PR−, and HER2 +; and triple negative (ER−, PR−, and HER2−). We sought the association between the subtype and race, which is categorized as non-Hispanic (NH) white, NH black, NH Asian Pacific Islander (API) and Hispanic men. Results: We identified 1515 cases of male breast cancer diagnosed during the study period; 188 were excluded because of unknown race or subtype, and the remaining 1327 were included in our final cohort. 96.8% of cases were ER positive and less than 3.2% of cases were ER negative. 1145 patients (86.1%) were HR+/HER2-, 139 patients (10.0%) were HR+/HER2+, 12 patients (0.7%) were HR-,HER2+, and 31 patients (2.3%) were triple negative (Table 1).Tumor subtype did not vary by race/ethnicity (p = 0.08). Conclusions: Our results indicate that unlike female breast cancer that male breast cancer subtype does not vary by race/ethnicity. Further research is warranted to determine how these findings may impact the treatment and prognosis of male breast cancer. [Table: see text]

A low cost training phantom model for radio-guided localization techniques in occult breast lesions

Radio-guided localization (RGL) for identifying occult breast lesions has been widely accepted as an alternative technique to other localization methods, including those using wire guidance. An appropriate phantom model would be an invaluable tool for practitioners interested in learning the technique of RGL prior to clinical application. The aim of this study was to devise an inexpensive and reproducible training phantom model for RGL. We developed a simple RGL phantom model imitating an occult breast lesion from inexpensive supplies including a pimento olive, a green pea and a turkey breast. The phantom was constructed for a total cost of less than $20 and prepared in approximately 10 min. After the first model's construction, we constructed approximately 25 additional models and demonstrated that the model design was easily reproducible. The RGL phantom is a time- and cost-effective model that accurately simulates the RGL technique for non-palpable breast lesions. Future studies are warranted to further validate this model as an effective teaching tool.

The Influence of Radiology Image Consultation in the Surgical Management of Breast Cancer Patients

BACKGROUND

Patients referred to comprehensive cancer centers arrive with clinical data requiring review. Radiology consultation for second opinions often generates additional imaging requests; however, the impact of this service on breast cancer management remains unclear. We sought to identify the incidence of additional imaging requests and the effect additional imaging has on patients' ultimate surgical management.

METHODS

Between November 2013 and March 2014, 153 consecutive patients with breast cancer received second opinion imaging reviews and definitive surgery at our cancer center. We identified the number of additional imaging requests, the number of fulfilled requests, the modality of additional imaging completed, the number of biopsies performed, and the number of patients whose management was altered due to additional imaging results.

RESULTS

Of 153 patients, the mean age was 55 years; 98.9% were female; 23.5% (36) had in situ carcinoma (35 DCIS/1 LCIS), and 76.5% (117) had invasive carcinoma. Additional imaging was suggested for 47.7% (73/153) of patients. After multidisciplinary consultation, 65.8% (48/73) of patients underwent additional imaging. Imaging review resulted in biopsy in 43.7% (21/48) of patients and ultimately altered preliminary treatment plans in 37.5% (18/48) of patients (Fig. 1). Changes in management included: conversion to mastectomy or breast conservation, neoadjuvant therapy, additional wire placement, and need for contralateral breast surgery. Fig. 1 Impact of second-opinion imaging reviews on the management of breast cancer patients

CONCLUSIONS

Our analysis of second opinion imaging consultation demonstrates the significant value that this service has on breast cancer management. Overall, 11.7% (18/153) of patients who underwent breast surgery had management changes as a consequence of radiologic imaging review.

Surgical Options and Locoregional Recurrence in Patients Diagnosed with Invasive Lobular Carcinoma of the Breast

PURPOSE

Recent consensus guidelines on margins for breast-conserving surgery (BCS) recommend the use of "no ink on tumor" as the standard for an adequate margin. The recommendations extend to invasive lobular carcinoma (ILC), but the data on this subset are limited. We reviewed our modern dataset on margin status with outcomes of ILC.

METHODS

We performed a retrospective cohort study on 736 patients with a diagnosis of stage I-III ILC treated at our cancer center between May 1997 and December 2007. Clinicopathologic data were extracted from the Clinical Research Information Systems Database. Margin status was defined using the latest ASCO/ASTRO/SSO consensus guideline criteria.

RESULTS

The initial surgery performed was mastectomy in 352 patients (48 %) and BCS in 384 patients (52 %). In multivariate analysis, tumor size and multifocality were significantly associated with high rates of mastectomy and positive surgical margins at initial BCS. After initial BCS, additional surgery was performed in 92 patients (24 %). During a 72-month median follow-up period, 12 (3.1 %) ipsilateral breast tumor recurrences (IBTR) and 5 (1.3 %) other locoregional recurrences (LRR) were observed. Patients with margins with ink on tumor who did not receive further surgery were found to have significantly increased LRR [odds ratio (OR) 5.5; p = 0.02] and IBTR (OR 8.5; p = 0.006), whereas patients with close margins (1-3 mm) and margins within 1 mm were not.

CONCLUSIONS

Our study supports the validity of using "no ink on tumor" as the standard for a negative margin for pure and mixed ILC treated with multimodality therapy.

Simple sequence repeat marker development and genetic mapping in quinoa (Chenopodium quinoa Willd.)

Quinoa is a regionally important grain crop in the Andean region of South America. Recently quinoa has gained international attention for its high nutritional value and tolerances of extreme abiotic stresses. DNA markers and linkage maps are important tools for germplasm conservation and crop improvement programmes. Here we report the development of 216 new polymorphic SSR (simple sequence repeats) markers from libraries enriched for GA, CAA and AAT repeats, as well as 6 SSR markers developed from bacterial artificial chromosome-end sequences (BES-SSRs). Heterozygosity (H) values of the SSR markers ranges from 0.12 to 0.90, with an average value of 0.57. A linkage map was constructed for a newly developed recombinant inbred lines (RIL) population using these SSR markers. Additional markers, including amplified fragment length polymorphisms (AFLPs), two 11S seed storage protein loci, and the nucleolar organizing region (NOR), were also placed on the linkage map. The linkage map presented here is the first SSR-based map in quinoa and contains 275 markers, including 200 SSR. The map consists of 38 linkage groups (LGs) covering 913 cM. Segregation distortion was observed in the mapping population for several marker loci, indicating possible chromosomal regions associated with selection or gametophytic lethality. As this map is based primarily on simple and easily-transferable SSR markers, it will be particularly valuable for research in laboratories in Andean regions of South America.

Determination of the non-ionic detergent insolubility and phosphoprotein associations of glycosylphosphatidylinositol-anchored proteins expressed on T cells

Glycosylphosphatidylinositol (GPI)-anchored proteins are poorly solublized in non-ionic detergents such as Triton X-100 and Nonidet P40, but are easily solublized by detergents with high critical micelle concentrations such as octylglucoside. This solubility profile has been suggested to be due to the localization of GPI-anchored proteins to lipid microdomains rich in cholesterol and sphingolipids. Additionally, GPI-anchored proteins expressed on haemopoietic cells have been shown to associate with src-family tyrosine kinases and heterotrimeric G proteins. Despite these observations, the non-ionic detergent insolubility of GPI-anchored proteins on haemopoietic cells has not been quantified nor has a relationship between the non-ionic detergent insolubility of these proteins and their association with signal-transduction molecules been identified. Here we show that GPI-anchored proteins found on T-cell tumours and activated T cells, although significantly more insoluble then transmembrane proteins, are not uniform in their detergent insolubility. Whereas CD59 was between 4% and 13% soluble, CD48 was between 13% and 25% soluble, CD55 was between 20% and 30% soluble, and CD109 was between 34% and 75% soluble. The ability of these GPI-anchored proteins to associate with phosphoproteins was correlated with their detergent insolubility: the more detergent-insoluble that a GPI-anchored protein was, the greater the level of phosphoprotein associations. These experiments reveal a relationship between non-ionic detergent insolubility and association with signal-transduction molecules and suggest a cause-and-effect relationship between these two properties. In total, these experiments support the hypothesis that the association of GPI-anchored proteins with signalling molecules is due to their sorting to lipid microdomains.

The nature of membrane anchorage determines kinase association and detergent solubility of CD4

The presence of a glycosylphosphatidylinositol (GPI) anchor on a membrane protein is thought to influence aspects of the protein's biochemistry. While it has been demonstrated that a GPI-anchor is sufficient for altering the detergent solubility of integral membrane proteins, it has not been shown that the anchor is sufficient for changing the phosphoprotein associations of membrane proteins. In order to define the influence of GPI-anchors on the biochemistry of membrane proteins we compared the phosphoprotein associations and detergent solubility of wild-type and GPI-anchored CD4 expressed on HSB cell transfectants. While wild-type CD4 was mostly associated with lck kinase, GPI-anchored CD4 was associated with the 'GPI-anchored pattern of phosphoproteins'. The Triton X-100 solubilities of the two forms of CD4 were also distinct: wild-type CD4 was > 95% soluble, whereas GPI-anchored CD4 was only 65% soluble. These results underscore the deterministic role of the GPI-anchor in the properties associated with GPI-anchored proteins.