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Original Clinical Science—General

OPTN Vascularized Composite Allograft Waiting List

Current Status and Trends in the United States

Wainright, Jennifer L. PhD1; Wholley, Christopher L. MSA2; Cherikh, Wida S. PhD1; Musick, Jennifer M. BA3; Klassen, David K. MD4

Author Information
doi: 10.1097/TP.0000000000002232
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Vascularized composite allograft (VCA) transplants include multiple types of organs, including upper limb, craniofacial, scalp, abdominal wall, penis, larynx, and uterus. These diverse organs meet the 9 requirements set forth in the Organ Procurement and Transplantation Network (OPTN) Final Rule1 to be classified as VCAs (Table 1). Vascularized composite allografts are a developing area in the field of transplantation, and work in the field did not accelerate until 2008. After that year, several VCA transplants occurred during most years. Although most VCA transplants have used organs donated by deceased donors, there also have been 6 living donor uterine transplants performed in the United States since 2016.2

TABLE 1
TABLE 1:
Nine criteria that define a VCA

VCA transplants generally are not considered lifesaving transplants akin to heart, liver, or lung transplants, but VCA transplants have a profound effect on recipients' lives.3,4 These effects include increased independence in self-care and activities of daily living (upper limb),5 ability to chew, swallow, breath without a tracheostomy, smell, and engage in nonverbal expression and gestures that enhance interpersonal communication and relationships (craniofacial)6,7; reduced morbidity from suprapubic catheter infections and the ability to experience intimacy (penile)8; and ability to carry a pregnancy (uterine).9

The OPTN has been responsible for policy making for solid organ transplantation since 1987. Since that time, the OPTN has maintained the waiting lists for all deceased donor organ transplants. As a result of this core responsibility and the clinical similarities between VCAs and solid organs, the OPTN was granted oversight of VCA transplants on July 3, 2014,4 and developed foundational VCA transplant policies that went into effect on that date.10 At the same time, the OPTN implemented a national VCA waiting list to provide a national allocation system for greater transplant access to VCA candidates and transition away from localized practices.

According to OPTN Policy, all candidates for VCA transplantation—including those expecting to receive living donor organs—must be registered on the organ-specific OPTN VCA waiting list before receiving a transplant.11 VCA candidates listed for VCA organs begin to accrue waiting time when they are registered on the VCA waiting list. For candidates who were listed at their transplant hospital before implementation of the OPTN VCA waiting list—now all transplanted or removed from the waiting list for other reasons, waiting time began when they were listed on their hospital's waiting list.

Organ Procurement Organizations (OPOs) allocate VCAs to candidates who have compatible blood types and are willing to accept a VCA with the donor’s physical characteristics (eg, skin tone or size of graft). OPOs access the VCA candidate list, which is a secure, deidentified spreadsheet available electronically through UNetsm to all OPOs. The VCA candidates appear on the spreadsheet grouped by VCA type and compatible blood type. Per OPTN policy, OPOs offer VCAs first to candidates in the OPO's region, then to candidates beyond that region. Within each of these classifications, candidates are ranked by waiting time, although the VCA waiting list currently is small enough that waiting time does not play a large role in allocation. When a VCA is allocated, the host OPO must document how the organ was allocated, the rationale for allocation, and any reasons for organ offer refusals.12

It is important for the OPTN to examine and understand patterns in VCA waiting list activity. The purpose of this study is to characterize the OPTN VCA waiting list in terms of composition, removal patterns, waiting time, and resulting transplants, as well as to describe trends over time.

MATERIALS AND METHODS

Cohort

The waiting list cohort includes all candidates on the OPTN VCA waiting list between July 3, 2014 and February 28, 2018 (n = 54), including candidates who were added to their hospital's waiting list before implementation of the OPTN VCA waiting list. Transplant data include all VCA transplants that occurred between July 3, 2014 and February 28, 2018, regardless of listing date (n = 28).

Data Sources

This study used data from the OPTN, whose data system includes data on all donors, waitlisted candidates, and transplant recipients in the United States, submitted by the members of the OPTN, and has been described elsewhere (https://optn.transplant.hrsa.gov/data/about-data/). The Health Resources and Services Administration, U.S. Department of Health and Human Services (HRSA), oversees the activities of the OPTN contractor. Institutional review board exemption was obtained from HRSA.

The VCA transplant programs submit waiting list data about their candidates to the OPTN on the VCA Candidate Registration Worksheet. These data include the type of VCA needed, blood type, histocompatibility data, demographic information, donor exclusion criteria, and donor acceptance information, such as exact structures and skin tone needed. VCA transplant programs submit waiting list removal data on the VCA Candidate Removal Worksheet for both VCA transplant recipients and VCA candidates who are removed from the waiting list without receiving a transplant. VCA transplant programs submit data about VCA recipients on the OPTN Transplant Recipient Registration form.

Analyses

Data on new additions to the waiting list use the date on which a candidate was added to the OPTN waiting list, with some candidates (n = 6, including 3 bilateral upper limb, 2 craniofacial, and 1 scalp) waiting for a VCA at their transplant hospital before the implementation of the OPTN VCA waiting list. Counts of VCA candidates on the waiting list by month include all candidates who were waiting on the OPTN VCA waiting list on the first day of each month between July 2014 and March 2018. For VCA recipients, time on the waiting list is calculated as the number of days between being added to the OPTN VCA waiting list and the date of transplant. For VCA candidates still waiting for a transplant, time on the waiting list is the number of days between being added to the OPTN VCA waiting list and February 28, 2018.

RESULTS

Composition of the VCA Waiting List

Between July 3, 2014 and February 28, 2018, 54 candidates were added to the OPTN VCA waiting list, including 10 bilateral upper limb, 10 unilateral upper limb, 10 craniofacial, 1 scalp, 1 craniofacial with scalp, 4 abdominal wall, 3 penile, and 15 uterine candidates. New additions to the VCA waiting list increased in 2016 with the introduction of uterine and penile transplants in the United States (Figure 1). In 2017, however, new additions for penile transplants dropped to zero, and there was a decrease in the number and proportion of new candidates added to the waiting list for upper limb and craniofacial. In the first 2 months of 2018, 2 craniofacial candidates, 1 upper limb candidate, and 1 uterine candidate were added to the VCA waiting list.

FIGURE 1
FIGURE 1:
VCA candidates added to the OPTN VCA waiting list July 3, 2014 to February 28, 2018, by VCA type and year of listing.

These changes in new listings have resulted in a corresponding shift in the composition of the VCA waiting list (Figure 2). Overall, candidate numbers were relatively stable from July 2014 through mid-2016, then increased and leveled off through 2017, with changes in the proportion of the list waiting occurring for each type of VCA. Through 2015, the waiting list consisted only of upper limb, craniofacial, scalp, and abdominal wall candidates. Beginning in early 2016, however, the waiting list has increasingly included candidates for penile and uterine transplants, with the waiting list on February 28, 2018 including 6 (33.3%) upper limb, 4 (22.2%) craniofacial, 1 (5.6%) craniofacial/scalp, 1 (5.6%) abdominal wall, 1 (5.6%) penile, 5 (27.8%) uterine, and no laryngeal candidates.

FIGURE 2
FIGURE 2:
Candidates on the OPTN VCA waiting list by VCA type and Month July 3, 2014 to February 28, 2018.

Characteristics of VCA Candidates

Of the 54 VCA candidates who were on the OPTN VCA waiting list between July 3, 2014 and February 28, 2018, 53.7% are male (Table 2). Excluding types of VCA organs that are specific to male (penile) or female (uterine) candidates, however, the majority of upper limb (65.0%), head and neck (including craniofacial, scalp, and craniofacial with scalp; 83.3%), and abdominal wall (75.0%) candidates are male. VCA candidates overall are relatively young, with 74.1% younger than 45 years at listing. Two candidates (3.7%) were younger than 18 years, 27 (50.0%) were aged 18 to 34 years, 11 (20.4%) were 35 to 44 years, 7 (13.0%) were 45 to 54 years, and 7 (13.0%) were older than 55 years at listing. Most VCA candidates are white (79.6% overall), with this pattern seen for all VCA organs except abdominal wall (50.0% black, 25% white, 25% Hispanic). Candidates across the United States have been listed for and received VCA transplants, with the majority of VCA programs located in the eastern half of the country.

TABLE 2
TABLE 2:
Characteristics of VCA candidates on the OPTN VCA waiting list between July 3, 2014 and February 28, 2018

Removal Reasons and Waiting times

The majority of 54 VCA candidates on the waiting list since its implementation have received deceased donor (n = 22) or living donor (n = 6) transplants, but 2 candidates died, 2 decided against transplantation, 1 candidate's condition improved, 1 candidate's condition deteriorated, and 2 were removed from the waiting list for other reasons.

The OPTN VCA waiting list is small relative to the number of deceased donors who could potentially donate VCA organs,10 and some VCA candidates have received transplants after quite short waits on the OPTN waiting list (Figure 3). Some VCA candidates, however, have waited over 3 years to receive a transplant. Of the 18 candidates waiting on the OPTN VCA waiting list as of February 28, 2018, 6 (33.3%) have been waiting for under 6 months, 4 (22.2%) between 6 months and 1 year, 4 (22.2%) between 1 and 2 years, 3 (16.7%) between 2 and 3 years, and 1 (5.6%) over 3 years (Figure 4).

FIGURE 3
FIGURE 3:
Time on the OPTN waiting list (days) for upper limb and craniofacial VCA transplant recipients who received deceased donor transplants July 3, 2014 to February 28, 2018.
FIGURE 4
FIGURE 4:
Time on the waiting list (days) for candidates still waiting on the OPTN VCA waiting list as of February 28, 2018.

VCA Transplants

Since implementation of the OPTN VCA waiting list on July 3, 2014, transplant hospitals in the United States have performed 22 deceased donor and 6 living donor VCA transplants through February 28, 2018 (Figure 5). These include 10 upper limb (6 bilateral; 4 unilateral), 5 craniofacial, 1 scalp, 1 abdominal wall, 1 penile, and 10 uterine transplants (4 deceased donor; 6 living donor). There has been a shift over time that echoes patterns seen in the composition of the VCA waiting list, with all VCA transplants before 2016 being upper limb, craniofacial, scalp, or abdominal wall transplants, and more than half of the 19 VCA transplants performed since January 2016 being the newly introduced uterine (52.6%) and penile (5.3%) transplants. This change in the proportion of VCA types represented on the waiting list was accompanied by a large increase in the number of transplants in 2016 (n = 13), followed by a sharp decrease in 2017 (n = 6).

FIGURE 5
FIGURE 5:
VCA transplants in the United States after implementation of the OPTN VCA waiting list July 3, 2014 through February 28, 2018.

DISCUSSION

A total of 54 candidates—largely male, white, and relatively young—have been added to the OPTN VCA waiting list since July 3, 2014, resulting in 22 deceased donor and 6 living donor VCA transplants. Registrations increased in 2016 after uterine and penile transplants were introduced in the United States, resulting in a shift in the composition of the VCA waiting list. Waiting times for VCA candidates vary greatly, with some VCA candidates receiving deceased donor transplants quickly and others waiting more than 3 years for their transplants.

The shift in the VCA waiting list’s composition from largely craniofacial and upper limb candidates to a more heterogeneous mix of VCA organ types may be explained by a variety of factors. One important potential cause is the challenge of securing funding for upper limb and craniofacial transplants. Most of the early VCA transplants were conducted under institutional review board protocols and funded through research grants or institutional funding.13 More recently, some VCA transplant programs are attempting to obtain coverage on a case by case basis by demonstrating that VCA transplants are an extension of their clinical practice.3 This approach is not yet widely practiced and funding issues likely will remain a limiting factor for VCA transplant case volume until they are resolved. Another potential cause for the shift is a limited number of appropriate candidates for upper limb and craniofacial transplants. Although some estimates suggest that a relatively large number of individuals could benefit from a VCA transplant,3,14,15 programs must screen potential candidates carefully to increase the likelihood of adherence to the immunosuppression regimen and physical therapy needed to attain successful outcomes.3,5,7,13,14,16,17 A final potential limiting factor is availability of donor organs for VCA transplants. Twelve OPOs recovered VCA organs between July 2014 and February 28, 2018, with most of these OPOS still having very limited experience. Expanding both the number of OPOs that are participating in VCA organ recovery and the experience of participating OPOs will be important in expanding the field. It is likely that all of these factors have played a role in the changes seen in VCA transplantation.

The variation seen in VCA candidates' sex, race, and age warrants further investigation to determine if these findings reflect differences among groups in need for VCA transplants or differences in access. It may be that some demographic groups in the United States have a disproportionate need for VCA transplants, resulting in that group making up a disproportionate share of the VCA waiting list. Some groups may be at higher risk of accidents that lead to the need for VCA transplantation, for example. Alternatively, they may be more amenable to the idea of receiving a visible organ from a deceased donor. Provider referrals for VCA transplantation have an impact on both the size of the waiting list and its composition. The developing nature of VCA transplantation and lack of awareness in the medical field may contribute to the low numbers of referrals for transplant evaluation and variation seen among demographic groups. The small number of VCA programs located in the western half of the United States raises questions about access to VCA transplantation for potential candidates who live in that area of the country. Vascularized composite allograft transplantation is still an emerging field, however, and trends in the field may shift rapidly in the future.

Variation in waiting times for VCA candidates is to be expected, given the developing nature of the field and varying levels of VCA experience among OPOs and transplant programs. Longer waiting times for some VCA candidates could be due to the relatively small number of programs performing VCA transplants and the resulting low VCA volume and lack of experience in most OPOs. Waiting time for VCA transplants is also affected by candidate-specific issues, such as blood type and histocompatibility matching, and additional matching requirements (eg, skin color) that are not applicable in solid organ transplantation. Candidates with long waiting times in our cohort did not have any obvious characteristics in common, although patient size, skin tone, blood type, and level of sensitization may have played a role for some of these candidates. Increased transplant program and OPO experience with VCA donation and transplantation may decrease waiting time in the future.

This study provides a comprehensive examination of the OPTN VCA waiting list, including emerging trends such as uterine and penile transplantation. We must acknowledge, however, our limited ability to make predictions about the future of the VCA waiting list based on existing data. Uterine transplantation, although occurring in other countries before 2016,9 emerged in the United States in 2016 and greatly changed the composition of the OPTN VCA waiting list. It remains to be seen whether penile transplantation, also introduced in the United States in 2016, will become a common event or will remain an infrequent procedure.

Our ability to predict trends in the future also will be affected by outcomes experienced by existing VCA recipients. Some single and multicenter studies have been published and suggest positive results for recipients,14,18-22 as do reports from the international registry.21 Systematic data collection for VCA recipients by the OPTN, however, is in its early stages,5,14 and the number of cases for each type of VCA transplant is still small. Further complicating the issue is the lack of consensus on standardized outcomes assessment for VCA recipients.10 Unlike solid organs that have clear and commonly understood definitions for a successful transplant (eg, kidney recipients not needing dialysis), outcomes for VCA recipients are more multifactorial and differ across VCA organ types. The outcomes for existing VCA recipients likely will have a profound—and currently impossible to predict—effect on future practice patterns and resulting VCA waiting list trends.

Although future patterns in listing practices are difficult to predict in the developing field of VCA transplantation, the field clearly is in a period of rapid transition. The VCA transplant community must carefully monitor both demand and outcomes during this time to determine how to best serve candidates in need of VCA transplants.

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