Improved nationwide survival of sarcoma patients with a network of reference centers

BACKGROUND

We investigated the impact of the implementation of a network of reference centers for sarcomas (NETSARC) on the care and survival of sarcoma patients in France since 2010.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centers with specialized multidisciplinary tumor boards (MDTBs), funded by the French National Cancer Institute (INCa) since 2010. Its aims are to improve the quality of diagnosis and care of sarcoma patients. Patients' characteristics, treatments, and outcomes are collected in a nationwide database. The objective of this analysis was to compare the survival of patients in three periods: 2010-2012 (non-exhaustive), 2013-2015, and 2016-2020.

RESULTS

A total of 43 975 patients with sarcomas, gastrointestinal stromal tumors (GISTs), or connective tissue tumors of intermediate malignancy were included in the NETSARC+ database since 2010 (n = 9266 before 2013, n = 12 274 between 2013 and 2015, n = 22 435 in 2016-2020). Median age was 56 years, 50.5% were women, and 13.2% had metastasis at diagnosis. Overall survival was significantly superior in the period 2016-2020 versus 2013-2015 versus 2010-2012 for the entire population, for patients >18 years of age, and for both metastatic and non-metastatic patients in univariate and multivariate analyses (P < 0.0001). Over the three periods, we observed a significantly improved compliance to clinical practice guidelines (CPGs) nationwide: the proportion of patients biopsied before surgery increased from 62.9% to 72.6%; the percentage of patients presented to NETSARC MDTBs before first surgery increased from 31.7% to 44.4% (P < 0.0001). The proportion of patients with R0 resection on first surgery increased (from 36.1% to 46.6%), while R2 resection rate decreased (from 10.9% to 7.9%), with a better compliance and improvement in NETSARC centers.

CONCLUSIONS

The implementation of the national reference network for sarcoma was associated with an improvement of overall survival and compliance to guidelines nationwide in sarcoma patients. Referral to expert networks for sarcoma patients should be encouraged, though a better compliance to CPGs can still be achieved.

Sclerosing Epithelioid Fibrosarcoma (SEF) versus Low Grade Fibromyxoid Sarcoma (LGFMS): Presentation and outcome in the nationwide NETSARC+ series of 330 patients over 13 years

Sclerosing Epithelioid Fibrosarcoma (SEF) and Low Grade Fibromyxoid Sarcoma (LGFMS) are ultrarare sarcomas sharing common translocations whose natural history are not well known. We report on the nationwide exhaustive series of 330 patients with SEF or LGFMS in NETSARC+ since 2010.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centers with specialized multidisciplinary tumor boards (MDTB). Since 2010, (i) pathological review has been mandatory for sarcoma,and (ii) tumour/patients' characteristics have been collected in the NETSARC+ nationwide database. The characteristics of patients with SEF and LGFMS and their outcome are compared.

RESULTS

35/73 (48%) and 125/257(49%) of patients with SEF and LGFMS were female. More visceral, bone and trunk primary sites were observed in SEF (p < 0.001). 30% of SEF vs 4% of LGFMS patients had metastasis at diagnosis (p < 0.0001). Median size of the primary tumor was 51 mm (range 10-90) for LGFMS vs 80 (20-320) for SEF (p < 0.001). Median age for LGFMS patients was 12 years younger than that of SEF patients (43 [range 4-98] vs 55 [range 10-91], p < 0.001). Neoadjuvant treatment was more often given to SEF (16% vs 9%, p = 0.05). More patients with LGFMS were operated first in reference centers (51% vs 26%, p < 0.001). The R0 rate on the operative specimen was 41% in LGFMS vs 16% in SEF (p < 0.001). Median event-free survival (EFS) of patients with SEF and LGFMS were 32 vs 136 months (p < 0.0001). The median overall survival (OS) was not reached. Fifty-months OS was 93% vs 81% for LGFMS vs SEF (p = 0.05). Median OS was 77 months after first relapse, similar for SEF and LGFMS. In multivariate analysis, age, tumor size, metastasis at diagnosis were independent prognostic factors for OS in LGFMS.

CONCLUSIONS

Although sharing close molecular alterations, SEF and LGFMS have a different natural history, clinical presentation and outcome, with a higher risk of metastatic relapse in SEF. Survival after relapse is longer than with other sarcomas, and similar for SEF and LGFMS.

Epithelioid hemangio-endothelioma (EHE) in NETSARC: The nationwide series of 267 patients over 12 years

EPITHELIOID HEMANGIOENDOTHELIOMA

A NATIONWIDE STUDY: Epithelioid hemangioendothelioma (EHE) is an ultrarare sarcoma whose natural history and treatment is not well defined. We report on the presentation and outcome of 267 patients with EHE in the NETSARC+ network since 2010 in France.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centres with specialised multidisciplinary tumour boards (MDTB), funded by the French National Cancer Institute (NCI), Institut National du Cancer (INCA). Since 2010, presentation to an MDTB and second pathological review are mandatory for sarcoma patients. Patients' characteristics are collected in a nationwide database regularly monitored with stable incidence since 2013. The characteristics of patients with EHE at diagnosis are presented as well as progression-free survival (PFS), overall survival (OS), and outcome under treatment.

RESULTS

Two hundred and sixty-seven patients with EHE were included in the NETSARC+ database since 2010. Median age in the series was 51 (range 10-90) years, 58% were women. Median tumour size was 37 mm (4-220). Forty-eight percent, 42%, and 10% were visceral, soft parts, or bone primaries. The most frequent sites were liver (28%), lung (13%). 40% were reported to have systemic (i.e. multifocal or metastatic disease) at diagnosis. With a median follow-up of 20 months, OS and PFS rates at 24 months were 82% and 67%, with 10-year projected OS and PFS of 62% and 21% respectively. Male and M+ patients at diagnosis had a significantly worse OS, but not PFS. Local treatment was associated with a favourable survival in localised but not in patients with advanced stage at diagnosis. For 23 patients receiving medical treatment, PFS and OS were 50.2% and 33.2% at 60 months were respectively.

CONCLUSIONS

EHE is a frequently metastatic sarcoma at diagnosis with a unique natural history. This study shows in a nationwide series over 12 years that most patients progressed but are still alive at 10 years, both in localised and metastatic stages.

Expression and prognostic significance of PDGF ligands and receptors across soft tissue sarcomas

Background

While the anti-PDGFRA antibody olaratumab failed to confirm an impact on survival in unselected advanced soft tissue sarcoma (STS) patients, the level of expression and the prognosis of platelet-derived growth factor (PDGF) receptors and ligands in STS remain unclear.

Patients and methods

We analyzed PDGF ligands and receptors' expression levels in a series of 255 patients with different histologies of STS [gastrointestinal stromal tumor (GIST), myxoid liposarcoma (MLPS), sarcoma with complex genomics, synovial sarcoma (SyS)] with Agilent single-color micro-arrays. We explored expression levels as prognostic values in univariate and multivariate analysis using R software (version 3.4.2).

Results

Complex patterns of correlation of expression between ligands and receptors were observed for each histotype. PDGFA levels were highest in SyS and lowest in MLPS (P < 4 × 10⁻⁹), PDGFB and C levels were lower in GIST (P < 2 × 10⁻¹⁵ and P < 3 × 10⁻⁹) while PDGFD expression was similar across histological subtypes. PDGF receptor (PDGFR) A expression was lowest in MLPS (P < 0.002), whereas PDGFRB and L expressions were lowest in GIST and SyS (P < 0.0004). Interestingly, high PDGFA expression levels were associated with higher risk of metastasis (P = 0.006), whereas PDGFD levels above average were associated with a reduced risk of metastasis (P = 0.01) in univariate and multivariate analysis.

Conclusions

The expression of PDGF ligands and receptors varies across sarcoma histological subtypes. PDGFA and D expression levels independently and inversely correlate with the risk of metastatic relapse.

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The expression of PDGF ligands and receptors substantially varies across sarcoma histological subtypes.

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PDGFA and D expression levels independently and inversely correlate with the risk of metastatic relapse.

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The differential expression of ligands might be used as biomarker of efficacy for PDGFRα antibodies in STS.

Specific immune landscapes and immune checkpoint expressions in histotypes and molecular subtypes of sarcoma

Soft tissue sarcomas are a group of rare and aggressive connective tissue neoplasms for which curative therapeutic opportunities are limited in advanced phase. Clinical trials assessing immunotherapy in these tumors have so far reported limited efficacy. The objective of this study is to provide a description of the immunologic landscape of sarcomas to guide the next clinical trials of immunotherapy in these diseases. The gene expression profile of 93 immune checkpoint (ICP) and membrane markers (MM) of immune cells was analyzed in a series of 253 soft tissue sarcoma (synovial sarcoma, myxoid liposarcoma, sarcoma with complex genomic and GIST) using Agilent Whole Human Genome Microarrays. The unsupervised hierarchical clustering of gene expression level was found able to properly group patients according to the histological subgroup of sarcoma, indicating that each sarcoma subgroup is associated with a specific immune signature defined by its gene expression pattern. Using the prognostic impact of CIBERSORT signature on metastatic-free survival in each subgroup, specific target could be proposed for each of the four groups: Treg through ICOS and GITR in GIST, M0 macrophages in all four sarcoma subtypes, OX40 in SS, CD40 in GIST and SS. The immune landscape of sarcoma was found to be as heterogeneous as the histotypes and molecular subtypes, but strongly correlated to the histotype. Histotype adapted immunotherapeutic approaches in each sarcoma subtypes must be considered in view of these results, consistently with the already reported specific response of histotypes of ICPs.

Multicenter clinical experience of real life Dalbavancin use in gram-positive infections

Dalbavancin, a lipoglycopeptide with prolonged half-life approved for the treatment of acute bacterial skin and soft tissue infections, can be used for the treatment of infections caused by gram-positive bacteria requiring long term treatment such as endocarditis, prosthetic joint infections (PJI) or osteomyelitis. Clinical data are limited in these settings.

OBJECTIVES

To evaluate indications, safety, tolerability and long-term outcomes of dalbavancin-treated patients. Patients and methods Our multicenter, retrospective study includes patients who received dalbavancin in Austria from September 2016 to March 2018. 90-day outcomes and tolerability were determined.

RESULTS

A total of 101 patients were included in 3 centers (57% male, median age 65 years). The treated infections were PJI (31%), osteomyelitis (29%), endocarditis (25%) and acute bacterial skin and soft tissue infections (12%). Concomitant use of other antimicrobial substances was common (63%). The mean total cumulative dose of dalbavancin was 3,357mg (±2,283mg). Clinical success rate was 89%. Side effects occurred in 3/101 patients.

CONCLUSION

In this real-life study dalbavancin was primarily used in off-label indications for treatment of PJI, osteomyelitis and endocarditis. Success rate was high (89%), tolerability and safety were excellent in this setting. Dalbavancin may therefore be used in these off-label indications as alternative treatment approach.

Management and prognosis of malignant peripheral nerve sheath tumors: The experience of the French Sarcoma Group (GSF-GETO)

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNST) are a rare subtype of soft tissue sarcoma. They can arise in irradiated fields, in patients with type 1 neurofibromatosis (NF1), or sporadically. MPNST exhibit an aggressive behaviour, and their optimal management remains controversial. An unsolved issue is whether NF1-related and sporadic forms of MPNST have a different prognosis, and should be managed differently.

MATERIAL AND METHODS

Adult and paediatric patients with histologically confirmed MPNST treated between 1990 and 2013 in French cancer centres of the GSF/GETO network, were included in this retrospective study.

RESULTS

A total of 353 patients (37% with NF1 and 59% with sporadic tumours) were analysed. Median age at diagnosis was 42 years (range 1-94). The majority of tumours developed in the limbs, were deep-seated and of high grade. Two hundreds and ninety four patients underwent a curative intent surgery. Among them, 60 patients (21%) had neoadjuvant treatment (mainly chemotherapy), and 173 (59%) had adjuvant treatment (mainly radiotherapy). For operated patients, median progression free and overall survival (OS) were 26.3 months and 95.8 months, respectively. In multivariate analysis, poor-prognosis factors for OS were high grade, deep location, locally advanced stage at diagnosis, and macroscopically incomplete resection (R2). NF1 status was not negatively prognostic, except in the recurrence or metastatic setting, where NF1-related MPNST patients treated with palliative chemotherapy showed worse survival than patients with sporadic forms.

CONCLUSION

To our knowledge, our series is the largest study of patients with MPNST reported to date. For operated patients, we showed a worse prognosis for NF1-related MPNST, due to different clinical features at diagnosis, more than NF1 status itself. The French sarcoma group is now conducting correlative analyses on these patients, using the latest molecular tools.

Soluble urokinase plasminogen activator receptor predicts mortality in patients with systemic inflammatory response syndrome

OBJECTIVE

The soluble urokinase plasminogen activator receptor (suPAR) reflects inflammation. However, the prognostic value of suPAR measurements, particularly at the very early onset of systemic inflammatory response syndrome (SIRS), is less well defined.

METHODS

The prognostic potential of suPAR levels in patients with SIRS was evaluated. From November 2010 until April 2013, 902 adult patients presenting with SIRS were investigated. Blood samples for laboratory testing of inflammation markers were collected simultaneously with initial blood cultures. suPAR testing was performed using suPARnostic(©) assay.

RESULTS

Analyses of receiver operating characteristics curves revealed areas under the curve (AUCs) of 0.818 for predicting overall mortality within 48 h (36/902 patients died), 0.739 for 30-day mortality (117/902 died) and 0.706 for predicting 90-day mortality (151/902 died). AUCs for procalcitonin (0.777, 0.671 and 0.638), interleukin-6 (0.709, 0.593 and 0.569) and C-reactive protein (0.66, 0.594 and 0.586) as well as renal function and age were markedly lower. Using multivariable regression analyses, suPAR levels (P < 0.001) remained significant predictors of 48-h mortality, whereas suPAR levels (P < 0.001) and bacteraemia (P = 0.002 and P = 0.001, respectively) remained significant predictors of 30- and 90-day mortality. Using Kaplan-Meier survival plots, patients with suPAR <9.15 ng mL(-1) at SIRS onset had a clear benefit.

CONCLUSION

suPAR plasma level determined at early SIRS is predictive for mortality.

Procalcitonin fails to predict bacteremia in SIRS patients: a cohort study

BACKGROUND

Procalcitonin (PCT) has previously been proposed as useful marker to rule out bloodstream-infection (BSI). The objective of this study was to evaluate the sensitivity of different PCT cut-offs for prediction of BSI in patients with community (CA)- and hospital-acquired (HA)-BSI.

METHODS

A total of 898 patients fulfilling systemic-inflammatory-response-syndrome (SIRS) criteria were enrolled in this prospective cohort study at the Medical University of Graz, Austria. Of those 666 patients had positive blood cultures (282 CA-BSI, 384 HA-BSI, enrolled between January 2011 and December 2012) and 232 negative blood cultures (enrolled between January 2011 and July 2011 at the emergency department). Blood samples for determination of laboratory infection markers (e.g. PCT) were collected simultaneously with blood cultures.

RESULTS

Procalcitonin was significantly (p < 0.001) higher in SIRS patients with bacteremia/fungemia than in those without. Receiver operating characteristic curve analysis revealed an area under the curve (AUC) value of 0.675 for PCT (95% CI 0.636-0.714) for differentiating patients with BSI from those without. AUC for IL-6 was 0.558 (95% CI 0.515-0.600). However, even at the lowest cut-off evaluated (i.e. 0.1 ng/ml) PCT failed to predict BSI in 7% (n = 46) of patients. In the group of patients with SIRS and negative blood culture 79% (n = 185) had PCT levels > 0.1.

CONCLUSION

Procalcitonin was significantly higher in patients with BSI than in those without and superior to IL-6 and CRP. The clinical importance of this is questionable, because a suitable PCT threshold for excluding BSI was not established. An approach where blood cultures are guided by PCT only can therefore not be recommended.

Comparison of clinical presentation and laboratory values at admission between PCR-confirmed influenza A H1N1 infection and influenza-like disease, South-East Austria

PURPOSE

Reliable and rapid diagnosis of influenza A H1N1 is essential to initiate the appropriate antiviral therapy and preventive measures. As PCR assays are time-consuming and rapid antigen tests have a limited sensitivity, official influenza case definitions are used in many clinical settings. These, however, are based exclusively on clinical criteria and have only a moderate potential to differentiate between influenza and other febrile diseases. Only limited data on the differences in clinical and laboratory parameters between influenza and non-influenza febrile diseases are available to date.

METHODS

This was a retrospective case-negative control series that was conducted in Styria, southeast Austria. We analyzed the differences in clinical presentation and laboratory admission parameters between patients with PCR-confirmed H1N1 influenza infection (n = 199) and those with influenza-like disease and negative influenza PCR results (ILD group; n = 252).

RESULTS

In the multivariable analysis lower C-reactive protein (CRP) level, lower white blood cell (WBC) count, fever, wheezing, cough, and the absence of nausea or sudden onset remained significant predictors of H1N1 influenza in adult patients (n = 263). Lower CRP level, lower WBC count, and cough remained significant predictors in pediatric patients (<16 years; n = 188).

CONCLUSION

Lower CRP level, lower WBC count, and cough were significant predictors of H1N1 in both the adult and pediatric patient group. These data may help to develop an improved case definition for suspected H1N1 infection which combines clinical findings and easily available laboratory parameters.

Clinical presentation of Puumala virus infections in southern Austria in the peak year 2012

In 2012, an extraordinary rise in Puumala infections causing nephropathia epidemica (NE) was observed in southern Austria. We investigated differences in epidemiology, clinical presentation, laboratory results, treatment parameters, and outcome between patients in 2012 and previous years (2007-2011). All patients diagnosed with Puumala virus infections between 2007 and 2012 using a point of care Puumala IgM test at the microbiology laboratory, Department of Internal Medicine, Medical University of Graz, were included. In 2012, 42 and in 2007-2011 a total of 40 patients were diagnosed with NE. In 2007-2011, patients presented more frequently with arthromyalgias (25% vs 7%, p = 0.027), while lower back pain was reported more often in 2012 (21% vs 5%, p = 0.029). Other symptoms occurred at the same rate. In 2012, patients were diagnosed significantly faster (time from first contact with a physician to diagnosis 1.3 ± 0.2 vs 2.7 ± 0.4 days, p = 0.01). Significantly fewer patients required haemodialysis in 2012 (2.4% vs 20%, p = 0.01). There were no significant differences in laboratory parameters between the two groups. In the peak year 2012, patients were diagnosed faster and fewer patients required haemodialysis possibly because of the earlier diagnosis and earlier onset of therapy.

Successful management of nosocomial ventriculitis and meningitis caused by extensively drug-resistant Acinetobacter baumannii in Austria

Nosocomial infections caused by the Gram-negative coccobacillus Acinetobacter baumannii have substantially increased over recent years. Because Acinetobacter is a genus with a tendency to quickly develop resistance to multiple antimicrobial agents, therapy is often complicated, requiring the return to previously used drugs. The authors report a case of meningitis due to extensively drug-resistant A baumannii in an Austrian patient who had undergone neurosurgery in northern Italy. The case illustrates the limits of therapeutic options in central nervous system infections caused by extensively drug-resistant pathogens.

Forest fragmentation genetics in a formerly widespread island endemic tree: Vateriopsis seychellarum (Dipterocarpaceae)

Habitat fragmentation and changed land use have seriously reduced population size in many tropical forest tree species. Formerly widespread species with limited gene flow may be particularly vulnerable to the negative genetic effects of forest fragmentation and small population size. Vateriopsis seychellarum (Dipterocarpaceae) is a formerly widespread canopy tree of the Seychelles, but is now reduced to 132 adult individuals distributed in eleven sites. Using ten microsatellite loci, a genetic inventory of all adult trees and a sample of 317 progeny, we demonstrate that despite its restricted range, overall genetic diversity was relatively high (H(E) : 0.56). The juvenile cohort, however, had significantly lower allelic richness (adults R(S) : 3.91; juveniles R(S) : 2.83) and observed heterozygosity than adult trees (adults H(O) : 0.62; juveniles H(O) : 0.48). Rare alleles were fewer and kinship between individuals was stronger in juveniles. Significant fine-scale spatial genetic structure was observed in remnant adults, and parentage analysis indicated that more than 90% of sampled progeny disperse <25 m and pollen dispersed <50 m. The molecular data confirmed that two populations were derived entirely from self-fertilized offspring from a single surviving mother tree. These populations produce viable offspring. Despite this extreme genetic bottleneck, self-compatibility may provide V. seychellarum with some resistance to the genetic consequences of habitat fragmentation, at least in the short term. We discuss our findings in the context of other rare and threatened dipterocarp species which are vulnerable to miss-management of genetic resources and population fragmentation.

Back from the brink: potential for genetic rescue in a critically endangered tree

Rare plant species are vulnerable to genetic erosion and inbreeding associated with small population size and isolation due to increasing habitat fragmentation. The degree to which these problems undermine population viability remains debated. We explore genetic and reproductive processes in the critically endangered long-lived tropical tree Medusagyne oppositifolia, an endemic to the Seychelles with a naturally patchy distribution. This species is failing to recruit in three of its four populations. We evaluate whether recruitment failure is linked to genetic problems associated with fragmentation, and if genetic rescue can mitigate such problems. Medusagyne oppositifolia comprises 90 extant trees in four populations, with only the largest (78 trees) having successful recruitment. Using 10 microsatellite loci, we demonstrated that genetic diversity is high (H(E) : 0.48-0.63; H(O) : 0.56-0.78) in three populations, with only the smallest population having relatively low diversity (H(E) : 0.26 and H(O) : 0.30). All populations have unique alleles, high genetic differentiation, and significant within population structure. Pollen and seed dispersal distances were mostly less than 100 m. Individuals in small populations were more related than individuals in the large population, thus inbreeding might explain recruitment failure in small populations. Indeed, inter-population pollination crosses from the large donor population to a small recipient population resulted in higher reproductive success relative to within-population crosses. Our study highlights the importance of maintaining gene flow between populations even in species that have naturally patchy distributions. We demonstrate the potential for genetic and ecological rescue to support conservation of plant species with limited gene flow.

Comparison of fluorescence in situ hybridisation using peptide nucleic acid probes, Gram stain/acridine orange leukocyte cytospin and differential time to positivity methods for detection of catheter-related bloodstream infection in patients after haematopoietic stem cell transplantation

In 46 febrile neutropenic patients who had undergone haematopoietic stem cell transplantation, the fluorescence in situ hybridisation using peptide nucleic acid probes (PNA FISH), Gram stain/acridine orange leukocyte cytospin (Gram/AOLC), and differential time to positivity (DTP) methods were performed for detection of catheter-related bloodstream infections (CRBSIs). As compared with the DTP method (which detected 11 patients with CRBSI), the PNA FISH and the Gram/AOLC methods detected ten of 11 CRBSI patients, resulting in a sensitivity, specificity, negative predictive value and positive predictive value of 91%, 100%, 97% and 100%, respectively, for the PNA FISH method as well as for the Gram/AOLC method.

Quality and variability of osteoporosis data in general practice computer records: implications for disease registers

OBJECTIVE

To determine the extent to which routinely collected general practitioner computer data could be used to create disease registers of patients with osteoporosis, and to report any improvement in data quality since previous studies.

STUDY DESIGN

Audit using anonymized data extracted from general practice computer records from across England.

METHODS

Morbidity Query Information and Export Syntax (MIQUEST) software was used to extract structured data from the 78 volunteer practices that participated in the study. The data were aggregated and analysed.

RESULTS

There were 100-fold differences in the rates of recording of relevant data. Many patients receiving treatment had no diagnostic codes. Data about secondary causes of osteoporosis and fractures were more consistently recorded than data relating to falls. There were no data to indicate whether fractures were low impact. T-scores, the gold-standard measure of bone density, were very infrequently recorded.

CONCLUSIONS

Sufficient data about secondary causes of osteoporosis exist, and these could be searched to identify patients at risk. Meanwhile, fracture recoding could be improved, including likely fragility fractures, and T-scores could be added to computer records. A systematic approach is needed to raise the computer records to a standard where they can be used as valid and reliable disease registers.

A regulatory light chain of ciliary outer arm dynein in Tetrahymena thermophila

Ciliary beat frequency is primarily regulated by outer arm dyneins (22 S dynein). Chilcote and Johnson (Chilcote, T. J., and Johnson, K. A. (1990) J. Biol. Chem. 256, 17257-17266) previously studied isolated Tetrahymena 22 S dynein, identifying a protein p34, which showed cAMP-dependent phosphorylation. Here, we characterize the molecular biochemistry of p34 further, demonstrating that it is the functional ortholog of the 22 S dynein regulatory light chain, p29, in Paramecium. p34, thiophosphorylated in isolated axonemes in the presence of cAMP, co-purified with 22 S dynein and not with inner arm dynein (14 S dynein). Isolated 22 S dynein containing phosphorylated p34 showed approximately 70% increase in in vitro microtubule translocation velocity compared with its unphosphorylated counterpart. Extracted p34 rebound to isolated 22 S dynein from either Tetrahymena or Paramecium but not to 14 S dynein from either ciliate. Binding of radiolabeled p34 to 22 S dynein was competitive with p29. Phosphorylated p34 was not present in axonemes isolated from a mutant lacking outer arms. Two-dimensional gel electrophoresis followed by phosphorimaging revealed at least five phosphorylated p34-related spots, consistent with multiple phosphorylation sites in p34 or perhaps multiple isoforms of p34. These new features suggest that a class of outer arm dynein light chains including p34 regulates microtubule sliding velocity and consequently ciliary beat frequency through phosphorylation.