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\begin{document}

\title{Safety and efficacy of alendronate to treat osteopenia in children
during therapy for acute lymphoblastic leukemia. A retrospective cohort
study of sequential outcomes.}



\author[1]{Ronald Barr}%
\author[2]{Paula MacDonald}%
\author[2]{Amy Cranston}%
\author[3]{Misha Virdee}%
\author[4]{Troy Farncombe}%
\author[3]{Uma Athale}%
\affil[1]{McMaster Children's Hospital}%
\affil[2]{Hamilton Health Sciences}%
\affil[3]{McMaster University}%
\affil[4]{hamilton Health Sciences}%


\vspace{-1em}



  
  \date{May 16, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Background. Low bone mineral density (osteopenia) is encountered in
children with acute lymphoblastic leukemia (ALL) before, during and
after treatment. Prior experience with alendronate, an oral
bisphosphonate, demonstrated high tolerability and evident clinical
efficacy. However, concerns have been expressed about the long-term
safety and utility of such agents in children. Procedure. Of 217
children with ALL treated on Dana Farber Cancer Institute protocols 69
received alendronate for a mean of 87 weeks after dual energy X ray
absorptiometry (DXA). DXA was repeated following completion of
alendronate, and again 5-9 years later in a subgroup of 32 children.
Lumbar spine areal bone mineral (LS aBMD) Z scores were obtained and
values corrected for height, age and weight (HAW) were calculated for
subjects 3-18 years of age. Results. Almost 80\% (N=172) of the children
remain in continuous complete remission at a mean of 14.5 years from
diagnosis. Of those who receive alendronate, which was almost uniformly
well tolerated, 7/69 (10.3\%) relapsed compared to 19/89 (21.3\%) who
did not receive the drug. The mean unmodified LS aBMD Z score rose from
-1.78 to -0.47. This gain was statistically significant for both
unmodified (p \textless{}0.0001) and HAW corrected Z scores -1.32 to
-0.42; p \textless{}0.0001). There was a modest median loss of LS aBMD
(Z score 0.045) subsequently in the subgroup (N=32) of subjects on
long-term follow up. Discussion. Alendronate appears to be well
tolerated and moderately effective in osteopenic children with ALL.
Whether it offers protection against relapse of leukemia needs further
study.%
\end{abstract}%



\sloppy


\textbf{Introduction}

Bony morbidity is common in children with acute lymphoblastic leukemia
(ALL). Pain is a frequent symptom at
diagnosis,\textsuperscript{1}associated with an expanding cell mass in
the medullary cavity, and vertebral fractures at this time are prominent
and often unrecognized clinically.\textsuperscript{2} Osteopenia,
reflecting loss of bone mineral, is demonstrable before the initiation
of therapy\textsuperscript{3} and becomes more evident with the onset of
treatment.\textsuperscript{4} The contributing factors include
glucocorticoid and methotrexate medication, cranial irradiation (now
used much less frequently) and reduced physical
activity.\textsuperscript{5}

Additional bony morbidity is seen in the form of osteonecrosis that
shares an etiology with osteopenia, from exposure to high cumulative
doses of corticosteroids, although the pathogenesis is
different.\textsuperscript{6} Both osteopenia\textsuperscript{7} and the
symptoms of osteonecrosis\textsuperscript{8} may be ameliorated by the
administration of bisphosphonates.

These compounds are structural analogues of natural inorganic
pyrophosphate which explains their very high affinity for bone because
they bind to crystals of hydroxyapatite and impede their breakdown, so
suppressing bone resorption.\textsuperscript{9} The third generation
bisphosphonates, including alendronate and pamidronate, have side chains
containing nitrogen. These agents bind to and inhibit farnesyl
pyrophosphate synthase, an important enzyme in the mevalonic acid
pathway. In turn this results in dysregulation of osteoclast metabolism
with eventual apoptosis.\textsuperscript{9} Bone resorption remains
suppressed for the duration of treatment. With oral agents only about
50\% of the absorbed dose is retained in the skeleton, the remainder
being excreted in the urine. The amount of bisphosphonate retained
varies considerably among patients and between clinical disorders,
probably reflecting variations in bone turnover.\textsuperscript{8}

In our preliminary experience from 2000, intravenous pamidronate was
effective in redressing the depletion of bone mineral but poorly
tolerated;\textsuperscript{10} however, oral alendronate, with 5 fold
greater potency,\textsuperscript{9} was well tolerated and retained
clinical efficacy,\textsuperscript{11} despite low
bioavailability.\textsuperscript{12}

Nonetheless, concerns have been expressed about the safety and efficacy
of bisphosphonates in children.\textsuperscript{13} While there have
been no reports in childhood of the uncommon but dramatic problem of
osteonecrosis of the jaw encountered in adults,\textsuperscript{14} even
in those children undergoing invasive dental procedures while receiving
a bisphosphonate,\textsuperscript{15} the long-term impact of these
drugs on growing bones is uncertain.\textsuperscript{16} Likewise,
although bisphosphonates may exert anti-tumor
effects,\textsuperscript{17,18} minor hematological abnormalities have
been described with the administration of these
agents\textsuperscript{19} and longer term adverse sequelae on
hematopoiesis should be considered, including relapsed disease.
Consequently, we have undertaken studies of the short and long-term
efficacy and safety of bisphosphonates in children with ALL.

\textbf{Patients and Methods}

Between January, 2000 and April, 2015 a total of 223 children and
adolescents were diagnosed with ALL at McMaster Children's Hospital
(MCH) in Hamilton, Canada. Six of them were infants, less than 12 months
of age, who received very intensive chemotherapy according to Interfant
protocols\textsuperscript{20} and were excluded from this study. Among
the 9 early deaths, 5 occurred during remission induction (2.3\%) and
one child was withdrawn from treatment by her family at the end of
induction while another returned to his native country at the same
juncture. The study sample of 217 were treated on regimens
00-001\textsuperscript{,21} 05-001\textsuperscript{22} and
11-001\textsuperscript{23} of the Dana Farber Cancer Institute Childhood
ALL Consortium in which MCH had been a member since 1985. These regimens
were characterized by high cumulative doses of glucocorticosteroids and
asparaginase. Details of their disease and clinical outcomes are given
in Table 1. For the purposes of this report the study sample was
followed until December 31, 2020.

It was our standard practice, in the time period 2000-2015, to undertake
dual energy x-ray absorptiometry (DXA) on all
children\emph{\textgreater{}} 3 years of age at diagnosis and at
intervals of 6 months thereafter for the duration of treatment; two
years after remission induction\textsuperscript{24}. These examinations
were performed with Hologic densitometers QDR 4500A and Discovery A
(Hologic Inc., Waltham, MA). Each whole body scan results in radiation
exposure of 20 microSv, less than 1/10\textsuperscript{th} of a chest
x-ray.\textsuperscript{25} Local normative data on body
composition,\textsuperscript{26} including bone mineral density
(BMD),\textsuperscript{27} were generated for 3-18 year olds and
corrections for height, age and weight (HAW) were developed for BMD of
the lumbar spine.\textsuperscript{28}

Children and adolescents with lumbar spine areal BMD (LS aBMD) Z scores
of \emph{\textless{}} - 2.0 and those who were less osteopenic but had
related bony morbidity, e.g. fractures, were candidates for treatment
with a bisphosphonate, oral alendronate in all of them. Alendronate was
administered weekly, in doses according to body weight (Table 2), to
coincide with scheduled clinic attendance for chemotherapy, and all
patients received daily supplemental calcium in the form of TUMS to
provide 30 to 40mg/kg/d. Alendronate was administered while the children
were fasting, as recommended.\textsuperscript{12}

The study was approved by the Hamilton Integrated Research Ethics Board,
project 3479 C.

Statistical analyses

Patient demographics including BMD were summarized using descriptive
measures expressed as mean (standard deviation) or median (minimum,
maximum) for continuous variables and number (percent) for categorical
variables. Associations between categorical outcomes and clinical groups
were assessed using Fisher's Exact test or chi-squared test. Impact of
bisphosphonate therapy on BMD was tested using paired sample t test. The
limit for statistical significance was set at two tailed \selectlanguage{greek}α \selectlanguage{english}= 0.05.
Statistical software SPSS version 26 (IBM SPSS Statistics for Windows,
Version 26.0. Armonk, NY: IBM Corp) was used for analysis.

\textbf{Results}

Within the sample, the age range was 1 to 18 median 4 years (mean 5.7,
SD 4.3) at the time of diagnosis and the M:F ratio was 116:101 (1.15).
The majority had standard risk disease and almost 80\% remain in
continuous remission (Table 1). The interval from diagnosis to December
31, 2020 was 5.7 to 21.1 median 14.7 years (mean 14.5, SD 4.2).

The recipients of alendronate (n=69, 32\%) were 1 to 18 median 6 years
(mean 7.0 SD 5.2) of age at diagnosis and the M:F ratio was 37:32
(1.19). In the group who received alendronate 41\% had high risk disease
compared to 35\% in the other group. Alendronate was administered for a
mean (SD) of 87.1 (67.3) weeks; median 77, range 4 to 387 weeks. Two
subjects were excluded from this analysis of duration of administration;
one with Noonan syndrome received the drug for 6.5 years on the advice
of an endocrinologist and another received prescriptions for 7.5 years
but was felt to be largely non-compliant and had a LS aBMD Z score after
this interval of -2.0. Both subjects were retained in the analysis of
efficacy. LS aBMD prior to administration in the entire group of
recipients is shown in Table 3.

SAFETY: Our experience with IV pamidronate in children with ALL has been
reported.\textsuperscript{10} The side effects, including hyperpyrexia,
were such that we abandoned the use of this agent. Alendronate was
tolerated well overall and adherence was very high as a result of the
schedule of administration. None of the participants experienced an
acute phase reaction and only a few reported mild and short-lived
gastrointestinal symptoms which did not interfere with compliance.
However, one subject was truly intolerant, with symptomatic esophagitis,
and so was withdrawn from further analyses.

Among those who received a course of alendronate, 7/68 (10.3\%)
relapsed, none during chemotherapy, of whom two died compared to 19/89
(21.3\%), four during post-induction chemotherapy with four deaths, in
those who did not receive the drug and were not lost to follow up. The
difference in relapse rates is not statistically significant (p=0.06).
An additional child who received alendronate was diagnosed with ALL 16
years after the original diagnosis. The phenotype was demonstrably
different from that of the primary disease and so the new disease was
deemed to be a second cancer, recognizing that this is a rare
event.\textsuperscript{29,30}

EFFICACY

The interval from completion of the course of alendronate to the next
DXA examination was a mean (SD) of 100.5 (86.5) weeks; median 79, range
-30 to 465 weeks. One subject's last DXA was 6 months before finishing
alendronate. The LS aBMD following alendronate is shown in Table 3 and
represents a statistically significant increase, whether expressed as Z
score (mean gain 1.31, p\textless{}0.0001) or HAW corrected Z score
(mean gain 0.90, p\textless{}0.0001). While most of the subjects - 44/68
(65\%) -- still had negative Z scores, the majority (85\%) gained BMD
and 50/68 (74\%) were within the normal range of -1.0 to +1.0. The
correlation between duration of alendronate administration and the size
of the gain in BMD was not statistically significant (r=0.017, p=0.891,
nor was the correlation between the interval from completion of
alendronate to next DXA examination and the size of the gain in BMD
(r=-0.122, p=0.327).

A subgroup of 32 subjects had further DXA examinations, as part of their
long term follow up, 5-9 years after finishing alendronate. Twenty-two
of them (69\%) still had negative Z scores although only half of those
were osteopenic (LS aBMD Z score \textless{} -1.00). The results of the
sequential DXA examinations on this subgroup are shown in Table 4 and
Figure 1. The gains in BMD between time points 1 and 2 and between time
points 1 and 3 were highly statistically significant
(p\textless{}0.0001), but there was no significant difference in BMD
between time points 2 and 3 (p=0.090). There was no relationship of Z
scores or changes in Z scores to age or sex. Nine subjects had further
scans more than 10 years from diagnosis as part of a cross-sectional
study of long-term survivors; 8 had higher BMD Z scores than prior to
receiving alendronate and only one was still osteopenic with a score of
-1.6.

\textbf{Discussion}

Bisphosphonates are manifestly effective in the treatment of
osteoporosis in adults by inhibiting osteoclast-mediated bone
resorption. Experience in children with low bone mineral is less
extensive but generally supports the same
conclusion.\textsuperscript{19} This is exemplified by a report on a
small number (n=22) of children with a variety of chronic illnesses
associated with loss of bone mineral, none with malignant
disease.\textsuperscript{31} In a randomized clinical trial (RCT) the
participants received either oral alendronate weekly or placebo for one
year. Volumetric bone density of the lumbar spine increased
significantly in the experimental group but not in those receiving
placebo. Likewise, the cross-sectional moment of inertia per unit length
of the femoral shaft - an estimate of mechanical strength - increased
significantly only in the experimental group.\textsuperscript{31}

A recent report from the Cincinatti Children's Hospital Medical Center
is of a 7 year retrospective chart review describing the outcomes of
intravenous bisphosphonate infusions in patients less than 21 years of
age.\textsuperscript{32} Among the patients who were excluded were all
of those (N=12) who had received cancer chemotherapy, but 29 of the
study sample (N=123) were categorized as having glucocorticoid-induced
osteoporosis. In the 42 patients who had at least two DXA examinations
available for comparison there was a significant gain in LS aBMD) at one
year after bisphosphonate infusion.

In the non-randomized study reported here, involving only children with
ALL (n=68) on active therapy who received oral alendronate weekly for a
shorter time than in the RCT reported by Rudge et
al.,\textsuperscript{31} LS aBMD increased significantly as measured by
Z score with and without HAW correction. The sequential results from DXA
examinations are indicative of a short-term gain in LS aBMD from the
administration of alendronate, blunting an otherwise downward
trajectory. These changes occurred at an age when bone mass is
increasing in healthy children, adolescents and young adults. In a
population of healthy Caucasian subjects in Ohio, who were studied
serially by DXA between the ages of 8-30 years,\textsuperscript{33} the
rate of accumulation of bone mass began to slow in mid to late teens in
females (N=343) with peak BMD attained in the early 20s, while in males
(N=312) the corresponding rate began to slow in late teens to early 20s
with peak BMD attained by mid to late 20s. Comparable Canadian data have
been reported.\textsuperscript{34} Achieving a normal peak bone mass by
age 30 is important in the prevention of osteoporosis in older adult
life.\textsuperscript{35} Consequently, rendering the subjects in this
study osteopenic from the treatment of ALL, despite a temporary and only
partial reprieve by the administration of alendronate, has put them at
risk of fragility fractures in later life. In a separate study from our
centre,\textsuperscript{36} LS aBMD during maintenance/continuation
therapy of ALL was shown to be predictive of later fractures in children
who did not receive a bisphosphonate. The results in the small number of
subjects (n=9) reported here, who were studied more than a decade after
diagnosis, are intriguing, being suggestive of late improvement in LS
aBMD, but longitudinal examination of a larger cohort will be required
to evaluate this observation. A recent Dutch-Canadian collaborative
study has demonstrated the predictive value of age and weight at
diagnosis in relation to LS aBMD and to subsequent development of
symptomatic fractures in children with
ALL,\textsuperscript{37}complementing our established practice of HAW
correction of Z scores for aBMD of the lumbar spine.\textsuperscript{28}

The results of bone morphometry and measures of bone strength,
determined by peripheral quantitative computed tomography
(pQCT)\textsuperscript{38} in our study of long term survivors of ALL
(more than 10 years from diagnosis), have been reported
separately.\textsuperscript{39} There were no statistically significant
differences in any of 19 metrics between those who had received
bisphosphonate (n=14, pamidronate in 5) and those who had not (n=58).
This may represent adaptive restructuring of trabecular bone by
thickening of a reduced number of trabeculae to maintain bone
strength.\textsuperscript{40} Again, the improvement in LS aBMD
following discontinuation of long-term steroid therapy has been reported
in young adults with sarcoidosis.\textsuperscript{41}

There have been few prior studies of bone by pQCT in children with ALL.
Brennan et al. in the UK reported on 53 survivors on average almost 5
years after completion of treatment which did not include cranial
radiation.\textsuperscript{42} There was no deficit in LS aBMD but
reduced BMD in the trabecular bone of the distal radius was revealed.
More recently, a group of 50 survivors in the US were studied within two
years of completing treatment without cranial radiation, and again one
year later.\textsuperscript{43} A large group of healthy subjects
afforded the provision of Z scores. Initial deficits were shown in both
trabecular and cortical BMD in the tibia. Subsequent changes in the
cortical outcomes varied by the duration of the interval since
completion of therapy. Interestingly, there were no associations of the
outcomes with leukemia risk category, total glucocorticoid dose or
antimetabolite therapy.

With respect to the short-term safety of oral alendronate, this has been
assessed in detail in randomized clinical trials conducted in young
people. In a study of 32 adolescents with anorexia nervosa who received
the drug or placebo daily for one year, the authors stated ''We found
alendronate to be well tolerated and safe''.\textsuperscript{44} A more
recent trial in 139 children with osteogenesis imperfecta, involving
daily oral alendronate for two years, prompted the authors' observation
''Importantly, ALN was associated with few adverse events. In particular
gastrointestinal symptoms were not more common in patients receiving ALN
than in those receiving placebo''.\textsuperscript{45} In a systematic
review of bisphosphonates in children and adolescents with secondary
osteoporosis Ward and colleagues noted that oral alendronate appeared to
be well tolerated for intervals up to 3 years.\textsuperscript{46} A
report of the use of oral alendronate in post-menopausal osteoporosis
stated that the drug was efficacious and well tolerated over a 10 year
period.\textsuperscript{47} In our non-randomized study gastrointestinal
symptoms were infrequent and minor in degree, with one exception, and no
other adverse sequelae were recorded. The retrospective study by
Nasomyont and colleagues\textsuperscript{32} determined that ``In 468
patient years of bisphosphonate exposure there were no reports of ONJ
(osteonecrosis of the jaw) or AFF (atypical femoral fracture) in medical
record.'' In a systematic review published in 2020 no cases of ONJ in
children were identified.\textsuperscript{48}

The other safety issue addressed in our study is that of the
relationship of bisphosphonates to the risk of cancer, in this instance
relapse of ALL. We are not aware of this having been studied previously
in children. By contrast, it has been a topic of considerable interest
in the context of adults. Pre-clinical data and some, but not all,
clinical trials suggest an anti-neoplastic effect of
bisphosphonates.\textsuperscript{49} A recent study using murine models
of ALL showed a significantly shorter survival in animals receiving
zoledronic acid, a third generation bisphosphonate, as well as
chemotherapy compared to those receiving chemotherapy alone, but this
was not seen using xenografts of human B precursor and T cell
ALL.\textsuperscript{50}

A large study in the UK, using data extracted from the General Practice
Research Database, examined 41,826 subjects who had been exposed to oral
bisphosphonates and an equal number of matched
controls,\textsuperscript{51} investigating the risk of developing
cancer overall as well as specific neoplasms. It was reported that there
was a significant protective effect in general and specifically in
relation to breast and colorectal cancers. No such effect was evident
for leukemias and lymphomas, but in no instance was the risk of cancer
increased. In comparison, the results of a population-based cohort study
in South Korea, using the National Health Insurance Services database,
showed no association between exposure to oral alendronate or
residronate and the risk of breast, ovarian or cervical
cancer.\textsuperscript{52} This study involved 14,847 users and 204,525
unmatched controls.

A systematic literature review of the prognostic effect of
bisphosphonate exposure in adult patients with a solid tumor found
improved overall survival as well as cancer-specific and recurrence-free
survival.\textsuperscript{53} For individual cancer types there was an
apparent benefit in overall survival for patients with gastro-esophageal
cancer and longer cancer-specific survival in those with breast cancer.
In a separate study, exposure to alendronate was associated with a lower
risk of bone metastases in osteoporotic women with breast
cancer.\textsuperscript{54}

Against this background our finding that there was no increased
frequency of relapse in children receiving oral alendronate while
undergoing active therapy for ALL may offer a measure of reassurance.
Whether there was a protective effect is intriguing -- the proportion of
patients who relapsed after receiving alendronate was less than 50\% of
that in those who did not receive the drug, and more patients who
received alendronate had high risk disease - but cannot be addressed
with confidence. However, in a recent report,\textsuperscript{55} B cell
ALL cells were shown to mediate resorption of trabecular bone by a
RANK-RANKL (receptor activator of nuclear factor kB ligand) mechanism
through activation of osteoclasts. The authors postulated that combining
an anti-resorptive agent with chemotherapy may reduce the risk of
relapse by disrupting this B cell activity.

This was a retrospective cohort study with a small number of patients.
Other limitations are the variability in the duration of alendronate
administration, although this reflects variation in the timing of
responsiveness to this medication, and the lack of reliable information
on fractures. A much larger longitudinal study with well-matched
controls, perhaps in the form of a randomized trial to examine the
efficacy of a bisphosphonate in osteopenic children with ALL, would be
valuable.

Conflict of Interest statement. The authors have no conflicts of
interest to declare

Acknowledgements. We acknowledge the contributions of Jo-Ann Fowler BScN
and Sarah Beasley BScN to the collection of data from clinical records.

Figure legend. Sequential lumbar spine bone mineral density Z scores in
children and adolescents with acute lymphoblastic leukemia who received
alendronate.

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\end{enumerate}\selectlanguage{english}
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\verb`TABLE 1.docx`  available at \url{https://authorea.com/users/406883/articles/555620-safety-and-efficacy-of-alendronate-to-treat-osteopenia-in-children-during-therapy-for-acute-lymphoblastic-leukemia-a-retrospective-cohort-study-of-sequential-outcomes}

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\verb`TABLE 2.docx`  available at \url{https://authorea.com/users/406883/articles/555620-safety-and-efficacy-of-alendronate-to-treat-osteopenia-in-children-during-therapy-for-acute-lymphoblastic-leukemia-a-retrospective-cohort-study-of-sequential-outcomes}

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\verb`TABLE 3.docx`  available at \url{https://authorea.com/users/406883/articles/555620-safety-and-efficacy-of-alendronate-to-treat-osteopenia-in-children-during-therapy-for-acute-lymphoblastic-leukemia-a-retrospective-cohort-study-of-sequential-outcomes}

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\verb`TABLE 4.docx`  available at \url{https://authorea.com/users/406883/articles/555620-safety-and-efficacy-of-alendronate-to-treat-osteopenia-in-children-during-therapy-for-acute-lymphoblastic-leukemia-a-retrospective-cohort-study-of-sequential-outcomes}

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