2.1 Methods
Treatment-naïve children ≤15years with biopsy-proven, osteosarcoma
uniformly treated on OGS-2012 chemotherapy protocol and surgery
post-NACT from January 2013-December 2020 were retrospectively analysed.
OGS-2012 is an indigenous non-MAP protocol with lesser cumulative doses
of alkylating agents and anthracyclines compared to MAP and St Jude OS99
(Supplemental Figure S1, Supplemental TABLE S1).2,3,4MRI scan was the imaging modality of the primary with staging done by
Non-Contrast Computed Tomography (NCCT) of thorax and bone scan. In
metastatic disease, only oligometastatic lung metastases or other sites
which were surgically resectable were treated. Children were started on
NACT if there was no indication for upfront surgery otherwise.
Reassessment was done at 10-12 weeks with MRI scan of the primary and if
initially metastatic to lungs, with NCCT of the thorax. Type of surgery
was decided by the surgical team based on imaging and clinical profile.
Limb Salvage Surgery (LSS) was done wherever feasible. There was a
higher threshold for amputation, being reserved for cases with fungating
or bleeding primary, with excruciating pain and where LSS was not
possible. Those who had progressive disease prior to attaining local
control were excluded from this cohort. Response to preoperative
chemotherapy was assessed histologically on the surgical specimen and
tumor necrosis noted in percentage.13 All metastatic
sites which persisted on response assessment were also addressed
surgically in this curative cohort. All children received uniform
adjuvant chemotherapy with ifosfamide and cisplatin irrespective of the
histological response. Those who had high frequency sensorineural
hearing loss (SNHL) as detected by pure tone audiometry performed as per
protocol were prescribed carboplatin or etoposide or HDMTX depending on
the degree of SNHL. The primary objective of this study was to assess
Event Free Survival (EFS) and Overall Survival (OS) based on TN at
various cut-offs on a non-HDMTX based chemotherapy protocol, OGS-2012 in
whole cohort, localized and metastatic osteosarcoma who were treated
with a curative intent. The secondary objective was to delineate
clinical and laboratory parameters predictive of TN on the same
chemotherapy backbone. Children who had extracorporeal radiotherapy or
cryoablation as limb salvage procedure where whole specimen was not
available for assessment of TN were excluded from the analysis.