Prognostic Value of Depth of Invasion in Squamous Cell Carcinoma of the Oral Cavity of Size 4 cm or Less

PURPOSE/OBJECTIVE(S)

We aimed to evaluate the role of the depth of invasion (DOI) as an independent prognostic factor in the absence of other adverse features in squamous cell carcinoma (SqCC) of the oral cavity with a size of 4 cm or less.

MATERIALS/METHODS

We performed a retrospective analysis in a multi-institutional cohort of patients with oral cavity SqCC, size of 4 cm or less. We included those who were treated with upfront surgery with negative resection margins from 2010 to 2021 and those with one or no nodal metastasis. Those who were treated with postoperative radiotherapy were excluded. The DOI and other adverse features, such as close resection margins, lymphovascular invasion, perineural invasion, and nodal metastasis, were evaluated in univariate and multivariate analyses for their association with locoregional recurrence (LRR).

RESULTS

A total of 155 patients were included with a median follow-up of 23.7 months. 56 patients (36.1%) had DOI greater than 5 mm. 26 patients (16.8%) experienced LRR and one experienced distant metastasis. Multivariate analysis showed that DOI was the only prognostic factor associated with a higher rate of LRF (p = 0.004). The 2-year LRF rates of those with DOI ≤ 5 mm and DOI > 5mm were 4.7% and 30.3%, respectively.

CONCLUSION

This study implies that DOI greater than 5 mm may be an independent prognostic factor of the SqCC of the OCC and may be indicated for adjuvant radiotherapy.

Pilot study on interfractional and intrafractional movements using surface infrared markers and EPID for patients with rectal cancer treated in the prone position

OBJECTIVE

To evaluate interfractional and intrafractional movement of patients with rectal cancer during radiotherapy with electronic portal imaging device (EPID) and surface infrared (IR) markers.

METHODS

20 patients undergoing radiotherapy for rectal cancer with body mass index ranging from 18.5 to 30 were enrolled. Patients were placed in the prone position on a couch with a leg pillow. Three IR markers were put on the surface of each patient and traced by two stereo cameras during radiotherapy on a twice-weekly basis. Interfractional isocentre movement was obtained with EPID images on a weekly basis. Movement of the IR markers was analysed in correlation with the isocentre movement obtained from the EPID images.

RESULTS

The maximum right-to-left (R-L) movement of the laterally located markers in the horizontal isocentre plane was correlated with isocentre translocation with statistical significance (p = 0.018 and 0.015, respectively). Movement of the surface markers was cyclical. For centrally located markers, the 95% confidence intervals for the average amplitude in the R-L, cranial-to-caudal (C-C) and anterior-to-posterior (A-P) directions were 0.86, 2.25 and 3.48 mm, respectively. In 10 patients, intrafractional movement exceeding 5 mm in at least one direction was observed. Time-dependent systematic movement of surface markers during treatment, which consisted of continuous movement towards the cranial direction and a sail back motion in the A-P direction, was also observed.

CONCLUSION

Intrafractional movement of surface markers has both cyclic components and time-dependent systematic components. Marker deviations exceeding 5 mm were mainly seen in the A-P direction. Pre- or post-treatment EPID images may not provide adequate information regarding intrafractional movement because of systematic movement in the A-P direction during radiotherapy.

ADVANCES IN KNOWLEDGE

This work uncovered a sail back motion of patients in the A-P direction during radiotherapy. Pre- or post-treatment EPID images may not provide accurate positioning of patients in the A-P direction because of this time-dependent intrafractional motion.