Unknown primary head and neck cancer treated with intensity-modulated radiation therapy: To what extent the volume should be irradiated

Is bilateral radiotherapy necessary for patients with unilateral squamous cell carcinoma of unknown primary of the head and neck region?

Background and Purpose

Squamous cell carcinoma of unknown primary (SCC-CUP) of the head and neck region remains a clinical challenge, with uncertainty surrounding the necessity of contralateral irradiation of cervical lymphatic drainage in cases of unilateral involvement.

Materials and Methods

A retrospective study was conducted at the Department of Radiation Oncology, University Medical Center Mainz, on a cohort of 50 patients with unilateral SCC-CUP of the head and neck region treated between 2005 and 2019. 30 patients received bilateral and 20 received unilateral cervical radiotherapy. The majority (n = 38, 76 %) were treated with modern IMRT/ VMAT (Intensity-modulated Radiation Therapy/ Volumetric Modulated Arc Therapy) techniques.

Results

After a median follow-up of 64.5 months, locoregional recurrences occurred in 26 % of cases (n = 13/50), all of which were ipsilateral and predominantly within the volume of the previous irradiated CTV (clinical target volume) (85 %, n = 11/13). No patient treated unilaterally developed a contralateral recurrence in the neck. After 3 years, we observed 7 locoregional recurrences in the bilateral irradiated group (n = 7/30, 23 %), and 5 locoregional recurrences in the unilateral irradiated group (n = 5/20, 25 %). After 3 years, 12 patients had died in the bilateral irradiated group (n = 12/30, 40 %), and 7 in the unilateral irradiated group (n = 7/20, 35 %). 7 Patients showed distant metastases after 3 years in the bilateral irradiated group (n = 7/30, 23 %), and 2 in the unilateral irradiated group (n = 2/20, 10 %). Locoregional control (LRC) at 5 years was 66.2 % in the bilaterally irradiated group, and 70.0 % in the unilaterally irradiated group. Overall survival (OS) was 52.6 % (bilateral) and 64.0 % (unilateral). Distant metastasis-free survival (DMFS) was 74.7 % (bilateral) and 84.4 % (unilateral). No significant differences were observed in OS (p = 0.37), LRC (p = 0.91), and DMFS (p = 0.91) between the groups.Acute toxicity ≥ °2 accordingly CTCAE (Common Terminology Criteria of Adverse Events) was high with 97% while late toxicity ≥ °2 was moderate with 31%. There was no statistically significant difference between the group of unilateral and bilateral irradiated patients.

Conclusion

These data suggest that contralateral cervical irradiation may be of limited benefit in patients with SCC-CUP, as recurrences occured ipsilaterally, and predominantly within the area of prior irradiation. Unilateral irradiation seems to be adequate for carefully selected patients.

Long-term results of radio(chemo)therapy in metastatic carcinoma to cervical lymph nodes from an unknown primary. Adult Comorbidity Evaluation 27 score as a predictor of survival

PURPOSE

To evaluate the effectiveness and toxicity of curative (chemo)radiotherapy in patients with metastatic carcinoma to cervical lymph nodes from an unknown primary.

METHODS

Retrospective study of 90 consecutive patients, treated with curative radiotherapy from 2003 to 2018 (median age 59 years; current/former smokers 76%) was conducted. The distribution of nodal staging was as follows: N1: 12%, N2a: 21%, N2b: 43%, N2c: 10%, N3: 13%. In 62% of patients, neck dissection was performed before radiotherapy. Concomitant chemotherapy was given to 64% of patients.

RESULTS

The median follow-up of surviving patients was 86 months. The median total radiotherapy dose achieved was 70 Gy. The 5‑ and 10-year locoregional control were 84% in both cases, while 5‑ and 10-year distant control were 90% and 89%, respectively. A primary tumor in the head and neck area was detected in only 2 patients. No patient had an initial failure in the pharyngeal axis or contralateral cervical nodes. The 5‑ and 10-year overall survival were 55% and 42%, respectively. Severe early toxicity occurred in 71%; severe late toxicity in 33% of patients. Multivariate analysis demonstrated N‑status (hazard ratio [HR] 2.424; 95% confidence interval [CI] 1.121-5.241; p = 0.024) and comorbidity scores assessed by ACE-27 (Adult Comorbidity Evaluation; HR 3.058; 95% CI 1.489-6.281; p = 0.002) as two independent prognostic factors for overall survival.

CONCLUSION

The results of our work study demonstrate the high effectiveness of curative (chemo)radiotherapy on the pharyngeal axis and bilateral cervical nodes with long-term locoregional and distant control in 3/4 of the treated patients. N‑status and comorbidity scores were shown as strong prognostic factors influencing overall survival.

Evaluation of risk-tailored individualized selection of radiation therapy target volume for Head and Neck Carcinoma of Unknown Primary

PURPOSE

Intensity-modulated radiation therapy (IMRT) has enabled risk-tailored approach to elective mucosal and nodal clinical target volumes (CTVs) in treatment of head and neck carcinoma of unknown primary (HNCUP). This study report outcomes following such approach.

METHODS

HNCUP patients treated with definitive IMRT between 2005 and 2018 were reviewed. Local failure (LF), regional failure (RF), distant metastasis (DM), overall survival (OS) and grade ≥3 late toxicity (LT) were analyzed. Multivariable analysis (MVA) was used to identify OS predictors for entire cohort and cN2-3 subgroup.

RESULTS

A total of 203 patients were eligible: cN1 (7%), cN2a (14%), cN2b (46%), cN2c (14%) and cN3 (19%). Among 118 patients with known HPV status (by p16 staining), 81 (68%) were positive. IMRT target volume spared contralateral tonsil (55%), bilateral or contralateral sides of hypopharynx (72%), nasopharynx (72%), larynx (87%) and contralateral uninvolved neck (21%). Median follow-up was 5 years. Five-year LF, RF, DM, OS, and LT were 3%, 14%, 10%, 79%, and 7% respectively. Four patients developed mucosal recurrence: 3 within and 1 at the margin of the elective mucosal CTV. None of ipsilateral neck irradiation patients failed in the contralateral uninvolved neck. MVA identified cN2c-N3, HPV-negative status and older age as predictors for inferior OS. Within cN2-3 subgroup (n=189): cN2c-N3, HPV-negative status and older age predicted lower OS, while concurrent chemotherapy was associated with better OS.

CONCLUSION

Definitive IMRT with risk-adaptive radiation volume de-escalation for HNCUP resulted in high probability of tumor control with acceptable rate of late toxicity.

Interferon-induced transmembrane protein 1 (IFITM1) is essential for progression of laryngeal squamous cell carcinoma in an Osteopontin/NF-κB-dependent manner

OBJECTIVE

To assess the expression levels of IFITM1 in human tissue samples and laryngeal squamous cell carcinoma (LSCC) cells, and to explore the potential mechanisms of IFITM1 in LSCC progression.

METHODS

Quantitative PCR and immunohistochemical (IHC) assays were performed to detect IFITM1 expression in 62 LSCC tissues and corresponding normal tissues. We further detected the effects of IFITM1 on the proliferation, migration and invasion of LSCC cells and NF-κB signaling pathway through colony formation assay, wound healing assay and transwell assay, respectively.

RESULTS

We demonstrated the possible involvement of IFITM1 in the progression of LSCC. We found the upregulated expression of IFITM1 in human LSCC tissues and cells, and analyzed the correlations between IFITM1 expression and osteopontin. Our data further confirmed that IFITM1 affected cell proliferation, migration, and invasion of LSCC cells via the regulation of NF-κB signaling pathway.

CONCLUSIONS

We investigated the potential involvement of IFITM1 in the progression of LSCC, and therefore confirmed that IFITM1 was a potential therapeutic target for LSCC.

Sparing the Larynx and Hypopharynx With Radiation Therapy for Squamous Cell Carcinoma of Unknown Primary Site and Predominant Adenopathy in Level IIA

PURPOSE

There is controversy about the need to target the mucosa of the larynx and hypopharynx during radiation therapy (RT) for squamous cell carcinoma of an unknown primary site (SCCA-UP). By 1997, the policy in our department was to target only the oropharynx and nasopharynx in patients with SCCA-UP metastatic to the level II cervical nodes. The purpose of this study was to report the rate of cancer recurrence in the larynx or hypopharynx using an approach that excluded these areas from the RT target volumes.

METHODS AND MATERIALS

The inclusion criteria for this study were RT in our department for SCCA-UP between January 1, 1997, and December 31, 2019; no history of surgery that could disrupt the cervical lymphatics; predominant adenopathy in level IIA; and neck stage N1-2c. We excluded N3 because the incidental dose to the larynx and hypopharynx is usually high in patients with a >6-cm nodal conglomerate.

RESULTS

The study population was comprised of 50 patients with a median follow-up after RT of 7.1 years. No patient developed recurrent cancer in a mucosal site (0/50), 2% (1/50) developed a neck recurrence in a high-dose area with synchronous distant metastases, and 2% (1/50) developed distant metastases with no evidence of local or regional recurrence.

CONCLUSIONS

When delivering RT for SCCA-UP metastatic predominantly to level IIA, it is not necessary to target the mucosa of the larynx or hypopharynx. The extent to which the incidental RT dose to these areas contributes to cancer control is not evaluated in this study.

Patterns of Failure After Intensity Modulated Radiation Therapy in Head and Neck Squamous Cell Carcinoma of Unknown Primary: Implication of Elective Nodal and Mucosal Dose Coverage

Purpose

We evaluated the geometric and dosimetric-based distribution of mucosal and nodal recurrences in patients with metastatic head and neck squamous cell carcinoma to cervical lymph nodes of unknown primary after intensity modulated radiation therapy using validated typology-indicative taxonomy.

Methods and Materials

We reviewed the data of 260 patients who were irradiated between 2000 and 2015 and had a median follow-up time for surviving patients of 61 months. The mucosal and nodal recurrences were manually delineated on computed tomography images demonstrating the recurrences. The images were overlaid on the treatment plan using deformable image registration. The locations of the recurrences were determined relative to the original planning target volumes and doses using centroid-based approaches. Subsequently, the pattern of failures were classified into 5 types based on combined spatial and dosimetric criteria: A (central high dose), B (peripheral high dose), C (central elective dose), D (peripheral elective dose), and E (extraneous dose). For patients with type A failure with simultaneous nontype A lesions, the overall pattern of failures was defined as type A.

Results

Thirty-two patients had mucosal or nodal recurrences. The most common clinical nodal stage was N2b (66%). Preradiation therapy neck dissections were performed in 6 patients. The median dose delivered to clinical tumor volume 1 was 66 Gy. The majority (84%) had total/partial pharyngeal mucosa elective irradiation. Twenty-three patients had nodal recurrences, 8 had mucosal recurrences, and 1 had both nodal and mucosal recurrences. Twenty-one patients (91%) had type A nodal failure, and 7 of the mucosal failures (89%) were type C.

Conclusions

The majority of nodal recurrences occurred within the high-dose area, demanding the need for identification of radioresistant areas within malignant nodes. Future studies should focus on either dose escalation of high-risk volumes or novel radiosensitizers.

Radiotherapeutic management of cervical lymph node metastases from an unknown primary site - experiences from a large cohort treated with modern radiation techniques

Purpose

To analyze management and outcomes following (chemo)radiation therapy in patients with cervical lymph node metastases from an unknown primary site (CCUP) in a large single-center cohort.

Methods

Between 2008 and 2019, 58 patients with CCUP were treated with (chemo)radiation therapy at the University of Freiburg Medical Center and were included in this analysis. Overall survival (OS), locoregional progression-free survival (PFS) and distant metastasis-free survival (DMFS) were calculated using the Kaplan-Meier method. The use of diagnostic procedures and their impact on oncological outcomes was analyzed by Cox regression, and treatment-related toxicities were quantified.

Results

Median follow-up was 29.9 months (range 4.6–121.9). Twenty-one patients (36.2%) received definitive RT, 35 (60.3%) underwent adjuvant RT, and 2 (3.4%) were treated for oligometastatic disease. Concurrent chemotherapy was prescribed in 40 patients (69.0%). 89.6% of patients completed the prescribed RT, and 65.0% completed the prescribed simultaneous chemotherapy. Locoregional recurrence was observed in 7 patients (12.1%) and distant metastases in 13 cases (22.4%). OS was 81,1, 64.9% and 56,6% after 1, 3 and 5 years, respectively.

Univariate analysis of age, gender, extracapsular spread, tumor grading, neck dissection, diagnostic utilization of ¹⁸F-fluorodeoxyglucose positron-emission tomography and concomitant chemotherapy showed no effect on OS (p > 0.05 for all), while smoking was significantly associated with decreased survival (p < 0.05). There was a trend towards impaired OS for patients with advanced nodal status (pN3) (p = 0.07). Three patients (5.2%) experienced grade 3 radiation dermatitis, and 12 (22.4%) developed grade 3 and 1 (1.7%) grade 4 mucositis.

Conclusions

RT of the panpharynx and cervical lymph nodes with concurrent chemotherapy in case of risk factors demonstrated good locoregional control, but the metachronous occurrence of distant metastases limited survival and must be further addressed.

GEORCC recommendations on target volumes in radiotherapy for Head Neck Cancer of Unkown Primary

Head Neck Cancer of Unknown Primary (HNCUP) is a rare condition, representing approximately 5-10% of all head neck cancers. Radiotherapy, adjuvant or radical, is usually employed in the treatment of those patients. To date, no specific guidelines for the optimal definition of the target volume to be irradiated have been published. In recent years, there have been advances in the knowledge of the molecular biology of HNCUP, its diagnostic imaging and the implementation of sophisticated radiotherapy techniques with enhanced precision in target localization and treatment delivery. These progresses have provided valuable information about the natural history of HNCUP that will allow for establishment of the best treatment for each patient, including standardized, consistent and reproducible target volumes definitions. Several recommendations regarding how to choose volumes when contouring HNCUP in clinical practice are reported, in order to achieve a high rate of loco-regional control while avoiding unnecessary toxicity.

Cervical lymph node carcinoma metastasis from unknown primary site: a retrospective analysis of 154 patients

Despite advances in diagnosis and treatment, the existence of cervical lymph node carcinoma of unknown primary site (CCUP) has always been an urgent problem worldwide. There is still no consensus on the optimal management for CCUP. In this retrospective review, we analyze the clinical characteristics of CCUP patients treated at our institution and examine how these characteristics and treatments were associated with survival. Clinicopathologic features, treatments, and survival outcomes of 154 CCUP patients were collected from the hospital records and analyzed. Survival was estimated by Kaplan–Meier methods and compared by the log‐rank test. Cox proportional hazards regression analysis was used to assess the factors independently associated with overall survival (OS) and progression‐free survival (PFS). Median follow‐up period was 26.44 months (range, 0.53–146.53 months). Multivariate analysis showed N stage, pathologic type, and lymph node extranodal extension (ENE) to be independent prognostic factors for OS in CCUP patients, but not PFS. Subgroup analysis of patients who received radiotherapy showed that radiotherapy to the pharyngeal mucosa was associated with better OS (P = 0.045), but not with better PFS. Advanced N stage, nonsquamous cell carcinoma, and lymph node ENE predict poor prognosis in patients with CCUP. In addition, radiotherapy to suspicious mucosa is accompanied by better OS. These study findings should be useful to clinicians when selecting the treatment approach.

Effectiveness of primary surgery versus primary radiotherapy on unknown primary head and neck squamous cell carcinoma: a systematic review protocol

REVIEW QUESTION

The review question is: what is the effectiveness of primary surgery versus primary radiotherapy on disease-free survival and quality of life in adults with an unknown primary, head and neck squamous cell carcinoma?

Five-year outcomes of an oropharynx-directed treatment approach for unknown primary of the head and neck

PURPOSE

Squamous cell carcinoma of unknown primary (SCCHNUP) is commonly treated with comprehensive radiation to the laryngopharynx and bilateral necks. In 1998, we established a departmental policy to treat SCCHNUP with radiation directed to the oropharynx and bilateral neck.

METHODS

From 1998-2011, 60 patients were treated - N1: 18%, N2: 75% and N3: 7%. 82% underwent neck dissection. 55% received IMRT and 62% underwent concurrent chemoradiotherapy.

RESULTS

At median follow-up of 54months, 5 patients failed regionally and 4 emerged with a primary (tongue base, hypopharynx and thoracic esophagus). Five-year rates of regional control, primary emergence, distant metastasis, disease-free survival and overall survival were 90%, 10%, 20%, 72% and 79%, respectively. The 5year rate of primary emergence in a non-oropharynx site was 3%.

CONCLUSION

This is the first demonstration that an oropharynx-directed approach yields low rates of primary emergence in SCCHNUP with excellent oncologic outcomes.

Total Mucosal Irradiation with Intensity-modulated Radiotherapy in Patients with Head and Neck Carcinoma of Unknown Primary: A Pooled Analysis of Two Prospective Studies

AIMS

To determine the clinical outcomes of an intensity-modulated radiotherapy technique for total mucosal irradiation (TM-IMRT) in patients with head and neck carcinoma of unknown primary (HNCUP).

MATERIALS AND METHODS

A single-centre prospective phase II trial design was used in two sequential studies to evaluate TM-IMRT for HNCUP. Patients were investigated for primary tumour site using examination under anaesthetic and biopsies, computed tomography ± magnetic resonance imaging (MRI) or 18-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT). Patients received IMRT to the potential primary tumour sites and elective cervical nodes. Concomitant chemotherapy was used in patients who received primary radiotherapy or those with nodal extracapsular extension.

RESULTS

Thirty-six patients with HNCUP were recruited; 72% male. Twenty-five patients (69.4%) had p16-positive disease. Two year mucosal and local nodal control rates were 97.1% (95% confidence interval 91.4-100) and 89.8% (78.4-100), respectively. One mucosal primary was detected 7.3 months after TM-IMRT and three patients died from recurrent/metastatic squamous cell carcinoma of the head and neck. Twelve patients (33%) developed grade 3 (Late Effects in Normal Tissue-Subjective, Objective, Management and Analytical; LENT-SOMA) dysphagia with a 1 year enteric tube feeding rate of 2.7%. The high-grade subjective xerostomia rate (LENT-SOMA) at 24 months after IMRT was 15%.

CONCLUSIONS

At a median follow-up of 36.1 months, the use of TM-IMRT was associated with good local control. Toxicity was comparable with previously reported TM-IMRT regimens encompassing similar mucosal volumes.

A model and nomogram to predict tumor site origin for squamous cell cancer confined to cervical lymph nodes

BACKGROUND

The current study was conducted to develop a multifactorial statistical model to predict the specific head and neck (H&N) tumor site origin in cases of squamous cell carcinoma confined to the cervical lymph nodes ("unknown primaries").

METHODS

The Surveillance, Epidemiology, and End Results (SEER) database was analyzed for patients with an H&N tumor site who were diagnosed between 2004 and 2011. The SEER patients were identified according to their H&N primary tumor site and clinically positive cervical lymph node levels at the time of presentation. The SEER patient data set was randomly divided into 2 data sets for the purposes of internal split-sample validation. The effects of cervical lymph node levels, age, race, and sex on H&N primary tumor site were examined using univariate and multivariate analyses. Multivariate logistic regression models and an associated set of nomograms were developed based on relevant factors to provide probabilities of tumor site origin.

RESULTS

Analysis of the SEER database identified 20,011 patients with H&N disease with both site-level and lymph node-level data. Sex, race, age, and lymph node levels were associated with primary H&N tumor site (nasopharynx, hypopharynx, oropharynx, and larynx) in the multivariate models. Internal validation techniques affirmed the accuracy of these models on separate data.

CONCLUSIONS

The incorporation of epidemiologic and lymph node data into a predictive model has the potential to provide valuable guidance to clinicians in the treatment of patients with squamous cell carcinoma confined to the cervical lymph nodes.

[Target volumes in cervical lympadenopathies of unknown primary: toward a selective customized approach? On behalf of REFCOR]

The treatment of carcinomas of unknown primary revealed by cervical lymphadenopathy is based on neck dissection and nodal and pan-mucosal irradiation to control the neck and avoid the emergence of a metachronous primary. The aim of this review was to assess diagnostic and therapeutic approaches and criteria that may be used for a customized selective approach to avoid severe toxicities of pan-mucosal irradiation. A literature search was performed with the following keywords: cervical lymphadenopathy, unknown primary, upper aerodigestive tract, cancer, radiotherapy, squamous cell carcinoma, variants. The diagnostic workup includes a head and neck scanner or MRI, ((18)F)-FDG PET CT, a panendoscopy and tonsillectomy. Squamous cell carcinoma represents over two thirds of cases. The number of metastatic cervical nodes, nodal level, and histological variant (associated with HPV/EBV status) may determine the primary site origin and might be weighted for the determination of radiation target volumes on a multidisciplinary basis. A selective customized approach is relevant to decrease radiation toxicity only if neck and mucosal control is not impaired. Although no recommendation can yet be made in the absence of sufficient level of evidence, the relevance of systematic pan-mucosal irradiation appears questionable in a number of clinical situations. Accordingly, a customized selective redefinition of target volumes may be discussed and be prospectively evaluated in relation to the therapeutic index obtained.

Clinical evaluation of intensity-modulated radiotherapy for head and neck cancers

Radiotherapy and surgery are the principal curative modalities in treatment of head and neck cancer. Conventional two-dimensional and three-dimensional conformal radiotherapy result in significant side effects and altered quality of life. Intensity-modulated radiotherapy (IMRT) can spare the normal tissues, while delivering a curative dose to the tumour-bearing tissues. This article reviews the current role of IMRT in head and neck cancer from the point of view of normal tissue sparing, and also reviews the current published literature by individual head and neck cancer subsites. In addition, we briefly discuss the role of image guidance in head and neck IMRT, and future directions in this area.

Efficacy and toxicity of chemoradiotherapy using intensity-modulated radiotherapy for unknown primary of head and neck

PURPOSE

No single standard treatment paradigm is available for head-and-neck squamous cell carcinoma of an unknown primary (HNCUP). Bilateral neck radiotherapy with mucosal axis irradiation is widely used, with or without chemotherapy and/or surgical resection. Intensity-modulated radiotherapy (IMRT) is a highly conformal method for delivering radiation that is becoming the standard of care and might reduce the long-term treatment-related sequelae. We report the Dana-Farber Cancer Institute experience with IMRT-based treatment for HNCUP.

PATIENTS AND MATERIALS

A retrospective study of all patients treated at the Dana-Farber Cancer Institute for HNCUP with IMRT between August 2004 and January 2009. The primary endpoint was overall survival; the secondary endpoints were locoregional and distant control, and acute and chronic toxicity.

RESULTS

A total of 24 patients with HNCUP were included. Of these patients, 22 had Stage N2 disease or greater. All patients underwent neck computed tomography, positron emission tomography-computed tomography, and examination under anesthesia with directed biopsies. Of the 24 patients, 22 received concurrent chemotherapy, and 7 (29%) also underwent induction chemotherapy. The median involved nodal dose was 70 Gy, and the median mucosal dose was 60 Gy. With a median follow-up of 2.1 years, the 2-year actuarial overall survival and locoregional control rate was 92% and 100%, respectively. Only 25% of the patients had Grade 2 xerostomia, although 11 patients (46%) required esophageal dilation for stricture.

CONCLUSION

In a single-institution series, IMRT-based chemoradiotherapy for HNCUP was associated with superb overall survival and locoregional control. The xerostomia rates were promising, but the aggressive therapy was associated with significant rates of esophageal stenosis.

Improved dosimetric and clinical outcomes with intensity-modulated radiotherapy for head-and-neck cancer of unknown primary origin

PURPOSE

To compare differences in dosimetric, clinical, and quality-of-life endpoints among a cohort of patients treated by intensity-modulated radiotherapy (IMRT) and conventional radiotherapy (CRT) for head-and-neck cancer of unknown primary origin.

METHODS AND MATERIALS

The medical records of 51 patients treated by radiation therapy for squamous cell carcinoma of the head and neck presenting as cervical lymph node metastasis of occult primary origin were reviewed. Twenty-four patients (47%) were treated using CRT, and 27 (53%) were treated using IMRT. The proportions of patients receiving concurrent chemotherapy were 54% and 63%, respectively.

RESULTS

The 2-year estimates of overall survival, local-regional control, and disease-specific survival for the entire patient population were 86%, 89%, and 84%, respectively. There were no significant differences in any of these endpoints with respect to radiation therapy technique (p>0.05 for all). Dosimetric analysis revealed that the use of IMRT resulted in significant improvements with respect to mean dose and V30 to the contralateral (spared) parotid gland. In addition, mean doses to the ipsilateral inner and middle ear structures were significantly reduced with IMRT (p<0.05 for all). The incidence of severe xerostomia in the late setting was 58% and 11% among patients treated by CRT and IMRT, respectively (p<0.001). The percentages of patients who were G-tube dependent at 6 months after treatment were 42% and 11%, respectively (p<0.001).

CONCLUSIONS

IMRT results in significant improvements in the therapeutic ratio among patients treated by radiation therapy for head-and-neck cancer of unknown primary origin.

IMRT and IGRT in head and neck cancer: Have we delivered what we promised?

Intensity-modulated radiation therapy (IMRT) is a revolutionary new paradigm that aims at improving the therapeutic ratio by increasing the dosegradient between target tissues and surrounding normal structures thereby offering probability of better loco-regional control with decreased risk of complications. IMRT is relatively intolerant to set-up uncertainties, warranting periodic image-guidance, making Image-Guided Radiation Therapy (IGRT) a natural corollary to IMRT. There are several challenges associated with the planning, delivery, and quality assurance of the IMRT and IGRT processes that must be addressed to realize the full potential of such exciting and promising technology. Given the complexities involved, it is quite intuitive to understand that IMRT and IGRT are resource-intensive, demanding increased labor, rigour, and expenses too. Other disadvantages associated with high-precision techniques include potentially increased risk of marginal failures, decreased dose homogeneity, and an increase in total body dose with increased risk of secondary carcinogenesis. The aim of this review is to define the role of IMRT and IGRT in contemporary head and neck oncologic practice through a critical appraisal of pertinent literature. Despite relatively short follow-up and limited clinical outcomes data, the weight of evidence suggests that loco-regional control is not inferior (either comparable or even better) and toxicity lesser with IMRT resulting in potentially improved quality-of-life, prompting the widespread adoption of such technology in community practice. Ongoing clinical trials in head and neck IMRT are currently addressing issues to optimize the IMRT process, adopting functional imaging for dose-painting, and incorporating adaptive re-planning strategies to further improve outcomes.