Treatment for retropharyngeal metastatic undifferentiated squamous cell carcinoma from an unknown primary site: results of a prospective study with irradiation to nasopharyngeal mucosa plus bilateral neck

Systematic review of the CUP trials characteristics and perspectives for next-generation studies

BACKGROUND

Research on therapeutic strategies for patients with unknown primary cancer (CUP) has been underwhelming. This paper summarized and evaluated the CUP therapeutic research over the previous five years. Based on this evaluation, recommendations for clinical trial designs are made to improve the impact of CUP research on patients.

METHODS

Published and ongoing research were evaluated. PubMed was searched from January 1, 2015, to November 1, 2021. The start date of 2015 was chosen to identify research published after ESMO issued new diagnostic and therapeutic guidelines. The US National Library of Medicine indexed ongoing clinical trials.

FINDINGS

Of the 244 CUP studies indexed in PubMed, 11.9% were prospective studies, and 4.9% were clinical trials. The review protocol deemed 65 publications eligible for full-text review. Eleven studies evaluating therapeutic regimens were retained. The two prospective studies and non-randomized trials showed promising outcomes for site-specific treatments. Randomized clinical trials were less promising; however, the trials had recruitment challenges resulting in biased accrual and the inability to keep pace with advancing diagnostics and therapeutics. Most of the 35 ongoing studies were phase II single-arm trials assessing immune checkpoint inhibitors (ICI) or site-specific therapies among CUP patients with suspected favorable prognoses.

CONCLUSION

Our evaluation suggests two prospective clinical trial designs that addressed recent study design and recruitment challenges. A visionary approach uses a multi-arm, multistage randomized trial to address rapid advancements in diagnosis and therapy. A pragmatic approach utilizes a single-arm trial with historical controls to overcome comparison group and recruitment challenges.

Long-term results of elective mucosal irradiation for head and neck cancer of unknown primary in Chinese population: The EMICUP study

Objective

Controversy still exists regarding the volume of radiation for head and neck cancer of unknown primary (HNCUP). Theoretically, elective mucosal irradiation (EMI) should achieve a balance between survival and toxicity. This prospective study was conducted to evaluate the long‐term benefit of EMI in Chinese HNCUP patients.

Methods

A phase II, single‐arm trial was performed at two centers in China. HNCUP patients with pathologically confirmed metastatic squamous cell carcinoma or poorly differentiated carcinoma were enrolled. Patients with metastatic lymph nodes limited to level IV and/or the supraclavicular fossa were excluded. The EMI approach was specifically customized to Chinese patients by differentiating HNCUP as putative nasopharyngeal carcinoma (NPC) or non‐putative NPC. The primary endpoint was 3‐year mucosal recurrence‐free survival (MRFS).

Results

A total of 48 patients were enrolled between 02/02/2010 and 08/01/2018; 46 patients were analyzed, including 24 putative NPC and 22 non‐putative NPC patients. No primary recurrence was observed during a median follow‐up period of 70 months, and only 1 patient experienced out of field recurrence in the contralateral neck. The 3‐year MRFS was 90.6% (95%CI: 76.4%‐96.4%). The 5‐year MRFS, regional‐recurrence free survival (RRFS) and overall survival (OS) were 90.6% (95%CI: 76.4%‐96.4%), 86.0% (95%CI: 71.1%‐93.7%), and 90.6% (95%CI: 76.4%‐96.4%), respectively. No grade 4 acute or late toxicities occurred, and the most frequent grade 3 acute toxicity was oral mucositis (45.7%).

Conclusion

To the best of our knowledge, this is the first prospective study to evaluate the long‐term outcomes of EMI in Chinese HNCUP patients. Excellent MRFS and OS rates were observed. Further randomized studies are warranted.

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.